Patent ID: 12235146

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG.1shows a schematic illustration of an injection system100, for example for an internal combustion engine. The injection system100has a high-pressure pump110, a high-pressure region120, a pressure sensor130, and multiple injectors140.FIG.1additionally shows a control unit200that is configured to control the injection system100. During the operation of the injection system100, fluid is delivered from a fluid accumulator (not shown) into the high-pressure region120by way of the high-pressure pump110, whereby the pressure of the fluid is additionally increased by way of the high-pressure pump110to the desired pressure. The high-pressure region120has a rail which is connected to the injectors140and from which the injectors140are fed with fluid. The control unit200actuates the injectors140, whereby the fluid is injected from the high-pressure region120into combustion chambers, for example of the internal combustion engine, for combustion. The pressure sensor130detects a measurement signal310(shown inFIG.2) that characterizes the pressure profile of the pressure within the high-pressure region120. The pressure sensor130transmits the measurement signal310to the control unit200, which in turn processes the measurement signal310and controls the injection system100based on the results.

FIG.2shows a first pressure profile diagram300. In the first pressure profile diagram300, the measurement signal310of the pressure sensor130is plotted versus the time. The measurement signal310is segmented into a first pressure region320, an injection region330, a second pressure profile340, and a pump region350. The first pressure profile320represents the profile of the pressure signal prior to the injection using the injector140. The injection region330represents the profile of the measurement signal310during the injection using the injector140. It can be seen here that the pressure within the high-pressure region120decreases due to the injection using the injector140. The second pressure profile340represents the profile of the measurement signal310after the injection using the injector140and before the pumping phase in which fluid is introduced into the high-pressure region120using the high-pressure pump110. The pump region350of the measurement signal310represents the profile of the measurement signal310during the pumping phase. It can be seen here that the pressure within the high-pressure region120increases due to the introduction of fluid into the high-pressure region120using the high-pressure pump110.FIG.2additionally illustrates the pressure difference360between the first pressure profile320and the second pressure profile340. The times required for the segmentation are known, because the control unit200itself performs the actuation of the injectors140. In this way, the measurement signal310of the pressure sensor130can be advantageously easily and accurately segmented. The method is additionally robust with respect to slight time shifts.

FIG.3shows a first kernel density estimation diagram400, with a first probability density function410and a second probability density function420being illustrated in the first kernel density estimation diagram400. With the kernel density estimation, it is sought to ascertain the pressure value with the statistically greatest probability of presence. In order to ascertain the pressure value within the first pressure profile or within the second pressure profile, that is to say during the plateau phases prior to the injection or after the injection, of the phases with relatively constant pressure in the injection system100. The first probability density function410accordingly has a first maximum, a first pressure level430prior to the injection using the injector140. The second probability density function420has a second maximum, a second pressure level440after the injection using the injector. The first pressure level430and the second pressure level440are illustrated inFIG.3. The pressure difference450that arises due to an injection using an injector140can be advantageously accurately ascertained from these pressure levels430,440. The method is advantageously robust with respect to briefly occurring extreme values (for example, brief high or low pressure values).

FIG.4shows a second pressure profile diagram500. The second pressure profile diagram500illustrates a first pressure profile510, a second pressure profile520and a third pressure profile530in bar versus the time. The first pressure profile510starts at approximately 355 bar and is initially constant until the point in time at which the pressure falls to approximately 345 bar due to an injection using the injector140, whereupon the first pressure profile is subsequently constant until it increases due to a pumping phase. The second pressure profile520initially starts at approximately 352 bar and is subsequently constant, then decreases to approximately 347 bar due to an injection, subsequently remains constant, and subsequently increases again due to a pumping phase. The third pressure profile530starts at approximately 351 bar, is subsequently constant, decreases slightly to 350 bar due to a relatively small injection, and is subsequently constant. A subdivision of the pressure profiles into pre-injection and post-injection is illustrated inFIG.4on the basis of the line thicknesses. The greater line thickness represents the pressure profiles prior to the respective injection, whereas the smaller line thickness represents the pressure profiles after the respective injection using the injector140.

FIG.5shows a kernel density estimation diagram600, illustrating a first probability density function610relating to the first pressure profile510, a second probability density function620relating to the first pressure profile510, a first probability density function630relating to the second pressure profile520, a second probability density function640relating to the second pressure profile520, a first probability density function650relating to the third pressure profile530, and a second probability density function660relating to the third pressure profile530. Here, the first probability density functions610,630,650each represent the probability density functions prior to the injection using the injector140. Here, the second probability density functions620,640and660represent the probability density functions after the injection using the injector.FIG.5additionally shows a first pressure difference670, a second pressure difference680and a third pressure difference690. The first pressure difference670is the difference between the maximum of the first probability density function610of the first pressure profile510and the second probability density function620of the first pressure profile510. The second pressure difference680is the difference between the maxima of the second probability density function630of the second pressure profile520and the second probability density function640of the second pressure profile520. The third pressure difference is the difference between the maxima of the first probability density function650of the third pressure profile530and the second probability density function660of the third pressure profile530. Accordingly, the pressure difference of the individual injections using the injector can be advantageously easily and accurately ascertained on the basis of the ascertained maxima/the peaks.

FIGS.4and5show that, due to the good robustness of the method, it is sufficient for the measurement signal of the pressure sensor to be segmented merely into a segment prior to the injection and a segment after the injection in order to achieve an advantageously good and accurate ascertainment of the fluid injection quantity.

FIG.6shows a diagram with pressure profiles that have been transformed using a fast Fourier transformation (FFT). The diagram700illustrates a first FFT pressure profile710at 250 bar, a second FFT pressure profile720at 300 bar, and a third FFT pressure profile730at 350 bar. The frequency in hertz is plotted on the X axis. The amplitude in the unit [bar] as illustrated on the Y axis. The diagram700shows the pressure profiles in the case of a constant temperature. The peaks of the profiles represent different oscillation modes. It can be seen from the diagram how the natural frequency of the individual oscillation modes increases with increasing pressure. The peaks shift to the right with increasing pressure. This is attributable to the fact that the speed of sound of the fluid increases due to an increased pressure. By inference, it is possible from this to ascertain the speed of sound as a function of the pressure. This in turn is used in ascertaining the injection quantity. The accuracy with which the injection quantity is ascertained can thus be additionally further increased.

FIG.7shows a correlation diagram800. Each point in the correlation diagram800corresponds to an individual injection, for which the pressure in the high-pressure region, the temperature and the injection duration have been varied. The injection quantity measured using the Akribis measuring system is shown on the X axis, and the injection quantity ascertained using the method according to the present disclosure is illustrated on the Y axis. Akribis is an injection quantity measuring system that ascertains the injection quantity using a test stand. It involves a piston (one per injector) that is deflected as a result of the injection. The injected mass can be determined very accurately from piston area, deflection and density of the test medium. This type of measurement system is referred to as a quantity indicator. As an alternative to this, there are also pressure indicators (for example Mexus 2.0) or pipe indicators. The system constant was set in a one-off manner for the injection system under test, and thus for the entire data set, in accordance with this correlation diagram. The system constant was ascertained using regression. It can accordingly be seen from the correlation diagram800that the ascertainment of the fluid injection quantity in accordance with the present method advantageously accurately corresponds to the actually injected quantities ascertained by series of measurements.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.