Method for adjusting the control of an injection nozzle

Abstract

The invention relates to a method for adjusting a time for the start and end of the control of an injection nozzle of an internal combustion engine of a motor vehicle, comprising the following steps: - Control of the injector, wherein the control triggers an injection process, wherein the injector injects fuel into a combustion chamber of the internal combustion engine during the injection process, wherein the injection process continues throughout the entire control and is terminated by terminating the control; - Monitoring of the combustion air ratio during control, whereby the monitoring checks whether the combustion air ratio is within a target range; - Correction of the combustion air ratio during control, if the combustion air ratio is outside the target range; - Determination of a correction value as a measure of the frequency of corrections during control; - Determining whether the correction value is above a correction threshold; and - Adaptation of a first time point for the start of the control and / or a second time point for the end of the control if the correction value is above the correction threshold.

Description

[0001] The present invention relates to a method for adjusting a time for the start and termination of the control of an injection nozzle of an internal combustion engine of a motor vehicle according to claim 1.

[0002] It is known from the prior art to monitor and adjust the combustion air ratio during an injection process if it lies outside a target range.

[0003] From DE 10 2008 006 327 A1, a method for controlling an internal combustion engine with a plurality of injection valves for injecting fuel into individual combustion chambers of the engine is known. The method comprises controlling the injection valves to meter a first target total fuel quantity using a first injection strategy, determining the first actual total fuel quantity injected during control with the first injection strategy, and controlling the injection valves to meter a second target total fuel quantity using a second injection strategy. In the second injection strategy, at least one of the injection valves is controlled differently compared to the first injection strategy.Furthermore, the procedure includes determining a second actual total fuel quantity injected during control with the second injection strategy and determining an operating behavior of at least one of the injection valves as a function of the first actual total fuel quantity and the second actual total fuel quantity.

[0004] DE 103 07 004 B3 discloses a method for controlling an internal combustion engine with a lambda control system, which is intended to improve emission values, particularly after a cold start during the idling phase. The technical essence of the method lies in the use of a temperature-dependent adaptation value to determine the required amount of fuel before the lambda control system is operational. For this purpose, in a first phase after starting and under the fulfillment of activation conditions, such as a cold start and idling, an adaptation value is taken from a characteristic curve and weighted over the number of combustion cycles to calculate the fuel quantity.In a second phase, with lambda control running and adaptation conditions fulfilled, such as continued idling, a new adaptation value is determined from the controller parameters, preferably the integral part of the lambda controller, and then used for adaptation and storage in the temperature-dependent characteristic curve.

[0005] DE 10 2018 218 020 B4 discloses a method for controlling fuel injection by a fuel injection unit, based on the calculation of the injection duration and an injection flow rate used for this calculation. The technical essence of the method lies in the fact that the injection flow rate is calculated within the framework of a first PID controller, whereby an error component calculated when determining a gas fraction (e.g., oxygen) in the exhaust gas is used to determine this injection flow rate. This error component is preferably the integral component of a further PID controller, which is designed as a lambda controller. The calculated injection flow rate serves to compensate for deviations caused by aging or manufacturing defects of the injection unit and thus reduce the control effort of the lambda controller.

[0006] JP 2008 - 101 625 A discloses an injection quantity learning control device for a common-rail injection system of an internal combustion engine, which determines the actual fuel quantity of the multiple injections, in particular the pilot injection, during idle operation based on a combination of a cylinder-to-cylinder correction (FCCB) to level out speed fluctuations between the cylinders and an idle speed correction (ISC) to adapt the mean engine speed to a target speed.

[0007] DE 103 37 228 A1 discloses a method for operating an internal combustion engine with an exhaust aftertreatment system comprising at least one pre-catalyst and a downstream main catalyst, in which a lambda control based on the difference between a lambda setpoint and an actual lambda value measured downstream of the pre-catalyst is used to calculate a control intervention for mixture control. The essential feature of the method is flash adaptation, in which, at the end of a quasi-steady-state operating condition, the integral component of the lambda control is stored as an adaptation value for the mixture feedforward control for this operating condition, used immediately, and then set to zero in order to achieve a fast and accurate adaptation of systematic mixture feedforward errors without compromising the stability of the lambda control.

[0008] In contrast, the present invention is based on the objective of adapting the amount of fuel to be injected to conditions that may change under certain circumstances.

