KR20190035532A - Method for calibrating a force or pressure sensor - Google Patents

Abstract

The present invention relates to a method for calibrating a sensor (20) formed as a force sensor or a pressure sensor on or in a fuel injector (170) of an internal combustion engine (160) receiving a fuel from a high-pressure accumulator (175). The method detects one or more signal characteristic curves (S, S′) of the sensor (20) in one or more events including a fuel pressure change in the fuel injector (170), and one or more corresponding reference characteristic curves (R_1, R_2) of a reference sensor (190) for measuring a variable characterized by a pressure in a volume unit fluidly connected to the fuel injector (170). The sensor (20) is calibrated based on the one or more signal characteristic curves (S, S′), the one or more reference characteristic curves (R_1, R_2), and a transfer function between the reference sensor (190) and the sensor (20).

Description

METHOD FOR CALIBRATING A FORCE OR PRESSURE SENSOR [0002]

The present invention relates to a method for correcting a sensor provided for detecting the opening and / or closing of a fuel injector, formed as a force sensor or a pressure sensor in or in the fuel injector of an internal combustion engine, And a computer program.

Today's internal combustion engines include fuel injectors that allow fuel to flow into the combustion chambers as desired. In particular, for the precise control of the internal combustion engine, as well as compliance with exhaust emission and output requirements, the specific points of the injection processes, in particular the opening and closing of the injection valves of the fuel injectors and hence the injection start and injection end points, It is desirable to detect it as accurately as possible.

From DE 10 2010 000 827 A1 it is known, for example, a fuel injector in which the above-mentioned specific points can be deduced by providing a sensor for detecting pressure fluctuations.

According to the present invention, a computer unit and a computer program for performing the method as well as a method for correcting a sensor formed as a force sensor or a pressure sensor, each having the features of the patent independent claims, are proposed. Preferred embodiments are subject to the dependent claims and the following description.

The method according to the invention is used for correcting a sensor formed as a force sensor or a pressure sensor in or in the fuel injector of an internal combustion engine. In this case, the fuel injector is supplied with fuel from the high-pressure accumulator. Force sensors or pressure sensors on or in the fuel injector of an internal combustion engine are typically provided to detect the opening and / or closing of the fuel injector. In this case, the sensor may be provided in the fuel injector in the same manner as described in DE 10 2010 000 827 A1, or in a similar manner. A pressure fluctuation amount is detected by the so-called NC-sensor (Needle Closing Sensor) in the control chamber of the valve of the fuel injector or at another position, for example, the high pressure bore of the injector.

On the other hand, in one or more events involving pressure fluctuations in the fuel in the fuel injector, one or more signal characteristic curves of the sensor and one or more of the reference sensors measuring the variables characterized by the pressure in the volume part in fluid communication with the fuel injector A corresponding reference characteristic curve is detected. The sensor may then comprise one or more signal characteristic curves; One or more reference characteristic curves; And a transfer function between the reference sensor and the sensor. The reference sensor may in particular be arranged apart from the fuel injector.

Only the pressure fluctuations can generally be detected by the sensors mentioned above or on the fuel injector, which is sufficient to detect specific points of view such as the injection start point or the injection end point. In this regard, complicated electronic circuits are unnecessary. However, if, for example, an accurate determination of the pressure level (for example in the case of rail pressures, for validity checking if necessary) is required, for example, to know the level of pressure fluctuations, with the signals detected by the sensor, It is also necessary to immediately know the absolute level of the pressure fluctuation or sensor signal, or at least the relative level. In this case, deviations can also be significant over the useful life of the sensor.

Now, however, through the proposed calibration or adjustment using the reference sensor, in a very simple manner, a sensor on or within the fuel injector can also be used to obtain a meaningful signal on the absolute or relative pressure variation of the fuel in the fuel injector . In this case, as the reference sensor, in principle, all sensors capable of detecting the absolute or relative pressure fluctuation amount in the fuel volume portion in fluid connection with the injector are considered. In this case, a pressure sensor (so-called rail pressure sensor, RPS) for a high pressure accumulator (so-called rail) is very suitable because the pressure sensor is a sensor provided at all. In this case, the parameter characterized by the pressure in the volume part in fluid connection with the fuel injector is the rail pressure.

