JP2008516153A - Method and apparatus for monitoring fuel injection - Google Patents

Abstract

The present invention monitors a fuel injection in a diesel engine using an injector connected to an internal combustion engine, in particular a shared high pressure reservoir (common rail), for the purpose of detecting possible defects in the fuel injection system and It relates to an apparatus for carrying out the method. The method uses a high pressure pump valve activation signal to detect defects, and further uses pressure, fuel volume and fuel temperature measurements, filtering and balance checking.
[Selection] Figure 1

Description

  The present invention monitors a fuel injection in a diesel engine using an injector connected to an internal combustion engine, in particular a shared high pressure reservoir (common rail), for the purpose of detecting possible defects in the fuel injection system and The present invention relates to an apparatus using the method.

Background of the invention

  Common rail fuel injection systems for internal combustion engines are well known in the art. In this system, high-pressure fuel supplied from a high-pressure fuel pump is stored in a shared reservoir (ie, common rail). The high pressure fuel in the rail is injected into each cylinder of the engine through an injector connected to the common rail. In summary, the rail serves as a reservoir that stores high pressure fuel and distributes it to each fuel injector.

  The rail pressure depends on the opening of the valve, which is activated by an electronic control unit (ECU). The ECU measures the difference between the actual pressure value and the required pressure value, thereby generating a valve open / close signal.

  However, the common rail injection system may suffer from defects such as fuel leakage from the reservoir, overflow in the injector, clogging of the fuel filter, malfunction of the high pressure pump, blocking of the fuel return line, and the like. Said defects can result in high fuel consumption and even engine failure. Therefore, it is well known in the prior art to provide the injection system with a fuel injection system defect detection means.

For example, Japanese patent number JP8-4777--.
Disclosed is a fuel injection system having a pressure sensor for detecting a pressure in the common rail, and a means for measuring a pressure difference in the common rail before and after fuel injection from the fuel injection valve, that is, a pressure drop in the common rail during the fuel injection period. ing. Further, the defect detection means evaluates the pressure of the common rail before and after fuel injection, and determines that the injection system is defective when the pressure difference is greater than a predetermined limit.

Another prior art document, namely European Patent Application No. EP 0860601-.
An electronic control unit (ECU) is disclosed that measures the pressure and temperature of fuel in a common rail and determines the bulk modulus of fuel based on the pressure and temperature of the fuel. The ECU uses the determined bulk modulus to calculate an estimate of the change in pressure in the common rail during the fuel injection period. If the difference between the estimated value of pressure change and the pressure change actually measured within the fuel injection period is large, the ECU determines that the fuel injection system has failed.

Another European patent application number EP 1336745--
In order to evaluate the amount of fuel actually injected into the engine, the intake air flow rate and the exhaust gas lambda are measured and the calculated fuel amount is calculated to substantially meet the needs of the vehicle user. Describes a method for controlling injection of an internal combustion engine of a vehicle, in which closed-loop control is performed so as to be equal to the fuel amount of Furthermore, the difference between the nominal fuel quantity and the estimated fuel quantity is used to calculate a correction factor by which the nominal fuel quantity is corrected.

US Patent No. US5727516--.
The fuel pressure in the shared fuel supply line between the end of injection and the start of the fuel supply period is monitored at clearly timed measurement points, and the pressure difference between the measurement points is activated by the injector. When detected above a predetermined limit value indicating a failure, the high pressure fuel supply to the shared fuel supply line is shut off by shutting off the high pressure fuel pump and at the same time the pressure in the shared fuel supply line is rapidly reduced. In order to do so, a method for controlling the operation of an internal combustion engine is disclosed, in which fuel injection through the working nozzle is maintained.

  In summary, in the prior art, the control method is mainly focused on measuring the pressure value in the common rail. However, in the common rail type fuel injection system, the fuel pressure in the common rail varies in a very wide range in order to control both the total fuel injection amount and the injection speed according to the operating conditions of the engine. For some applications, the pressure ranges from 10 MPa to 150 MPa. In such a common rail fuel injection system, the change is so great that it is impossible or inaccurate to determine the defect by measuring the pressure.

  Further, conventional methods utilize values measured when the engine is operating at idle. However, the operating state, i.e., the value when the vehicle is running, is significantly different from the idling value. This is one factor that makes accurate defect detection difficult.

It is an object of the present invention to provide a means for the accurate determination of fuel injection system deficiencies.
Another object of the present invention is to determine fuel injection system deficiencies under transient conditions.

The above objective is achieved by a defect detection method based mainly on the measurement and processing of the start signal from the ECU to the high pressure pump valve.
The ECU generates an activation signal that controls opening / closing of the valve to maintain a predetermined level of fuel pressure in the rail. The activation signal is a function of the total amount of fuel flowing through the injector per stroke, the target pressure in the rail, the engine speed, and the fuel temperature. Based on this relationship, the present invention uses the activation signal for defect detection and further uses pressure, engine speed, and fuel temperature measurements.

