Patent Application
20080041344
The present invention relates to a fuel injection valve and a method of operating such a fuel injection valve for controlling fuel flow into an internal combustion engine. More particularly, the fuel injection valve comprises a nozzle arrangement that provides a substantially constant flow rate for a predetermined range of valve needle movement.
A fuel injection valve can employ a number of control strategies for governing the quantity of fuel that is introduced into the combustion chamber of an internal combustion engine. For example, some of the parameters that can be manipulated by commonly known control strategies are the pulse width of the injection event, fuel pressure, and the valve needle lift.
The “pulse width” of an injection event is defined herein by the time that a fuel injection valve is open to allow fuel to be injected into the combustion chamber. Assuming a constant fuel pressure and a constant valve needle lift, a longer pulse width generally results in a larger quantity of fuel being introduced into the combustion chamber.
However, fuel pressure need not be constant from one injection event to another and fuel pressure can be raised to increase the quantity of fuel that is introduced into the combustion chamber. Conversely fuel pressure can be reduced to inject a smaller quantity of fuel into the engine, for example during idle or low load conditions.
As yet another example, some types of fuel injection valves can control valve needle lift to influence the quantity of fuel that is introduced into a combustion chamber. An increase in needle lift generally corresponds to an increase in the quantity of fuel that is injected and some fuel injection valves can be controlled to hold the valve needle at an intermediate position between the closed and fully open positions to allow a flow rate that is less than a maximum flow rate. To control valve needle lift a fuel injection valve can employ mechanical devices or an actuator that is controllable to lift and hold the needle at intermediate positions between the closed and fully open positions.
European Patent Specification No. EP 0615065 B1 (“Shibata”) discloses a fuel injection valve for injecting a liquid fuel using an injection pump with a cam driven plunger that reciprocates to increase fuel pressure to actuate the fuel injection valve. The cam has a low-speed area where the fuel supply rate of the pump is low and a high-speed area where the fuel-supply rate is high so that the plunger is movable at a variable speed. The injection valve has an elongated pin formed on the nozzle needle for keeping the size of the fuel passage at the injection port substantially constant when the pin is positioned in the injection hole even when the nozzle needle moves, whereby the fuel injection mass flow rate is substantially constant until the pin is lifted out of the injection hole. Shibata discloses an apparatus and method that can be employed to shape the fuel injection mass flow rate during the course of an injection event whereby the fuel injection rate is initially low (while the pin is positioned in the injection hole), and then raised to a higher fuel injection rate (when the pin is lifted from the injection hole). However, because the injection pump is mechanically operated using a cam and plunger arrangement, the shape of the fuel injection mass flow rate is generally the same for each injection event. For each injection event the nozzle needle is continuously moving from the closed position to the fully open position and then back to the closed position, with the pin at the end of the nozzle needle providing a restriction that produces the step shaped injection pulse. Shibata does not disclose an apparatus or method for regulating fuel mass flow by actuating a valve needle that is operable to hold the valve needle at intermediate positions and a method whereby the valve needle lift is variable both during an injection event and from one injection event to another injection event. That is, Shibata does not disclose an apparatus or method that allows partial valve needle lift to an intermediate position for the duration of an injection event so that the lower mass flow rate is provided for the entire injection event, and that also allows valve lift to a fully open position for another injection event.
A difficult task for known control strategies is controlling the quantity of fuel that is injected into an engine's combustion chamber under idle or low load conditions. Under such conditions the fuel injection valve is required to inject only a small amount of fuel into the combustion chamber, and even small variations in the quantity of fuel that is injected into the combustion chamber can result in a significant variance in the injected quantity of fuel that can cause unstable operation. Under high load conditions, variations in the quantity of fuel of the same order of magnitude have less impact on engine operation because they represent a much smaller variation in the difference between the desired quantity of injected fuel versus the actual quantity of injected fuel, when this difference is considered as a percentage of the total quantity of injected fuel.
