FR2862714A1 - Injection system monitoring method for e.g. heat engine, involves opening and closing dosage unit during usage of signal to find instant from which flow of fuel across pressure regulation valve starts to reduce, for detecting fault in unit - Google Patents

Abstract

The method involves using a signal to determine an instant from which flow of fuel across a pressure regulation valve (130) starts to reduce due to progressive reduction of quantity of fuel supplied to a fuel accumulator (110) to detect a possible fault in a dosage unit (160). The dosage unit is progressively opened and closed during usage of the signal. Independent claims are also included for the following: (a) a computer program to execute a method of monitoring an injection system; (b) a computer readable recording medium on which a computer program is recorded to execute a method of monitoring an injection system; and (c) an apparatus for controlling an injection system.

Description

Purpose of the invention

  From this state of the art, the present invention aims to develop a method and a computer program complementary to monitor an injection system of an internal combustion engine and a control device for the implementation of of this process, allowing a precise differentiation of the dosage unit as a source of error of the injection system.

  DESCRIPTION OF THE INVENTION To this end, the invention relates to a process of the type defined above, characterized in that during the operation of the signal the dosing unit is gradually opened or closed. Advantages of the invention The method according to the invention, consisting in exploiting the chronological evolution of the signal representing the pressure in the fuel accumulator while the dosing unit is at the same time controlled to close or open gradually. Depending on the time, the following reasons arise: the closing or opening of a dosing unit has no concrete influence on the pressure in the fuel accumulator nor consequently on the signal used. The signal representing the pressure can be operated in a very precise manner from the point of view of a possible defect in the dosing unit.

  Advantageously, the signal is used to determine at least a certain moment which differs in that it corresponds both to the determination of the actual flow rate, ie to the flow rate actually delivered. at this moment by the metering unit to the fuel accumulator, and the determination of a theoretical flow rate that the dosing unit would provide at this time to the fuel accumulator if it corresponded to the standard.

  If for a first predefined rotational speed of the internal combustion engine, the signal is used to determine a first moment, from which the fuel flow through a pressure control valve of the injection system starts to decrease. As a result of the progressive reduction in the amount of fuel supplied to the fuel accumulator, a first actual flow rate actually supplied by the metering unit after the first instant to the fuel accumulator is determined as the flow rate of a fuel. injection system high pressure fuel pump for a first rotational speed.

  If the signal is used for a first predefined rate of the internal combustion engine from the point of view of the determination of a second instant, from which the flow of fuel through a pressure control valve of the injection system cuts at least substantially completely, it determines a real flow rate that the metering unit actually provides at the second time for the fuel accumulator, as known fuel consumption of the internal combustion engine for the first speed of rotation preferably including leaks and injection quantities of injectors of the injection system.

  In both cases, a theoretical flow rate is determined which would be supplied to the dosing unit at the first and / or second instant for the fuel accumulator if the dosing unit met a standard, and in the event of a fault, it is closed. dosing unit, taking into account components of the injection system if a difference between the theoretical flow determined and the actual flow determined at the first and / or second time is greater than a tolerance range, predefined. Preferably the process is repeated for at least one other rotational speed.

  Advantageously, the method according to the invention is characterized in that it concludes that a defect of the dosing unit as a component of the injection system, if a difference between the theoretical flow determined and the actual flow obtained is greater than a predefined acceptable tolerance range.

  Advantageously, the safety of the decision concerning the existence of a defect, in particular in the dosing unit, is considerably increased if the comparison theoretical value / real value evoked above is carried out for several speeds of rotation each set at one speed. constant level at different times.

  Advantageously, for the signal representing the evolution of the pressure in the fuel accumulator two alternatives can be chosen. On the one hand, the control signal of a pressure control valve can be used as a signal if a control circuit for regulating the pressure in the fuel accumulator by the pressure regulating valve is activated. Therefore, preferably for determining the first or second time a control circuit is operated to regulate the pressure in the fuel accumulator by means of the pressure regulating valve while the dosing unit is gradually closes, and for this purpose a control signal of the pressure control valve is used as a signal representing the chronogram of the pressure in the fuel accumulator.

