Method of controlling operation of a fuel injector activated by a solenoid
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PHINIA DELPHI LUXEMBOURG SARL
- Filing Date
- 2022-02-11
- Publication Date
- 2026-06-26
AI Technical Summary
Existing closed-loop control methods for fuel injectors fail to effectively account for variations in the fuel injector's opening delay, resulting in poor ICLC performance, especially under non-nominal conditions.
By determining the minimum drive pulse, closing response, and total operating time of the fuel injector, the difference in opening delay is calculated, and control is performed based on these parameters. This simplifies current measurement requirements and reduces additional hardware complexity and cost.
It improves the closed-loop control performance of the fuel injector, enhances operational stability and accuracy under non-nominal conditions, and reduces the complexity of electronic hardware and actuators.
Smart Images
Figure CN116685764B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to methods for determining the operating characteristics of a fuel injector, particularly the opening response / delay of the fuel injector. These parameters can then be used to control the injector. It applies specifically, but not exclusively, to direct-acting fuel injectors. Background Technology
[0002] Modern fuel injectors typically use electric actuators (e.g., piezoelectric or solenoid-operated actuators) to operate a needle valve. The valve opens and closes to distribute fuel into the combustion chamber via the movement of a needle away from its seat. Generally, an activation pulse of a certain 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 chamber depends on the pulse duration. Fuel injectors can be of the type where the actuator directly removes the needle from the valve seat to dispense fuel; for example, against a bias spring device; this is called a direct injector, and such injectors are used for both gasoline and diesel fuel. This invention is particularly applicable to such direct injectors.
[0003] In alternative designs, many modern fuel injectors are hydraulically operated, where the actuator (e.g., a solenoid) does not directly actuate the needle. Instead, the actuator operates a hydraulic valve (system) to control the pressure in the fuel injector, thereby indirectly removing the needle from the valve seat and selectively dispensing fuel.
[0004] Therefore, in retrospect, a solenoid-controlled fuel injector is operated by sending drive pulses (activation profiles) to the solenoid actuator of the fuel injector. Activation of the solenoid causes the needle of the needle valve to lift from its seat to dispense fuel. The needle of this needle valve device can be directly activated by the solenoid through the movement of the needle plug / needle assembly. The amount of fuel dispensed in the solenoid-controlled fuel injector is achieved by changing the activation of the solenoid via the activation profile, which includes one or more pulses sent to the solenoid actuator, and typically the fuel quantity is controlled by the duration of the pulses.
[0005] The characteristics of the fuel injector vary over time. Therefore, closed-loop control and compensation strategies are required. Thus, the injector is typically compensated over time by implementing various learning strategies, where the behavior and characteristics (e.g., parameters) of the fuel injector are learned over time to calculate correction values with respect to, for example, the duration of the activation pulse, and these correction values, or "fine-tuning," are applied during real-time injector operation. This strategy is commonly referred to as ICLC (Injector Closed-Loop Compensation).
[0006] Many current methods do not account for, for example, the physical opening delay (OD) of the gasoline injector (e.g., OD variation), leading to poor ICLC performance under non-nominal conditions (i.e., the injector's OD varies with the years of use). In extreme cases, the corrected injector may behave worse than its initial behavior.
[0007] These problems are known to be overcome by implementing injector current measurement methods within the ECU to capture changes in the current slope during the freewheeling phase (just after the boost voltage is applied at 0V). This method has several constraints: for example, electronic hardware constraints, meaning that the existence of a specific current measurement within the ECU requires additional functional circuitry to implement this function, leading to additional complexity and cost. There are also electronic actuator constraints: a reasonably long freewheeling phase is required to capture the opening delay OD (considering the margin after the peak and before hold), and many injector suppliers do not allow this. There are also injector drivability constraints; the injector's opening delay must occur during this specific detection window. Furthermore, there are time-varying injector constraints: the opening delay may drift over time, but the drifting opening delay should always be within the detection window. This means that excessively large opening delay drifts cannot be detected.
[0008] One object of the present invention is to provide a closed-loop control method for a fuel injector that takes into account, for example, variations in opening delay, and overcomes these drawbacks. Summary of the Invention
[0009] In one aspect, a method is provided for controlling the operation of a solenoid-activated fuel injector, the fuel injector including an actuator comprising a solenoid, and the fuel injector being adapted to control a needle valve according to an activation pulse sent to the solenoid to control the needle valve to dispense fuel via movement of a needle from and to a valve seat, the method comprising the steps of:
[0010] a) Determine the minimum drive pulse (MDP1) required to open the needle valve of the injector;
[0011] b) Determine the closure response (CR) of the injector during the MDP state. MDP1 The closing response is defined as the duration between the end of the activation pulse (t3) and the time of needle valve closure (t4).