To control the quantity of fuel injected during idle and low load conditions, if the control strategy manipulates only pulse width, this strategy can result in a pulse width that is too short to provide consistent and efficient combustion. Accordingly, simply shortening pulse width at idle or low load conditions to reduce the quantity of injected fuel is not a desirable strategy.
A pulse width sufficiently long for idle or low load conditions can be achieved by reducing the fuel pressure. For liquid fuels this is a viable strategy, but it requires a system for controlling fuel pressure, adding to the cost and complexity of the fuel injection system. For example, known liquid fuel systems can reduce fuel pressure by returning a portion of the high-pressure fuel to the fuel tank. With liquid fuels, there are limitations on how low the pressure can be reduced since a minimum fuel pressure is required to atomize the fuel when it is introduced into the engine's combustion chamber. However, this approach is more difficult with a gaseous fuel. Since a gas is a compressible fluid, compared to a liquid fuel, much more gaseous fuel must be returned to the fuel tank for a comparable reduction in fuel pressure, and if the gaseous fuel tank is pressurized, there can be times when the tank pressure exceeds the fuel rail pressure, making return flow impossible. Consequently, it can be difficult to rapidly reduce the pressure of a gaseous fuel without venting some of the fuel to atmosphere, which is undesirable. Accordingly, it can be difficult to control fuel pressure to achieve the desired responsiveness for controlling the fuel injection mass flow rate during an injection event or from one injection event to the next. It can also be difficult to control fuel pressure and injection valve operation to accurately inject the exact quantity of fuel with the precision desired for each injection event, and again, only small variations in fuel quantity can cause unstable operating conditions. Therefore, controlling fuel injection pressure alone is not a desirable strategy for regulating fuel mass flow rate through a fuel injection valve.
If a fuel injection valve is operable to control valve needle lift, flow rate can be controlled to provide a sufficiently long pulse width to inject the desired quantity of fuel for an engine that is idling or operating under low load conditions. As shown in Japanese Patent Publication No. 60-031204, a fuel injection valve can be provided with a stopper that is movable to limit the lift of the valve needle. This type of mechanical arrangement adds considerable complexity to the fuel injection valve and, consequently, higher manufacturing costs, space requirements for installing the injection valve assembly, maintenance costs, and reliability concerns.
In another approach, fuel injection valves are known that control the quantity of injected fuel by employing variable orifice areas. That is, the injection valve can have two sets of orifices whereby the valve is operable to inject fuel through only one set of orifices when a smaller quantity of fuel is to be injected, and fuel is injected through both sets of orifices when a larger quantity of fuel is to be injected. U.S. Pat. No. 4,546,739 discloses an example of such an injection valve. Like other known mechanical solutions this arrangement adds complexity and the associated disadvantages of higher manufacturing costs, maintenance costs, and concerns for reliability.
Another type of fuel injection valve can be directly actuated by a strain-type actuator, which can be commanded to lift the valve needle to any position between its closed and open position. Co-owned U.S. Pat. Nos. 6,298,829, 6,564,777, 6,575,138 and 6,584,958, which are hereby incorporated by reference in their entirety, disclose examples of directly actuated fuel injection valves that employ a strain-type actuator. For example, if the strain-type actuator is a piezoelectric actuator, by controlling the charge applied to the actuator the valve needle lift can be commanded to the desired lift position. However, even with this approach there can be variability of fuel flow from one injection event to the next because the actual valve needle lift may not always accurately match the commanded lift. Variability in the actual valve needle lift can be caused by a number of factors, including, for example, one or more of variations in combustion chamber pressure, variations in fuel pressure, the effects of differential thermal expansion/contraction within the fuel injection valve, and component wear within the fuel injection valve. Accordingly, even with a fuel injection valve that employs an actuator that allows lift control, there can be factors that cause variability in the actual lift that can still be large enough to cause variability in the quantity of injected fuel.
