EP1818527A1

EP1818527A1 - Method and apparatus for inhibiting/ throttling current-controlled fuel injectors in a multi-fuel endothermic engine

Info

Publication number: EP1818527A1
Application number: EP06125180A
Authority: EP
Inventors: Vincenzo Baroni
Original assignee: A E B Srl
Current assignee: A E B Srl
Priority date: 2006-02-10
Filing date: 2006-11-30
Publication date: 2007-08-15
Anticipated expiration: 2026-11-30
Also published as: ES2331203T3; EP1818527B1; ATE438796T1; DE602006008265D1; ITPR20060008A1; PL1818527T3

Abstract

An apparatus (9) for inhibiting / throttling a fuel injector (1), in a multi-fuel endothermic engine, inserted in an electrical drive circuit and current-controlled by measuring a value of a control current circulating in a measuring section (5) of the drive circuit, comprises means for inserting / removing an inhibiting /throttling current in an electrical drive circuit, upstream of the measuring section, so that said inhibiting / throttling current is added to a drive current delivered by an electrical power supply (2) inserted in the drive circuit. A method for inhibiting / throttling a fuel injector, in a multi-fuel endothermic engine, current controlled.

Description

The present invention relates to an apparatus and a method for inhibiting / throttling a fuel injector, in a multi-fuel endothermic engine, placed in an electrical drive circuit and current-controlled by measuring a value of a control current circulating in a measuring section of the drive circuit.
The present invention finds application in the field of fuel management systems for multi-fuel endothermic engines, i.e. internal combustion engines, able to work with different fuels, used separately and/or simultaneously.
This type of engine entails, for example, a combined operation with petrol / gas (methane or LPG), or Diesel oil / gas, alcohol / gas, petrol-alcohol / gas, petrol-hydrogen /gas, etc.
Endothermic engine with multiple, typically dual, fuels, are usually provided with various fuel systems (in particular, a fuel system for each type of fuel used), arranged in parallel and each provided with a single autonomous control unit.
In operation with multiple fuels, one fuel can be identified as "primary" and the other fuel (or the other fuels) as "alternative". During operation, both total and partial, with alternative fuel, the injectors of the primary fuel (usually constituted by petrol, alcohol or Diesel oil) must be inhibited or otherwise must be subjected to flow control / throttling. Therefore, the injectors (used for injecting the primary fuel) are inhibited partially or totally. In this regard, it should be noted that the car control unit activates / deactivates the injector autonomously, without any possibility of interfering with its operation, i.e. it is not possible to intervene from within the control unit to inhibit the injector, during operation with alternative fuel. Therefore, the injectors must be partially or totally disconnected from the exterior to enable operation with alternative fuel.
Said inhibition of an injector can be interpreted by the diagnostic system of the injectors (carried out by the control unit itself) as a malfunction, because the control system performs tests to detect the presence of the injectors and their correct operation. The detection of a malfunction can cause numerous drawbacks, such as the undesired activation of error indicator lights, activation of recovery strategies or even the complete shut-down of the engine.
Therefore, during operation with alternative fuel it is necessary to prevent the diagnostic system of the injectors to interpret the control or throttling of the flow of an injector, due to the use of an alternative fuel, as a malfunction of the injector itself, so the engine can function without the problems described above.
It should be noted that the injection entails, from a mechanical viewpoint, an opening / closing of a valve. Said opening / closing is obtained by activating a magnetic actuator, or exciting / de-energising a coil, to establish / remove a magnetic field. Therefore the switch, from the electrical viewpoint, is constituted by an inductor (associated to a corresponding resistor).
Hence, the control circuit of the injector, managed by the control unit, comprises an electrical power supply (e.g., the battery of the car), arranged in series with the injector (which represents a strongly inductive ohmic load) and to a switch (constituted for example by a transistor).
Operatively, in order to activate the injector it is necessary to close the switch, so that in the coil of the injector a sufficient current circulates to excite the actuator magnetically; vice versa, to deactivate the injector, the control unit commands the opening of the switch.
With regard to the control of the activation / deactivation of the injector, two different technical solutions are known, depending on whether there is voltage control or current control.
The voltage control of the activation / deactivation of the injector entails applying, when the switch closes, a known voltage to the ends of the injectors, for a predetermined time, sufficient to activate the injector.
The current control of the activation / deactivation of the injector entails measuring the current circulating in the coil of the injector; in this way, the voltage applied at the ends of the injector when the switch is closed is maintained until the measured current reaches a desired value, whereat the injector is activated; subsequently, the control unit (the control system) reduces the voltage applied to the inductor, to a minimum value, sufficient to maintain the injector active (i.e., to maintain the injector coil excited). It should be noted that said current control enables to apply particularly high voltages to the injector coil, with no risk of damaging the circuit (the applied voltage has a high value only for a relatively short time, sufficient to make the current circulating in the injector reach the desired value, necessary to activate the injector).
Thus, the current control device of the primary fuel supply system operates to obtain a predetermined current profile within the injector.
