EP1926900A1

EP1926900A1 - Method and device for monitoring a fuel metering system

Info

Publication number: EP1926900A1
Application number: EP06793414A
Authority: EP
Inventors: Hans Georg Bossemeyer; Michael Hackner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2005-09-15
Filing date: 2006-09-11
Publication date: 2008-06-04
Anticipated expiration: 2026-09-11
Also published as: JP2009508054A; DE102005043971A1; US20090199627A1; CN101263291A; KR20080055832A; KR101046825B1; CN101263291B; EP1926900B1; JP4646261B2; WO2007031492A1; US8191411B2

Abstract

A device and a method for monitoring a fuel metering system are described, in which system fuel is fed from a low-pressure region into a high-pressure region. The pressure in the high-pressure region is sensed. A fault is detected on the basis of the pressure profile in the high-pressure region. The type of fault is detected on the basis of the shape of a pressure reduction curve. The profile of the pressure variable over time is approximated with a function such as a hyperbolic function. The type of fault is identified on the basis of the variable which characterizes the function.

Description

description

title

Method and device for monitoring a fuel metering system

The invention is based on a method and a device for monitoring a Kraftstoffzumesssystems according to the preamble of the main claims.

From DE 195 20 300 a device for detecting a leak in a fuel supply system in an internal combustion engine, in particular a self-igniting internal combustion engine is known. In the device described there is the

Fuel from at least one fuel pump under pressure from a fuel tank in a so-called high pressure area promoted. From the high pressure region of the fuel via injectors, which are commonly referred to as injectors, enters the individual combustion chambers of the internal combustion engine. Usually, the pressure in the high pressure region is detected by means of a pressure sensor. This pressure sensor is usually used to adjust or regulate the pressure in the high pressure range. In the prior art, the pressure is evaluated so that the pressure curve is detected and compared with an expected pressure curve. In the event of a deviation between an expected pressure curve and the actual pressure curve, the device detects a leak.

The disadvantage of this type of error monitoring is that it is only recognized whether a leak occurs or whether there is no leakage.

According to the invention, it has been recognized that different errors result in different pressure profiles. In particular, it was recognized that the leakages differ by the type of flow. In particular, a distinction is made between laminar and turbulent flows. Furthermore, pressure-dependent leak widening or leakage shrinkage are possible. This means that the cross-sectional area of the leakage opening changes depending on the pressure. This gives rise to the possibility that out of the form of Pressure drop curve and the leakage type is detected. By assigning the measured pressure profile to predetermined pressure curves, which occur with certain leakages or which occur in the event of a defect of various components, the error can be reliably assigned to a specific type of fault and thus to the defective component. That is, based on the course of the pressure, the type of error and thus the defective component can be reliably detected. In particular, this approach allows a much safer leakage detection. With the conventional procedure, a leakage is detected in any case in case of a deviation. With the new invention, certain pressure gradients that are not based on leakage, but identified in the prior art as leakage, certainly recognized as such. As a result, unnecessary error reactions, such as the replacement of components, can be avoided.

It is particularly advantageous if the course of the pressure variable over time is approximated by a function. This approximation of the pressure curve yields at least one or more variables characterizing the function. This means that the characteristic quantities which best approximate the pressure curve are determined. Based on this characterizing size, the type of fault and / or the defective component is detected.

drawing

FIG. 1 shows the essential elements of a fuel metering system

Block diagram shown. FIG. 2 shows the procedure according to the invention and FIG

In Figure 3, different pressure curves over time applied.

Description of the embodiment

FIG. 1 shows, by way of example, essential elements of a fuel metering system, in particular a diesel internal combustion engine. With 100, the internal combustion engine is designated. This fuel is supplied via a first injector 110 and a second injector 120. The injectors 110 and 120 are connected via fuel lines with a rail 130 in connection. At least one sensor 140, which emits a pressure variable p which characterizes the pressure in the high-pressure region, is arranged on the rail. This print size is also referred to as rail pressure in the following. Instead of the output signal of the sensor 140, other variables characterizing the rail pressure can be evaluated accordingly.

The rail 130 is acted upon by a high-pressure pump 150 with fuel. This

High-pressure pump is associated with an actuating element 160, with which the amount of fuel delivered by the high pressure pump 150 and thus the rail pressure can be controlled. This control element 160 and the injectors 110 and 120 are acted upon by a control unit 170 with drive signals. The control unit also processes the output signal p of the sensor 140. Usually, the rail and the line between the high-pressure pump 150 and the injectors as high-pressure region and the area before the high-pressure pump is referred to as low-pressure region.

In the illustrated embodiment, only two injectors are shown. The procedure is applicable to any number of injectors. For clarity, only two injectors are shown. It can also be provided more adjusting elements. Thus, in particular, a further adjusting element can be provided by means of which the rail pressure can be controlled. Such an actuating element is designed, for example, as a solenoid valve which connects the high-pressure region to the low-pressure region. Furthermore, the control unit evaluates the signals of further sensors or controls further control elements for controlling the internal combustion engine 100. Furthermore, the approach is not limited to systems with a rail. It can also be used on systems with multiple rails or even on systems without a rail. Instead of the rail pressure then a size corresponding to the rail pressure is evaluated.