Engine instability at idle and low load conditions can cause higher engine fuel consumption, exhaust emissions, noise and vibration. Accordingly, there is a need for an apparatus and method that provides a more consistent means of controlling the quantity of fuel injected during each injection event when an engine is idling or under low load conditions and that improves combustion stability under such conditions.
For compression ignition engines that burn a gaseous fuel it can be beneficial to shape the rate of fuel injection to begin an injection event with an initial low mass flow rate, followed by a higher mass flow rate until the end of the fuel injection event. An example of this is disclosed in co-owned and co-pending U.S. patent application Ser. No. 10/414,850, entitled, “Internal Combustion Engine With Injection Of Gaseous Fuel”, which is hereby incorporated by reference in its entirety. It can be difficult to operate a conventional fuel injection valve to provide the stepped flow characteristic that is needed to achieve this result. If a fuel injection valve that provides a substantially constant mass flow rate for a predetermined range of valve needle movement can be made so that this constant mass flow rate corresponds to the initial low mass flow rate for a stepped injection event, such a feature can be useful for improving injection consistency and engine performance for all operating conditions from idle through to full load.
A fuel injection valve introduces a fuel into an engine. The fuel injection valve comprises: a. a valve body that comprises a nozzle and that defines a fuel cavity disposed within the valve body; b. a valve needle movable within the nozzle between a closed position at which the valve needle is seated against a valve seat associated with the nozzle, and a fully open position at which the valve needle is spaced furthest apart from the valve seat to allow the fuel to flow from the fuel cavity and into the engine through the nozzle; and c. an actuator for actuating the valve needle that is operable to hold the valve needle at intermediate positions between the seated and fully open positions, whereby valve needle lift is variable during an injection event and from one injection event to another injection event. That is, the valve needle lift is variable in that, for example, the valve needle can be commanded to, and if desired, held at, different positions at different times during a single injection event. Valve needle lift is also variable from one injection event to another injection event in that the shape of a plot of valve needle lift against time can be different for different injection events, for example with a relatively low needle lift and a rectangular shape for engine idle conditions and a step shape for high load conditions with the second step being substantially larger than the first step.
When the valve needle is positioned between a first intermediate position proximate to the closed position and a second intermediate position spaced from the first intermediate position, the valve needle and the valve body are shaped to cooperatively provide a constant flow area between the valve needle and the valve body. The constant flow area restricts flow through the nozzle so that mass flow rate is substantially constant for a range of valve needle movement with boundaries of the range of movement defined by the first and second intermediate positions.
To reduce the variability in flow rate when the valve needle is positioned between the first and second intermediate positions, the constant flow area is preferably smaller than the open flow area between the valve seat so that the constant flow area controls the fuel mass flow rate through the fuel injection valve when the valve needle is positioned between the first and second intermediate positions.
The constant flow area can be provided by an annular gap between the valve needle and the valve body or by grooves formed in the valve body or the valve needle. The raised portions between the grooves can act as guides for the valve needle to add consistency to the positioning of the valve needle on the valve seat.
In preferred embodiments, the fuel injection valve further comprises a strain-type actuator for directly actuating the valve member. The strain-type actuator can comprise a transducer selected from the group consisting of piezoelectric, magnetostrictive, and electrostrictive transducers. An electronic controller can be programmed to send command signals to the actuator to move the valve needle between the closed position and the fully open position and to positions therebetween according to predetermined waveforms.
The fuel injection valve can further comprise an amplifier disposed between the actuator and the valve member to amplify the strain produced by the actuator to cause larger corresponding movements of the valve member. The amplifier can be a hydraulic displacement amplifier, or it can employ at least one lever to amplify the strain mechanically.
In preferred embodiments, the fuel is introducible into the fuel cavity in the gaseous phase. The fuel can be selected from the group consisting of natural gas, methane, ethane, liquefied petroleum gas, lighter flammable hydrocarbon derivatives, hydrogen, and blends thereof.