  Alternatively, it is also possible to use as signal the output signal of a pressure sensor which directly captures the evolution of the pressure in the fuel accumulator. Thus, in order to determine the first and the second instant, a control circuit is used to regulate the pressure in the fuel accumulator by the pressure regulating valve by controlling the pressure regulator valve with a constant control signal in the time, while the dosing unit is gradually formed, and a measurement signal at the output of the pressure sensor of the control circuit is used as the chronological evolution of the pressure in the fuel accumulator.

  Another possibility to conclude a defect in a component of the injection system, but in a manner not targeted to a defect of the dosing unit, exists if during a linear opening or closing of the dosing unit, the signal hardly varies in a linear way.

  The object of the invention as defined above is also satisfied by a computer program and a control apparatus for carrying out the method as described and a data carrier comprising the program of computer. The advantages of this solution correspond essentially to the advantages mentioned above with reference to the claimed process.

  It is furthermore advantageous that the control apparatus 35 makes it possible to generate a real characteristic for the dosage unit actually used by means of events coming from the method according to the invention. It is necessary to integrate a learning function in the control device. In principle, for the learning function of the actual characteristic curve, the method according to the invention is executed once. Obviously, the method can be repeated from time to time, and in particular be run at low speed to ensure, if necessary, a new correction. It is then advantageous to provide the control apparatus for controlling the dosage unit actually used in the future according to the indications provided by the actual characteristic generated. This allows a much higher control accuracy for the dosing unit, the dosing of the fuel supply and thus the operation of the combustion engine which becomes much more precise.

  Drawings The present invention will be described below in more detail with the aid of embodiments shown in the accompanying drawings in which: - Figure 1 shows the schematic diagram of an injection system according to the invention, - the FIG. 2 shows the timing diagram of an inverse signal proportional to a variation of pressure in the fuel accumulator and corresponding to the control signal of a dosing unit for carrying out the method of the invention; FIG. 3 shows the timing diagram of the fuel flow in the metering unit during the implementation of the method of the invention; FIG. 4 shows the control signal of a pressure control valve, regulated for the implementation of the process of the invention; FIG. 5 shows the fuel flow rate in the pressure control valve for carrying out the process of the invention; FIG. 6 shows a characteristic I / Q of the dosing unit actually used.

  Description of embodiments

  Figure 1 shows the structure of an injection system 100 of an internal combustion engine (the engine is not shown) for carrying out the invention. The injection system is in particular a so-called common rail system. This system comprises a fuel accumulator 110 which contains high pressure fuel to supply it to the injectors, or injection valves 180 of the internal combustion engine. The fuel accumulator 110 receives fuel from the reservoir 200 on the low pressure side. An electric fuel pump 150 draws fuel into the tank 200 and supplies it to a metering unit 160. The metering unit 160 supplies a quantity of fuel metered to the high pressure pump 170 downstream in response to a signal. control unit S1 from a control apparatus 140. The high pressure fuel pump 170 compresses the fuel supplied to it by the metering unit 160 and feeds the fuel accumulator 110 to the desired pressure. the fuel accumulator 110 is connected to a control circuit formed by a pressure sensor 120 of the control apparatus 140 and a pressure control valve 130 for regulating the pressure in the fuel accumulator. The pressure sensor 120 captures the actual actual pressure in the fuel accumulator 110 and transmits this information as a measurement signal P to the control apparatus 140. The control apparatus compares this actual pressure with a control signal. preset set pressure and forms a pressure control deviation and a control signal S2 representing the pressure control deviation thus formed. This control signal is transmitted to the pressure control valve 130. The regulation signal S2 controls the pressure control valve 130 so that the control deviation is, if possible, zero.

