GB2515359A

GB2515359A - Solenoid-actuator-armature end-of-motion detection

Info

Publication number: GB2515359A
Application number: GB1320692.5A
Authority: GB
Inventors: Perry Robert Czimmek
Original assignee: Continental Automotive Systems Inc
Current assignee: Continental Automotive Systems Inc
Priority date: 2013-06-19
Filing date: 2013-11-22
Publication date: 2014-12-24
Also published as: GB201320692D0

Abstract

An apparatus and method comprising a solenoid armature end of motion detector 102 , a current measurement module and a voltage measurement module. When current is generated within a coil of an electromagnetic solenoid, the current through a resistor is detected as a differential voltage across the resistor. The voltage is differentiated to infer acceleration from the original differential voltage to provide a time rate of change of current. This derivative of the current is used to infer an acceleration component of motion of the armature in the solenoid to the energized position. The reverse motion of the armature is detected in a similar fashion by differentiating the voltage across the solenoid coil to provide the derivative of that voltage and thereby the detection of the acceleration component of motion of the armature in the solenoid to the de-energized position. The improvement in accuracy for detecting such opening and closing events provides an improved technique for adjusting the dynamic flow of a fuel injector for an internal combustion engine.

Description

SOLENOID-ACTUATOR-ARMATURE END-OF-MOTION DETECTION

CROSS-REFERENCE TO RELATED APPLICATIONS

100011 This application is related to the following provisional application: Integral Subtraction Differentiator, invented by Perry Czimmek and Hamid Sayar, filed on the same day as this provisional patent application, and identified by Attorney Docket Number 2012P02236U5.

BACKGROUND

100021 Embodiments of the invention relate, generally, to control electronics for automotive applications and, more particularly, to determination of operation and control of fuel injectors or other automotive solenoids.

100031 There is a continued need for improving the emissions quality of internal combustion engines. Meanwhile, there is pressure to improve performance of individual components, while maintaining maximum fuel economy.

These pressures apply to engines fueled with alternative fuels, such as ethanol, as well as to engines fueled with gasoline or diesel.

100041 Additionally, new applications of fuel components on exhaust aftertreatment and reductant delivery require long term stability to properly meter materials to restore particulate traps and nitrogen oxide traps.

100051 A fuel injector is an example of a component that directly influences emissions and fuel economy. An engine control unit maps the characteristic of the fuel injector into an engine calibration. This map depends upon the performance and repeatability of the fuel injector over an expected range based upon particular engine combustion stoichiometry demands.

10006] During an engine cold start or initial start, the calibration necessary to accomplish the start will have a limited tolerance band for which variation of associated components is permitted, and the larger the deviation of any components from a calibration point will result in an off-stoichiometric fueling that materializes as high tail-pipe hydrocarbon emissions and carbon particulate emissions, if the fueling is rich for the available air; or nitrogen oxide generation, if the fueling is lean for the available air. The worst emissions are during the first few minutes of engine operation, after which the catalyst and engine approach operating temperature.

10007] In the case of the fuel injector, there is a static mass flow approximately determined by a flow metering orifice geometry and a fuel pressure upstream of the orifice. This metering and the fuel pressure are predetermined by the manufacturer to match the size of the engine and the expected calibration map of the engine. This static flow is divided into precisely timed dynamic flows by selectively energizing a solenoid coil and thereby opening the injector for predetermined periods of time to meter the quantity to the engine in such a way that the calibration map correlates with a relatively high degree of precision to the actual metered flow of the injector. The calibration map brings into the calculation the pressure and temperature of the incoming air, as well as other engine conditions such as fuel pressure, if detected.

10008] Deviation due to aging and wear of the injector from an initial manufactured set point may be accommodated by slow adaptive control algorithms in the engine control unit. These adaptive control algorithms may measure oxygen content, or lambda, of the exhaust gas, and compare the measured oxygen content to an expected value to monitor conformance to the calibration map of the engine. This is relatively slow and may not satisfactorily perform adjustments to the injector dynamic flow to meet transient, or initial, emissions control demands.