The valve needle can be an inward opening valve needle whereby the valve needle is movable in an inward direction opposite to the direction of fuel flow when moving from the closed position towards the open position. In this embodiment the nozzle can comprise a closed end with at least one orifice through which the fuel can be injected when the valve needle is spaced apart from the valve seat. In preferred embodiments, the nozzle comprises a plurality of orifices through which the fuel can be injected when the valve needle is spaced apart from the valve seat and the collective open area of the plurality of orifices is greater than the constant flow area. When the valve needle is in the fully open position, the collective open area of the plurality of orifices provides the smallest restriction for the fuel flowing through the nozzle and thereby governs the mass flow rate of fuel flowing through the fuel injection valve.
In another embodiment the fuel injection valve can further comprise a third intermediate position spaced from the second intermediate position, defining a boundary of a second range of valve needle movement between the second and third intermediate positions. When the valve needle is positioned between the second and third intermediate positions the valve body and the valve needle can be shaped to cooperatively provide a second constant flow area that restricts flow through the nozzle so that mass flow rate is substantially constant but higher than the mass flow rate when the valve needle is positioned between the first and second intermediate positions.
By way of example, preferred embodiments are illustrated and described of a fuel injection valve for injecting a fuel directly into a combustion chamber of an engine. Without departing from the spirit and scope of this disclosure, persons skilled in this technology will understand that other arrangements for the valve body and the valve needle of the fuel injection valve are also possible. The scope of the disclosed fuel injection valve includes nozzles and valve needles that are shaped to cooperate with each other so that, when the valve needle is positioned between a first intermediate position proximate to the closed position and a second intermediate position spaced from the first intermediate position, a substantially constant pressure drop occurs when the fuel is flowing through the nozzle so that mass flow rate is substantially constant for a range of valve needle movement with boundaries of the range of movement defined by the first and second intermediate positions.
A method regulates fuel mass flow rate into an engine through a nozzle of a fuel injection valve. The method comprises: actuating a valve needle to control valve needle lift, which is variable during an injection event and from one injection event to another injection event, responsive to measured engine operating conditions, comprising engine load and speed; commanding a valve needle to move to a position between first and second predetermined intermediate positions, which are between a closed position and a fully open position when a predetermined constant fuel mass flow rate is desired, wherein the fuel injection valve is designed to allow a substantially constant fuel mass flow rate when the valve needle is positioned between the first and second intermediate positions and the pressure of the fuel is constant; and commanding the valve needle to move to positions between the closed and fully open positions, but not between the first and second intermediate positions, when a fuel mass flow rate different from the predetermined constant fuel mass flow rate is desired.
Preferably the method further comprises commanding the valve needle to the mid-point, between the first and second intermediate positions when the substantially constant mass flow rate is desired. Because there can be some variability between the commanded needle position and the actual needle position, commanding the valve needle to the mid-point of the range of movement reduces the likelihood of the actual valve needle position being outside of the range of movement defined by the predetermined first and second intermediate positions. Overall, this reduces variability in the fuel mass flow rate delivered into the combustion chamber.
In preferred embodiments of the method, the substantially constant fuel mass flow rate corresponds to the desired fuel mass flow rate for idle or low load conditions. As indicated already, under these conditions an engine is most susceptible to variations in fuel mass flow rate because the required amount of fuel to be injected is already small, compared to when the engine is operating under higher loads, and even small variations in fuel mass flow rate can have an adverse effect on stable engine operation, with corresponding adverse impacts on engine performance characteristics such as engine emissions, noise, and/or efficiency.
In a preferred embodiment of the method, providing a flow restriction within the nozzle with a constant flow area when the valve needle is positioned between the first and second intermediate positions regulates the substantially constant fuel mass flow rate. When the second intermediate position corresponds to a larger valve needle lift than that of the first intermediate position, fuel mass flow rate can be substantially and progressively increased by moving the valve needle from the second intermediate position toward the fully open position.