[0012] c) Determine the total working time (TOD) during the MDP state of the injector from steps a) and b). MDP1 The total working time is defined as the time between the start of the activation pulse and the closing time of the needle valve.
[0013] d) Determine the value (TOD) from the value determined in step c).MDP1 ) and the stored value of the total working time (TOD) of the reference injector during the MDP state. refMDP The difference between (ΔTOD) MDP );
[0014] e) Determine the difference between the opening delay (ΔOD) of the injector and the opening delay of the reference injector stored from step d);
[0015] f) Control the operation based on the parameters described in e).
[0016] In step e), the difference e) can be calculated from the following formula: ΔOD = ΔTOD MDP .
[0017] The method may include using the value calculated in step e) and the stored reference value OD of the opening delay of the reference injector. ref The opening delay OD1 of the injector is determined, and the value of OD1 is used in step f) to subsequently control the operation of the injector.
[0018] Parameter TOD MDP1 It can be calculated from the following formula:
[0019] TOD MDP1 =MDP1+CR MDP1 .
[0020] The method may include the step of analyzing the voltage signal on the solenoid actuator to determine the valve closing point t4.
[0021] The valve closing time can be determined by identifying glitch signals.
[0022] The method may include performing a scan, which includes a series of actuations of the fuel injector with different drive (actuation pulse) durations, and determining the values in steps a) and / or b) based on the scan.
[0023] The minimum driving pulse state can be determined by analyzing the value of the closure response obtained in the scan.
[0024] Although the term "activation pulse" is written in the singular, it can be considered an activation profile and can include a series of pulses. Therefore, the term "end of activation pulse" should be interpreted as referring to the end of the hold pulse or final activation pulse in the activation profile. Attached Figure Description
[0025] The invention will now be described by way of example with reference to the accompanying drawings, in which:
[0026] - Figure 1 A simplified curve of activation (logic) pulse 1 sent to the solenoid of the fuel injector activated by the solenoid versus time is shown, and curve 2 shows the fuel injection rate (i.e. from the needle valve).
[0027] - Figure 2 This illustrates a closed-loop control method from the prior art;
[0028] - Figure 3 A prior art method for determining the turn-on delay is shown, and the enlarged first half of the current curve 4 and the voltage curve are shown in more detail.
[0029] - Figure 4 The curve of the closure response CR relative to the activation pulse width of the solenoid actuator is shown;
[0030] - Figure 5 The method is illustrated. Detailed Implementation
[0031] Figure 1 A simplified curve of activation (logic) pulse 1 sent to the solenoid (or its actuator) of the fuel injector activated by the solenoid versus time is shown, and curve 2 shows the fuel injection rate (i.e., from the needle valve). The pulse width (PW) of the activation pulse is shown; it begins at time point t1 and ends at t3. The opening and closing of the needle valve is generally hysteretic; it begins / ends from the activation pulse, respectively. The needle valve opens at point t2 and closes at point t4; therefore, fuel is injected between these times; HO refers to the time between these times, which is called the hydraulic opening or needle valve opening time. The closing response (CR) (often alternatively called the closing delay (CD)) is the time between points t3 and t4. t4 is the closing time (CT). The opening delay (OD) is between t1 and t2, from the start of the activation pulse to the start of the needle valve opening. This parameter is important for control. The total operating duration (TOD) is defined as the time between the start of the activation pulse t1 and the valve closing time t4 (closing time CT).
[0032] Figure 2 A prior art closed-loop control method is illustrated. Reference numeral 3 shows the voltage on the solenoid, which is defined or more precisely set according to the activation profile or pulse sent to the (sowary) actuator, and can be seen to initially appear as an initial large-amplitude activation pulse 100 for moving the needle / bolt, followed by a series of small "holding" pulses 101 for holding the bolt in the open position. Reference numeral 4 indicates the corresponding current through the solenoid of the actuator.
[0033] The curve below shows the injection rate 5 corresponding to voltage curve 3. Various timings are shown in the legend. Figure 1"t2" can be considered any point in time within arrow T1 or T2 (i.e., the start of the injector (needle valve) opening or the end of the injector (needle valve) opening), or any time in between. Figure 1 The “t4” can be considered to be at the end of arrow T4.
[0034] "t_open" is the same as the open delay OD. An open time point of 6 (which is the same as...) can exist. Figure 1 The change in t2 (which is the same as t2) is shown by Δt_open. TI_hydr and Figure 1 The HO values are the same. It can be seen that after t3, there is a spurious signal G in the voltage signal, which can be observed when the needle valve closes due to the needle hitting the valve seat.