10009] As such, improved techniques for adjusting the injector dynamic flow

BRIEF SUMMARY

10010] Embodiments of the invention are directed to electromagnetic solenoid armature end of motion detection and control. A power switch, upon receipt of a turn-on signal, generates a current within a coil of an electromagnetic solenoid, wherein the current through a resistor is detected as a differential voltage across the resistor. The voltage is differentiated to infer acceleration from the original differential voltage to provide a time rate of change of current. This derivative of the current is used to infer an acceleration component of motion of the armature in the solenoid to the energized position. The reverse motion of the armature is detected in a similar fashion by differentiating the voltage across the solenoid coil to provide the derivative of that voltage and thereby the detection of the acceleration component of motion of the armature in the solenoid to the de-energized position.

BRIEF DESCRIPTION OF THE DRAWINGS

10011] FIG. 1 is a diagrammatic representation of an example of a functional application. in accordance with embodiments of the invention, for the open detection and close detection of a fuel injector.

10012] FIG. 2 is a simplified schematic diagram of an embodiment of the invention.

10013] FIG. 3 is a plot of oscilloscope data showing relation of current signal for detection of an opening event.

10014] FIG. 4 is a plot of oscilloscope data showing relation of voltage signal for detection of a closing event.

10015] FIG. 5 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of solenoid fuel injector opening from the second derivative of current through the solenoid coil.

100161 FIG. 6 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of solenoid fuel injector closing from the first derivative of voltage across the solenoid coil.

10017] FIG. 7 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of several signals and the generation of fuel injector time open for a 2.5 millisecond command pulse.

10018] FIG. 8 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of several signals and the generation of fuel injector time open for a 5 miffisecond command pulse.

10019] FIG. 9 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of opening and closing of a fuel injector.

10020] FIG. 10 is a plot of oscilloscope data of function of an embodiment of this invention in the detection of opening and closing of a fuel injector demonstrating detection of multiple events at opening and closing, showing the capability of embodiments of the invention to detect bounce of the armature due to mechanical elastic collision.

10021] FIG. 11 is a schematic of a prototype embodiment of the invention.

DETAILED DESCRIPTION

10022] Embodiments of the invention are directed to addressing the shortcomings of the prior art discussed above in the Background section. Adjustment of fuel injector dynamic flow may be improved by providing to an engine control unit information about the actual time that a fuel injector is open for a given width of a command pulse, then an adjustment on that pulse, or on one or more subsequent pulses, may be made for deviations from the original offset adjustment to the calibration. This detection of actual time the fuel injector is open would require detection of flow or detection of movement of the internal valve of the injector. It is, therefore, desirable to be able to detect the opening and closing event of the fuel injection valve and thereby determine the time the injector was open and flowing fuel.

100231 Embodiments of the invention are directed to detecting a closing event and an opening event of the armature in a solenoid control valve, or fuel injector. The detection of motion of the metering component of the fuel injector may be accomplished by detection of motion of an associated component. In the case of a solenoid fuel injector, this component may be the armature portion of the control valve. The armature of a solenoid fuel injector is a movable component of a magnetic circuit. A moving magnetized armature changes the flux in a magnetic circuit at a rate proportional to the rate of change of position of the armature. A moving magnetized component induces an electric current in the solenoid coil according to Faraday's Law of Induction: the induced electromotive force in a closed circuit is equal the negative of the time rate of change of the magnetic flux through the circuit: dt' vct, = 100241 This may be detected as a voltage from the induced current into a shorted load in one case by solving for VE, which is the case for the energized solenoid: = "C 100251 This may be additionally detected as an induced voltage on an open load in another case, which is the case for the dc-energized solenoid:

VE

10026] In order to detect the motion of the armature from the energized solenoid, given a voltage source to energize the solenoid, the current through the solenoid coil with respect to time may be detected to infer velocity, ±.

Further, the current may be differentiated to infer the acceleration component of motion of the armature. An additional differentiation to detect change in acceleration may be used to detect impact of the armature on the stator at the end of motion.

10027] In order to detect the motion of the armature from the dc-energized solenoid, the open voltage of the coil wifi present itself on the opened leg of the electrical circuit. This open voltage is directly a function of rate of change of flux which also contains the time rate of change of flux as a function of armature velocity, ±. This voltage may be differentiated to again infer the acceleration component of motion of the armature. An additional differentiation to detect change in acceleration also may be used to detect impact of the armature, which is coupled to the valve motion component, and thereby the closing of the valve inside the fuel injector.

10028] Embodiments of the invention generate this diferentiated signal knowledge, and, from this knowledge, it is then possible to estimate the movement of the solenoid armature with respect to time and perform further differentiation to obtain the additional derivatives of motion.