Because the reference sensor is provided spaced apart from the sensor, the different functions of the pressure fluctuations for one sensor and the other sensor can be taken into account by the transfer function. Although the pressure fluctuations are diffused based on the fuel circuit in fluid connection, different effects may occur in the fuel injector of the other side from the high pressure accumulator in one side, for example, through the throttle effect or the volumetric effect or pressure wave superposition. In this case, the transfer function may be predetermined in the range of, for example, simulation and / or test measurements, and stored in the executing computer unit.

As a matter of fact, corrections for a plurality or all of the sensors at or in the fuel injectors of the internal combustion engine can be performed in the same manner. The assignment of the sensor's signal characteristic curve to the actual pressure variation, which is determined in the category of correction, can then be stored in the characteristic map or the like.

Preferably, the one or more events include pressure fluctuations within the supply of the high-pressure accumulator, particularly through a pump head of the high-pressure pump, or pressure fluctuations in the high-pressure accumulator. The pressure fluctuations upstream or within the high pressure accumulator act uniformly on all of the fuel injectors so that a particularly simple correction can be performed in this manner. In addition, the value of the pressure variation during the pump heads is also generally known.

Preferably, the one or more events include a reduced pressure (or pressure drop) of the high pressure accumulator. For this purpose, a desired pressure reduction can be performed in a high pressure accumulator, for example using a pressure regulator or pressure regulating valve (DRV), which acts uniformly on all fuel injectors. Such an event is preferably set such that it does not take place between injections of injectors in order to prevent the effect of the injection by time.

As an alternative to the approach described above, for example, when DRV is not provided, or alternatively, it is also desirable that one or more events include injection of fuel through the corresponding fuel injector or other fuel injector of the internal combustion engine. In this way, a pressure drop may also occur through the associated high-pressure line and into the high-pressure accumulator, acting on other fuel injectors as well.

Particularly preferably, in a plurality of events involving different pressure fluctuations, one signal characteristic curve and one reference characteristic curve, each based on the correction of the sensor, are detected. In this way, the calibration of the sensor can be performed more accurately on the one hand, and on a larger scale, on the other hand. The different pressure fluctuations may be caused, for example, in the case of a pump head of a high-pressure pump, by a variation in the amount of fuel transferred. In the case where a pressure drop in the high pressure accumulator is caused as intended, the target pressure may be set to different values. And in the case of injection through a fuel injector, the pressure fluctuations can be variable by the injection durations at different times.

Preferably, the sensor is calibrated at preset, especially regular time intervals. In this way, any deviations that occur over the useful life of the sensor can be considered.

The correction should preferably be carried out in a period other than the normal injection processes since the correction is usually carried out in the usual injection processes or in the category of normal fuel transfers into the high pressure accumulator, Time is needed.

A control unit of a computer unit according to the present invention, for example an automobile, is configured to perform the method according to the present invention, in particular in terms of program technology, for example in a so-called correction mode.

It is also desirable to implement the above method in the form of a computer program, since this approach results in particularly low costs, especially if the running-side control device is used for other tasks anyway . Storage media suitable for providing computer programs are, in particular, magnetic, optical and electronic memories such as hard disks, flash memories, EEPROMs, DVDs, and the like. It is also possible to download the program via a computer network (Internet, intranet, etc.).

Further advantages and embodiments of the present invention are set forth in the specification and the accompanying drawings.

The invention is schematically illustrated in the drawings in accordance with embodiments and is described below with reference to the drawings.

1 is a schematic diagram of an internal combustion engine with a common rail system suitable for carrying out the method according to the invention;
Figure 2 is a schematic view of a solenoid valve in which the method according to the invention can be carried out.
Figure 3 is a signal characteristic curve in the performance of the method according to the invention in one preferred embodiment.
Figure 4 is a reference characteristic curve and signal characteristic curve in performing a method according to the present invention in another preferred embodiment.
Figure 5 is a graph showing correction in the performance of a method according to the invention in another preferred embodiment.

