Method for controlling a solenoid-operated fuel injector

Abstract

1. A method of controlling a fuel injector, the injector including an electrically controlled actuator configured to control a needle valve by movement of the needle to and from its seat, the method comprising the steps of: a) determining for the fuel injector a plot of a quantity of fuel (Q) delivered by the fuel injector versus a pulse width of an actuator actuation pulse sent to the actuator; b) providing a modified plot of a quantity of fuel delivered by the fuel injector versus a pulse width of an actuator actuation pulse based on the plot of step a); and c) using the modified plot to subsequently control activation of the fuel injector, wherein step b) comprises the steps of: d) identifying a spoon region in the plot of step a); and e) reproducing the plot of step a) without data from the spoon region of the plot of step a).

Description

[Technical Field]

[0001] This application relates to a method of controlling a solenoid-controlled fuel injector. This application has particular, but not exclusive, application to direct-acting and solenoid-actuated fuel injectors. This application further relates to a method of applying trim in controlling a fuel injector. [Background technology]

[0002] Current fuel injectors typically use an electric actuator (e.g., a piezo- or solenoid-operated actuator) to operate a needle valve, which opens and closes to dispense fuel into the combustion chamber via movement of the needle of the needle valve away from a valve seat. Typically, an activation pulse of a specific duration (pulse width) is sent to the electric actuator (e.g., a solenoid actuator) to operate the fuel injector. The amount of fuel injected into the combustion space depends on the duration of the pulse. Fuel injectors may also be of the type in which the actuator directly moves a pintle / needle away from a valve seat, for example against a biasing spring means, to dispense fuel; these are referred to as direct injectors, and these types of injectors are used for both gasoline and diesel. Typically, the actuator is configured to move a pintle / needle arrangement, where the needle is connected to the pintle as is well known in the art; it should be noted that references to the pintle can be interpreted as references to the needle, and vice versa. The present invention is particularly applicable to these types of direct injectors. The actuator may be a solenoid or piezo controlled actuator.

[0003] In an alternative design, many current fuel injectors are hydraulically operated rather than using an actuator (e.g., a solenoid) to directly actuate the needle; the actuator operates a hydraulic valve (system) to control the pressure within the fuel injector, indirectly moving the needle from its seat and selectively dispensing fuel.

[0004] This type of (e.g., gasoline) injector is compensated over time by learning, analyzing its behavior, calculating corrections, and applying these trims during the next injector operation. This strategy is called ICLC (Injector Closed Loop Compensation).

[0005] Most injector controls do not take into account the bounce of the physical pintle of a gasoline injector, which results in a spoon-shaped region, or "dip," that occurs in a plot of injected fuel versus pulse length. These occur in the plot at the beginning of the pulse duration leading to or following the full lift area of ​​the injector flow curve (pulse versus flow delivery curve). As used herein, the term "spoon" should be interpreted to mean one or more dips or spoon regions in a plot of delivered fuel Q versus (activation) pulse duration (e.g., delivered to a solenoid actuator) from a first point in time where the delivered fuel decreases with a small increase in pulse duration, to a point in time where the quantity of fuel delivered Q returns to the local peak value it had at the first point in time, i.e., before the dip).

[0006] For ECU control of fuel injection, spooning creates a problem because multiple pulse widths applied to the injector in the spoon area result in the same fuel delivery, making it difficult to control. It is preferable to have only one quantity linked to one pulse duration and no more. To solve this type of problem, for control purposes, a chart or plot (e.g., stored in the ECU as a MAP or relationship) of fuel quantity (delivery) versus (e.g., solenoid) pulse width control is provided, and the plot is such that as the pulse width increases, only the injected fuel quantity increases, i.e., monotonically. Therefore, the injector behavior is then mapped with a monotonic pulse-to-fuel quantity curve to meet this condition.

[0007] This kind of modified monotonic curve / plot is then used for ICLC trim decisions (pulse correction), which can be done, for example, by comparing with a target behavior (called MASTER) at some predetermined fuel delivery learning points (ICLC breakpoints).

[0008] Therefore, although a monotonic curve is essential for determining ICLC trim, the physical behavior of this injector differs somewhat due to the assumptions made by generating the monotonic curve. This difference is not compensated for and gives rise to local errors.