  The central function of defect detection is triggered only when all filtered input variables are within certain limits and the balance flag is TRUE. Corrections depending on the fuel quantity and temperature are applied to the activation signal. The central function generates a general defect message if the modified activation signal is outside a predetermined calibration period.

DESCRIPTION OF PREFERRED EMBODIMENTS

(Detailed Disclosure of the Present Invention)
The present invention is described in detail below with reference to the accompanying drawings.
FIG. 1 shows a flowchart of the method.
FIG. 2 shows a flow chart of the balance check block.

FIG. 3 is a schematic diagram of the setup for the method.
The setup for application of the method of the invention (FIG. 3) includes a pressure sensor in the rail to measure the actual pressure value. On the other hand, the engine speed (n) is preferably sensed by a sensor located on the output shaft of the engine. There are also temperature sensors located in the fuel system. The ECU receives signals from the sensors described above and processes the signals to detect possible defects.

  According to the method, the actual fuel pressure value (P actual), the engine speed (n) and the actual fuel temperature (T fuel) are measured when the vehicle is running, ie under transient conditions. The measurements can be sampled continuously or at predetermined time intervals. The ECU generates an activation signal on the valve to keep the valve open. The magnitude of this signal is i valve. The ECU immediately calculates the target pressure (p set) and the intended fuel injection amount (q inj). If all of these values, i.e. P actual, T fuel, i valve, p set, q inj and n meet certain criteria, the ECU generates a fault message.

As shown in FIG. 1, the method has the following steps:
-Measure the start signal (i valve) from the ECU to the valve of the pressure pump;
-Apply an equilibrium check (EQLCHECK) to this signal (i valve) to determine if it is in equilibrium;
-Measure the actual pressure (P actual) in the rail;
-Calculate the difference (P diff) between the actual pressure (P actual) value and the preset pressure (P set) value calculated immediately by the ECU;
-Apply an equilibrium check (EQLCHECK) to the pressure difference value (P diff) to determine if it is in equilibrium;
-Apply a filter to the actual pressure value (P actual) and make sure that the filtered value is within the interval represented by the predetermined minimum pressure value (P min) and maximum pressure value (P max). Check;
-Measure engine speed (n);
-Apply a filter to engine speed (n) and ensure that the filtered value is within the interval defined by the preset minimum speed value (n min) and maximum speed value (n max) Do;
-Take the target injected fuel quantity (q inj) calculated by the ECU:
-Apply a filter to the fuel quantity (q inj) and the filtered value is within the interval defined by the preset minimum fuel quantity (q min) and maximum fuel quantity (q max) Check if it exists;
-Measure the fuel temperature (T fuel);
-Apply a filter to the fuel temperature (T fuel) and the filtered value is defined by the preset minimum fuel temperature value (T min) and maximum fuel temperature value (T max) Check whether it is inside;
-Apply a filter to the activation signal (i valve) and the filtered value is within the interval defined by the preset minimum signal value (i min) and maximum signal value (i max). Check whether or not;
-Determine the correction value (i corr) of the starting signal (i valve) from the correction map using the value of the fuel temperature (T fuel) and the injection amount (q inj);
― If a) the starting signal (i valve) and the pressure difference (P diff) are in equilibrium, and b) the actual pressure (P actual), the engine speed (n) and the fuel quantity (q inj) And the fuel temperature (T fuel) are within the respective filter settings, then the next modified signal is pre-set minimum start signal value (i min) and maximum start signal value (i max) Check if it is within the range defined by
If the result of this check is negative, generate a general failure message indicating that a problem exists in the fuel injection system.

The filter used in the system is preferably a primary system:
y (k) = a * y (k-1) + (1-a) * x (k)
Where k is the index signal or measured signal of the same filter, x is its input signal, and y is its output signal. In the above equation, a is a parameter defined by the manufacturer and / or user. If the value of a is close to 0, the y (k) value is close to the x (k) value. On the other hand, if a is closer to 1, the gap between the x (k) and y (k) values increases. This filter is provided here for clarity purposes only, and those skilled in the art can develop many filters that are equally suitable for the purposes of the present invention.

  For greater accuracy, the minimum pressure value (P min) and the maximum pressure value (P max) in the pressure filter are not entered as preset values in the system, rather they are the fuel quantity (q inj ) Is calculated immediately using the measured value. This takes into account the influence of the fuel quantity (q inj) on the actual pressure (P actual), thus giving even greater accuracy. In this embodiment of the invention, two experimentally or computationally determined tables / related fuel quantities (q inj) are associated with the minimum pressure value (P min) and the maximum pressure value (P max). A curve / function is used. Accordingly, the measured fuel quantity (q inj) is used to determine the instantaneous minimum and the instantaneous maximum limit for the pressure filter.