  Usually, but this is not essential for the present invention, the pressure sensor 120, the control apparatus 140, the metering unit 160, the high pressure pump 170 and the fuel accumulator 110 form another circuit. regulating to regulate the pressure in the fuel accumulator. The pressure regulating deviation generated in the control apparatus 140 and described above with reference to the first control circuit is also used as control for the other control circuit. In response to this control deviation, the metering unit 160 is controlled by the control signal S1 to provide the amount of fuel to the high pressure fuel pump 170 which allows this pump 170 to compress the fuel to a pressure. to make the regulatory gap null.

  The high-pressure fuel pump 170 is in principle also controlled with a signal S3 from the control apparatus 140. The predifination of the set pressure used for the comparison between the theoretical value and the actual value to define the difference of The regulation is advantageously defined according to a certain speed (rotation speed) N of the internal combustion engine and is recorded in the control unit.

  The method according to the invention will be described below with reference to the above described structure of the injection system and referring to Figures 2 to 6 below.

  The purpose of the method is to detect a possible defect of a component of the injection system 100 in a manner as accurate with respect to the components. The components of the injection system are those already described with reference to Figure 1 and bearing references 110-170.

  The first two exemplary embodiments of the invention described hereafter provide a practical information on whether the dosing unit 160 is defective or not. Except in the case of serious defects in the injection system. no longer allowing the internal combustion engine to function normally and which can simply disengage.

  A first embodiment of the invention provides for operating the internal combustion engine at a predefined constant speed N; at the same time, the first control circuit already described above is operated with reference to FIG. 1 to regulate the pressure in the fuel accumulator 110 by means of the pressure regulating valve 130. To detect a possible fault or a possible error in the behavior of the metering unit 160, it is controlled with the control signal S1 of the control apparatus 140 so that starting from a substantially total opening, it is closes with time. Typically the control signal S1 is a modulated pulse width signal; the information concerning the gradual closure at the dosing unit 160 is done by increasing the TV working ratio of this signal over time. Figure 2 shows this situation.

  FIG. 3 shows the variation of the flow rate Q of the metering unit 160 as a function of the variation of the working ratio represented in FIG. 2. Both in FIG. 2 and in the other following figures 3 to 5 it is assumed that at time t = 0 the dosing unit 160 is fully open. Also for the increasing closure between tap at t> 0 and shown in FIG. 2 for the metering unit 160, according to FIG. 3, it does not matter that the flow rate> in the metering unit 160 remains constant until at the moment ti. The reason for this is that during the period of time 0 <-t5t1, because of its geometric transfer rate, the fuel pump 170 can not absorb the maximum possible flow rate of the metering unit 160 for the set rotational speed. In other words, regardless of its opening, the metering unit 160 can only receive the quantity of fuel that can be taken from the outlet of the fuel pump 170. This output flow rate is limited to the level QZ in the time interval 0 <_t <_t1.

  According to the first exemplary embodiment, this time ti is determined at which the first regulation circuit is activated to regulate the pressure by the pressure regulating valve 130 by exploiting the regulation signal S2. The control signal S2 for controlling the pressure regulating valve 130 represents the evolution of the pressure in the fuel accumulator 110 for the regulation operation of the first regulating circuit. As already indicated above for the description of the figure, this pressure is substantially constant in the time interval 0 <t <t1 because the quantity of fuel QZ supplied by the dosing unit 160 is constant. The first control circuit serves in all cases to stabilize the disturbances not taken into account here. The control signal S2 whose working ratio is shown in FIG. 4 is for this reason substantially constant during this time interval.

  It is only for times t> tl that the quantity of fuel supplied by the metering unit 160 decreases slowly with respect to the quantity of fuel consumed by the internal combustion engine, including the leaks in the engine. the injectors and the pressure regulating valve, and the pressure would decrease in the pressure accumulator 110 if it was not compensated by the first regulating circuit, in particular by a suitable control of the pressure regulating valve 130. The beginning of the compensation of the pressure leakage by the first regulating circuit appears in Figure 4 at the inflection of the curve of the TV working ratio of the regulation signal S2. The time t1 whose meaning has been given above corresponds to t o the moment at which the inflection of the curve of FIG. 4 occurs; this instant appears clearly in FIG. 4 and can thus be determined from the regulation signal S2.

