JP3727339B2 - Fault diagnosis method in high pressure circuit of internal combustion engine high pressure injection device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault diagnosis method in a high pressure circuit of an internal combustion engine high pressure injection apparatus.
Prior art high pressure injectors essentially have a fuel tank and a high pressure injector supply circuit, which itself has a pump that supplies fuel to the manifold at high pressure. Further, fuel is supplied to a plurality of injectors by this pump. This pump has a pressure regulating solenoid valve for supplying fuel at a predetermined pressure.
What is important in this type of device is that the high-pressure circuit is continuously used to prevent the operation of the device from being disturbed by fluctuations in setting adjustments in the pressure sensor, failure of the control member or injector, or leakage in the circuit. To monitor.
DISCLOSURE OF THE INVENTION An object of the present invention is to provide a diagnostic method that can immediately indicate any failure or malfunction if it occurs.
According to the invention, the object is to monitor the quantity correlated with the pressure generated by the high-pressure pump in successive control cycles and to compare the pattern of the quantities in the successive cycles with a reference value. And a step of generating a fault signal if the pattern does not have a predetermined relationship with a reference value, and the control cycle includes a duty cycle of a current supplied to a pressure regulating solenoid valve of the high pressure pump Measuring a pressure supplied by the high-pressure pump, calculating a current supply duty cycle based on an error between the required pressure value and the measured pressure value, and calculating the calculated duty cycle. The step of obtaining the reference pressure value based on the above and comparing the measured pressure value with the reference pressure value A step, in successive control cycles of the predetermined number, the measured pressure value is resolved by having the step of generating a fault signal if not consistent with the reference pressure value within a predetermined tolerance.
[Brief description of the drawings]
Next, advantageous embodiments of the present invention will be described based on examples with reference to the accompanying drawings.
FIG. 1 is an overall view of a hydraulic system in an injection apparatus to which a diagnostic method according to the present invention is applied.
FIG. 2 is a detailed view of a pressure regulator in the hydraulic system of FIG.
FIG. 3 is a block diagram of the method according to the invention.
FIG. 4 shows maximum and minimum reference pressure graphs as a function of engine speed.
FIGS. 5A, 5B and 5C show the pressure and duty cycle at three different operating conditions obtained by the injector locked in the open position.
FIG. 6 is a diagram showing the relationship between the pressure used for the compatibility test and the duty cycle.
Embodiment First of all, a high-pressure injection device for an internal combustion engine will be generally described with reference to FIG. The device indicated by reference numeral 1 has a tank 2 placed at atmospheric pressure, which is connected to a radial piston pump 6 via a supply conduit 5. This pump has a pressure regulating solenoid valve (or pressure regulator) connected to the tank 2 via a discharge conduit 8.
Pump 6 supplies fuel at high pressure along line 11 to manifold 10. The manifold 10 distributes the fuel to each injector, and suppresses pressure fluctuations caused by the operation of the pump and the opening of the injector. The manifold 10 is preferably constituted by a parallelepiped steel body, in which a cylindrical cavity extending along the longitudinal direction of the manifold is formed, and a conduit 11 is formed by a central hole 12. Connected with. The manifold 10 also has four holes 13, which are spaced along the length of the manifold, and four high pressure (1500 bar or higher) supply conduits 14 of the four injectors 15 of the engine 16; It is connected. Each injector 15 is also connected to a conduit 17 for recirculating fuel to the tank 2 (to operate the injector).
A known pressure sensor 18 is attached to one end of the manifold 10.
The pressure regulator 7 is preferably configured as shown in FIG. 2 and has a body 20 that defines a conical pedestal 21 for a spherical shutter 22. The push rod 23 applies a combined force of the spring 24 and the solenoid 25 that cooperates with the core 26 to the shutter 22. In this case, the core 26 is integrated with the rod 27, and the rod 27 itself is pushed. It is integrated with the rod 23. The shutter 22 separates the inlet conduit 28 connected to the body of the pump 6 from the outlet conduit 29 connected to the conduit 8. In this case, by changing the current supply to the solenoid 25, the force in the closing direction acting on the shutter 22 is adjusted, and thus the output pressure of the pump 6 is adjusted.