In particular, current control systems for injectors usually operate in two phases: the first one giving an initial current peak to favour the rapid opening of the injector, the second one reducing the current to such values as to keep the injector open and at the same time to minimise electrical power dissipation. The first phase is obtained by powering the injectors with the maximum available voltage (in the case of systems provided with positive voltage booster with higher than battery voltage) until the desired current is reached, the second phase instead is typically obtained using voltages that are equal to or lower than battery voltage, in order to keep the current at the desired value.
For these reasons, said current control of the activation / deactivation of the injector, which constitutes a new generation fuel system (which enables to drive the injectors with particularly high currents, possibly by means of devices for boosting the power supply voltage), is used ever more frequently in modem endothermic engines. In particular, this system for driving the injectors with current control has become a standard on direct injection fuel systems, where the times available for the injection of the fuel are typically one fourth of those available in traditional injection systems and fuel pressures upstream of the injectors are very high, so it is necessary to use injectors having particularly large coils (corresponding to inductance value in the order of 2 ÷5 mH or even higher). Such as a system for driving the injectors with current control enables to obtain very high currents in very short times, consequently reducing the opening times of the injectors, assuring greater force, metering precision and better performance.
In this view, it is necessary to consider the aforesaid problem of inhibiting the switches, during operation with alternative fuels of a multi-fuel engine, said inhibition having to be accomplished outside the control unit, without the latter diagnosing a malfunction of the inhibited injector.
With regard to the fuel systems that provide for voltage control of the activation / deactivation of the injector, two technical solutions are known, i.e, two types of devices able to inhibit the injectors without the control unit diagnosing a malfunction of the injector.
A first solution entails a stage of interrupting the injector command, usually a relay, is a circuit stage able to make a little current circulate on the injectors and related drive stages. The quantity of this current is not sufficient to activate the injectors, but it is able to deceive the control/diagnosis stages of the mixture management system (or of the control unit), avoiding unjustified error interpretations.
In a second solution, the connection between the injector and the fuel supply is interrupted, switching it to fictitious injector, usually constituted by a device defining an inductance / resistance having electrical characteristics similar to the injector itself, or otherwise such as to cause the control unit not to note the difference. If the currents at play are relatively low, or otherwise they are not verified with precision by the diagnostic stage (this is the case of traditional engines, with voltage control of the activation / deactivation of the injector), this solution is technically and commercially applicable, because it enables to use relatively small and economical injector simulation stages.
However, if the engine fuel supply system exploits a current control of the activation / deactivation of the injector (e.g. in the case of direct injection engines), known technical solutions have limitations and problems, such as to make them inapplicable in fact.
In particular, the currently available conventional flow interruption and injector simulations devices described above in fact are no longer able to function correctly because new generation fuel systems carry out very accurate checks of the currents actually circulating on the injectors.
All inhibition / simulation devices that reduce the current circulating in the injector introducing an additional resistor in the drive circuit (first technical solution) would immediately put the diagnostic system in the condition of detecting an anomaly.
The inhibition / simulation devices of the type with fictitious injector described above (second technical solution) would also be in fact unusable, because, as a result of the high currents at play, far higher than those of traditional injectors and of sophisticated diagnostic checks conducted by the injector control unit, would entail the use of fictitious injectors having nearly identical electrical characteristics to those of the real injectors. Therefore, it would be necessary to insert inductance-resistance circuits able to simulate the injector, with considerable cost and above all considerable bulk (and hence very expensive), introducing also sizeable heat dissipation problems, since the currents and voltages at play take on very high values.
The object of the present invention is to eliminate the aforesaid drawbacks and to make available an apparatus for inhibiting / throttling a fuel injector, in an internal combustion engine with multiple fuel systems, able to inhibit the injector during the operation of the engine with alternative fuels, in the presence of a system for driving the injector with current control, preventing control and diagnosing devices from detecting said inhibition (or from interpreting it as a malfunction of the injector itself).
Said object is fully achieved by the apparatus of the present invention, which is characterised by the content of the claims set out below and in particular in that it comprises means for inserting / removing an inhibiting / throttling current in the electrical drive circuit, upstream (downstream) of the measuring section, so that said inhibiting / throttling current is added to (subtracted from) a drive current delivered by an electrical power supply inserted in the drive circuit.
An object of the present invention is also a method, which is characterised by the content of the claims set out below and in particular in that it comprises the following steps:

inserting an inhibiting / throttling current in the electrical drive circuit, upstream (downstream) of the measuring section, so that said inhibiting / throttling current is added to (subtracted from) a drive current delivered by an electrical power supply inserted in the drive circuit;
possibly removing the inhibiting / throttling current, to cancel the injector inhibiting effect caused by the previous insertion step, the repetition in succession of said steps for a time interval producing a throttling of the flow rate of fuel delivered by the injector in said time interval.

This and other characteristics shall become more readily apparent from the following description of a preferred embodiment, illustrated purely by way of non limiting example in the accompanying drawing tables, in which:

Figure 1 shows a general diagram of the apparatus of the present invention;
Figure 2 shows charts depicting a profile of particularly significant quantities in the method of the present invention;
Figure 3 shows charts depicting a profile of the quantities of Figure 2, but according to a variant of the method of Figure 2;
Figure 4 shows charts depicting a profile of the quantities of Figure 2, but according to a further variant of the method of Figure 2;
Figure 5 shows charts depicting a profile of the quantities of Figure 2, but according to a variant of the method of the present invention;
Figure 6 shows a general diagram of the apparatus of Figure 1, according to an embodiment variant;

The present invention relates to an apparatus and a method for inhibiting / throttling fuel injectors in an endothermic engine with multiple fuel systems, said inhibition or throttling being indispensable during the operation of the engine with fuels that are alternative to the primary fuel. In particular, the present invention applies to current controlled injectors, as shall be clarified hereafter. Moreover, it should be noted that the present invention applies to an injector or also, advantageously, to a plurality of injectors; for the sake of simplicity, the description that follows shall refer to a single fuel injector. With reference to Figure 1, the numeral 1 designates an inductance, which schematically represents a fuel injector to be inhibited / throttled; the injector is constituted, from the electrical viewpoint, by a coil with a small resistor in series (the resistor is not shown in the circuit of Figure 1, for the sake of simplicity).
The numeral 2 designates an electrical power supply, generally constituted by the battery of the vehicle. The numeral 3 designates a switch, constituted, in the illustrated example, by a transistor. The power supply 2, the injector 1 and the switch 3 are inserted in an electrical circuit for driving the injector 1. The opening / closing of the switch 3 is managed automatically by a control unit 4, which also provides to measure, for diagnostic and control purposes, a value of a control current circulating in measuring section 5 of the drive circuit, according to the prior art.
The control unit 4 manages the opening / closing of the switch 3, to operate a corresponding activation / deactivation of the injector 1, performing a current control, according to a prior art technique described below.
The control unit 4, closing the switch 3, applies to the switch an activation voltage, determined by the electrical power supply 2, connected to the drive circuit through a switch 6, able to connect / disconnect the power supply 2 from the switch 1. It should be noted that, in the illustrated drive circuit, there is also a supplementary power supply 7, provided with a corresponding switch 8, also managed by the control unit 4. The supplementary power supply 7, comprising e.g. a positive voltage booster, enables to apply to the injector 1 a particularly high activation voltage, higher than the battery voltage (e.g. 80 V, as opposed to about 12 V usually made available by the battery). Once the switch 3 is closed, in the drive circuit circulates a driving current (delivered by the power supply 2 and/or by the power supply 7), which flows through the injector 1; the value of the of the driving current increases gradually, said gradualness being due to the effect of the inductance of the injector 1.
Said current control operated by the control unit 4 on the injector 1 provides for the control unit 4 to continue to apply to the injector 1 said activation voltage (keeping the switch 3 closed), until the value of the control circuit circulating in a measuring section 5 of the drive circuit reaches a desired value, corresponding to the activation of the injector 1 (hence said desired value depends essentially on the nature of the injector 1). When the desired value is reached, the control unit commands a substantial reduction in the voltage applied to the injector 1, bringing it from the activation value to a maintenance value, whereto corresponds a circulation of a maintenance current in the drive circuit. Said maintenance current serves the purpose of maintaining the coil of the injector 1 energised (to prevent the injector 1 from deactivating in the long run); moreover, the maintenance current, measured in the section 5, allows the control unit 4 to verify the correct operation of the injector 1.
The present invention makes available an apparatus 9 comprising means 10 for inserting / removing an inhibiting / throttling current in the electrical drive circuit, upstream of the measuring section 5, so that said inhibiting / throttling current is added to the drive current delivered by the electrical power supply 2 and/or by the supplementary power supply 7.
Thus, the apparatus 9 for inhibiting / throttling the injector 1 originally injects a supplementary current (the inhibiting / throttling current), which is added to the drive current, upstream of the measuring section 5. Therefore, the control current measured by the control unit 4 (which constitutes, as is well known, a device for controlling the current circulating in the injector 1) is increased, by effect of the introduction of the inhibiting / throttling current. In this way, said introduction of the inhibiting / throttling current originally entails that the control unit 4 detects that said desired current value is achieved before the drive current actually circulating in the injector in fact reaches said value. Hence, the control unit 4, having detected a control current having the desired value, operates said reduction of the voltage applied to the inductor 1 (from the activation value to the maintenance value), without the activation of the switch 1. Therefore, said introduction of the inhibiting / throttling current entails the inhibition of the switch 1, without any alteration in the operation of the control unit 4 and of the drive circuit.