1, there is shown schematically an internal combustion engine 160 suitable for carrying out the method according to the present invention. By way of example, the internal combustion engine 160 includes four combustion chambers and associated cylinders 165, respectively. One fuel injector 170 including one sensor 20 is assigned to each combustion chamber 165. Each fuel injector 170 is connected to a high pressure accumulator 175, i.e., a so-called rail or common rail, and is supplied with fuel from the high pressure accumulator. As a matter of fact, the method according to the present invention can also be used in an internal combustion engine comprising any other number of cylinders, for example, one, two, three, five, six, eight, ten or twelve cylinders .

Further, the high-pressure accumulator 175 receives fuel from the fuel tank 195 via the high-pressure pump 161, and a low-pressure pump 196 may also be provided in the fuel tank. The high-pressure pump 161 is connected to the internal combustion engine 160, and more precisely, for example, in such a manner that the high-pressure pump is driven through the crankshaft of the internal combustion engine or through the camshaft which is again connected to the crankshaft.

Control of the fuel injectors 170 for metering and injecting fuel into each combustion chamber 165 is performed through a computer unit formed as an engine control unit 180. [ In this case, each fuel injector 175 can be controlled individually. Further, the engine control unit 180 is configured to detect the fuel pressure in the high-pressure accumulator 175 using the pressure sensor 190. [

A pressure regulating valve 191 for the high pressure accumulator 175 is also provided for regulating and setting the pressure in the high pressure accumulator, respectively. There is also shown an air exhaust system 141 for venting exhaust air or exhaust gas from cylinders 165 as well as an air supply system 140 for introducing air into cylinders 165, Are connected through a so-called turbocharger 141 and an exhaust gas recirculation valve 142 here.

In FIG. 2, a portion of the fuel injector 170 of FIG. 1 is shown schematically in more detail. In this case, the high-pressure chamber 2 and the low-pressure chamber 3 are disposed inside the injector body 1. [ The two chambers are separated from each other by a valve piece (4).

The high-pressure chamber 2 communicates with the high-pressure accumulator or the common rail according to FIG. 1 through the supply channel 5. The low-pressure chamber 3 is connected to the fuel tank according to Fig. 1 through a return line 21 or the like.

The high-pressure chamber 2 can be connected to the combustion chamber or the cylinder of the internal combustion engine according to Fig. 1 via fuel nozzles not shown. The injection nozzles are controlled by a nozzle needle in a known manner, and in Fig. 2 only the nozzle spaced end formed as a plunger (or control piston) 6 among the nozzle needles is shown. The plunger (6) is displaceably disposed in the control chamber (7) disposed in the valve piece (4). The control chamber 7 is in communication with the high pressure chamber 2 via a supply throttle 8 and is preferably in communication with the low pressure chamber 3 via a throttled discharge channel 9, ) Is controlled by the control valve assembly (10).

When the discharge channel is blocked by the control valve assembly 10 and the nozzle needle is in its closed position, the same high pressure as in the high-pressure chamber 2 is formed in the control chamber 7, The plunger 6 is compressed downward and the nozzle needle connected with the plunger is held in the closed position to block the injection nozzles.

When the discharge channel 9 is opened by the control valve assembly 10 (or through the lift of the valve armature or the closing body 11), a reduced pressure in the control chamber 7 compared to the high-pressure chamber 2 And the plunger 6 is displaced upwardly in Fig. 2 together with the nozzle needle, i. E. The nozzle needle is adjusted to its open position, whereby the fuel is injected into the combustion chamber through the injection nozzles.

The control valve assembly 10 comprises a sleeve-like closing body 11 (valve armature) which is clamped towards the seat concentric with respect to the outlet of the discharge channel 9 by a closing spring 12 formed as a helical compression spring . In the example of Fig. 2, the sheet is formed as a flat surface on which a sleeve-like closure body 11 rests as a linear annular edge. However, basically differently formed sheets can also be provided.