  At the instant t = ti, the flow pZ passing through the dosing unit and corresponding to the opening degree of the metering unit 160 is identical to the quantity of fuel supplied to the injectors taking into account any losses. .

  At time t1 it is possible to determine the actual flow that the metering unit 160 would actually supply at time t1 to the fuel accumulator. This flow is determined in a simple way. The actual flow rate then corresponds to the amount transferred by the high pressure pump 170 at this time.

  This quantity transferred by the high-pressure pump 170 is obtained by multiplying the rotation speed of the high-pressure pump which is in a known fixed ratio with the predefined constant speed N of the heat engine and the known quantity transferred by the high-pressure pump. by rotation multiplying by a yield.

  In order to detect a defect or faulty behavior deviating from the normal behavior of the metering unit 160 actually used, according to the invention, the actual flow rate calculated above of the metering unit 160 is compared and which is identical to the instant at the flow rate of the high-pressure pump 170 at a known theoretical flow rate for a standardized behavior of the dosing unit. If the difference resulting from this comparison between the actual transfer rate and the theoretical transfer rate is beyond a predefined permissible tolerance range, it can be assumed that the behavior of the dosing unit 160 is tainted with an error and is apparently defective. The defect can occur, for example, in an insufficient precision manufacturing of different components of the dosing unit.

  The decision regarding the existence of a defect in the dosing unit 160 can further be confirmed in that this decision is not based on the result of a comparison of the flow rate but on that of several comparisons. These different comparisons are distinguishable from each other because they are made for situations o different operation of the internal combustion engine or the injection system 100.

  Hereinafter will be described different possibilities of setting appropriate, different operating points.

  A second embodiment of the method of the invention provides for operating the control signal S2 of the pressure control valve 130 not at time t1 but at another time t2. As it appears in FIG. 4, the instant t2 is later than the instant ti. In particular, the time interval i.e. ti5t5t2 corresponds to the further closing of the metering unit 160. As the dosing unit closes, it decreases the amount of fuel. supplied to the high pressure pump 170 and the fuel accumulator 110 which would normally result in a pressure drop in the fuel accumulator if this fall was not regulated or compensated as indicated by the first regulator circuit. More precisely: to compensate for this pressure drop it is necessary that in response to its regulation signal S2, the pressure regulating valve 130 closes more and more to reduce the fuel outlet of the fuel accumulator 110 by the pressure regulating valve 130 to the fuel tank 200. To carry out such a control of the pressure regulating valve 130, the working ratio of the regulation signal S2 according to FIG. time ti5t <t2.

  However, at a certain point, it will happen that the first regulating circuit and in particular the pres-35 Sion regulation valve 130 is no longer able to compensate even more for the loss of pressure caused by the further decrease. The fuel flow QD through the pressure regulating valve 130 then collapses completely as shown in FIG. 5. This instant corresponds to the instant t2. already mentioned above. It is generally detected from the control signal S2 whose TV working ratio according to FIG. 4 reaches its upper saturation limit. Time t2 is also suitable for determining the actual flow rate of dosing unit 160 at this time. This actual flow rate then corresponds to the known fuel consumption of the internal combustion engine for which, before the set rotation speed N, preferably taking into account the fuel losses, leaks and control quantities supplied to the injectors 180 of the fuel injection system. injection.

  The calculation of the theoretical flow rate at time t2 is analogous to the calculation given above of the reference flow rate at time t1. At time t2, it must be taken into account that the current of the control signal S1 for the metering unit 160 is much greater than at the instant t1 because the working ratio of this control signal if at moment ti continued to increase significantly according to Figure 2.