[0009] This problem is solved by a method according to claim 1 and by a motor vehicle according to claim 8. Embodiments of the invention are specified in the dependent claims.

[0010] The method according to claim 1 comprises controlling the injection nozzle. The control triggers an injection process. During the injection process, the injection nozzle injects fuel into a combustion chamber of the internal combustion engine. The injection process continues throughout the entire control process and is terminated by terminating the control process.

[0011] During the control process, the air-fuel ratio is monitored. In this context, the air-fuel ratio refers specifically to the ratio between the actual mass of air available in the combustion chamber for fuel combustion and the minimum mass of air theoretically required for stoichiometrically complete combustion. For example, an air-fuel ratio of 1 means that exactly the amount of air theoretically required for complete fuel combustion is present in the combustion chamber. If the air-fuel ratio is less than 1, less air is available. If the air-fuel ratio is greater than 1, more air is available.

[0012] Monitoring the air-fuel ratio involves checking whether it remains within a target range. Preferably, this target range might be, for example, between 0.9 and 1.1. If the air-fuel ratio falls outside this range, it is corrected by a control system to bring it back within the target range. This correction can be performed automatically, triggered by the air-fuel ratio falling outside the target range. This correction can be achieved, for example, by adjusting the fuel pressure.

[0013] A correction value is determined as a measure of the frequency of corrections during the control process. This correction value can be determined, in particular, over several combustion cycles. The more frequently and significantly the air-fuel ratio is corrected, the higher the correction value will be. The correction value is therefore a measure of how often the air-fuel ratio had to be corrected to remain within the target range.

[0014] The system determines whether the correction value exceeds a correction threshold. If it does, a first time for the start of the control action and / or a second time for its termination are adjusted. This adjustment of the timings can be performed fully automatically and triggered by the correction value exceeding the threshold. Specifically, a single instance of exceeding the correction threshold can trigger the adjustment. Alternatively, the timings can be adjusted only after the correction value has repeatedly exceeded the threshold. This can also depend on how the correction value is calculated; for example, the correction value can be time-dependent.In this case, for example, it can exceed the correction threshold and then fall below the correction threshold again.

[0015] Adjusting the injection timing is advantageous for adapting the duration of the injection process, thereby reducing the frequency of adjustments to the air-fuel ratio. Specifically, it is beneficial to adjust the timing to accommodate changing conditions, thus minimizing the need for adjustments to the air-fuel ratio. This timing adjustment can be particularly advantageous if, after a break-in period, the combustion conditions and / or mechanical properties of the injector nozzle change.

[0016] According to one embodiment of the invention, the adaptation of the first and / or second time point is only performed if the correction value exceeds the correction threshold more frequently than a specified frequency threshold. This prevents unnecessary and overly frequent adjustments of the time points. Preferably, the time points should only be adapted if the correction value remains above the correction threshold for an extended period. A correction of the combustion air ratio may also be necessary and performed if environmental conditions such as temperature or air pressure fluctuate. However, in such cases, an adaptation of the time points is unnecessary or may even be detrimental if the environmental conditions change again.

[0017] According to one embodiment of the invention, the frequency threshold can be time-dependent. In the context of this description, this means in particular that the frequency threshold is a number of corrections per unit of time. The unit of time can, in particular, refer to an operating time of the internal combustion engine.

[0018] According to one embodiment of the invention, the frequency threshold can depend on the mileage of the motor vehicle. For the purposes of this description, this is understood to mean, in particular, that the frequency threshold is a number of corrections per kilometer driven.

[0019] According to one embodiment of the invention, the frequency threshold can be an absolute numerical value. In the context of this description, this is understood to mean, in particular, a value that is neither time-dependent nor dependent on the operating time of the internal combustion engine.

[0020] According to one embodiment of the invention, the injection process can comprise a first phase, a second phase, and a third phase. During the first phase, a valve needle of an injection nozzle valve can be moved ballistically. For the purposes of this description, this means, in particular, that the valve needle opens the valve without active resistance or braking. The valve needle can only be slowed down by air resistance, flow resistance, and / or friction.

[0021] In the third phase, the valve can be fully open. The second phase is a transitional phase between the first and third phases. Adjustments to the air-fuel ratio are only made in the first and second phases. These are the phases in which adjustments to the air-fuel ratio are most frequently necessary due to changing conditions.