The sleeve type closed body 11 is axially displaceably guided on a guide rod 13 coaxial with the longitudinal axis 30 of the injector body 1 and is rotatably supported by the inner periphery of the closed body 11 and the guide rod 13 ) Is actually formed as a leak-free throttle gap or sealing gap. If the closed body 11 takes the closed position shown in Fig. 2, it is formed inside the closed body 11 and communicates with the control chamber 7 through the discharge channel 9, The pressure chamber 14 holding the same fluid pressure as the pressure chamber 7 is shut off against the low pressure chamber 3.

On the closing body 11, a star armature 15 of an electromagnet assembly 16, which is provided as an actuator for the operation of the control valve assembly 10, is disposed. The electromagnet assembly 16 includes a magnetic coil 17 in a known manner which includes an annular external pole 18 and an internal pole 19, Is disposed inside the electromagnet assembly which is concentric with respect to the rod (13). When the magnetic coil 17 is supplied with current, the armature 15 is magnetized by the poles 18 and 19 so that the closing body 11 is able to counteract the force of the closing spring 12, And the control valve assembly 10 is opened.

The control valve assembly 10 is closed during the closed phase of the nozzle needle connected with the plunger 6, that is to say when the injection nozzles are closed and not only within the pressure chamber 14 but also within the control chamber 7 The same fluid pressure is formed. Immediately before the nozzle needle is closed, the pressure in the control chamber 7 is lower than the high pressure in the supply channel 5 due to the low pressure at this point in the lower portion of the nozzle seat of the nozzle needle and consequent closing movement of the plunger 6 Descend. Immediately after closing the nozzle needle, a surge of pressure in the control chamber 7 occurs due to the now stationary plunger 6, and the control chamber pressure rises to the pressure in the supply channel 5.

Since the pressure of the control chamber 7 is also present in the pressure chamber 14 when the closing body 11 is closed, the guide rod 13 inside the closing body 11 is always controlled at the end face at the valve position It is loaded by the chamber pressure. Now, it is provided that the control chamber pressure is transmitted using the guide rod 13 to the sensor 20 schematically shown in Fig. 2, i.e., the force sensor or the pressure sensor. In this way, the signal of the sensor 20, which corresponds to the pressure characteristic curve in the control chamber and allows at least specific time points such as open and close times to be detected, can be obtained.

In other words, in the above configuration, the guide rod 13 is provided on the one hand to axially guide the sleeve-like closing body 11 and on the other hand to the pressure chamber 14 or the control chamber 7 communicating with the pressure chamber 14 And is used as a force transmitting member between the sensors 20, thereby having a dual function. Also preferably here, the sensor 20 in the low-pressure region of the fuel injector is disposed close to the opening of the return line 21 in the example shown in the figure.

The sensor 20 is preferably formed as a piezoelectric element capable of tapping with a voltage depending on the pressing of the guide rod 13. [ Unlike the illustrated embodiment in which the electromagnet assembly 16 is provided as an actuator, fuel injectors including other actuators may also be provided. Piezoelectric actuators that can vary in length depending on the applied voltage can be considered.

In Fig. 3, a signal characteristic curve is shown in performing the method according to the present invention in a preferred embodiment. In this regard, the voltage U of the sensor 20 is shown over time t.

In this case, the signal characteristic curve S is a signal representing the pressure or pressure fluctuation amount in the fuel injector detected and output by the sensor, in the case of the pump head of the high-pressure pump. In the case shown, the signal variance is confirmed by the value [Delta] U for a period [Delta] t after the start of the pump lift, for example.

The pressure sensor 190 on the high pressure accumulator, for example, is now used to detect and correspondingly convert the rail pressure as a parameter characterized by the pressure in the volume in fluid communication with the fuel injector 170, The allocation of the voltage change amount to the actual pressure change amount can be performed in the signal characteristic curve S. For the sake of conversion, the above transfer function can be considered.

