CN111247323A

CN111247323A - Method for determining needle opening delay of fuel injector

Info

Publication number: CN111247323A
Application number: CN201880067871.1A
Authority: CN
Inventors: T·科切特; A·吉兰达
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2017-10-18
Filing date: 2018-10-09
Publication date: 2020-06-05
Anticipated expiration: 2038-10-09
Also published as: CN111247323B; EP3698035A1; GB2567809B; GB2567809A; GB201717099D0; WO2019076691A1

Abstract

A method of determining a delay on opening (ODinjx) of a solenoid actuated fuel injector, the fuel injector including a solenoid actuated valve adapted to actuate a needle valve, the needle valve including a needle adapted to move from a closed state to an open state to a closed state during an operating cycle of the fuel injector, the method comprising the steps of: a) providing different solenoid actuator drive pulse duration information (Ton) for a series of test injection cycles; b) determining, for each cycle, a closing time (VCT) of the solenoid actuated valve; c) determining a Needle Closure Time (NCT) for each cycle; d) determining a needle descent start time (NFST) for each cycle; e) determining a Control Chamber Fill Time (CCFT) for each cycle from the values determined by steps d) and b); f) determining, for each cycle, a Needle Closure Delay (NCD) from the values in steps b) and c); g) providing a test pattern by plotting the values of the needle closure duration NCD against the sum of the values of Ton, VCD and CCFT; h) determining a CCFT threshold; i) determining, from the determined graph, a value of the sum at an intersection with the graph at which a degree of NCD is a threshold of the CCFT; j) -determining the opening delay (ODInjx) according to the value of the determined sum.

Description

Method for determining needle opening delay of fuel injector

Technical Field

The invention relates to a method of determining needle Opening Delay (OD) of a fuel injector. The needle opening delay may be considered as the time lag between the time the start pulse is sent to the fuel injector and the time the needle begins to move away from its seat to dispense fuel.

Background

Modern fuel injectors typically use an electrical actuator (such as one operated by a piezo or solenoid) for actuating a valve that opens and closes to dispense fuel to the combustion chamber via movement of a needle away from a base. Typically, a start pulse of a certain duration is sent to the fuel injector to start the fuel injector via a start actuator. Modern fuel injectors are hydraulically operated because, unlike direct actuation of the needle with an actuator, the actuator is used to operate a valve (system) to control the pressure in the fuel injector to indirectly operate the fuel injector by using these pressures to move the needle toward or away from the needle base to selectively dispense fuel. Thus, a distinction is made between the opening and closing of an actuator operated valve and the opening and closing of a needle.

There is typically a time delay between the rising edge of the pulse (i.e., the start of actuation) and the needle opening; this is called the turn-on delay.

Some designs of fuel injectors also typically provide switching signals, often provided by additional wiring, where the signals on the wiring provide a means of detecting when two moving parts in the fuel injector system are in contact with or separated from each other. This may be, for example, detecting when the valve needle and the nozzle/needle seat are in contact with or separate from each other or when the needle reaches its end point (full opening point) after opening (moving away from the valve seat). Many prior art systems use this switching signal to determine the opening time of the injector needle or other component. However, the use of a switching signal that determines the needle on time is sometimes unreliable.

Disclosure of Invention

In one aspect, a method of determining a delay of opening (ODInjx) of a solenoid actuated fuel injector including a solenoid actuated valve adapted to actuate a needle valve including a needle adapted to move from a closed state to an open state to a closed state during an operating cycle of the fuel injector is provided, the method comprising the steps of:

a) providing different solenoid actuator drive pulse duration information (Ton) for a series of test injection cycles;

b) determining, for each cycle, a closing time (VCT) of the solenoid actuated valve;

c) determining a Needle Closure Time (NCT) for each cycle;

d) determining a needle descent start time (NFST) for each cycle;

e) determining a Control Chamber Fill Time (CCFT) for each cycle from the values determined by steps d) and b);

f) determining, for each cycle, a Needle Closure Delay (NCD) from the values in steps b) and c);

g) providing a test pattern by plotting the value of the needle closure duration NCD relative to the sum of the values of Ton, VCD and CCFT;

h) determining a CCFT threshold;

i) determining, from the determined graph, a value of the sum at an intersection with the graph at the CCFT threshold for the degree of NCD;

j) -determining the opening delay (ODInjx) according to the value of the determined sum.