Thus, the time interval over which the control unit 4 commands the application, to the injector 1, of the activation voltage (typically equal to the maximum value made available by the power supplies) undergoes a reduction, which is the greater the higher the value of the introduced inhibiting / throttling current.
The device 9 also, originally, inserts into the circuit a steady state current, whose value is lower than the inhibiting / throttling current, during the maintenance step, i.e. when the control unit 4 applies the maintenance voltage to the injector 1. Said steady state current reduces in the same way the current circulating on the injector, also in the maintenance step, assuring a permanent inhibition of the injector (hence avoiding phenomena of undesired excitation of the injector coil, by effect of a prolonged circulation in the coil of a maintenance current with relatively high value, during the operation of the engine with alternative fuel).
Therefore, the device of the present invention enables to achieve, in particular, two important results.
A first result is that, when the means 10 for inserting / removing the inhibiting / throttling current are inserted, the primary fuel injector 1 no longer has the ability to open and let the fuel flow, because the quantity of energy transferred to the injector is no longer sufficient for the purpose, since the time and maximum value of the drive current circulating in the injector have been reduced.
A second result is that the energy expenditure necessary to cause the control unit 4 (i.e. the control unit of the drive circuit) to interpret said inhibition condition as normal is minimised, because the contribution of supplementary current needed to achieve the purpose is reduced by the fact that part of the current that already flows on the inductive winding of the injector 1 is exploited.
Another reason for the minimisation of the energy expenditure, with consequent possibility to use small and economical components, is that the injection of the inhibition / throttling current can be protracted, advantageously, for very short time intervals, in particular when the control unit 4 verifies whether the required currents have been reached (control current measurement), whereupon the injector 1 can be completely disconnected, blocking or permanently limiting the flow of the inhibiting / throttling current.
In the illustrated embodiment, the insertion / removal means 10 are operatively active in an insertion node 11, situated upstream of the measuring section 5 (i.e. between the measuring section 5 and the power supply 7). It should be noted that, in general, the measuring section 5 is situated downstream of the injector 1; in this situation, the insertion node 11 is situated downstream of the injector 1, i.e. between the injector 1 and the measuring section 5. In this way, advantageously, the inhibiting / throttling current is prevented from circulating in the coil of the injector 1.
The means 10 for inserting / removing the inhibiting / throttling current in turn comprise a current generator 12, connectable to the electrical drive circuit through an electrical connection branch 13 defining the insertion node 11, and a switch 14, inserted in said electrical connection branch 13.
The apparatus 9 also comprises, originally, means 15 for managing / controlling the means 10 for inserting / removing the inhibiting / throttling current. The managing / controlling means 15 comprise a programmable logic 16, operatively connected to the insertion / removal means, in particular able to command the switch 14 inserted in said electrical connection branch 13. Said programmable logic 16 is able to insert / remove the inhibiting / throttling current, based on a predefined timing, or also based on an evaluation of one or more measured quantities, or based on any other criterion.
In this view, the means 15 for managing / controlling the means 10 for inserting / removing the inhibiting / throttling current are able to accomplish a succession of insertions / removals in a time interval (in particular, the time interval during which the engine operates with alternative fuel), to throttle the flow rate of fuel delivered by the injector 1 (main) in said time interval.
Moreover, the managing / controlling means 15 comprise a stage 17 of measuring a value of current circulating in the electrical drive circuit (constituted for example by a TA), to manage / controlling the inserting / removing means 10 according to said measured current. In this way, the means 15 for managing / controlling the means 10 for inserting / removing the inhibiting / throttling current originally enable to insert the inhibiting / throttling current limited to the instants in which the controlling current is measured (e.g. coinciding with the up ramps of the measured current, which flows in the injector 1). This allows, advantageously, to limit the currents at play, with consequent energy and economic saving, associated with the use of components dimensioned for lower currents.
Therefore, the apparatus of the present invention enables to obtain numerous advantages.
A first advantage is to allow the inhibition / throttling, during operation with alternative fuel, of the activation of the primary fuel injector 1, whilst allowing the passage of a current, measured by the control unit 4 (i.e. the fuel control and management unit), so that the unit 4 itself interprets said measured current as the nominal operating current of the injector (i.e. the drive current circulating in the drive circuit when the injector 1 is active).
In particular, the apparatus 9 originally allows to reduce or eliminate the current circulating in the main injector 1, making it possible to manage said injector, offsetting said reduction with an injection of supplementary current upstream of the measuring section 5.
The present invention also makes available a method for inhibiting / throttling a fuel injector 1, in a multi-fuel endothermic engine, placed in an electrical drive circuit and current-controlled by measuring a value of a control current circulating in a measuring section 5 of the drive circuit.
Said method originally comprises the following steps:

inserting an inhibiting / throttling current in the electrical drive circuit, upstream of the measuring section 5, so that said inhibiting / throttling current is added to a drive current delivered by an electrical power supply 7 inserted in the drive circuit;
possibly removing the inhibiting / throttling current, to cancel the injector inhibiting effect caused by the previous insertion step, the repetition in succession of said steps for a time interval producing a throttling of the flow rate of fuel delivered by the injector 1 in said time interval.

In particular, said insertion of an inhibiting / throttling current in the electrical drive circuit takes place in an insertion node 11, situated downstream of the injector 1, the measuring section 5 being situated downstream of the injector 1 (and downstream of the insertion node 11 itself).
Moreover, said method comprises a step of managing / controlling the means for inserting / removing the inhibiting / throttling current. Said step of managing / controlling the insertion / removal means in turn comprises a step of measuring a value of current circulating in the electrical drive circuit, to manage / control the insertion / removal means as a function of said measured current.
Said method originally enables to insert the inhibiting / throttling current only in the instants in which the control current is measured. In this way, advantageously, a reduction is obtained of the electrical power consumed in the method itself. The method also comprises a step of inserting a steady state current in the electrical drive circuit, upstream of the measuring section, so that said steady state current is added to a drive current delivered by an electrical power supply 2 inserted in the drive circuit, said steady state current having a lower value than the inhibiting / throttling current.
Two possible embodiments of said method are shown in Figures 2 and 3, which show the profile over time of the following quantities:

voltage across the ends of the injector 1, applied by the power supply 2 and/or by the power supply 7 (designated by the letter V);
drive current (designated by the reference I_P);
inhibiting / throttling current (designated by the reference I_I);
control current (designated by the reference I_C).