Figure 4 schematically shows reference characteristic curves and signal characteristic curves in the performance of the method according to the invention in another preferred embodiment. In this regard, the pressure p in the high pressure accumulator (left graph) and the voltage U of the sensor (right graph) are shown over time.

In the left graph, a pressure drop in the high-pressure accumulator is caused, for example, by using a pressure regulating valve, based on two pressures (p ₁ and p ₂ ). Related pressure characteristic curves which can be used as reference characteristic curves (R ₁ and R ₂ ) in the context of the method according to the invention can be detected by a pressure sensor for a high pressure accumulator. In this case, the corresponding pressure drops in the high pressure accumulator are respectively? P ₁ and? P ₂ .

In the right graph, the signal characteristic curve S 'of the sensor in the fuel injector belonging to the reference characteristic curve R ₂ is shown. In this case, the signal characteristic curve S 'includes a voltage variation amount of? U'. That is, in this way, it is possible to perform the assignment of the voltage change amount to the actual pressure fluctuation amount within the signal characteristic curve S '(similar to the case according to Fig. 3). Again, the transfer function is considered to translate the pressure drop in the high pressure accumulator into the pressure drop in the fuel injector. It is emphasized here that each pressure drop in the reference characteristic curve (although only one signal deviation is shown in Fig. 3) is assigned a corresponding signal deviation in the signal characteristic curve.

5, in another preferred embodiment, in order to be able to perform the assignment of the voltage variation amounts [Delta] U in the signal characteristic curve to the actual pressure fluctuation amount [Delta] p, the correction in the performance of the method according to the present invention Respectively. Three characteristic curves (K ₁ , K _2, and K ₃ ) are shown that enable the allocation of the voltage variation of the sensor to the actual amount of pressure variation for different initial pressures in the high pressure accumulator and thus correction. In this case, an adjustment to the different amplitudes of the sensor signal is also considered.

It is also contemplated that the amount of pressure variation in the fuel injector for different initial pressures in the high pressure accumulator may affect the sensor or associated signal characteristic curve differently.

Claims (10)

A method for calibrating a sensor (20) formed as a force sensor or pressure sensor in or in a fuel injector (170) of an internal combustion engine (160) fed from a high pressure accumulator (175)
At least one event characteristic curve (S, S ') of the sensor 20 and a pressure in the volume portion in fluid communication with the fuel injector 170 are obtained at one or more events including fuel pressure fluctuations in the fuel injector 170 One or more corresponding reference characteristic curves (R ₁ , R ₂ ) of the reference sensor 190 for measuring the variables characterized by the reference characteristics are detected,
The sensor (20) comprises one or more signal characteristic curves (S, S '); One or more reference characteristic curves (R ₁ , R ₂ ); And a transfer function between the reference sensor (190) and the sensor (20). The method of claim 1, wherein a pressure sensor for the high pressure accumulator (175) is used as the reference sensor (190). The system according to any one of the preceding claims, wherein the one or more events are selected from the group consisting of a pressure fluctuation in the supply portion of the high pressure accumulator (175), particularly through a pump head of the high pressure pump (161) And the sensor calibration method. 4. A method according to any one of claims 1 to 3, wherein the at least one event comprises a reduced pressure of the high pressure accumulator (175). 5. A method according to any one of claims 1 to 4, wherein the at least one event comprises the injection of fuel through the fuel injector (170) or another fuel injector of the internal combustion engine (160). 6. The method according to any one of claims 1 to 5, characterized in that in a plurality of events comprising different pressure fluctuations (? P ₁ ,? P ₂ ), each one signal characteristic curve (S, S ') and one reference characteristic curve (R ₁ , R ₂ ) are detected. 7. A sensor calibration method according to any one of claims 1 to 6, wherein the sensor (20) is calibrated in a predetermined, especially regular, time interval. A computer unit (180) configured to perform the method according to any one of claims 1 to 7. A computer program that, when executed on a computer unit (180), causes the computer unit (180) to perform the method according to any one of claims 1 to 7. 10. A machine-readable storage medium having stored thereon a computer program according to claim 9.

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