The turn-on delay may be determined as the determined sum at the intersection.

The control chamber fill time can be found according to the following equation:

CCFT＝NFST-VCT。

the Needle Closure Delay (NCD) can be found according to the following formula:

NCD＝NCT–VCT。

NFST and/or NCT may be determined based on the injector switching signal.

The closing time (VCT) of the solenoid actuated valve may be determined by analyzing the voltage across the solenoid of the solenoid actuated valve and identifying the time for a glitch.

The method may comprise: storing a reference map of NCD values for the reference injector relative to the sum of Ton, VCD and CCFT, and providing an accurate value of opening delay (referred OD _ injx) from the values found in step h) and data in said reference map.

The precise value of the opening delay (refined OD _ injx) may be determined according to:

refined OD_injx＝ODinjx+(ODref_map–pseudo_ODref_map)，

wherein ODInjx is the initial estimate of the opening delay found in step j);

ODref _ map is a value stored or determined for a reference injector, representing the sum (Ton + VCD + CCFT) when NCD is zero for the reference injector;

pseudo _ ODref _ map is a value of the sum (Ton + VCD + CCFT) when NCD is the CCFT threshold with reference to the reference picture.

The method may comprise: determining, for each cycle, the needle descent duration (NFD) according to steps c) and d); wherein NFD is determined according to the following formula: NFD-NFST, and wherein the needle closure delay, NCD, is determined according to the following formula: NCD ═ CCFT + NFD.

Drawings

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic diagram of a solenoid operated fuel injector system;

FIGS. 2a, 2b, 2c show three operating states of the injector with reference to needle position and current to ground through additional wiring;

fig. 3 shows a corresponding time line of the start pulse sent to the solenoid (upper graph), the middle graph showing the corresponding time line of the injection period as the time from needle opening to closing, and the lower graph showing the corresponding voltage state of the switching signal in the case of various open, closed and intermediate states corresponding to the operating state in fig. 2;

fig. 4 shows corresponding time lines for the actuation pulse, valve lift, needle command (position) and needle lift, respectively.

FIG. 5 shows a graph of the values of the sum (Ton + VCD + CCFT) plotted against CCFT/NCD;

FIGS. 6 and 7 show further graphs comparing values of various parameters for ballistic and non-ballistic (fully elevated) operation of a fuel injector;

fig. 8 illustrates a high-level method of refining the estimated value of the turn-on delay.

Detailed Description

Fig. 1 shows a schematic diagram of a solenoid operated fuel injector system comprising a fuel injector 1 (shown in schematic cross section) and comprising additional wiring 2 allowing to detect the operating state of the fuel injector. The figure shows the ECU portion 3, the harness portion 4, and the injector portion 5. The injector part shows the solenoid 6 of the actuator. The extra wiring 5 provides current paths 7 and 8 to ground as shown depending on the position of the needle. The operating state of the injector can be monitored by measuring the voltage on line 9, allowing the state of needle contact to be detected when the needle is fully closed, fully open and partially open.

Fig. 2a to 2c show three operating states of the injector with reference to the needle position and the current to ground through the extra wiring. Fig. 2a shows the needle in the closed state a, in which there is current flow to ground when the needle contacts the needle base (bottom contact) -the voltage on line 9 is 0V. Fig. 2B shows that in state B the needle is partially open and not in contact with ground through additional wiring, and therefore no current flows; the voltage on line 9 is high. Fig. 2C shows the needle when it is in the open position C and there is flow through the extra wiring via the top contact of the via 7 (needle fully open) to ground. The voltage on line 9 is 0V.

