Method, computer program, control unit, internal combustion engine and motor vehicle for determining the opening time of an injector having a solenoid valve

Abstract

The present invention relates to a method for determining an opening time point of an injector having a solenoid valve. The method comprises: determining an armature impact time point at which an armature of the solenoid valve stops on a valve needle of the solenoid valve; determining an opening delay time of the injector, the opening delay time corresponding to a time period between the armature impact time point and the opening time point of the solenoid valve; and determining the opening time point of the injector based on the armature impact time point and the opening delay time.

Description

[0001] The invention relates to a method for determining an opening time of an injector having a solenoid valve, as well as a computer program, a control unit, an internal combustion engine and a motor vehicle.

[0002] Injectors are used in internal combustion engines to inject fuel directly into the combustion chamber. Here, the engine control unit controls the switching valve integrated in the injector, thereby opening and closing the injection nozzle. The amount of fuel injected can be determined by the opening time of the switching valve.

[0003] In the case of electrical control of solenoid valve injectors, it can happen that these valves open and close only with a delay. The delay of the individual injectors is determined by tolerances, with the result that the injectors have different opening times for the same control time. This leads to undesirably different distributions of the fuel mass.

[0004] Patent document WO 2011 / 012518 A1 describes a method for operating a solenoid valve of an injector. The solenoid valve has a valve element with a valve needle and an armature that can be moved by an electromagnet. The solenoid valve is closed, for example, in a state without current. After the control of the electromagnet starts, the opening movement of the valve element (after a lift delay) begins, which is limited by a travel stop. The travel stop is used to determine the end of the movement of the valve element. The lift delay can be determined by the start of control, the end of the movement of the valve element and a predetermined movement time ("flight time"). The lift delay corresponds to the time period between the start of energizing the armature winding ("start of control") and the rise of the valve needle from its valve seat.

[0005] Patent document DE 10 2009 045 469 A1 describes a method for operating a fuel injection valve of an internal combustion engine, wherein a first delay time is determined, which characterizes the time difference between the time of a first change in a control signal for the valve and the time of a first change in the valve operating state corresponding to the first change in the control signal. At least one second delay time of the valve is inferred from the first delay time, which characterizes the time difference between the time of a second change in the control signal and the time of a second change in the valve operating state corresponding to the second change in the control signal, the second change being different from the first change.

[0006] Patent document EP 2 685 074 A1 describes a method for detecting the opening of an electromagnetically actuated fuel injection valve, which is actuated by applying a control signal. In this case, the coil voltage of the fuel injection valve is monitored after the injection valve is closed, and the length of the curve segments with the same sign as the second derivative of the coil voltage is determined. If the length of the curve segment exceeds a calibrated threshold value, it can be concluded that the injection valve is open.

[0007] The object of the present invention is to provide an improved method for determining an opening time of an injector having a solenoid valve, an improved computer program, an improved control unit, an improved internal combustion engine and an improved motor vehicle.

[0008] This object is achieved by a method according to claim 1 , a computer program according to claim 12 , a control unit according to claim 13 , an internal combustion engine according to claim 14 and a motor vehicle according to claim 15 .

[0009] Further advantageous embodiments of the invention are apparent from the dependent claims and the following description of preferred exemplary embodiments of the invention.

[0010] A first aspect of the invention relates to a method for determining an opening time of an injector having a solenoid valve. The method comprises:

[0011] - determining the armature impact time point at which the armature of the solenoid valve stops on the valve needle of the solenoid valve;

[0012] - determining an opening delay time of the injector, which corresponds to the time period between the armature striking time and the valve opening time; and

[0013] - Determining the opening time of the injector based on the armature impact time and the opening delay time.

[0014] The injector with a solenoid valve is also called a solenoid valve injector, which is used to inject fuel into the combustion chamber of an internal combustion engine. The injector is electromagnetically operated. For this purpose, the injector has a coil for generating a magnetic field, so that the coil can be used as an electromagnet. In the static state of the solenoid valve, the coil is not energized and therefore there is no magnetic field, the valve needle is pressed into the valve seat by a preload element, such as a spring, and the valve hole is closed, so that the solenoid valve is squeezed or maintained in a closed (valve) position. In order to open the solenoid valve, a current can be applied to the coil, thereby generating a magnetic field. In the opening phase, the magnetic force exceeds the preload force of the preload element. Therefore, in the opening phase, the armature arranged on the valve needle can be moved by the magnetic force so that the armature drives the valve needle and moves against the preload force. The valve needle is thereby lifted from the valve seat, the valve hole is opened (or released) and the solenoid valve is thus opened. In order to close the solenoid valve, the current acting on the coil is cut off, so that there is no magnetic field. Therefore, the valve needle is pressed into the valve seat again by the preload element, and the valve hole is blocked, so that the solenoid valve is in its closed valve position again.

[0015] The opening time point of the injector is the time point at which the valve needle lifts from the valve seat and exposes the valve hole so that fuel can be sprayed into the combustion chamber. In other words, the opening time point is the time point at which the valve needle begins to rise from the valve seat.

[0016] The method is used to determine the opening time of the injector or solenoid valve. Thus, a control current is applied to generate a magnetic field in the coil in order to initiate the opening phase of the solenoid valve.