In the examples shown in Figures 2 and 3 the voltage waveform relates to a system provided with positive voltage booster (or with auxiliary power supply 7); if the latter is not present, the waveform would be the same, just scaled to the value of voltage of the battery.
In the example shown in Figure 2, the drive current rises exhibiting a typical "inductive" profile, whilst the inhibiting / throttling current inserted in the drive circuit has constant value over time (2 A in the example shown in Figure 2). The control current measured by the control unit 4 in the measuring section 5, given by the sum of the drive current and of the inhibiting / throttling current, reaches the desired value for the activation of the injector 1 (i.e., 10 A in this example) after 0.2 ms; in that instant, the control unit 4 commands the reduction of the voltage applied from the activation value (80 V in this example) to the maintenance value. Naturally, in this instant the drive current actually circulating in the injector 1 is lower than the desired value (the difference is equal to the value of the inhibiting / throttling current), so that the injector 1 is not activated, thus being inhibited. It should be noted that, at steady state, the drive current circulating on the injector 1 is further reduced, and ultimately it may be zeroed, because with just the inhibiting / throttling current injected by the device 9 and measured by the control unit 4, the control unit 4 itself reaches the diagnostic conclusion that the injector 1 functions properly. The injector 1 is thereby not energised sufficiently to allow its opening and the control system of the unit 4 is not able to detect the current reduction on the injector 1.
In the example shown in Figure 3, the drive current rises showing a typical "inductive" profile, as in Figure 2. In this example, the applied method differs from the one in Figure 2 only in the shape of the inhibiting / throttling current inserted into the drive circuit, which has a profile that is variable over time; in particular, the inhibiting / throttling current is injected only for short periods, at the appropriate moments, i.e. during the up ramp of the drive current, to obtain the same result of inhibiting the injector 1, but with considerable energy saving. In this example, the desired value for the control current measured by the control unit 4 is obtained with a high injection of inhibiting / throttling current, for a very short time, but sufficient (and advantageous) to be measured by the control system of the unit 4, which at this point lowers the voltage applied to the injector 1 to the maintenance value. In this step, a reduced injection of current prevents the circulation on the injector 1 of a maintenance current able to determine its opening.
From these examples, it is readily apparent that it is not necessary for the injection of the inhibiting / throttling current to be continuous or to have constant value over time. It is sufficient to cause the injection of the inhibiting / throttling current to take place simultaneously with the time instants when the check by the unit 4 occurs, providing, even for just short periods, the additional current values necessary to cause the control unit 4 to interpret a situation of correct / nominal operation of the injector 1.
It should be noted that, although this latter arrangement (the injection of current only in proximity to the instants when the checks are made) leads to a further energy saving, it is nonetheless not indispensable; hence, it is possible to choose the current injection profile that is deemed must appropriate to minimise energy expenditure; what is important is that the current injection leads to keeping the injector 1 deactivated, without compromising the operation of the control unit of the main fuel injection system (i.e. of the unit 4), enabling operation with alternative fuel.
A step of determining the profile of the inhibiting / throttling current inserted in the drive circuit is originally operated in the course of managing / controlling the means 10 for inserting / removing the inhibiting / throttling current. In particular, said step of managing / controlling the insertion / removal means comprises a s step of measuring a value of current circulating in the electrical drive circuit, to manage / control the insertion / removal means 10 as a function of said measured current.