  Another possibility of setting other suitable operating points is to carry out the method according to the first and / or second exemplary embodiment not only for the N regime indicated above but also if possible several other regimes (speed rotation). For instants ti and / or t2 which can be determined in the same way for the other rotational speeds, as described above, there will then be other flows to compare and whose comparison confirms or questions the result of an earlier comparison.

  The instants t1 and / or t2 are not necessarily deduced from the regulation signal S2 for the control of the pressure regulating valve 130. These instants can also be determined alternatively from the output signal / measurement signal P of the pressure sensor 120 for each rotation speed set constantly because this output signal P unequivocally represents the variation in pressure produced by the fuel supply variation of the fuel accumulator 110. However, it is only it is interesting to exploit this output signal P in place of the regulation signal S2 only if the first control circuit is neutralized, that is to say if the regulation signal S2 has been set to a constant control level .

  It is not essential to determine the time when, starting from a virtually total opening, the dosing unit 160 is progressively closed. Moreover, the instant t1 can also be the one where, starting from at least one partial closure, an inverted control of the dosing unit 160 gradually opens as a function of time. The control of the dosing unit described lastly does not make it possible to determine the instant t2 because a necessary restart of the internal combustion engine with a very small supply of fuel supplied to the flow rate by the dosing unit would not be necessary. Not possible.

  An indication of a possible defect or possibly non-standard behavior for a component of the injection system is not obtained, however, only by the exploitation of data at times tl or t2. Moreover, the evolution of the control signal S2 of the pressure regulating valve 130 during the activation of the first regulation circuit, or the evolution of the output signal of the pressure sensor. 120 when the first regulation circuit is deactivated, in particular between instants t 1 and t 2, makes it possible to draw the conclusions relating to such a defect. To enable such conclusions to be drawn, the dosing unit 160 is commanded within the indicated time interval for this unit to open or close at least substantially linearly with time. The assumption of a constant fuel output of the fuel accumulator during this time interval towards the internal combustion engine with the possible losses, requires that the observed signals S2 or P also exhibit a linear behavior if the components injection system work properly. But if during this time interval these signals have no linear behavior in that for example they vary in step, it can be concluded that there is probably a fault in the dosing unit 160 or in the valve pressure regulator 130.

  Independently of those of the many possibilities ultimately used to determine a defect in the metering unit 160, the following remarks can be made: If such a defect has been found because of a single or multiple deviation, of unacceptable amplitude between the actual flow and the reference flow rate at the dosing unit 160, there are in principle two possibilities for the further procedure.

  The first possibility is to replace the tested metering unit as defective with a non-defective unit. For this non-defective metering unit, it is assumed that it behaves according to a characteristic curve (flow rate) I (QZ) recorded in the control apparatus 140 for standardized dosing units. Then a precise adjustment of the fuel flow in a non-defective metering unit is carried out by the control of this unit according to the recorded characteristic curve I (QZ).

  A second possible procedure consists of continuing to work with the dosing unit 16 which is defective or operating incorrectly for as long or until its defective, actual behavior has been compensated by an adapted or corrected command. . A correction of the command may for example consist of correcting the standardized characteristic recorded in the control device 140 according to the measurements given by the deviations noted in particular in several operating situations between the actual flow rate and the corresponding reference flow rate. . The corrected characteristic I (QZ) shown in FIG. 6 is thus obtained. This corrected characteristic results from the interpolation between a large number of possible points of support which have been determined by the comparisons indicated above between the quantities debited. With the aid of the corrected characteristic curve, it is also possible to control the dosing unit 160 which does not work entirely in an ideal manner with the aid of the control device 140.

  The method according to the invention as described is preferably in the form of a computer program. The computer program can optionally be registered with other computer programs of the controller on a data carrier. The data carrier may be a diskette, a compact disk, a flash memory or the like. The computer program stored on the data carrier can be sold as a product to customers. As an alternative to a data carrier transmission it is also possible to transmit the computer program without using hardware data support by means of an electronic communications network, in particular the Internet network.