Fig. 3 shows the corresponding time line of the start pulse 10 sent to the solenoid (upper graph), the middle graph shows the corresponding time line of the injection period 11 as the time from needle opening to closing, and the lower graph shows the corresponding voltage state on the switching signal line 9 in the case of various open, closed and intermediate states corresponding to the operating state in fig. 2. State a is the case of needle closure, the needle then starts to rise at P1, and the signal on switch line 9 goes high because there is no current path through the extra wiring when the needle is partially open/closed in transition state B. State C is a case where the needle reaches the full open point P2, and the signal on the switch line 9 becomes zero when current flows through the additional wiring due to the top contact. Because the needle is closed (partially closed) during state D, the voltage on the switch line becomes high again at point P3 when the needle is in the transition state (partially open), and the switch signal voltage becomes zero in state E at point P4 when the needle hits the needle base and is closed.

Therefore, from the state of the switching signal (by monitoring the state of the voltage), the needle descent start time at the point P3 can be determined. Thus, the figure shows the various states when the needle is fully raised, the top switch is activated and the switch signal goes to 0V. When the needle is returning toward the base, the short in the top switch disappears and the switching signal changes from 0V to 5V. Needle Closure Time (NCT) is point P4. NFD: the needle-down duration may also be calculated by the switching signal and determined as the period D between the points P3 and P4 of fig. 3.

Fig. 4 shows corresponding time lines for the actuation pulse 110, the valve lift 111, the needle command (position) 112 and the needle lift 112, respectively. The following comments are used in the drawings and the description:

NOT: time of opening of needle

NCT: time of needle closure

VCT: valve closure time

NFST: valve descent start time

CCFT: controlling chamber fill time

OD: needle opening delay

VCD: valve closure delay

NCD: the delay/duration of the needle closure is,

NOL: needle opening length/duration

NFD: duration of needle descent

Thus, the figure shows a corresponding timeline for various parameters in the operation of a solenoid injector. The upper graph 110 shows a start pulse having a length (duration) Ton. The valve lift 111 is shown below and shows the valve beginning to move/open at point P11 and closing at point P12. The assumed VCD is the time between the end of the start pulse and the VCT time. The lower graph 12 shows the needle active command and the lower graph 113 shows the actual movement of the needle and shows the small time span in which the needle is raised to allow fuel to be injected, and it shows the small bell shaped pulse within the time span NOL. As can be seen, there is a large time span between the start of the start pulse and the opening delay (the time at which the needle starts to rise). The needle descent duration is as shown, typically in the second half of the NOL. When viewing the graph, the following equations and formulas apply:

OD+NOL＝Ton+VCD+CCFT+NFD

CCFT＝NFST–VCT

when NOL is 0, NFD is 0

OD＝Ton+VCD+CCFT

NCD ═ CCFT + NFD, and when NOL ═ 0 and NFD ═ 0, NCD ═ CCFT

When NCD is CCFT, Ton + VCD + CCFT is OD

Detailed description of the invention

In some aspects of the invention, the needle opening delay is determined according to the following input parameters:

a) (actuator) Valve Closure Time (VCT). This parameter can be determined by analyzing the current/voltage across the solenoid actuator. Typically, when the solenoid valve is closed, there is a perceptible glitch in the voltage pattern, which can preferably be determined by looking at the value or second derivative of dV/dt. The glitch is determined by observing the inflection point in the current curve pattern and such techniques are well known in the art.

b) As described above, the pin closure time (NCT) information, i.e., the time at point P4 at the end of period D, may be provided by the switch signal. This provides the parameter NCT.

c) NFD: needle descent duration. This is also calculated from the switching signal and determined as the time period D in fig. 2, i.e., the duration between the point P3 and the point P4. This is optional and is only required in certain embodiments (see)

d) Fuel injector (actuator) drive pulse length information. (Ton)

e) The CCFT threshold. As will be described in detail below.

Using the above information, a graph of the sum (Ton + VCD + CCFT) values is plotted against NCD for a plurality of injector actuation cycles having different start pulse durations.

NCD was calculated by NCD ═ NCT-VCT. Fig. 5 shows this pattern.