The method can further comprise commanding the valve needle to a position between the second intermediate position and a third intermediate position when a second substantially constant mass flow rate is desired, where the second intermediate position corresponds to a larger valve needle lift than that of the first intermediate position and the third intermediate position corresponds to a larger needle lift than that of the second intermediate position. The fuel injection valve can be designed with flow restrictions such that the first restricted flow area is smaller than the second restricted flow area that is substantially constant when the valve needle is positioned between the second and third intermediate positions. In this embodiment of the method, the fuel mass flow rate can be substantially and progressively increased by moving the valve needle from the third intermediate position toward the fully open position. For example, the first constant mass flow rate can be selected when the engine is idling and the second constant mass flow rate can be selected when the engine is operating under predetermined low load conditions.
The method preferably comprises injecting the fuel from the nozzle directly into a combustion chamber of the engine. By injecting the fuel directly into the combustion chamber, the engine can maintain the compression ratio and efficiency of an equivalent engine burning diesel fuel. If the fuel is injected into the air intake system upstream of the intake valve, to avoid early detonation of the fuel it may be necessary to limit the amount of fuel injected and/or to reduce the engine's compression ratio.
The present method is particularly suitable for fuel that is in the gaseous phase when it is flowing through the nozzle. Accordingly, the method can further comprise introducing the fuel into the nozzle in the gaseous phase. For example, the fuel can be selected from the group consisting of natural gas, methane, ethane, liquefied petroleum gas, lighter flammable hydrocarbon derivatives, hydrogen, and blends thereof.
A preferred embodiment of the method further comprises directly actuating the valve needle with a strain-type actuator that can be activated to cause corresponding movements of the valve needle. Strain-type actuators are particularly suited to implementing the disclosed method because they can be controlled to command the valve needle to move to and be held at any intermediate position between the closed and fully open positions. The strain-type actuator preferably comprises a transducer selected from the group consisting of piezoelectric, magnetostrictive, and electrostrictive transducers.
The method can further comprise also controlling injection pulse width to assist with controlling the amount of fuel that is injected during an injection event, whereby pulse width is variable from one injection event to another injection event responsive to predetermined measured engine operating conditions. Whereas controlling pulse width alone is not a desired strategy for regulating the mass quantity of fuel injected, pulse width control can be combined with the disclosed method to provide greater flexibility so that the desired mass quantity of fuel can be introduced into the combustion chamber as determined from the measured engine operating conditions and with reference to an engine map. For example, some of the engine operating conditions can include engine speed and engine load. Other operating conditions can also be monitored and an electronic control unit can be programmed to determine if any adjustments should be made to correct for other variables such as fuel temperature; intake air temperature, fuel injection pressure, and in-cylinder pressure.
Similarly, the method can further comprise controlling injection pressure to assist with controlling the amount of fuel that is injected during an injection event, whereby fuel injection pressure is variable from one injection event to another responsive to predetermined measured engine operating conditions.
A method of regulating fuel mass flow rate into an engine through a nozzle of a fuel injection valve by controlling valve needle position, the method comprising: increasing fuel mass flow rate from zero to a first value by moving the valve needle from a closed position where it is urged against a valve seat to a first intermediate position; maintaining fuel mass flow rate substantially constant at about the first value when the valve needle is positioned between the first intermediate position and a second intermediate position, which is spaced from the first intermediate position; progressively increasing fuel mass flow rate beyond the first value by moving the valve needle from the second intermediate position towards a folly open position; increasing fuel mass flow rate to a maximum value by moving the valve needle to the folly open position; and actuating the valve needle to control valve needle lift responsive to measured engine operating conditions, comprising engine speed and load, wherein the valve needle position is variable during an injection event and from one injection event to another injection event.