The pressure is adjusted by supplying to the solenoid 25 a current (PWM-pulse width modulation) having a duty cycle modulated at a constant oscillation frequency. In this case, a closed loop adjustment is used that takes into account the actual pressure measured by the pressure sensor 18 and the desired pressure value.
The method according to the invention is for periodically inspecting the operation of the components of the device 1 and, more specifically, for determining: That is, the performance of the pump 6 that generates the required pressure, the correct sealing of the regulator 7, the absence of leakage in the circuit, the presence of an injector locked in the open position, the correct operation of the electrical circuit that controls the regulator 7 , As well as the sensitivity and correct operation of the pressure sensor 18.
According to the advantageous embodiment shown in FIG. 3, four tests are performed periodically. That is, four tests are cycled: maximum measured pressure (block 30); minimum measured pressure (block 31); duty cycle controlling the pressure regulator (block 32); and matching of measured pressure and duty cycle (block 33). Done.
More specifically, the maximum measured pressure test (block 30) is a maximum allowable value in which the pressure in the manifold 10 measured by the sensor 18 is set externally in a predetermined number (for example, five) of consecutive tests. For example, it consists of determining whether or not it exceeds 1600 bar. It is a failure of the following type that is represented by the pressure exceeding the maximum permissible value (indicated by line A in FIG. 4). This means that this is a variation of the setting adjustment in the sensor 18 (measurement error); or the regulator 7 locked in the closed position (the flow of fuel from the conduit 28 to the conduit 29 of the regulator 7 is blocked or significantly suppressed). Failure).
The minimum measured pressure test (block 31) consists of determining whether the measured pressure is below the minimum allowable value in a predetermined number, eg five consecutive tests. The minimum allowable value varies according to the engine speed as shown by curve B in FIG. The following types of obstacles are indicated by the pressure falling below the minimum allowable value. That is, this represents an injector locked in the open position; a pump failure (cannot secure the required fuel flow); a leak in the circuit; or a set adjustment variation in the sensor. Increasing the minimum tolerance associated with engine speed is important for detecting the presence of an injector locked in the open position. In other words, in this case, at high engine speeds, even if the injector is locked in the open position, there is a possibility that at low engine speeds it is an acceptable value and not below a value corresponding to efficient operation.
The duty cycle test (block 32) that controls the pressure regulator is determined by the duty cycle (percentage measurement) in a predetermined number (eg, 5 times for the maximum value and 25 times for the minimum value) of successive tests. It comprises determining whether a predetermined maximum value K2 (eg 97%) has not been exceeded or is below a predetermined minimum value K1 (eg 2%). The fact that the duty cycle has repeatedly exceeded the maximum value means that the pressure measured during this period is continuously below the reference value of the device controlling the regulator, which means that the minimum pressure It represents the same failure as the test and, in some cases, a failure of the electrical circuit that adjusts the duty cycle. On the contrary, the fact that the duty cycle is repeatedly low means that the reference value of the device controlling the regulator is continuously exceeded, which means that the setting adjustment in the sensor 18 is It represents that the fluctuation or regulator 7 is too dense.
Three examples of faults resulting from the injector being locked in the open position are shown in FIGS. 5A, 5B and 5C, which follow the injector lock in cycle 2 of the engine. The pressure curve (dashed line) and the duty cycle curve (solid line) in three different states are shown. More specifically, FIG. 5A relates to a high pressure condition, in which case a fault is detected based on the duty cycle being repeatedly over a predetermined limit value. FIG. 5B relates to a moderate pressure condition, and again the failure is detected based on an excessively high duty cycle value, although this is a slower course than in FIG. 5A. Further, FIG. 5C relates to a low pressure condition, in which case the fault is detected by detecting an excessively low pressure value a predetermined number of times.