  In yet another embodiment of the invention, the filtered value of fuel quantity (q inj) is used to determine a modified value (i corr) of the start signal as well as the value of fuel temperature (T fuel). Is done.

In the preferred embodiment of the invention, the activation signal is a current signal, but in other embodiments it may be a voltage signal.
On the other hand, the minimum activation signal value (i min) and the maximum activation signal value (i max) with which i corr is compared are determined statistically by examining a number of normal and failed vehicles.

  As shown in FIG. 2, in the preferred embodiment of the present invention, the balance check is made by applying at least two, preferably three, different filters to the input values. Each filter may have a different time constant. The absolute value of the difference between the output of each of two or more filters, for example, the first and second, and the first and third, is evaluated. The absolute value is compared against at least two constant predetermined limits, ie LIM1 and LMT2. The result of this balance check is positive if the absolute values are both less than their corresponding limits. The number of filters and their corresponding limits can be adjusted according to the desired accuracy, allowable calculation time, etc. If the input value changes rapidly, the outputs of the three filters are very different from each other. However, as the input value reaches equilibrium, the output becomes less different.

In summary, the present invention provides an accurate and fast way to predict failures in a fuel injection system. The fact that the measurements are made during transient conditions improves accuracy.
The present invention has been described in non-limiting examples above and in the accompanying drawings. However, the present invention is not limited to the presented examples. The present invention is as described in the claims.

FIG. 1 shows a flowchart of the method. Fig. 4 shows a flow chart of an equilibrium check block. FIG. 4 is a schematic diagram of a setup for the method.

Claims (5)

In a method for monitoring fuel injection in an internal combustion engine, in particular a diesel engine using an injector connected to a shared high-pressure reservoir (common rail), and detecting possible defects in the fuel injection system,
Measuring the activation signal (i valve) from the electronic control unit (ECU) to the valve of the pressure pump;
Applying an equilibrium check (EQLCHECK) to the signal (i valve) to determine if it is in equilibrium;
Measuring the actual pressure (P actual) in the rail;
Calculating the difference (P diff) between the actual pressure (P actual) under operation and the pressure (P set) value calculated by the ECU;
Applying an equilibrium check (EQLCHECK) to the pressure difference value (P diff) to determine whether it is in equilibrium;
Apply a filter to the actual pressure value (P actual) and check that the filtered value is within the interval represented by the predetermined minimum pressure value (P min) and maximum pressure value (P max) Step to do;
Measuring the engine speed (n);
Applying a filter to engine speed (n) and checking that the filtered value is within the interval defined by the preset minimum speed value (n min) and maximum speed value (n max) When;
Taking the target injected fuel quantity (q inj) calculated by the ECU:
A filter is applied to the fuel quantity (q inj) and the filtered value is within an interval defined by a preset minimum fuel quantity (q min) and a maximum fuel quantity (q max). A step to check that;
Measuring the fuel temperature (T fuel);
A filter is applied to the fuel temperature (T fuel) and the filtered value is within an interval defined by a preset minimum fuel temperature (T min) and maximum fuel temperature (T max). A step to check that;
Apply a filter to the activation signal (i valve) and make sure that the filtered value is within the interval defined by the preset minimum signal value (i min) and maximum signal value (i max) A step to check;
Determining a correction value (i corr) of the starting signal (i valve) from the correction map using the value of the fuel temperature (T fuel) and the injection amount (q inj);
If a) the start signal (i valve) and the pressure difference (P diff) are in equilibrium, and b) the actual pressure (P actual), the engine speed (n), the fuel quantity (q inj) Once it is found that the fuel temperature (T fuel) is within the respective filter settings, then the modified signal is pre-set with the minimum start signal value (i min) and the maximum start signal value (i max) ) Checking whether it is within the range defined by
Generating a general failure message indicating that a problem exists in the fuel injection system if the result of the check is negative. The method according to claim 1, wherein the minimum pressure value (P min) and the maximum pressure value (P max) are evaluated using the intended value of the fuel injection quantity (q inj) calculated by the ECU. A method characterized by. 3. A method according to claim 1 or claim 2, wherein the filtered value of the fuel quantity (q inj), together with the value of the fuel temperature (T fuel), determines the correction value (i corr) of the starting signal. A method characterized in that is also used. 4. The method according to any one of claims 1 to 3, wherein the minimum activation signal value (i min) and the maximum activation signal value (i max) with which the correction value (i corr) is compared are a number of normal Characterized in that it is statistically determined by investigating the vehicle and the faulty vehicle. A method according to any one of claims 1 to 4, wherein the balance check is
Applying at least two different filters to the input values, each filter having a different time constant;
Evaluating the absolute value of the output difference for each of the two or more filters;
Comparing the absolute value against at least two predetermined predetermined limits, namely LIM1 and LMT2;
A method comprising: affirmative if both absolute values are less than their corresponding limits, negative if otherwise, and outputting the result of the check.

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