[0017] In the method, the armature impact time point at which the armature stops on the valve needle is determined. For the purpose of explanation, the arrangement of the armature on the valve needle is first described. In the non-current state of the coil, the armature is in a static position in which the armature rests on a static seat arranged on the valve needle. When the coil is energized, the armature is lifted from the static seat due to the magnetic force and moves in the direction of the armature stop on the valve needle. That is, the armature is arranged on the valve needle in such a way that the armature can move between the static seat and the armature stop. Therefore, the armature impact time point is the time point at which the armature stops on the armature stop of the valve needle (in the opening phase of the solenoid valve). The armature free stroke can be derived from the armature impact time point, which corresponds to the movement section of the armature from the static position until it hits the travel stop of the valve.

[0018] In this method, an opening delay time is also determined, which corresponds to the time period between the armature impact time and the electromagnetic valve opening time. In the opening phase, the armature moves in the direction of the armature stop and finally stops there. In order to lift the valve needle from the valve seat, the preload force must be overcome. The opening delay time describes the duration between the armature impacting the armature stop and the actual opening of the electromagnetic valve. The opening delay time is decisively related to the preload force of the preload element in the injector. In addition, the opening delay time is related to the magnetic force generated by the energized coil. In other words, the opening delay time depends on the electromagnetic actuator of the injector, which includes a preload element, a coil, a valve needle with a stationary seat and an armature stop, and an armature.

[0019] In some embodiments, the influence of the preload element can be considered, for example, using a model. Here, the model can be an empirical model and / or a mathematical model. In other embodiments, the opening delay time can be approximated with a constant time period.

[0020] Furthermore, in the method, the opening time point of the solenoid valve is determined based on the armature striking time point and the opening delay time. In some embodiments, the opening time point can be determined by adding the opening delay time to the armature striking time point.

[0021] The method makes it possible to determine the opening time of a solenoid valve injector relatively easily and precisely. The method takes into account the design and / or dimensions of components of the solenoid valve injector, such as a solenoid actuator, which can be dependent on the inductance of the coil (which results from the number of turns of the coil, the dimensions of the coil and, if applicable, the material surrounding the coil), the free travel of the armature on the valve needle, etc.

[0022] In some embodiments, the armature impact time can be determined by evaluating the voltage trend. The voltage trend refers to the trend of the voltage acting on the coil. The voltage trend can be detected particularly simply and accurately by corresponding measurement technology. For example, the voltage raw signal can be detected. Therefore, the armature impact time can be determined particularly simply and accurately by evaluating the voltage trend (or analyzing the voltage variation curve).

[0023] In a further embodiment, evaluating the voltage profile can include evaluating a first time derivative of the voltage profile. During the opening of the injector, a change in the profile of the first time derivative of the voltage profile can be observed due to a change in the velocity of the armature and / or the valve needle and the mass moved. Thus, by evaluating the first time derivative of the voltage profile, the armature impact time can be determined relatively accurately and simply.

[0024] In another embodiment, the armature impact time point can correspond to an extreme value in the first-order time derivative of the voltage trend. During the process of injector opening, when the armature impacts the valve needle and then drives the valve needle, the voltage trend becomes flat. "Extreme value" means that the first-order time derivative has a maximum or minimum limit at the armature impact time point. Here, the maximum and minimum limits are maximum values ​​or minimum values. By determining the extreme value, the armature impact time point can be determined by calculation and thus simply.

[0025] In another embodiment, determining the armature impact time point may further include:

[0026] - determining the start and end time of an evaluation time period for evaluating the first-order time derivative of the voltage profile;

[0027] - forming a first difference quotient trend over the evaluation time period based on the starting time point;

[0028] - forming a second difference quotient trend over the evaluation time period based on the end time point; and

[0029] - constructing (or forming) an auxiliary function, which includes a quotient of the first difference quotient curve and the second difference quotient curve or a difference between the first difference quotient curve and the second difference quotient curve; and

[0030] - Determining an extreme value in the auxiliary function, wherein the extreme value corresponds to the armature impact time.

[0031] The above steps can determine the inflection point-like slope drop in the first-order time derivative of the voltage trend. Here, the time point of the inflection point-like slope drop corresponds to the armature impact time point. The above steps for determining the armature impact time point are generated by the following assumption, that is, the first-order derivative of the voltage trend can be approximated by two straight lines, namely, a first straight line from the starting time point and a second straight line from the ending time point. Here, on the one hand, the slope of the first straight line is constant until the following situation, that is, when passing forward, the inflection point-like slope drop ("inflection point") is exceeded. Here, "passing forward" means observing the first straight line in the direction of the ending time point from the starting time point. On the other hand, the slope of the second straight line is constant until the following situation, that is, when passing backward, the inflection point-like slope drop is reached. Here, "passing backward" means observing the second straight line in the direction of the starting time point from the ending time point. In order to compare the slope trends of the first straight line and the second straight line with each other, the difference quotient (trend) of the first and second straight lines can be formed and evaluated.

[0032] By determining the evaluation time period for determining the armature impact time, time periods in the voltage profile in which the armature impact time is implausible can be eliminated in a preliminary phase. The method can thus be implemented more resource-efficiently, for example on a control unit.

[0033] The difference quotient describes the ratio of the change of a first variable to the change of a second variable, wherein the first variable is related to the second variable. For example, the difference quotient can be used to determine the slope of a linear function. Therefore, in order to determine the difference quotient, the ratio between the distance between the measured values ​​determined at the first time point and the second time point and the distance between the first time point and the second time point can be determined. The time point can be selected arbitrarily here. In the present case, the first time point can be the current time point within the basic evaluation time period, wherein the current time point is always the current time step of the predetermined time-discrete evaluation grid (calculation grid). The measurement values ​​at the (measurement) time points spaced (substantially) equidistantly from each other are determined by the evaluation grid. The second time point can be constant, for example, the second time point can be the starting time point or the ending time point of the evaluation time period. The term "difference quotient" explicitly includes positive and negative values, that is, geometrically, the slope triangle well known for determining the difference quotient can be oriented in the direction of the x-axis (usually the time axis) or in the reverse direction of the x-axis.