[0009] Finally, no matter what number of ICLC quantity training points is selected, this phenomenon leads to poor ICLC performance in this particular area.

[0010] The usual way to solve this type of problem is to minimize this effect by injector hydraulic optimization, which can cause higher part-by-part sensitivity or requires excess force margin and hydraulic damping. Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to solve this type of problem. [Means for solving the problem]

[0012] In one aspect, there is provided a method of controlling a fuel injector, the injector including an electrically controlled actuator configured to control a valve needle by movement of a needle to and from a valve seat, the method comprising: a) determining, for the fuel injector, a plot of the quantity of fuel (Q) delivered by the fuel injector versus the pulse width of an actuator actuation pulse sent to the actuator; b) providing a modified plot of fuel quantity delivered by said fuel injector versus pulse width of actuator actuation pulses based on the plot of step a); c) using the modified plot to subsequently control activation of the fuel injectors; Step b) is d) identifying spoon regions in the plot of step a); e) regenerating the plot of step a) without the data from the spoon region of the plot of step a). The plot generated in step d) may have gaps in the spoon regions, i.e. in these regions there may be no stored relationship / MAP / plot data.

[0013] The spoon region represents pintle / needle bounce. Step c) may include comparing data from the plot generated in step b) with data from a reference plot to determine trim data for said subsequent control.

[0014] The actuator may be a solenoid-controlled actuator or a piezo-controlled actuator. The term stored "plot" or "curve" (e.g., relating quantity of fuel delivered Q to (actuator) pulse width) can be interpreted as a parameter related to relationship data (e.g., a stored relationship). The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 10 shows a plot / curve of pulse width applied to a solenoid of a solenoid-actuated fuel injector. [Figure 2] FIG. 2 illustrates this type of monotonic curve / plot based on the plot of FIG. 1. [Figure 3]FIG. 1 illustrates control dependent on nominal (e.g., ideal) fuel injector response. [Figure 4] FIG. 3 illustrates the errors in the plot of FIG. 2. [Figure 5] FIG. 4 is a diagram illustrating the relationship between fuel error and fuel demand. [Figure 6] FIG. 1 illustrates an example of the present invention. [Figure 7] FIG. 1 illustrates an example of the present invention. [Figure 8] FIG. 10 illustrates the identification of spoon regions. [Figure 9] FIG. 10 is a diagram showing the improvement results of an example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] As mentioned above, spoons present a problem for ECU control because multiple pulse widths applied to the injectors in the spoon area result in the same fuel delivery that is difficult to control.

[0017] 1 shows a plot / curve 1 of the pulse width applied to the solenoid of a solenoid-actuated fuel injector and the resulting amount of fuel injected for a typical injector. It should be noted that aspects of the present invention are equally applicable to injectors having a piezo actuator rather than a solenoid actuator.

[0018] As can be seen, there may be one or more spoon regions 2 where the fuel quantity drops off for small increases in pulse width. The main spoon area is indicated by reference numeral 2a.

[0019] In summary, to solve this type of problem, for control purposes, a chart / plot (e.g., stored in the ECU as a MAP) of fuel quantity (delivery) versus pulse width control is provided, and the plot is such that as pulse width increases, only the injected fuel quantity increases, i.e., monotonically increasing in the plot. Therefore, the injector behavior is then mapped using a monotonic pulse versus fuel delivery (quantity Q) plot / curve to satisfy this condition. Figure 2 shows this type of monotonic curve / plot 3 superimposed by plot 1 of Figure 1.

[0020] This modified monotonic curve is then used to control the injector, for example for ICLC trim decisions (pulse correction), and compared to a target behavior (called MASTER) at some predetermined fuel delivery learning points (ICLC breakpoints). Figure 3 illustrates this type of control, where reference numeral 4 refers to the nominal (e.g., ideal) fuel injector response. The applied trim is shown as arrow 5.

[0021] A monotonic curve is essential to determine the ICLC trim, but the physical behavior of this injector is curve 1. This difference is not compensated for and gives a local error shown by the shaded area 6 in Figure 4 (reference numbers as before).

[0022] Figure 5 shows the relationship between fuel error and fuel demand, with the error being predominant in the spoon area indicated by the dashed ellipse 7. Ultimately, this phenomenon leads to poor ICLC performance in this particular area, no matter what number of ICLC volume learning points are selected.