Moreover, the method according to the present invention originally provides for executing the step of inserting an inhibiting / throttling current in the electrical drive circuit in an insertion node 11, situated downstream of the injector 1, the measuring section 5 being situated downstream of the injector 1.
The method according to the present invention originally also provides for executing the step of inserting the inhibiting / throttling current at an up ramp of the drive current that flows through the injector 1 and for a limited time, with the advantage of minimising the electrical power used to inhibit the injector 1.
The present invention is based, originally, on the reduction or total elimination of the current on the main fuel injector, offsetting it with an adequate injection of supplementary current on the injector current measurement and control device, thereby enabling to shut off or throttle the primary fuel flow.
With regard, in particular, to the throttling of the primary fuel flow, the additional current is introduced in the measuring circuit with a certain delay (e.g. after about 0.8 ms) causing at this instant the closing of the injector 1, because the control system reads a current increase, and reacts consequently lowering (even zeroing) the drive voltage of the injector 1. Hence a certain quantity of fuel is allowed to flow through during the first 0.8 ms, then the flow of fuel is interrupted, thus achieving the goal of throttling the primary fuel flow.
The present invention also provides an embodiment variant, illustrated in Figures 5 and 6, according to which the apparatus 1 comprises means 10 for inserting / removing an inhibiting / throttling current in the electrical drive circuit, downstream of the measuring section 1, so that said inhibiting / throttling current is subtracted from a drive current delivered by an electrical power supply 2 inserted in the drive circuit. This variant is particularly advantageous in the cases in which the measuring section 5 is situated upstream of the injector 1.
In this case, the means 10 for inserting / removing the inhibiting / throttling current comprise, preferably, a current generator 12, connectable to the electrical drive circuit through an electrical connection branch 13, defining an insertion node 11, so that the current imposed by the generator flows through the branch 13 to ground, and a switch 14, inserted in said electrical connection branch 13.
Thus, according to said embodiment variant, the teaching of the present invention provides for subtracting current from the drive circuit downstream of the measuring section 5 and upstream of the injector 1, so that the injector is inhibited, without any malfunction being detected by the control unit. It should be noted that said current subtraction is equivalent to the introduction of a negative current, as illustrated in Figure 5.
It is noteworthy to observe that the expression "throttling" in the present application is intended to have the following meaning.
Because the inhibiting effect can be cancelled (as described above), thus enabling the injector, a succession of inhibiting and subsequent unabling of the injector in a given time interval is provided.
Therefore a throttling effect is obtained on the injector.
Hance, the inhibiting current is considered a inhibiting/throttling current.

Claims

Apparatus (9) for inhibiting / throttling a fuel injector (1), in a multi-fuel endothermic engine, placed in an electrical drive circuit and current-controlled by measuring a value of a control current circulating in a measuring section (5) of the drive circuit,
characterised in that it comprises means (10) for inserting / removing an inhibiting / throttling current in the electrical drive circuit, upstream (downstream) of the detection section (1), so that said inhibiting / throttling current is added to (subtracted from) a drive current delivered by an electrical power supply (2) inserted in the drive circuit.
Apparatus as claimed in claim 1, characterised in that the insertion / removal means (10) are operatively active in an insertion node (11) situated downstream of the injector (1), the measuring section (5) being situated downstream of the injector (1).
Apparatus as claimed in claim 1 or 2, characterised in that the means (10) for inserting / removing the inhibiting / throttling current comprise:
- a current generator (12), connectable to the electrical drive circuit through an electrical connection branch (13), defining an insertion node (11), in such a way that the current imposed by the generator flows through the branch (13) towards the insertion node (11);