The high-pressure pump 150 conveys the fuel from the low-pressure region, which in particular comprises the tank, into a high-pressure region, which in particular includes the rail 130. The amount of fuel delivered and thus the rail pressure can be adjusted by means of the first control element 160. This is preferably done by a control, which is part of the control unit 170. For this purpose, the control unit 170 detects the rail pressure p via the sensor 140 and compares it with a desired value and controls the actuating element 160 as a function of the deviation between the setpoint and the actual value. From the high pressure region of the fuel passes through the injectors 110 and 120 in the internal combustion engine. The injectors essentially contain an actuator, which can be designed as a solenoid valve or as a piezoelectric actuator. The control unit 170 acts on the - A -

Injectors 110 and 120 with such signals that the fuel is supplied at a predetermined time or to the predetermined angular position of the crankshaft of the internal combustion engine in a predetermined amount.

In such a system, a variety of errors may occur. Thus, the case may occur that leakage occurs in the high pressure region, i. that fuel from the high pressure area in the low pressure area or in the environment passes. Furthermore, the case may occur that an increased amount of fuel enters the internal combustion engine through the injectors. Such errors must be reliably detected. Usually, these errors are detected and signaled to the driver or stored in the control unit and read out as part of the maintenance. If such an error occurs, the error must be carefully searched during maintenance. According to the invention, it has now been recognized that the error can be assigned to a specific component of the system on the basis of the pressure profile. In particular, it was recognized that different pressure gradients occur with leaks of different components.

According to the invention, it is now provided that the pressure profile is evaluated and compared with different, in particular stored, pressure profiles. On the basis of this comparison, on the one hand the leakage is reliably detected and, on the other hand, the leakage of a specific component is assigned.

In Figure 2, the erfmdungsgemäße procedure is shown in detail as a flow chart. In a first step 200, it is checked whether an operating state exists in which a check is possible. If this is not the case, the query 200 takes place after a waiting time has elapsed. If the query 200 recognizes that a check is possible, then

Step 210 deliberately causes conditions that are necessary for testing. Thus, inter alia, in step 210, the high-pressure region is subjected to a test pressure. Furthermore, it is ensured by controlling the adjusting elements for regulating the rail pressure, in particular of the actuating element 160 and by controlling the injectors 110 and 120, that no further fuel is conveyed into the rail or removed from the rail. If additional actuators are provided, these must also be controlled accordingly. In step 220, the pressure curve over time or over the rotation of the crankshaft is then recorded. Subsequently, in step 230, the exponent of the pressure drop curve is determined. According to the invention, it was recognized that, in the event of a leakage, the pressure-dependent leakage flow rates and pressure change rates P tenzfünktionen the pressure to follow. Correspondingly, in the event of a leakage, the pressure drop over time or over the angular position of the crankshaft approximately follows a so-called hyperbolic function with exponent. In the special case of laminar flow without pressure-dependent leakage gap widening or shrinking, the pressure drop over time approximately follows an exponential function.

This means that different pressure values are recorded at different times or angular positions of the crankshaft or camshaft. Subsequently, the power function of the pressure change rate is determined above the pressure with which the power function comes closest to the measured values. In this case, arbitrary approximation methods can be used, in particular the adaptation of a hyperbolic or exponential function to the pressure curve over time.

According to the invention, it has been recognized that different flows, in particular flows with and without pressure-dependent leakage gap widening, have different exponents. There are various errors that correspond to leakage flows with and without pressure-dependent leakage gap widening. This means that the type of error can be detected on the basis of the exponent and thus assigned to a specific component or a small number of components. This assignment takes place in query 240. In this example, depending on the value of the exponent, a first error 250 or a second error 260 is detected. This is preferably done by storing the values of the exponent for different errors and / or for the error-free state in a characteristic field or in a characteristic curve or in a table. The query 240 then checks which of these stored values the measured exponent comes closest to and assigns a stored value to the exponent. From the

Table can then be read based on the stored exponent of the corresponding error. In this case, usually a certain range of values of the exponent will be assigned to a type of error.

As an alternative to the hyperbolic function, other functions that describe the pressure drop over time or the angular position can also be used. In particular, the course can be approximated with a straight line. In this case, for example, a size that characterizes the steepness of the pressure drop may be used. According to the invention, arbitrary functions for describing the pressure profile and any variables characterizing this function can be used to identify the type of fault or the defective component. In particular, exponential functions are also suitable.

FIG. 3 shows by way of example two curves of the rail pressure with and without pressure-dependent leakage gap widening over time. It can be seen from this figure that, when the pressure value is monitored at a specific point in time t 1, the pressure at different pressure curves has fallen to the same value. By means of an evaluation of the pressure at one or a few points in time is a

Assignment of the error to a component or a type of error is not always possible.

Claims

claims

1. A method for monitoring a fuel metering system in which fuel is conveyed from a low-pressure region into a high-pressure region, wherein a pressure variable characterizing the pressure in the high-pressure region is detected and an error is detected on the basis of the pressure variable, characterized in that starting from the course of the Print size the nature of the error is detected.

2. The method according to claim 1, characterized in that the course of the large pressure over time approximated by a function, a function characterizing the size determined and based on the function characterizing size the nature of the error is detected.

3. The method according to claim 1, characterized in that starting from the slope of the print size, the type of error is detected.

4. The method according to claim 2, characterized in that the print size is approximated with a hyperbolic function and, based on the exponent of the hyperbolic function, the type of error is detected.

5. The method according to claim 1, characterized in that starting from the course of the print size, the defective component is detected.

6. An apparatus for monitoring a Kraftstoffzumesssystems, is conveyed in the fuel from a low pressure region in a high pressure region, with means which detect the pressure in the high pressure region characterizing pressure variable and recognize from the course of the pressure variable an error, characterized in that means are provided that detect the nature of the error based on the progression of the print size.