[0023] invention Generally, in embodiments of the present invention, the problem of poor ICLC performance at the beginning of full lift is solved by spoon avoidance.

[0024] The inventors have determined that the problem and solution can be formulated with the goal of creating a system that avoids the spoon area while at the same time having pulse-to-quantity characteristics that remain monotonic.

[0025] In the conventional method, a monotonic pulse / quantity curve was used to provide the desired fuel quantity within the fuel quantity / width (reference curve) using all pulse widths.

[0026] Instead, according to a general aspect, certain areas of curve / plot 3 are avoided when determining the pulse width to apply to a fuel injector for a particular amount of fuel. Therefore, i.e., the spoon area / region is avoided; this type of pulse area (within the spoon) is not used when there is no other pulse width that gives the same required amount of fuel. This is effectively done by generating and storing (e.g., in an ECU) a modified plot of fuel quantity versus pulse duration that is based on the actual plot, but with portions effectively removed from the plot, so that the resulting plot is still monotonic. This modified plot is then used for control.

[0027] Figures 6 and 7 illustrate the present invention. Figure 6 shows a plot of the same fuel quantity versus pulse curve (without monotonic modification) 1 as before, but with the spoon region (indicated by reference numeral 8). In the present example, a new curve / plot 9 is created that does not include data in these spoon regions 8. Thus, a new (essentially monotonic) curve 9, like Figure 7, is provided (with a gap 10 along the spoon region 8), but this is not a problem since the pulse width can still be determined for any fuel delivery amount.

[0028] Therefore, the new curve (pulse / volume characteristic) is necessarily monotonic, giving only one pulse per volume. Due to this, when using this type of plot for control, some pulse widths are avoided to avoid spoon and volume bounce, i.e., pintle / needle bounce. Pulse avoidance can be achieved using optimal adaptive ICLC learning points. For two specific learning points, one placed before the removed area and one placed immediately after, the pulse length jumps to the next useful pulse length.

[0029] The spoon area can be detected by a more precise analysis of the hydraulic opening (HO) measurement versus pulse width (which is directly related to the amount of fuel delivered), see the negative slope. The size (pulse width length) and amplitude (HO amplitude) of each spoon are recorded to fully understand each spoon for each injector. Figure 8 shows an example plot showing three spoons (Spoon 1, Spoon 2, Spoon 3) of varying parameters. HO is the time between the opening and closing of the needle valve, and those skilled in the art will know various methods for determining these.

[0030] An individual Y axis (Delivery / HO axis) for the ICLC can be determined for each injector, for the start and end of each spoon. This avoids using undesired pulse widths (which may be thought of as the actuator on time (e.g., high level Ton)) and creates a single pulse width for the delivery response that perfectly matches the injector characteristics. Deliveries between two horizontal lines are prohibited and rounded to the nearest allowed point.

[0031] As a result, ICLC performance on the spoon is greatly improved. Optimization is performed on a per-injector basis, also increasing ICLC efficiency. Figure 9 shows the relative error using an embodiment of the present invention and is compared to the error in Figure 5.

Claims

1. 1. A method of controlling a fuel injector, the injector including an electrically controlled actuator configured to control a valve needle by movement of a needle to and from a valve seat, the method comprising: a) determining, for the fuel injector, a plot of the quantity of fuel (Q) delivered by the fuel injector versus the pulse width of an actuator actuation pulse sent to the actuator; b) providing a modified plot of fuel quantity delivered by the fuel injector versus the pulse width of the actuator actuation pulse based on the plot of step a); c) using the modified plot to subsequently control activation of the fuel injectors; Step b) is d) identifying spoon regions in the plot of step a); e) regenerating the plot of step a) without data from the spoon region of the plot of step a); Step c) comprises comparing data from the plot generated in step b) with data from a reference plot to determine trim data for the subsequent control.

2. The method of claim 1 , wherein the plot generated in step d) has gaps in the region of the spoon.

3. The method of claim 1 or 2, wherein the plot of step b) is monotonic.

4. The method of claim 3 , wherein the spoon region represents pintle / needle bounce.

5. The method of claim 1 , wherein the actuator is a solenoid-controlled actuator or a piezo-controlled actuator.

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