[0035] Time T1+T2, also known as t_open, is the time it takes for the injector to fully lift off; that is, for the injector to fully open. In some examples, the term "open delay" (OD) can be defined as the time from activation to full open (or to the start of open), and references to the term OD / open delay should be interpreted as encompassing both options. Therefore, in the example, the policy considers the change in T2 (here, point ΔT2) to be equal to the change in T1 (here, point ΔT1). The open offset is calibrated, and then T1 is known.
[0036] Figure 3 A prior art method for determining the turn-on delay is shown, and the first half of the current curve 4 and the voltage curve are shown in more detail. Figure 2 and Figure 3 The start of valve opening (t2) is indicated by reference numeral 6 in the figure. In the prior art method, the time offset 7 between the end of the first / initial high-amplitude pulse and the start of the first lower-amplitude hold pulse is a time window 8, where there is a nearly undetectable spurious signal at 6 to determine the opening time.
[0037] The problem of poor ICLC performance under opening delay deviation can be solved according to aspects of the invention by estimating the opening delay deviation according to the method described below. The inventors have determined that it is not necessary to determine the absolute OD (e.g., to provide strategies and closed-loop responses to reduce the impact of varying OD on fuel supply), and in several respects, the opening delay deviation (ΔOD) is determined and used around a nominal or reference value (which may be considered the so-called master OD).
[0038] The following formula (see Figure 1 The relevant parameters are:
[0039] OD + HO = PW + CR Equation 1 (see Figure 1 )
[0040] Where OD is the opening delay, HO is the hydraulic opening, PW is the pulse width, and CR is the closing response. Furthermore,
[0041] PW+CR=TOD Equation 2
[0042] TOD is defined as the time between the start of the pulse and the closure of the needle.
[0043] The inventors have determined that, under the lowest driving pulse state, the difference between the corresponding parameters of the nominal (standard, reference) injector and the actual injector (in test / to be controlled) is related as shown in the following formula (Δ represents the difference).
[0044] ΔOD+ΔHO=ΔMDP+ΔCR=ΔTOD Equation 3
[0045] Here, MDP stands for Minimum Drive Pulse, which is the minimum duration of the actuator drive pulse required for the valve to open and dispense (a very small amount) of fuel. This parameter is well known to those skilled in the art.
[0046] Under operating conditions close to MDP, the fuel supply value is very small, and the hydraulic opening values of the nominal / reference injector and the actual (test) injector are similar; therefore, ΔHO is close to zero. Under these conditions, the following holds true:
[0047] ΔOD = ΔTOD (Formula 4)
[0048] The inventors have utilized this simplified formula in the MDP state to allow a simplified method to determine the opening delay variation from the nominal / reference injector.
[0049] Typically, at the MDP, the OD and TOD parameters or characteristics of two injectors (nominal / reference injector and actual injector under test or observation (which will then be controlled)) are compared: for example, an older injector used in a vehicle injector. The opening delay variation can be calculated.
[0050] The parameters / characteristics of the nominal or reference injector (TOD) refMDP and OD refMDP The value of ) can be stored in the ECU, for example, in the MAP.
[0051] method
[0052] In the first step (during ICLC learning), a specific pulse width cycle (a series of injections with varying pulse durations) is performed at very low fuel levels (e.g., 0 mg to 2 mg). In other words, for the fuel injector under test, a scan is performed where the injector is operated sequentially with different actuation pulse widths (e.g., increasing pulse widths). The closing response CR is recorded for each pulse width. The closing response can be found by the time difference between the end of the activation pulse t3 (known to the ECU) and the needle valve closing time t4, which can be found by detecting spurious signals in the voltage signal at the solenoid actuator terminals. The term "spurious signal" is well understood by those skilled in the art and can be found from the first / second derivatives of the voltage curve / signal.
[0053] Figure 4 The curve of the closing response CR versus the activation pulse width of the solenoid actuator is shown, and the minimum drive pulse (MDP) (the minimum drive pulse required for the valve to open (i.e., when some fuel is injected)) is shown at point 9.
[0054] Therefore, in retrospect, the minimum drive pulse (MDP) is the minimum excitation time with the injected amount. This value (MDP) is determined during a series of injection cycles, and point 9 is determined by finding the minimum value of the V-shape in the curve of the pulse width versus CR. Other methods for determining the MDP are known in the art. As mentioned above, the closing response CR is found from the end of the activation pulse to the closing time of the needle valve, and the closing time of the needle valve can be determined by finding spurious signals in the voltage signal on the solenoid actuator. This technique and other techniques for determining the minimum drive pulse are well known in the art. Spurious signals are well known to those skilled in the art and can be considered as inflection points or local maxima / minimums in the signal.