[0034] The "trend of the difference quotient" refers to the trend of the difference quotient over a specific time period. According to the above embodiment, the first trend of the difference quotient is formed over the evaluation time period and based on the starting time point. This means that the difference quotient is determined relative to the starting time point for each (measurement) time point of the difference quotient over the entire evaluation time period. This applies to the second trend of the difference quotient accordingly.

[0035] For example, the first difference quotient direction and the second difference quotient direction can be determined as follows:

[0036] or in

[0037] in,

[0038] l1(t) = Direction of the first difference quotient

[0039] l2(t) = direction of the second difference quotient

[0040] t = time point in the evaluation period

[0041] t A = The start time of the evaluation period

[0042] t E = End time of the evaluation period

[0043] U'(t) = the first derivative of the voltage trend at time t

[0044] U'(t A ) = the first derivative of the voltage trend at the start time of the evaluation period

[0045] U'(t E ) = first-order derivative of the voltage trend at the end of the evaluation period

[0046] Furthermore, an auxiliary function is formed. In this case, the auxiliary function is formed in such a way that the first and second difference quotient curves can be directly compared with one another.

[0047] Therefore, the auxiliary function can include the quotient (ratio) of the first and second difference quotient trends. In one example, the auxiliary function can correspond to the quotient of the first and second difference quotient trends. Therefore, the auxiliary function can be, for example, the second difference quotient trend divided by the first difference quotient trend or conversely the first difference quotient trend divided by the second difference quotient trend. In other examples, the auxiliary function can include additional parameters. When the auxiliary function is constructed as a quotient, in some examples, the first difference quotient trend and the second difference quotient trend are formed so that the auxiliary function always provides a positive value. Alternatively, the auxiliary function can also be constructed to include the numerical value of the quotient. To this end, the auxiliary function can, for example, correspond to the numerical value of the quotient of the first difference quotient trend and the second difference quotient trend. The auxiliary function can be constructed, for example, as follows:

[0048]

[0049] in,

[0050] a(t) = auxiliary function

[0051] Alternatively, the auxiliary function may include the difference between the first difference quotient trend and the second difference quotient trend. For example, the auxiliary function may correspond to the difference between the first difference quotient trend and the second difference quotient trend. The auxiliary function may, for example, be the second difference quotient trend minus the first difference quotient trend or conversely the first difference quotient trend minus the second difference quotient trend.

[0052] The auxiliary function can be used to evaluate the first and second difference quotient trends. Therefore, it can be identified based on the auxiliary function at which time the distance between the first difference quotient trend and the second difference quotient trend is the largest. At this time, there is an extreme value in the auxiliary function. The armature impact time point corresponds to this extreme value in the auxiliary function. In other words, when the auxiliary function has an extreme value, there is an armature impact time point. Depending on how the auxiliary function is constructed, the extreme value can be a maximum value or a minimum value. Therefore, the armature impact time point can be determined by calculation (based on the first-order time derivative) and is therefore simple.

[0053] In another embodiment, the auxiliary function can be constructed as follows:

[0054]

[0055] in,

[0056]

[0057]

[0058] The formula symbols used here have already been explained above. If the auxiliary function is designed in this way, the armature impact time corresponds to a peak value in the form of an extreme value.

[0059] In some embodiments, the voltage trend can include the voltage trend in the boost phase. The boost phase is a phase during the opening control of the solenoid valve in which a high voltage, a so-called boost voltage, is applied to the solenoid valve, which boost voltage can reach 100 volts, for example. As a result, the current in the coil rises several times steeper than when the battery voltage is applied. The armature impact time point occurs in this boost phase. In some embodiments, the voltage trend can be evaluated when the boost phase is present. Therefore, the method can be implemented particularly resource-efficiently, for example on a controller.

[0060] In another embodiment, the opening delay time can be determined by a model that simulates the operating characteristics of the solenoid valve, in particular the opening characteristics and the closing characteristics. As described above, the opening characteristics are (mainly) related to the electromagnetic actuator of the injector and are decisively related to the preload element of the electromagnetic actuator. Correspondingly, the closing characteristics are also related to this. Therefore, there is a strong correlation between the opening characteristics and the closing characteristics. Therefore, the opening characteristics of the solenoid valve can be inferred from the closing characteristics of the solenoid valve. Since the closing characteristics can be determined relatively easily by known methods and the opening characteristics have a strong correlation with the closing characteristics, the opening delay time can be determined particularly easily by the above-mentioned operating characteristic model.

[0061] In some embodiments, the opening delay time can be determined based on the closing delay time of the injector. In other words, the opening delay time can be determined based on the closing delay time. Here, the closing delay time is the time between the current on the coil being cut off and the electromagnetic valve being closed. Due to the strong correlation between the opening characteristics and the closing characteristics of the electromagnetic valve, the opening delay time is also strongly correlated with the closing delay time.