(note that if at full elevation, NCD may alternatively be calculated according to the formula NCD-CCFT + NFD) ×

Determining a turn-on delay according to some aspects by finding an intersection between the curve and an NCD value corresponding to (i.e., equal to) a CCFT threshold; the CCFT threshold will be explained below. Thus, using the above input data, the NCD curve function is plotted by providing multiple injector operations (cycles) with different start pulse lengths (Ton). This may be performed using a "sweep" in which the fuel injector is activated with, for example, continuously increasing pulse activation durations and subsequent measurements of the above referenced parameters. During this scan Ton will increase, then it will gradually open the valve, then gradually open the needle. During this scan, NCD, VCD, CCFT and NOL will gradually increase.

The value of Ton is the start pulse duration. The value of VCD (valve closing delay) is determined from VCT (valve closing time) and is the time between the end of the start pulse and VCT. CCFT is determined to be NFST-VCT. As described above, NFST may be determined from the switching signal. Summarizing, the value of (Ton + VCD + CCFT) is plotted against NCD and shown in fig. 5 as mentioned.

As mentioned above, a threshold for the CCFT is determined; this may be considered the maximum CCFT. If CCFT is plotted against pulse length (Ton), the value will increase (during the ballistic range) and reach a plateau. This is the CCFT threshold, so this can be determined by looking at its stable value with increasing pulse length. Summarizing, CCFT with respect to pulse length (Ton) will rise and reach a stable segment, and the value at the stable segment will be used as a threshold. The CCFT threshold may be considered an NCD threshold, as will be explained below.

To reiterate, referring to fig. 5, a line, i.e., the threshold value of the CCFT on the NCD axis, is plotted horizontally on the y axis (NCD axis, at the CCFT threshold value), and is determined as the on-delay OD on the x axis at the intersection with the graph.

Fig. 6 and 7 also show graphs comparing the values of various parameters for both ballistic and non-ballistic (fully raised) operation of the fuel injector, reference numbers indicating a start pulse (long enough not to operate in ballistic mode in the case of fully raised) indicating a valve opening state signal indicating a needle signal and showing a needle raised state. This illustrates why OD ═ Ton + VCD + CCFT when NCD ═ CCFT (this is illustrated in fig. 4). Since CCFT cannot be measured at ballistic time, a fully elevated CCFT is used. The NCD threshold will be a value that depends on fully raising the CCFT. NCD will be plotted as a function of (Ton + VCD + fully elevated CCFT). The full boost CCFT may be calculated as explained above, and the valve closing time determined, for example, from a spike in the voltage pattern of the solenoid. CCFT ═ NFST-VCT, see fig. 3.

Precision of

In the above, the estimated value of OD was determined. However, to provide more accurate results, the initial estimate is refined to provide a more accurate estimate. This refinement method will be explained with reference to fig. 8. If the initial estimate is referred to as the "Pseudo" OD (such as Pseudo ODInjx) of the injector under test, it will be higher than the true OD (ODInjx) because the NCD threshold used (fully elevated CCFT) is higher than the CCFT corresponding to a very small number (typically 0.1 mg/stroke). Furthermore, at low values, data on NCD ═ is not available (Ton + VCD + CCFT). The curve 21 in fig. 8 is a curve obtained by the above method, and is the same as the curve in fig. 5. Thus, the data or part of the curve shown in dashed lines in the graph 21 in fig. 8 is often not available.

In a refined implementation, the stored NCD map relative to Ton + VCD + CCFT for an ideal (i.e., reference) fuel injector is provided. This stored reference map (reference injector OD) may be provided from data recorded on the hydraulic table/from the injection rate measurement device and stored on the ECU. FIG. 8 shows a plot/graph 20 of (Ton + VCD + CCFT) plotted against NCD for an ideal/reference injector, along with a graph 21 for the injector under test obtained by the method described above, and plots/graphs determined for the above method, a graph Inj for the injector under test _X20 should be substantially parallel to the curve Inj for the reference injector _Ref21. Again, note that at low values, data regarding the test injector is not available. Thus, the test pattern never intersects the X-axis, since even for very small numbers, the NCD is not zero (it is very small, but not zero), which corresponds to a small number of CCFT values. The delay depends on the hydraulic performance of the injector. However, this data is often available. Then, the following method steps are adopted:

i) the parameter OD is derived from the reference injector map, i.e., on the stored map/chart, using the zero crossing (y-axis)_ref _map _zeroWherein NCD is zero. Since it is fixed, it can be stored in a table.