10029] Figure 1 depicts an example application of embodiments of the invention.

An end-of-motion detector 102 is shown in Figure 1. An end-of-motion detector, in accordance with various embodiments of the invention may include either, or both, an open detect module and a close detect module.

Open event detection of the armature motion may be based upon measurement of current through the solenoid coil. Close event detection of the armature motion may be based upon the voltage across the solenoid coil.

10030] For measuring a current inflection point of back electromotive force ("EMF") due to motion of an armature in a solenoid: 10031] Where an input signal, a voltage, for example, represents the current through the solenoid coil load, as in Figure 3: 10032] The current inflection point is identified from the first derivative of the input signal, as in Figure 5: dVj(t) cit 10033] The first derivative contains the acceleration information of the armature motion, and the second derivative of the signal detects the change in acceleration at impact of the armature on the stator. Likewise, the voltage in Figure 4 is differentiated to detect the acceleration, as in Figure 6, and a subsequent differentiation would detect the impact.

10034] Figure 2 depicts an embodiment of the invention, including a current- measurement module 202, a solenoid-current differentiator 204, a voltage-measurement module 206, a solenoid-voltage differentiator 208, and an end-of-motion detector 102. In the embodiment, opening detection is accomplished by monitoring current. Differential amplifier A measures the solenoid-coil current, as a voltage differential across resistor RD.

Differential amplifier B, Rl, and Cl make up a differentiator. A subsequent differentiator, for determining an impact of the armature against the stator is made up of differential amplifier C, R2, and C2. An open detection comparator generates a logic pulse based on an open threshold of the second derivative of current.

100351 Closing detection is accomplished by monitoring voltage across the solenoid coil with differential amplifier D. And a derivative of that voltage is generated with a differentiator made up of differential amplifier E, R3, and C3. Close detection comparator generates a logic pulse based on a close threshold of the first derivative of the solenoid voltage.

10036] FIG. 3 is a plot of oscilloscope data showing relation of current signal for detection of an opening event. Figure 3 depicts real measured parameters from a functioning fuel injector. Injector current is shown. The coarse vertical dotted line identifies an inflection point in the current that is caused by the back electromotive force of the moving armature in the magnetic field. That corresponds with the movement and impact of the armature from a closed position to an open position. After that point, the current rises to a level that is limited by the resistance of the coil with the voltage impressed on the coil. And then the current turns off. After some period of time, the current decays back to zero, during which time the injector voltage, as shown in Figure 3. goes into a reverse direction due to the collapsing magnetic field of the collapsing current in the injector, which creates a negative voltage, the shape of which corresponds to the decay of the flux and the motion of the armature. The test pulse is also shown in Figure 3. The test pulse is a logic command pulse going from a low signal to a high signal that commands the fuel injector to open.

10037] FIG. 4 is a plot of oscilloscope data showing relation of voltage signal for detection of a closing event. Figure 4 is similar to Figure 3, except that it depicts a closing event where the coarse dotted line lines up with the collapsing voltage in the coil to identify the inflection point, which, in a similar manner as that discussed above, represents the back EMF in the opposite direction of the moving armature.

[0038] With reference to Figures 2-4, the injector current, for instance, is measured as a voltage through HO of the current-measurement module 202. So, the voltage coming out of differential amplifier A would have the same shape as the injector current shown in Figures 3 and 4.

10039] Differential amplifier D measures the voltage across the solenoid coil. That voltage shape corresponds to the injector voltage in Figures 3 and 4.

10040] The test pulse in Figures 3 and 4 is the pulse that's going into the power switch in Figure 2.

10041] FIG. 5 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of solenoid fuel injector opening from the second derivative of current through the solenoid coil. In Figure 5, the injector pulse is shown near the top of the diagram and is labeled Logic. The first derivative of solenoid current is shown near the bottom of Figure 5, and the second derivative of solenoid current is shown above the first derivative in Figure 5. The first derivative would be seen at the output of differential amplifier B in Figure 2. And the second derivative would be seen at the output of differential amplifier C. 10042] The signal labeled "detection" in Figure 5 shows high and low logic pulses corresponding to changes in the derivatives that would be seen at the output of the open detection comparator in Figure 2.