[0062] In some embodiments, the opening delay time can be determined using an opening delay time model. In some embodiments, the above-mentioned operating characteristic model can include an opening delay time model. In some embodiments, the above-mentioned operating characteristic model can be an opening delay time model. The opening delay time model can be, for example, a characteristic line or a characteristic field. The opening delay time model is constructed in such a way that the closing delay time enters as an input quantity and the opening delay time of the injector is obtained as an output quantity. In some embodiments, an opening delay time characteristic line can be used in such a way that the opening delay time is depicted with respect to the closing delay time. The closing delay time can usually be determined particularly easily with the aid of measurement technology and corresponding evaluation. Therefore, when the closing delay time is known, the opening delay time can be particularly easily inferred with the aid of the opening delay time model.

[0063] In some embodiments, the opening delay time model can be determined as follows. In a first step, the closing delay time of the injector for different control times is determined by a large number of tests for the injector. The control time is the duration of the coil being energized. In order to determine the closing delay time, known methods can be used, such as evaluating the second-order time derivative of the voltage trend on the coil after the control current is cut off. In the next step, the average closing delay time of the injector is formed by the test results. From the average closing delay time, a preload index (preload element model) for the injector can be derived, wherein the preload index corresponds to at least one measure of the preload of the preload element. In the next step, the opening delay time of the injector for different control times is determined by a large number of tests on the test bench and the average opening delay time is formed therefrom. The average closing delay time and the average opening delay time can be compared with the actual flow of the injector. The actual flow depends on the actual closing delay time and the actual opening delay time. By comparing the average value of the opening delay time and the closing delay time with the actual flow of the injector, the relationship between the average opening delay time and the average closing delay time can be adjusted. This relationship can eventually be stored in the opening delay time model. Therefore, the (average) opening delay time can be determined by the opening delay time model based on the preload force or the preload force indicator and the (average) closing delay time.

[0064] The method for determining the opening delay time model can be implemented for different injectors so that the model can describe a large number of injectors.

[0065] As indicated above, in some embodiments, the opening delay time may depend on the preload force of a preload element of the solenoid valve. The preload element forces the solenoid valve into the closed position.

[0066] In some embodiments, the preload force of the preload element can be approximated by a preload element model. The preload force can be determined particularly easily, at least approximately, by the preload element model. In this case, the preload element model can be determined mathematically and / or empirically, for example. In some embodiments, as described above, the preload element model can be derived from an average closing delay time. The preload element model is used to determine the opening delay time. The influence of the preload element on the opening delay time can be taken into account particularly easily by the preload element model.

[0067] In some embodiments, the opening delay time may be a predetermined constant duration. The predetermined constant duration may be injector-dependent and determined by preliminary tests on a test bench. The predetermined constant duration may be stored in a controller of the internal combustion engine. Thus, using a predetermined duration as the opening delay time is particularly resource-efficient, since no calculation or evaluation is required (in the controller) to determine the opening delay time.

[0068] Another aspect of the invention relates to a method for determining an opening time of an injector. The method according to the other aspect comprises:

[0069] - evaluating the time derivative of the voltage profile acting on the injector in the pressure increase phase, wherein the evaluation of the time derivative includes the evaluation of the second derivative of the voltage profile and the opening time corresponds to an extreme value of the second derivative which is present as a second extreme value in the pressure increase phase.

[0070] This alternative method is suitable for solenoid valve injectors which are designed without an armature and / or with armature free play.

[0071] It has been recognized that in the voltage increase phase for opening the solenoid valve, a double peak structure is present in the second derivative of the voltage profile.

[0072] In this alternative method, the opening time corresponds to the time at which the second extreme value is present in the second derivative. Therefore, the important second extreme value is the second peak value in the above-mentioned double peak structure. In other words, the second extreme value corresponds to the second maximum limit (in terms of time) in the second derivative of the voltage trend in the boost phase.

[0073] As mentioned above, the voltage profile on the coil can be detected by suitable measurement technology. Therefore, the second-order derivative can be determined based on the voltage profile. With this alternative method, the opening time can be determined mathematically and therefore precisely by determining the extreme value.

[0074] A second aspect of the invention relates to a computer program comprising instructions which, when executed by a computer, cause the computer to implement one of the above methods. The computer program may be stored on an electronic storage medium.

[0075] A third aspect of the present invention relates to a controller configured to implement one of the above methods.

[0076] A fourth aspect of the present invention relates to an internal combustion engine. The internal combustion engine may have the above-mentioned injector and may be controlled by the above-mentioned controller. The internal combustion engine is arranged and designed to implement one of the above-mentioned methods.

[0077] A fifth aspect of the present invention relates to a motor vehicle having the above-mentioned controller, which is arranged and designed to implement one of the above-mentioned methods.

[0078] Embodiments of the present invention are described herein by way of example and with reference to the accompanying drawings. In the drawings:

[0079] Figure 1a , Figure 1b A solenoid valve injector is schematically shown;

[0080] Figure 2A diagram schematically showing armature travel, control current and valve travel;

[0081] Figure 3 A method for determining an opening time point according to one embodiment is schematically shown;

[0082] Figure 4 Schematically illustrating a method for determining an opening delay time model;

[0083] Figure 5 Two curves schematically showing the first derivative of the voltage trend;

[0084] Figure 6 A method for determining the armature impact time is schematically shown;

[0085] Figures 7a to 7c Show according to Figure 6 illustrative examples of the method;

[0086] Figure 8a , Figure 8b Show according to Figure 6 Examples of results of the method;

[0087] Figure 9a , Figure 9b Show according to Figure 6 Examples of additional results of the method; and

[0088] Fig.10 A motor vehicle is schematically shown having a control unit according to one specific embodiment.