ii) additionally, a test injector (Pseudo) OD which is variable and which is used as explained above for determining a test injector_injxIs also used to determine the Pseudo OD specified by the reference injector_{ref_map}Is equivalent to Pseudo OD_ref。

iii) passing the two parameters through zero (pseudo OD as previously described) with the NCD threshold of the test injector_injx) Used together to obtain the true OD (using the formula below)_inj _x：

Estimated_refined OD_injx＝OD_{ref_map}+((pseudo)_OD_injx–pseudo_OD_{ref_map})

Thus, in summary, the true OD of the reference injector will be stored in the ECU as a calibrated value, which will be referred to as the OD_{Ref_map}. The Pseudo OD of the reference injector will also be stored as a calibration value according to the degree of NCD of the test injector, which will be referred to as Pseudo _ OD_{Ref_map}. Will be (pseudo) OD_injxAnd pseudo _ OD_{ref_map}Difference and OD_{Ref_map}Add to have an estimated OD of injx.

The invention is an indirect way of determining the OD of a fuel injector. Old systems measure the opening of the needle directly due to the switching signal. However, this system is sometimes unreliable.

Claims

1. A method of determining an opening delay, ODinjx, of a solenoid actuated fuel injector, the fuel injector including a solenoid actuated valve adapted to actuate a needle valve, the needle valve including a needle adapted to move from a closed state to an open state to a closed state during an operating cycle of the fuel injector, the method comprising the steps of:

a) providing different solenoid actuator drive pulse duration information Ton for a series of test injection cycles;

b) determining, for each cycle, a closing time VCT of the solenoid actuated valve;

c) for each cycle, determining a needle closure time, NCT;

d) determining a needle descent start time NFST for each cycle;

e) determining, for each cycle, a control chamber filling time CCFT value from the values determined by steps d) and b);

f) determining, for each cycle, a needle closure delay NCD from the values in steps b) and c);

g) providing a test pattern by plotting values of needle closure duration NCD against the sum of the values of Ton, VCD and CCFT;

h) determining a CCFT threshold;

j) determining the opening delay ODInjx according to the determined value of the sum.

2. The method of claim 1, wherein the turn-on delay is determined as the determined sum at the intersection.

3. The method according to claims 1 to 2, wherein the control chamber filling time is found according to the following equation:

CCFT＝NFST-VCT。

4. method according to claims 1 to 3, wherein the needle closure delay NCD is found according to the following formula:

NCD＝NCT–VCT。

5. a method according to any one of the foregoing claims, in which NFST and or NCT are determined on the basis of the switching signal of the fuel injector.

6. The method of claims 1-5, wherein the closing time VCT of the solenoid actuated valve is determined by analyzing a voltage across a solenoid of the solenoid actuated valve and identifying a time of a glitch.

7. The method according to any one of the preceding claims, the method comprising: storing a reference map of NCD values relative to the sum of Ton, VCD and CCFT for a reference injector, and providing an accurate value of opening delay referred OD _ injx from the value found in step h) and the data in said reference map.

8. The method of claim 7, determining the precise value of the opening delay, refined OD _ injx, according to:

refined OD_injx＝OD_injx+(OD_{ref_map}–pseudo_OD_{ref_map})

wherein, OD_injxIs the initial estimate of the opening delay found in step j);

OD_{ref_map}is a value stored or determined for a reference injector, representing the sum (Ton + VCD + CCFT) when the NCD for said reference injector is zero;

pseudo_OD_{ref_map}is the value of the sum (Ton + VCD + CCFT) when NCD is the CCFT threshold with reference to the reference picture.

9. The method of claims 1 to 8, the method comprising: for each cycle, determining the needle descent duration NFD according to steps c) and d); wherein NFD is determined according to the following formula: NFD-NFST, and wherein the needle closure delay, NCD, is determined according to the following formula: NCD ═ CCFT + NFD.