10043] Figure 5 depicts an open detection obtained from the second derivative where that X shows up and the vertical coarse dashed line are shown in the drawing. Throughout this document the terms "open" and "close" are synonymous with "energized" and "dc-energized." Open and close refer to solenoid actuated normally closed fuel injector valves. The corresponding terms energized and de-energized apply to solenoids regardless of whether they are connected to a valve that is either normally open or normally closed.

10044] There are two separate square wave pulses shown on the detection line in Figure 5. The first pulse does not really signify anything and may be ignored because of the shape of the second derivative.

10045] Figure 7, shows the logic pulses and omits the ignored first pulse shown in Figure 5. Figure 7 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of several signals and the generation of fuel injector time open for a 2.5 millisecond command pulse.

The logic pulse commands the injector to open. The open-detection signal now corresponds to the open detection where the solid vertical cursor is identifying it. The close-detection signal corresponds to the close detection where the dotted vertical line identifies it. The open detection and close detection pulses may be used to toggle logic circuits to measure the time open, which is shown as the time-open pulse near the bottom of Figure 7.

The logic pulse near the top of Figure 7 commands the injector to open (and then to close), and the time-open pulse, which indicates the time that the injector was actually open, near the bottom of Figure 7. As will be apparent to those having ordinary skill in the art, although a hardware implementation is shown in Figure 2, functionality in accordance with embodiments of the invention may be implemented via analog-to-digital converters and mathematical derivatives performed by software executed by a processor, such as a microcontroller, digital signal processor, and the

like, for example.

10046] FIG. 6 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of solenoid fuel injector closing from the first derivative of voltage across the solenoid coil. Figure 6 depicts using the injector voltage in a similar fashion to create a detection pulse that represents a closing event. The first derivative of the voltage across the solenoid coil, which is labeled in Figure 6 as the first derivative of FET Drain, is shown, and the rising edge of the detection signal represents an end-of-motion detection of a fuel injector that is closing. The detection signal shown in Figure represents the output of the close detection comparator shown in Figure 2.

10047] FIG. 8 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of several signals and the generation of fuel injector time open for a 5 millisecond command pulse. Figure 8 is similar to Figure 7, except that the command pulse is longer. An end user could use either the open detection, the close detection, or use both of them to determine a time that the fuel injector was open. An end user might be interested in the delay between of the logic pulse and the injector fully opening, for example. Likewise, the delay from the end of the logic pulse to the closing detection is the time for the injector to close. So, for instance, if those times start changing significantly, it can be inferred that the calibration is changing.

10048] FIG. 9 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of opening and closing of a fuel injector.

10049] FIG. 10 is a plot of oscilloscope data of function of an embodiment of the invention in the detection of opening and closing of a fuel injector demonstrating detection of multiple events at opening and closing, showing the capability of embodiments of the invention to detect bounce of the armature due to mechanical elastic collision. At the open detection and the close detection there are multiple pulses, more than one closing for example, and that indicates that the armature tube assembly of the injector valve is actually bouncing on impact, similar to a bouncing ball. In Figure 9, there is no bounce. And in Figure 10 there is bounce. For fuel injection, it is useful to be able to detect bounce of this type because it causes secondary injection and creates problems with the spray of the injector.

10050] FIG. 11 is a schematic diagram of a prototype embodiment of the invention.

10051] The foregoing detailed description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the description of the invention, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. For example, while the method makes reference to a low pass filter and a differential amplifier to generate the derivative of signals (in the solenoid-current differentiator 204 and the solenoid-voltage differentiator 208), any other method, such as a microcontroller, digital signal processor, or operational amplifier differentiator. may be used without departing from the scope of the invention. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention.