[0089] Figure 1a A solenoid valve injector (injector) 100 is schematically shown in a closed valve position, and Figure 1b The injector 100 is shown in an open valve position. The injector 100 has a solenoid valve, which comprises a valve needle 5 and a valve seat 15. The injector 100 has an electromagnetic actuator for actuating the solenoid valve, which comprises a coil 1, an armature 11 and a preload element 13.

[0090] The solenoid valve is a valve that is closed when no current is supplied. That is, in the non-energized state of the coil 1 , the valve needle 5 is arranged on the valve seat 15 in such a way that the spray hole 17 is closed by the valve needle 5 .

[0091] Here, the preload element 13 is designed to hold the solenoid valve in the closed position. To this end, the preload element 13 applies a preload force to the valve needle, so that the valve needle moves in the direction of the valve seat 15 and thus in the closing direction. In the example shown, the preload element 13 is designed as a spring.

[0092] The valve needle 5 has a stationary seat 7 and an armature stop 9 for an armature 11, between which the armature 11 can move. The stationary seat 7 and the armature stop 9 thus define the armature stroke or armature free stroke of the armature 11 relative to the valve needle 5. In addition, the injector 1 has a stroke stop 3, which limits the stroke (valve stroke) of the valve needle 5. In the closed valve position, the armature 11 is on the stationary seat 7, and in the open valve position, the armature 11 rests on the armature stop 9 and the stroke stop 3. By applying a control current I to the coil 1, the armature 11 can be moved from the stationary seat 7 to the armature stop 9 by a magnetic force. The armature 11 is held on the armature stop 9 by a magnetic force, so that the armature 11 drives the valve needle 5 against the preload force of the preload element 13 and thus lifts the valve needle 5 from the valve seat 15 until the armature 11 stops on the stroke stop 3. In this way, the injection opening 17 is exposed so that the fuel can be injected into the combustion chamber of the internal combustion engine through the injection opening 17 .

[0093] Figure 2 A control current diagram 20 showing the temporal course of the control current I on the coil 1, an armature stroke diagram 30 showing the temporal course of the armature stroke, and a valve stroke diagram 50 showing the temporal course of the valve stroke. The armature stroke is the stroke of the armature 5 between the stationary seat 7 and the armature stop 9. Figures 20, 30, 50 show the temporal course in a very schematic manner.

[0094] Here, the control current diagram 20 shows that a control current I is applied at a control time point 21 in order to open the solenoid valve. Here, the temporal trend has a steep edge immediately after the control time point 21, so that the control current I reaches the corresponding value (suction current) of the suction current phase 22 at the suction time point 23 relatively quickly. The time between the control time point 21 and the suction time point 23 corresponds to the boost phase in the opening phase of the solenoid valve. The steep edge enables smaller tolerances and higher repeatability of the fuel injection amount. The steep edge is achieved by applying a so-called boost voltage to the coil operation until the corresponding current value of the suction current phase 22 is reached. At the holding time point 25, the control current I drops from the suction current to the value (holding current) for the holding current phase 24. At the cut-off time point 27, the control current I is cut off and then reaches a zero value at the control end time point 29.

[0095] The armature stroke diagram 30 shows the time course of the armature stroke. After the control current I is applied at the control time 21, the armature 5 is lifted from the stationary seat 7 at the armature lifting time 31. Therefore, there is a lifting delay 33 between the application of the control current I and the lifting of the armature 5. At the armature impact time 35, the armature 5 hits the armature stop 9. The time period between the armature lifting time 31 and the armature impact time 35 corresponds to the flight time 37 of the armature 5.

[0096] After the armature 11 hits the armature stop 9, the armature 11 is held on the armature stop 9 for a period of time 39 due to the magnetic force of the coil 1. Due to the armature stop 9, the armature stroke relative to the stationary seat 7 no longer changes and is therefore constant within the period of time 39. After the control current I is switched off at the switch-off time 27, the armature 11 is no longer held on the armature stop 9 by the magnetic force of the coil 1. Therefore, at the armature return time 41, the armature 11 moves again in the direction of the stationary seat 7. There is a return delay 45 between switching off the control current I at the switch-off time 27 and the armature return time 41. At the armature stationary time 43, the armature 11 rests against the stationary seat 7 again.

[0097] The valve stroke diagram 50 schematically shows the course of the valve stroke of the solenoid valve. This refers to the stroke or deflection of the valve 5 relative to the valve seat 15. There is an opening delay time 52 between the armature impact time 35 and the opening time 51 of the solenoid valve. This is because the armature 11 impacts the armature stop 9 at the armature impact time 35 and drives the valve needle 5 against the preload force of the preload element 13. In this process, the armature 11 must mainly overcome the preload force of the preload element 13 until the valve needle 5 begins to rise from the valve seat 15 at the opening time 51.

[0098] At time 53, armature 11 strikes against travel stop 3, which represents the maximum valve travel of valve needle 5 and thus the open valve position. After armature 11 strikes armature stop 9, there is therefore an opening delay time 52, which the valve needle 5 elapses until the maximum valve travel is reached. The solenoid valve remains in this open position for a period of time 55 in order to inject fuel into the combustion chamber.

[0099] Furthermore, it can be seen from the valve stroke diagram 50 that there is a closing delay time 61 between switching off the control current I at the control time 27 and reaching the closed valve position at the valve closing time 59. After switching off the control current I, the previously established magnetic field also continues to weaken. Subsequently, the magnetic field weakens in such a way that the preload element 13 moves the valve needle 5 in the direction of the valve seat 15 at the time 57 until the solenoid valve is in the closed valve position at the valve closing time 59, i.e. the valve needle 5 closes the spray opening 17.