Claims (15)

  1) A method for monitoring an injection system (100) of an internal combustion engine, in particular a common rail system, comprising a fuel accumulator (110) and a metering unit (160) controlled for the fuel flow rate to be transferred to the fuel accumulator (110), according to which a signal is used representing the chronological evolution of the pressure in the fuel accumulator (110) with a view to a possible defect of a component of the injection system (100), characterized in that during operation of the signal the dosing unit (160) is progressively opened or closed.   2) A method according to claim 1, characterized in that for a first predetermined speed of rotation of the internal combustion engine, the signal is used to determine a first moment (t1), from which the fuel flow through a pressure control valve (130) of the injection system (100) begins to decrease due to the progressive decrease in the amount of fuel supplied to the fuel accumulator (110).   3) Method according to claim 2, characterized in that it determines a first actual flow that actually provides the metering unit (160) after the first moment (t) to the fuel accumulator (110), as flow a high pressure fuel pump (170) of the injection system (100) for a first rotational speed.   4) Process according to claim 1, characterized in that the signal is exploited for a first predefined speed of the internal combustion engine from the point of view of the determination of a second instant (t2), from which the flow of fuel passing through a pressure regulating valve (130) of the injection system (100) cuts at least substantially completely.   5) Method according to claim 4, characterized in that a real flow rate is determined that the metering unit (160) actually provides at the second instant (t2) for the fuel accumulator (110), as consumption of fuel known to the internal combustion engine for the first rotational speed preferably including leaks and control quantities of injectors (180) of the injection system (100).   6) Process according to any one of claims 3 or 5, characterized in that - one determines a theoretical flow that would be provided by the unit of dosage (160) at the first and / or second time (tl, t2 ) for the fuel accumulator (110) if the dosing unit meets a standard, and - conclude that there is a defect in the dosing unit (160) as a component of the injection system (100) if a difference between the determined theoretical flow rate and the actual flow rate determined at the first and / or second time (t1, t2) is greater than a pre-defined tolerance range.   7) Method according to claim 6, characterized in that the method is repeated for at least one other rotational speed.   8) Method according to any one of claims 2 and 4, characterized in that for determining the first or second time (tl, t2) operates a control circuit for regulating the pressure in the fuel accumulator (110). ) by means of the pressure regulating valve (130) while the dosing unit (160) is closed progressively, and for this purpose a control signal of the pressure regulating valve (130) is operated as a signal representing the timing chart of the pressure in the fuel accumulator (110).   9) Process according to any one of claims 2 and 4, characterized in that for determining the first or the second instant (ti, t2) is neutralized a control circuit for regulating the pressure in the fuel accumulator ( 110) by the pressure regulating valve (130) by controlling the pressure regulating valve (130) with a constant control signal over time, while the dosing unit (160) gradually closes, and a signal measurement at the output of the pressure sensor (120) of the control circuit is used as the chronological evolution of the pressure in the fuel accumulator (110).   A method according to claim 1, characterized in that the dosing unit (160) is controlled to open or close at least substantially linearly with time, and - it is concluded to a defect of a component of the injection system (100) if during the linear closure of the dosing unit (160) the signal does not substantially present a linear evolution.   11) computer program comprising means for performing the steps of the method according to any one of claims 1 to 10 when said program is executed by a computer.   12) A computer-readable recording medium on which is recorded a computer program comprising means for performing the steps of the method according to claim 11.   13) Control apparatus (140) for an injection system (100) of an internal combustion engine, characterized in that the control apparatus is for carrying out the method according to any of claims 1 to 10 .   A control apparatus (140) according to claim 13, characterized in that it is adapted to generate a real characteristic representing the actual behavior of the actually used metering unit (160), by correcting the normalized characteristic curve recorded for a standardized dosing unit according to the indications obtained in the implementation of the method according to claim 6 relating to the difference between the actual flow rates of the actual dosage unit and the theoretical flow rates of the standardized dosing unit.   15) control device (140) according to claim 14, characterized in that it controls the metering unit (160) actually used according to the indications corresponding to the actual characteristic curves.