- a switch (14), inserted in said electrical connection branch (13).
Apparatus as claimed in claim 1, characterised in that the insertion / removal means (10) are operatively active in an insertion node (11) situated upstream of the injector (1), the measuring section (5) being situated upstream of the injector (1).
Apparatus as claimed in claim 4, characterised in that the means (10) for inserting / removing the inhibiting / throttling current comprise:
- a current generator (12), connectable to the electrical drive circuit through an electrical connection branch (13), defining an insertion node (11), in such a way that the current imposed by the generator flows through the branch (13) to ground;

- a switch (14), inserted in said electrical connection branch (13).
Apparatus as claimed in any of the previous claims, characterised in that it comprises means (15) for managing / controlling the means (10) for inserting / removing the inhibiting / throttling current.
Apparatus as claimed in claim 4, characterised in that the management / control means (15) comprise a programmable logic (16), operatively connected to the insertion / removal means (10).
Apparatus as claimed in claim 4 or 5, characterised in that the management / control means (15) comprise a stage (17) for measuring a value of current circulating in the electrical drive circuit, to manage / control the insertion / removal means (10) as a function of said measured current.
Apparatus as claimed in any of the claims 6 through 8, characterised in that the means (15) for managing / controlling the means (10) for inserting / removing the inhibiting / throttling current are able to perform said insertion of the inhibiting / throttling current only in the instants when the control current is measured.
Apparatus as claimed in any of the claims 6 through 9, characterised in that the means (15) for managing / controlling the means (10) for inserting / removing the inhibiting / throttling current are able to accomplish a succession of insertions / removals in a time interval, to throttle the flow rate of fuel delivered by the injector (1) in said time interval.
Method for inhibiting / throttling a fuel injector (1), in a multi-fuel endothermic engine, placed in an electrical drive circuit and current-controlled by measuring a value of a control current circulating in a measuring section (5) of the drive circuit,
characterised in that it comprises the following steps:
- inserting an inhibiting / throttling current in the electrical drive circuit, upstream (downstream) of the detection section (5), so that said inhibiting / throttling current is added to (subtracted from) a drive current delivered by an electrical power supply (2) inserted in the drive circuit;

- possibly removing the inhibiting / throttling current, to cancel the effect of inhibiting the injector (1) caused by the previous insertion step, the repetition in succession of said steps for a time interval producing a throttling of the flow rate of fuel delivered by the injector (1) in said time interval.
Method as claimed in claim 11, wherein the step of inserting an inhibiting / throttling current in the electrical drive circuit takes place in an insertion node (11), situated downstream of the injector (1), the measuring section (5) being situated downstream of the injector (1).
Method as claimed in claim 11, wherein the step of inserting an inhibiting / throttling current in the electrical drive circuit takes place in an insertion node (11), situated upstream of the injector (1), the measuring section (5) being situated downstream of the injector (1).
Method as claimed in any of the claims 11 through 13, characterised in that it comprises a step of managing / controlling the means (10) for inserting / removing the inhibiting / throttling current.
Method as claimed in claim 14, characterised in that said step of managing / controlling the insertion / removal means (10) comprises a step of measuring a value of current circulating in the electrical drive circuit, to manage / control the insertion / removal means (10) as a function of said measured current.
Method as claimed in any of the claims 11 through 15, characterised in that it provides for inserting the inhibiting / throttling current only in the instants when the control current is measured.
Method as claimed in any of the claims 11 through 16, characterised in that it comprises a step of inserting a steady state current in the electrical drive circuit, upstream of the measuring section (5), so that said steady state current is added to a drive current delivered by an electrical power supply inserted in the drive circuit, said steady state current having a lower value than the inhibiting / throttling current.
Vehicle with multi-fuel engine, characterised in that it comprises at least one apparatus for inhibiting / throttling a plurality of fuel injectors, as claimed in any of the claims 1 through 10, or in that it implements a method as claimed in any of the claims 11 through 17.