[0100] Figure 3 A method 200 according to one specific embodiment is shown, by which an opening time 51 of a solenoid valve can be determined.

[0101] The armature impact time point 35 is determined in 210. According to one embodiment, the armature impact time point 35 can be determined by evaluating the voltage acting on the coil 1. The voltage or voltage signal on the coil 1 can be detected by appropriate measurement technology. According to one embodiment, the armature impact time point 35 is determined by analyzing the first-order derivative of the voltage time trend acting on the coil 1. For example, the armature impact time point 35 can correspond to the time point at which an extreme value appears in the first-order derivative of the voltage trend. Here, the important extreme value can be the extreme value of the derivative that first appears in the boost phase. The analysis of the voltage trend can be performed at least or only in the boost phase (existing between the control time point 21 and the suction time point 23).

[0102] The opening delay time 52 is determined in 220. The opening movement (opening characteristic) and closing movement (closing characteristic) of the valve needle 5 and thus the opening delay time 52 and the closing delay time 61 are decisively related to the preload element 13. Therefore, the opening delay time 52 of the solenoid valve can be determined based on the closing delay time 61 of the solenoid valve. In order to determine the opening delay time from the closing delay time, an opening delay time model can be used, which is described below with reference to Figure 4 Describe the model.

[0103] The closing delay time 61 can be determined by determining the valve closing time point 59 and the cut-off time point 27. The cut-off time point 27 can be determined by detecting the cut-off time point of the control current I. The valve closing time point 59 can be determined by a known method. When the valve closing time point 59 and the cut-off time point 27 are known, the closing delay time 61 can be determined, which corresponds to the time period between the cut-off time point 27 and the valve closing time point 59.

[0104] In some embodiments, the opening delay time 52 determined in 220 may be a predetermined constant duration. By this method, the closing delay time 61 does not need to be determined in advance, whereby the determination of the opening delay time 52 is particularly simplified.

[0105] In 230 , the opening time 51 is determined based on the armature impact time 35 and the opening delay time 52 . According to one specific embodiment, for this purpose the opening delay 52 is added to the armature impact time 35 in order to obtain the opening time 51 .

[0106] Figure 4 A method for determining an opening delay time model 300 is shown.

[0107] In 310 , the closing delay time 61 of the injector 100 is determined for different control times. For this purpose, tests can be carried out on a test bench. From a large number of closing delay times 61 for different control times, an average closing delay time of the injector 100 is formed.

[0108] At 320 , a preload indicator (preload element model) for the injector 100 is derived from the average closing delay time, wherein the preload indicator corresponds to at least one measure of the preload force of the preload element 13 .

[0109] The opening delay time 52 of the injector is determined for different control times on a test bench at 330. An average opening delay time of the injector 100 is formed from a large number of opening delay times 52 for different control times.

[0110] At 340 , the average closing delay time and the average opening delay time are compared to the actual flow rate of the injector 100 in order to adjust or explicitly describe the relationship between the average opening delay time and the average closing delay time.

[0111] In 350, the relationship between the average opening delay time and the average closing delay time is stored in an opening delay time model. In other words, the opening delay time model is determined or created in 250. Therefore, the (average) opening delay time can be determined based on the preload force or the preload force indicator and the (average) closing delay time through the opening delay time model.

[0112] The method 300 may be implemented for different injectors 100 in order to characterize a large number of injectors or closing delay times 61 using an opening delay time model.

[0113] Figure 5 A diagram is shown in which a first-order derivative 71 of a voltage trend according to a first example is shown. The first-order derivative 71 of the voltage trend is determined based on the original signal of the voltage (detected by the voltage sensor) and is therefore strongly contaminated by noise. Therefore, a subsequent evaluation of the original signal and the first-order derivative 71 of the voltage trend determined therefrom may lead to inaccurate results. Therefore, the original signal can be smoothed by a corresponding method for subsequent evaluation. For example, a smooth curve 73 of the first-order derivative of the voltage trend can be determined from the original signal by an orthogonal polynomial, which curve is relatively less contaminated by noise and is relatively smooth. Other methods for smoothing the voltage original signal are also feasible. It can be checked whether the provided voltage signal, i.e. the original signal, can be used or whether the original signal or the first-order time derivative must be smoothed in advance, for example, in a controller for subsequent evaluation.

[0114] Figure 6 Show according to the Figure 4 A method 400 for determining an armature impact time is provided according to a further embodiment of block 210 of method 200 .

[0115] In 410 , a starting time t of an evaluation time period for evaluating the first-order time derivative of the voltage profile is determined.A and end time t E In this case, as described above, a first-order time derivative of the voltage profile according to the raw signal or a smoothed first-order time derivative of the voltage profile can be used.

[0116] In 420, based on the starting time point t A A first difference quotient is formed over the evaluation period and moves toward l1.

[0117] In 430, based on the end time point t E A second difference quotient is formed over the evaluation period and moves toward l2.

[0118] In 440, an auxiliary function a(t) is constructed, the auxiliary function including a quotient formed by the first difference quotient trend and the second difference quotient trend. Alternatively, the auxiliary function a(t) may include a difference between the first difference quotient trend and the second difference quotient trend.

[0119] The auxiliary function is evaluated by determining an extreme value in the auxiliary function a(t) at 450. In this case, the extreme value corresponds to the armature impact time point.