[0022] According to one embodiment of the invention, the correction value can take into account the extent of the corrections during the control process. In this embodiment, the correction value therefore considers both the frequency and the extent of the corrections.

[0023] The motor vehicle according to claim 8 comprises a control unit and an internal combustion engine as a drive. The control unit is configured to carry out a method according to an embodiment of the invention.

[0024] Further features and advantages of the present invention will become clear from the following description of a preferred embodiment with reference to the accompanying figure. This figure shows Fig. 1 A schematic representation of a time-dependent curve of the amount of fuel injected into the combustion chamber during an injection process.

[0025] In Fig.In Figure 1, the x-axis represents the time during which the injector is activated. The y-axis represents the amount of fuel injected, for example, as volume or mass. The time-dependent curve in Figure 1 has a first phase (2), a second phase (3), and a third phase (4). In the first phase (2), the valve needle of the injector moves ballistically. The valve thus opens further and further during the first phase (2). Therefore, the amount of fuel injected increases continuously. In the third phase (4), the valve is fully open. The amount of fuel injected therefore increases continuously. The second phase (3), which lies between the first phase (2) and the third phase, can also be called the transition phase.

[0026] Particularly in the first phase (2) and the second phase (3), manufacturing tolerances often cause variations in the injected fuel quantity for the same injection duration. Furthermore, an injector nozzle can exhibit a break-in effect, meaning that after a certain operating period of the internal combustion engine, the time-dependent profile of the injected fuel quantity changes. If fluctuations in the injected fuel quantity occur, this affects the air-fuel ratio. For this reason, the air-fuel ratio is monitored and corrected if the fluctuations become so large that it falls outside a target range. The air-fuel ratio can be corrected, for example, by changing the fuel pressure or the amount of air supplied to the combustion chamber.

[0027] To determine the frequency and, if applicable, the extent of adjustments to the combustion air ratio, a correction value is calculated. This can, for example, include the number of adjustments made during a specific period. It is also possible for the correction value to encompass both the number and the quantity of adjustments made during a given period.

[0028] If the correction value exceeds a correction threshold, the injection nozzle's activation duration is adjusted to reduce the frequency of future air-fuel ratio corrections. This adjustment is achieved by modifying the first and second points in the activation sequence.

[0029] For example, if the air-fuel ratio needs to be adjusted particularly frequently to inject more fuel, the control duration can be lengthened. Conversely, if the air-fuel ratio needs to be adjusted particularly frequently to inject less fuel, the control duration can be shortened.

Claims

[1] Method for adjusting the timing of the start and end of the control of an injector of an internal combustion engine of a motor vehicle, comprising the following steps: - Control of the injector, wherein the control triggers an injection process, wherein the injector injects fuel into a combustion chamber of the internal combustion engine during the injection process, wherein the injection process continues throughout the entire control and is terminated by terminating the control; - Monitoring of the combustion air ratio during control, whereby the monitoring checks whether the combustion air ratio is within a target range; - Correction of the combustion air ratio during control, if the combustion air ratio is outside the target range; - Determination of a correction value as a measure of the frequency of corrections during control; - Determining whether the correction value is above a correction threshold; and - Adaptation of a first time point for the start of the control and / or a second time point for the end of the control if the correction value is above the correction threshold. [2] Method according to claim 1, characterized by , that the adaptation of the first time point and / or the second time point is only carried out if the correction value is more frequently than a frequency threshold above the correction threshold. [3] Method according to the previous claim, characterized by that the frequency threshold is time-dependent. [4] Method according to one of the two preceding claims, characterized by that the frequency threshold depends on the mileage of the motor vehicle. [5] Method according to claim 2, characterized by that the frequency threshold is an absolute numerical value. [6] Method according to any one of the preceding claims, characterized by , that the injection process comprises a first phase (2), a second phase (3) and a third phase (4), wherein during the first phase (2) a valve needle of a valve of the injection nozzle is moved ballistically, wherein in the third phase (4) the valve is fully open, and wherein the second phase (3) is a transition phase between the first phase (2) and the third phase (4), wherein the correction of the air-fuel ratio is carried out exclusively in the first phase (2) and the second phase (3). [7] Method according to any of the preceding claims, characterized by , that the correction value takes into account the extent of the corrections during the control process. [8] Motor vehicle comprising a control unit and an internal combustion engine as a drive, wherein the control unit is configured to perform a method according to one of the preceding claims.

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