Claims

CLAIMS1. An apparatus comprising: a current-measurement module configured to generate a current-measurement signal that represents current through a solenoid coil; a solenoid-current differentiator (Diff Amp. B, Ri, Ci &/or Diff Amp. C, R2, C2) configured to generate a mathematical derivative of the current-measurement signal; a voltage-measurement module Diff Amp. D) configured to generate a voltage-measurement signal that represents voltage across the solenoid coil; a solenoid-voltage differentiator (Diff Amp. E, R3, C3) configured to generate a mathematical derivative of the voltage-measurement signal; an end-of-motion detector configured to detect end of motion of a solenoid armature by comparing an end-of-motion threshold value to at least one of the mathematical derivative of the current-measurement signal and the mathematical derivative of the voltage-measurement signal.
2. The apparatus of claim 1, wherein the solenoid-current differentiator comprises a plurality of solenoid-current differentiators (Diff Amp. B, Ri, Cl & Dill Amp. C, R2, C2) configured to generate a respective plurality of successive mathematical derivatives of the current-measurement signal.
3. The apparatus of claim 2, wherein the mathematical derivative of the current-measurement signal is a second mathematical derivative of the current-measurement signal, wherein the second mathematical derivative is generated by differentiating a first mathematical derivative of the current-measurement signal.
4. The apparatus of claim 3, wherein the end-of-motion detector is configured to detect end of motion in an energized direction of the solenoid armature by comparing an energized end-of-motion threshold value to the second mathematical derivative of the current-measurement signal.
5. The apparatus of claim 1, wherein the end-of-motion detector is configured to detect end of motion in a dc-energized direction of the solenoid armature by comparing a de-energized end-of-motion threshold value to the mathematical derivative of the voltage-measurement signal.
6. The apparatus of claim 1, wherein the current-measurement module comprises a current-measurement differential amplifier electrically connected in parallel to a current-measurement resistor (Diff Amp. A, RU).
7. The apparatus of claim 1, wherein the solenoid-current differentiator comprises a first-solenoid-current-differentiator resistor electrically connected in parallel to a first-solenoid-current-differentiator differential amplifier and electrically connected in series to a first-solenoid-current-differentiator capacitor (Diff Amp. B, Rl, Cl).
8. The apparatus of claim 7, wherein the solenoid-current differentiator comprises a second-solenoid-current-differentiator resistor (R2) that is electrically connected: in series between an output of the first-solenoid-current-differentiator differential amplifier (DiE Amp. B) and a second-solenoid-current-differentiator capacitor (C2) and in parallel to a second-solenoid-current-differentiator differential amplifier (Duff Amp. C).
9. The apparatus of claim 1, wherein the voltage-measurement module comprises a voltage-measurement differential amplifier (Diff Amp. D) that is electrically connected in parallel to the solenoid coil.
10. The apparatus of claim 1, wherein the solenoid-voltage differentiator comprises a solenoid-voltage-differentiator resistor (1t3) electrically connected in parallel to a solenoid-voltage-differentiator differential amplifier (Diff Amp. E) and electrically connected in series to a solenoid-voltage-differentiator capacitor (C3).
11. The apparatus of claim 1, wherein the end-of-motion detector is configured to detect an end-of-motion event associated with opening a normally closed fuel-injector.
12. The apparatus of claim 1, wherein the end-of-motion detector is configured to detect an end-of-motion event associated with closing a normally closed fuel-injector.
13. A method comprising: generating a current-measurement signal that represents current through a solenoid coil; generating a mathematical derivative of the current-measurement signal; generating a voltage-measurement signal that represents voltage across the solenoid coil; generating a mathematical derivative of the voltage-measurement signal; detecting end of motion of a solenoid armature by comparing an end-of- motion threshold value to at least one of the mathematical derivative of the current-measurement signal and the mathematical derivative of the voltage-measurement signal.
14. The method of claim 13, wherein generating a mathematical derivative of the current-measurement signal comprises generating a respective plurality of successive mathematical derivatives of the current-measurement signal.
15. The method of claim 14, wherein the mathematical derivative of the current-measurement signal is a second mathematical derivative of the current-measurement signal, wherein the second mathematical derivative is generated by differentiating a first mathematical derivative of the current-measurement signal.
16. The method of claim 15, wherein detecting end of motion of the solenoid armature comprises detecting end of motion in an energized direction of the solenoid armature by comparing an energized end-of-motion threshold value to the second mathematical derivative of the current-measurement signal.
17. The method of claim 13, wherein detecting end of motion of the solenoid armature comprises detecting end of motion in a dc-energized direction of the solenoid armature by comparing a dc-energized end-of-motion threshold value to the mathematical derivative of the voltage-measurement signal.
18. The method of claim 13, wherein detecting end of motion of a solenoid armature comprises detecting an end-of-motion event associated with opening a normally closed fuel-injector.
19. The method of claim 1, wherein detecting end of motion of a solenoid armature comprises detecting an end-of-motion event associated with closing a normally closed fuel-injector.