[0120] Figures 7a to 7c A diagram is shown for deriving a method 400 for determining the armature impact time. Figure 5 As can be seen, the first derivative 71 based on the original signal shows an inflection point drop 75. The first derivative 71 of the voltage trend can be divided into an area before the inflection point drop 75 (to the left of the inflection point drop 75) and an area after the inflection point drop 75 (to the right of the inflection point drop 75). This applies to the smooth curve 73 of the first derivative of the voltage signal accordingly.

[0121] In both regions, the first-order derivative 71 of the voltage profile can be approximated by a linear function. For example, the following function can be used for the left region 77 and the right region 79.

[0122] f1(t)=m1*t+n1 or f2(t)=m2*t+n2

[0123] Here, f1(t) is the first linear function for the left area, f2(t) is the second linear function for the right area, m1 and m2 are the corresponding slopes of the straight lines generated by the functions, and n1 and n2 are the vertical intercepts (or displacement constants) of the straight lines.

[0124] Figure 7a The voltage trend (with linear functions f1(t) and f2(t) is shown. Figure 5 Here, the approximate function f(t) is for the (selected) starting time t Aand the (selected) end time t E The evaluation time period between is shown. An exemplary approximation function f(t) is as follows:

[0125]

[0126] If we consider the starting time t A and the left area between inflection point 81 or inflection point time point, the following applies:

[0127] and

[0128] If we consider the inflection point 81 and the end time point t E For the area to the right of , the following applies:

[0129] and

[0130] Figure 7b The above relationship of the slopes m1, m2 of the left and right regions is shown by showing the first difference quotient course l1 and the second difference quotient course L2, wherein:

[0131]

[0132]

[0133] from Figure 7b It can be seen that the inflection point 81 in the approximate function f(t) occurs at the time point t, at which the distance between the first difference quotient trend l1 and the second difference quotient trend l2 is the largest. This time point t of the maximum distance between the first difference quotient trend l1 and the second difference quotient trend l2 can be determined, for example, by constructing the auxiliary function a(t) as follows:

[0134]

[0135] Alternatively, the auxiliary function a(t) can also be designed as a difference between the first difference quotient curve l1 and the second difference quotient curve l2.

[0136] Since the first-order derivative of the voltage trend and thus the approximate function f(t) decreases continuously, the straight line of the linear functions f1(t), f2(t) has a negative slope and thus m1, m2 have negative values. Figure 7c In the curve of the auxiliary function a(t) shown in FIG. 8 , a (positive) peak 87 can be seen, wherein the peak 87 corresponds to the armature impact time 35 . In other words, the time of the peak 87 corresponds to the armature impact time 35 .

[0137] The inflection point in the first derivative of the voltage profile can thus be determined by the auxiliary function a(t). The time of the inflection point and thus the armature impact time can thus also be determined by calculation and thus in a simple manner.

[0138] Figure 8a and Figure 8b An exemplary evaluation of the voltage trend according to the second example is shown. A smooth curve 93 of the first derivative of the voltage trend according to the second example and the corresponding auxiliary function a(t) are shown here. It can be seen that the smooth curve 91 has an inflection point 93 at the time point of t=250 μs (microseconds), and the auxiliary function a(t) has a peak value (maximum limit) 95 at the same time point of t=250 μs.

[0139] Figure 9a A diagram is shown in which the first time derivative of the voltage profile according to the third example is shown. It can be seen that the first inflection-like drop 101 is followed by a flattening 103 of the profile. The flattening 103 is in turn followed by a second inflection-like drop 105 .

[0140] Figure 9b shows a graph with an auxiliary function a(t) for Figure 9a The voltage curve shown in the diagram in FIG. 1 is constructed. Here, the auxiliary function a(t) has a first peak value (maximum limit) 113 and a second peak value 115, the first peak value can be assigned to the first inflection point-like drop 101, and the second peak value can be assigned to the second inflection point-like drop 105. The armature impact time 35 corresponds to the first peak value 113. In other words, in order to determine the armature impact time 35 with the help of the auxiliary function a(t), in some embodiments, only the armature impact time 35 at the start time t A and end time t E The first peak value (maximum limit) 113 that occurs within the evaluation time period between . As an alternative to this, in other embodiments, the evaluation time period can be selected so that only one peak value occurs.

[0141] Fig.10 An exemplary controller 170 is schematically shown, which is configured to implement the above-mentioned method / model. The controller 170 is arranged in a schematically shown motor vehicle 180 and can control a schematically shown internal combustion engine 179. The controller 170 includes a processor 172, a memory (electronic storage medium) 174 and an interface 178. In addition, software (computer program) 176 is also stored in the memory 174, which is designed to implement the above-mentioned method. The processor 172 is designed to execute the program instructions of the software 176. In addition, the interface 178 is designed to receive and send data. For example, the interface can be an interface with a CAN bus of the motor vehicle 180, through which the controller 170 receives signals and sends control instructions.