The measured pressure / duty cycle conformance test (block 33) utilizes the relationship between the duty cycle (more specifically, the effective current supplied to regulator 7) and the pressure measured in manifold 10; This relationship is shown by curve C in FIG. In this figure, the reference pressure PR is shown as a function of the effective current. Since the curve C varies within a predetermined limit according to the regulator used, the reference value PR is assigned to the upper and lower tolerance values T (for example 300 bar), thereby two curves defining a certain tolerance range. D1 and D2 are determined.
This suitability test consists in determining the duty cycle value of the current supply to the solenoid valve 7 preferably as a function of the actual measured pressure and the required pressure, preferably according to a proportional integration algorithm (the required pressure is Calculated based on engine parameters described in another patent application by the applicant). By using the map, the reference value PR (curve C) corresponding to the determined duty cycle is obtained. Further, it is determined whether the pressure value measured by the sensor 18 matches the reference value PR within a predetermined allowable range (that is, whether the measured pressure value is within the predetermined allowable range). The fact that the pressure value is outside the predetermined range in a predetermined number of consecutive tests is substantially indicative of a setting adjustment variation in the sensor 18, in which case the suitability test is more than the other tests. Slow and other forms of failure are generally detected early.
If a negative determination is made in any one of the four tests (as indicated by OR gate 35 in FIG. 3), a fault signal is generated and the engine is stopped (block 36).
Thus, the described method provides a simple and reliable way to indicate faults in the hydraulic circuit that cannot be detected otherwise, such as when the injector is locked in the open position. Is performed by detecting an external factor that is not related to a failure caused by a transient change in the circuit control amount.
Obviously, the illustrated method can be modified without going beyond the scope of the present invention.

Claims (6)

In a fault diagnosis method in a high-pressure circuit of an internal combustion engine high-pressure fuel injection device of a type in which a high-pressure pump (6) is provided in a high-pressure circuit to supply fuel at a pressure value controlled in a control cycle,
Monitoring an amount correlated to the pressure generated by the high pressure pump (6) in sequential control cycles;
Comparing the pattern of quantities in the sequential cycle to a reference value;
If the pattern does not have a predetermined relationship with a reference value, a step of generating a fault signal is provided, and the control cycle is supplied to a pressure adjusting solenoid valve (7) of the high-pressure pump (6). With the step of changing the duty cycle of the current,
Measuring the pressure supplied by the high-pressure pump (6);
Calculating a current supply duty cycle based on an error between the required pressure value and the measured pressure value;
Determining a reference pressure value based on the calculated duty cycle;
Comparing the measured pressure value with a reference pressure value;
A step of generating a failure signal if the measured pressure value does not match the reference pressure value within a predetermined tolerance in a predetermined number of consecutive control cycles ,
A fault diagnosis method in a high-pressure circuit of an internal combustion engine high-pressure fuel injection device. The method of claim 1, wherein the step of determining a reference pressure value comprises reading the reference pressure value from a map in which the pressure value is stored as a function of duty cycle. The pressure supplied to the manifold (10) by the high-pressure pump (6) is measured, the measured pressure is compared with the maximum reference value, and the pressure measured in a predetermined number of consecutive control cycles exceeds the maximum reference value. The method of claim 1, wherein a fault signal is generated. The pressure supplied to the manifold (10) by the high pressure pump (6) is measured, the measured pressure is compared with the minimum reference value, and the pressure measured in a predetermined number of consecutive control cycles falls below the minimum reference value. 4. A method according to claim 1 or 3 , wherein a fault signal is generated if any. The method of claim 4 , wherein the minimum reference value varies as a function of engine speed. Wherein the control cycle is included the step of varying the duty cycle of the current supply to the pressure regulating solenoid valve (7) of the high-pressure pump (6),
Measuring the pressure supplied by the high-pressure pump (6) ,
Calculating the duty cycle of the current supply based on the error between the required pressure value and the measured pressure;
Compare the calculated duty cycle with the minimum and maximum reference values,
In successive control cycles of a predetermined number, if the calculated duty cycle is not within the allowable range defined by the minimum reference value and the maximum reference value of the generating a fault signal, one of claims 1 to 5 1 The method described in the paragraph .

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