[0055] Therefore, for the reasons mentioned above, the value CR of the corresponding closure response value of the MDP used in the test fuel injector was determined. MDP .
[0056] Next, determine the corresponding nominal total operating duration (TOD) for the actual fuel injector (which is being tested and controlled) at the MDP.
[0057] TOD MDP =MDP+CR MDP Formula 5 from Formula 2
[0058] TOD MDP1 =MDP1+CR MDP1 Where "1" refers to the actuator injector being tested / controlled.
[0059] MDP is known from the ECU logic.
[0060] Then the TOD used for the fuel injector under test MDP TOD Value MDP1 The TOD value at the MDP used for the nominal fuel injector (TOD) refMDP The two are compared (the latter is stored in the ECU) and the difference is determined.
[0061] TOD refMDP TOD MDP1 =ΔTOD MDP Equation 6
[0062] Therefore, according to Equation 4, the difference ΔOD between the opening delay of the reference injector and the injector under test can be obtained from Equation 4;
[0063] ΔOD=ΔTOD MDP
[0064] Example
[0065] Figure 5 The method is illustrated. The left side shows a curve of voltage I0 (i.e., present on the solenoid and measurable) and injected fuel X when the minimum drive pulse is applied to the main injector or nominal / reference injector. The right side shows a curve of voltage (i.e., present on the solenoid) and injected fuel when the minimum drive pulse is applied to the actual fuel injector to be controlled (old / aged injector).
[0066] In both cases, the small peaks in the curve (identified by the spurious signal in the voltage signal), denoted by reference numeral 11, indicate a very small fuel injection amount. The arrows at the bottom indicate the corresponding parameters for Opening Delay (OD), Minimum Drive Pulse (MDP), Total Operating Duration (TOD), and Closing Response (CR). Therefore, the ends of the arrows for TOD and CR coincide with the spurious signal obtained from valve closure.
[0067] At or near the activation pulse close to the MDP, ΔOD = ΔTOD. The characteristic of the TOD of the nominal injector (at the MDP) is considered known (and can be stored in the ECU as described above). The TOD of the injector under test is determined because we know the pulse width PW value (the MDP value at that point) and the CR (a specific cycle, as described at the beginning) at that PW (MDP) value.
[0068] Finally, the opening delay variation is estimated by the deviation from the nominal or reference value (i.e., the nominal or reference value of the reference injector that can be stored in the ECU). As a result, ICLC performance is significantly improved in the case of a non-nominal OD injector.
Claims
1. A method for controlling the operation of a fuel injector activated by a solenoid, the fuel injector including an actuator comprising a solenoid, and the fuel injector adapted to control a needle valve by means of an activation pulse sent to the solenoid to control the needle valve to dispense fuel via movement of a needle from and to a valve seat, the method comprising the steps of: a) Determine the minimum drive pulse MDP1 required to open the needle valve of the fuel injector; b) Determine the closing response CR of the fuel injector during the lowest drive pulse state. MDP1 The closing response is defined as the duration between the end of the activation pulse (t3) and the closing time of the needle valve (t4). c) From steps a) and b), determine the total operating time (TOD) during the lowest drive pulse state of the fuel injector. MDP1 The total working time is defined as the time between the start of the activation pulse and the closing time of the needle valve. d) Determine the total working time (TOD) determined from step c). MDP1 The stored value of TOD, representing the total operating time of the reference injector during the lowest drive pulse state. refMDP The difference between ΔTOD MDP ; e) Determine the difference ΔOD between the opening delay of the fuel injector and the opening delay of the reference injector stored from step d); f) Control the operation based on the difference determined in step e).
2. The method according to claim 1, wherein, In step e), the difference ΔOD is calculated from the following formula: ΔOD = ΔTOD MDP .
3. The method of claim 2, wherein the method comprises calculating the difference in step e) and a reference value OD of the stored opening delay of the reference injector. ref The opening delay OD1 of the fuel injector is determined, and the value of the opening delay OD1 is used in step f) to subsequently control the operation of the fuel injector.
4. The method according to claim 1, wherein, In step c), the total working time TOD MDP1 It is calculated from the following formula: TOD MDP1 =MDP1+CR MDP1 。 5. The method of claim 1, the method comprising the step of analyzing the voltage signal on the actuator to determine the time point (t4) at which the needle valve closes.
6. The method according to claim 5, wherein, The timing of the needle valve closure is determined by identifying false signals.
7. The method of claim 1, the method comprising performing a scan, the scan comprising a series of actuations of the fuel injector with different actuation pulse durations, and determining the values in step a) and / or step b) based on the scan.
8. The method according to claim 7, wherein, The minimum driving pulse state is determined by analyzing the value of the closure response obtained in the scan.