In a preferred method, the first value is the fuel mass flow rate that is commanded when the engine is operating under idle or low load conditions.
The preferred method can further comprise commanding the valve needle to move according to a stepped waveform with a relatively low mass flow rate during a first step and a higher mass flow rate during a second step and wherein the first value is the fuel mass flow rate that is commanded for the first step.
The method preferably comprises moving the valve needle by actuating a strain-type actuator that can be commanded to produce a linear displacement that is transmitted to the valve needle. With such an actuator, the plot of displacement over time can follow any commanded shape, and need not be the same shape for each injection event. For example, for idle conditions, a small displacement with a substantially rectangular shape can be commanded. For higher loads, a step-shape can be employed with a relatively low initial displacement followed by a higher actuator displacement.
The drawings illustrate specific embodiments of the invention, but should not be considered as restricting the spirit or scope of the invention in any way.
The schematic views are not drawn to scale and certain features may be exaggerated to better illustrate their functionality.
The disclosed features for influencing the flow characteristics through a fuel injection valve are independent from the type of actuator employed to cause valve needle movements. Any actuator that can be controlled to influence the speed of valve needle actuation and/or to control valve needle position between the closed and fully open positions can benefit from the disclosed arrangement. For example, an electromagnetically actuated fuel injection valve can employ the disclosed features because the rate of opening for an electromagnetic valve can be controlled to a certain degree by controlling the rate of force rise. That is, using an electromagnetic actuator, the speed of valve needle movement can be kept slow during the beginning of a fuel injection event, prolonging the time when the fuel is introduced at a constant relatively low fuel mass flow rate before the fuel mass flow rate increases during the later part of the fuel injection event.
In preferred embodiments, injection valve 100 comprises a strain-type actuator for directly actuating valve needle 110 and providing the advantage of facilitating control over valve needle movements. A directly actuated fuel injection valve is defined herein as one that employs an actuator that can be activated to produce a mechanical movement that directly corresponds to a movement of the valve needle. In such a directly actuated fuel injection valve, the mechanical movements originating from the actuator can be amplified by one or more mechanical levers or a hydraulic amplifier, but the movements of the actuator always correlate to corresponding movements of the valve needle. In the example illustrated by
Actuator 120 can be commanded to change the amount of strain during an injection event to move valve needle 110 to a different open position, or to reduce the strain to zero to end an injection event.
Spring 126 biases valve needle 110 in the closed position and helps to ensure that no spatial gaps form between actuator 120, transmission assembly 130 and valve needle 110.
In the illustrated example, transmission assembly 130 further comprises hydraulic fluid reservoir 134. Compared to the time interval of a fuel injection event, there are much longer periods of time between injection events and when the engine is not running, when there is sufficient time to allow some fluid flow between reservoir 134 and amplification chamber 132 through the small gaps provided between the adjacent surfaces of plunger 124, valve needle 110, and valve body 102 and conduits 136 and 138. Such flow between reservoir 134 and amplification chamber 132 can compensate for leakage of hydraulic fluid and small dimensional changes between components that can be caused, for example, by differential temperature expansion/contraction and wear.
Seals 137 and 139 seal against leakage of the hydraulic fluid into fuel cavity 104, which is necessary when valve 100 is employed to inject a gaseous fuel. If the fuel is a liquid fuel and it is conveniently employed as the hydraulic fluid, seal 139 is not necessary.
Strain-type actuators are generally controllable to produce any amount of strain between zero and a maximum amount of strain that is producible by a given actuator. That is, a strain-type actuator can be commanded to move valve needle 110 to an intermediate position where it can be held for a desired length of time. A controller can be programmed to command the actuator to change the amount of strain so that valve needle 110 is moved from the intermediate position to another open position or the closed position. This allows the movements of valve needle 110 to be commanded to follow a predetermined waveform, which provides more flexibility to control the fuel mass flow rate during an injection event, and this flexibility can be employed to improve combustion characteristics to increase performance or efficiency, and/or reduce the exhausted emissions of undesirable combustion products such as particulate matter or oxides of nitrogen or carbon, and/or reduce engine noise.