[0142] Reference numerals list

[0143] 1 coil

[0144] 3 travel stop

[0145] 5 valve needle

[0146] 7Stationary seat

[0147] 9 Armature stop

[0148] 11 Armature

[0149] 13 Preload element

[0150] 15 Valve seat

[0151] 17 nozzles

[0152] 20 Control current diagram

[0153] 21 Control time point

[0154] 22 suction current stage

[0155] 24 Holding current stage

[0156] 25 Keep Time Point

[0157] 27 Cut-off time point

[0158] 29 Control end time point

[0159] 30 Armature stroke diagram

[0160] 31 Armature lifting time point

[0161] 33 Rise delay

[0162] 35 Armature impact time point

[0163] 37 (armature) flight time

[0164] 39 Time period of maximum armature travel

[0165] 41 Armature return time point

[0166] 43 armature stationary time point

[0167] 45 Return Delay

[0168] 50 valve stroke diagram

[0169] 51 Opening time

[0170] 52 Open delay time

[0171] 53 The time when the armature hits the travel stop

[0172] 55 Time period of maximum valve travel

[0173] 57 The valve needle starts to move toward the valve seat

[0174] 59 Valve closing time

[0175] 61 Close delay time

[0176] 71 The first derivative of the first voltage trend

[0177] 73 Smoothed trend of the first derivative of the first voltage trend

[0178] 75 inflection point decline

[0179] 81 Turning Point

[0180] 91 The first derivative of the second voltage trend

[0181] 93 inflection point decline

[0182] 95 Peak (maximum limit)

[0183] 101 The first turning point decline

[0184] 103 Flattening of the first-order derivative of voltage trend

[0185] 105 The second turning point decline

[0186] 111 First peak (maximum limit)

[0187] 115 Second peak (maximum limit)

[0188] 170 Controller

[0189] 172 processors

[0190] 174 Memory (electronic storage media)

[0191] 176 Software

[0192] 178 Interface

[0193] 179 Internal combustion engine

[0194] 180 Motor Vehicles

[0195] 100 Injector

[0196] 200 Method for determining the opening time point

[0197] 210 Determine the armature impact time point

[0198] 220 Determine the opening delay time

[0199] 230 Determine the opening time

[0200] 300 Method for determining / creating an opening delay time model

[0201] 310 Determine the average closing delay time

[0202] 320 Determine the preload element model

[0203] 330 Determine the average opening delay time

[0204] 340 compared with the actual flow rate of the injector

[0205] 350Create Open Delay Time Model

[0206] 400 Method for determining the time point of armature impact

[0207] 410 Determine the start time point and end time point of the evaluation period

[0208] 420 Forming the first difference quotient trend

[0209] 430 Forming the second difference quotient trend

[0210] 440 Constructing auxiliary functions

[0211] 450 Determine the extreme value of auxiliary function

[0212] a(t) auxiliary function

[0213] l1 The first difference quotient trend

[0214] l2 The second difference quotient trend

[0215] t A The start time of the evaluation period

[0216] t E End time of the evaluation period

Claims

1. A method for determining an opening time point (51) of an injector (100) having a solenoid valve, comprising: - determining an armature impact time (35) at which the armature (11) of the solenoid valve stops on the valve needle (5) of the solenoid valve; - determining an opening delay time (52) of the injector (100), which corresponds to the time period between the armature impact time point (35) and the solenoid valve opening time point (51); and - determining the opening time (51) of the injector based on the armature impact time (35) and the opening delay time (52).

2. The method according to claim 1, wherein: The armature impact time (35) is determined by evaluating the voltage profile.

3. The method according to claim 2, wherein: Evaluating the voltage profile includes evaluating a first-order time derivative of the voltage profile.

4. The method according to claim 3, wherein: The armature impact time (35) corresponds to an extreme value in the first time derivative of the voltage profile.

5. The method according to claim 3, wherein: Determining the armature impact time point also includes: - determining the start and end time of an evaluation time period for evaluating the first-order time derivative of the voltage profile; - forming a first difference quotient trend over the evaluation time period based on the starting time point; - forming a second difference quotient trend over the evaluation time period based on the end time point; and - constructing an auxiliary function, the auxiliary function comprising a quotient of the first difference quotient trend and the second difference quotient trend or a difference between the first difference quotient trend and the second difference quotient trend; and - Determining an extreme value in the auxiliary function, wherein the extreme value corresponds to the armature impact time.

6. The method according to claim 5, wherein: The auxiliary function (a(t)) is constructed as follows: in, in, t = time point in the evaluation period t A = The start time of the evaluation period t E = End time of the evaluation period U'(t) = first derivative at time t U'(t A ) = the first derivative at the start time of the evaluation period U'(t E ) = the first derivative at the end time point of the evaluation period.

7. The method according to claim 2, wherein: The voltage trend includes the voltage trend in the boost phase.

8. The method according to claim 1, wherein: The opening delay time (52) is determined using a model that simulates the operating characteristics of the solenoid valve.

9. The method according to claim 8, wherein: This model simulates the opening and closing characteristics of a solenoid valve.

10. The method according to claim 1, wherein: The opening delay time (52) is determined as a function of the closing delay time (61) of the injector (100), wherein the closing delay time is the time between switching off the current to the coil and closing the solenoid valve.

11. The method according to claim 7, wherein: The opening delay time (52) is determined using an opening delay time model.

12. The method according to any one of claims 1 to 5, wherein: The opening delay time (52) is a predetermined constant duration.

13. A computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to carry out the method according to any one of the preceding claims.

14. A controller (170) configured to implement the method according to any one of claims 1 to 12.

15. An internal combustion engine having a controller (170) according to claim 14, wherein: The internal combustion engine (179) is arranged and designed to carry out the method according to any one of claims 1 to 12.

16. A motor vehicle (180) having an internal combustion engine (179) according to claim 15, wherein: The motor vehicle (180) is arranged and designed to carry out the method according to any one of claims 1 to 12.

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