By way of example, actuator 120 is depicted schematically in
While strain-type actuators can be commanded to produce a desired strain, there are variable effects such as temperature, wear, fuel pressure, intake manifold pressure and combustion chamber pressure, that can influence valve needle position differently from one injection event to another. Accordingly, even if an actuator is commanded to produce a given strain that normally corresponds to a desired valve needle position, the actual valve needle position may be different, and variances between actual position and the desired position can be significant enough to reduce combustion efficiency, especially when the engine is at idle or under low load conditions.
The features illustrated in
With reference now to the illustrated embodiment of
In
Reference is now made to
Another embodiment of a nozzle with an inward opening valve needle is shown in
Another embodiment of a nozzle arrangement with an outward opening valve needle is shown in
For a fuel injection valve that controls needle lift to control fuel mass flow rate, with a conventional fuel injection valve, if Qa represents the desired fuel mass flow rate for idle or low load conditions, the needle is commanded to be lifted by distance L1 to deliver the desired flow rate. Because of the steep slope of line 600 near lift L1, even small deviations from position L1 can result in a significant variation in the actual fuel mass flow rate.
Solid line 610 shows a curve that is representative of a fuel injection valve that employs the features of the present disclosure. For example, at idle or low load conditions, the valve needle can be commanded to a position at the mid-point, between L1 and L2. Because the slope of line 610 between L1 and L2 is much flatter than the scope of line 600 for the same range of valve needle movement, the fuel injection valve of line 610 can be operated with improved consistency to improve engine performance, efficiency, and/or reduce emissions of unwanted combustion products like particulate matter and oxides of nitrogen or carbon, and/or reduce engine noise. The embodiments illustrated in
Broken line 620 plots the flow characteristics for a fuel injection valve 1 such as the ones illustrated in
The disclosed fuel injection valve was developed for gaseous fuels, but the same features can be beneficial for fuel injection valves that inject a liquid fuel. However, for a liquid fuel, there are additional considerations that must be taken into account such as cavitation and maintaining adequate pressure for atomization of the fuel. Cavitation can occur when a sudden pressure drop lowers the fuel pressure below the vaporization pressure and some of the fuel is vaporized before the fuel is discharged from the injection valve. Problems associated with cavitation and atomization can be avoided, for example, by employing one or more of the following strategies: (i) introducing the fuel to the fuel injection valve with an initial pressure that is high enough to ensure that fuel pressure remains above the vaporization pressure and adequately high after the restricted flow area to atomize the fuel when it exits the fuel injection valve; (ii) sizing the restricted flow area to limit the pressure drop so that fuel pressure is not reduced to less than the vaporization pressure or the minimum pressure required to atomize the fuel upon exiting the fuel injection valve; (iii) providing a smooth entrance into the restricted flow area to reduce turbulence that can cause low pressure regions; and (iv) manufacturing the nozzle and valve needle from materials that will not be damaged by exposure to the conditions associated with cavitation. With liquid fuels, it is possible to employ the disclosed features and realize many of the same benefits that can be achieved with gaseous fuels. For example, it is possible to achieve more stable performance and reduce engine noise under idle and low load conditions by reducing variability in the quantity of injected fuel.
While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.
This application is a continuation of International Application No. PCT/CA2005/001062, having an international filing date of Jan. 8, 2005, entitled “Fuel Injection Valve”. International Application No. PCT/CA2005/001062 claimed priority benefits, in turn, from Canadian Patent Application No. 2,473,639 filed Jul. 9, 2004. International Application No. PCT/CA2005/001062 is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CA05/01062 | Jan 2005 | US |
| Child | 11621324 | Jan 2007 | US |
