EP1647693B1 - Driving method of a control circuit and actuating device - Google Patents

Abstract

The method involves supplying a bridge circuit (2) of an actuation device (1) with a continuous signal. A measurement signal, representing a position of an actuated part of an actuator of the device, is produced based on result of comparison of a measured intensity of the signal with high threshold, low threshold and very low threshold. Conduction in branches of the circuit (2) is selectively interrupted based on the measurement signal. An independent claim is also included for an actuation device having actuators acting on a fuel injector.

Description

The invention relates to the field of fuel injection control for an internal combustion engine intended for example to equip a motor vehicle.

The invention more particularly relates to a fuel injection control for atomizing the injected fuel in the form of very fine droplets.

The fuel injection devices currently used on internal combustion engines fitted to motor vehicles or road vehicles, operate conventionally on the model of a valve whose open or closed state is permanently controlled, the dosage of fuel injected then being done directly by the opening time.

Such injection systems comprise an electric fuel supply pump which supplies, through the channel of a distribution manifold, all the injectors under pressure having a constant difference with the pressure prevailing in the intake manifold. thanks to a pressure regulator. By electronically controlling the electromagnet actuating the valve of each injector, it controls the start and the opening time thereof and then determines a precise fuel flow for each of the injectors. Thus, the amount of fuel injected depends solely on the opening time of the electro-injectors.

The injectors of the electromagnetically controlled needle type, which are the most commonly used, however, have limits which slow down the improvement of engine performance, especially in terms of pollution control. In particular, the time taken to open or close the needles are still too high, about 1 to 2 ms, which prevents the distribution of the injection correctly throughout the opening time of the valve. In addition, the minimum opening time, which determines the minimum dose of fuel that can be injected, is still too important for certain operating points of the engine.

Known needle injectors also have injection orifices of relatively large diameters for allow the required quantities of fuel to be discharged for full load and high engine operation. This arrangement generates fuel jets having drops of large dimensions, which slows the vaporization of the fuel (and therefore the preparation of the fuel mixture) and is able to promote the phenomenon of wall wetting.

Indeed, the non-vaporized fuel tends to be deposited on the walls of the intake duct or the direct injection combustion chamber. Such a deposit causes metering problems, particularly acute transients for lack of knowledge of the amount of fuel that actually enters the corresponding combustion chamber. This wetting phenomenon is one of the important causes of high pollutant emissions during cold engine starts.

Moreover, with a conventional needle injector, the opening of the needle when the latter begins to leave its seat, it forms a liquid bubble that disappears when the needle is completely raised, the fluid flow is regulating then. This change in the nature of the flow makes it impossible to precisely control the instantaneous flow rate of the injector.

Some have tried to solve these problems by developing injectors using piezoelectric actuators to manipulate the needle so as to lower the opening and closing time of the needle, but such systems that still operate according to the principle of a valve, retain significant disadvantages related in particular to the significant dispersion affecting the size of the drops in the fuel jet at the end of the nose of the injector.

All of the problems mentioned above thus result in a vaporization of the fuel which can be incomplete and inhomogeneous during the preparation of the fuel mixture in the combustion chamber, imprecise dosages, with the consequence of incomplete combustion resulting in the formation of a high amount of gaseous pollutants and an energy deficit altering the efficiency of the engine.

The document FR-A-2 801 346 discloses a fuel injection device for an internal combustion engine equipped with an injector having a nozzle fueled and at the end of which is provided an injection port, means for cyclic vibration of the nozzle such as a transducer controlled in duration and intensity by the electronic engine control system, and shutter means biased by resilient return means against the end of the nozzle, said elastic return means being formed by a rod passing through the body of the injector to a cavity located at the opposite end relative to the injection orifice, said rod cooperating with a mass and damping means housed in said cavity, the vibration of the nozzle and shutter means ensuring the ejection of a predetermined amount of fuel.

The document FR-A-2,846,808 discloses an actuator device provided with an actuator, an actuator control electronic topology comprising a bridge circuit with a DC source between the first and second terminals of the circuit, the actuator being connected between the third and the fourth terminal of the circuit, having a switch connected between the first and third terminals and a switch connected between the second and fourth terminals. The bridge circuit further has a first diode connected between the first and fourth terminals and a second diode connected between the second and third terminals. Such an actuating device is relatively simple. However, the need has arisen to improve the accuracy of the control in position.

The control method, according to one aspect of the invention, is intended for an actuating device provided with at least one actuator acting on a fuel injector having an actuated part and an electric control member for moving the actuated part. so as to oscillate between two positions. The control circuit comprises a bridge in which an electrical control member is connected. The method comprises the steps of supplying the bridge circuit with a continuous signal, producing at least one measurement signal representative of the position of the actuated part, selectively controlling the conduction in at least one branch of the bridge as a function of the measurement signal , the step of producing the measurement signal comprising comparing the intensity respectively measured at a high threshold, at a low threshold and at a very low threshold to determine the moment when the current in the electrical element of control is zero and thus wait until the very low current threshold has been crossed to restart the actuating device, and the elaboration of the measurement signal according to the result of the comparison. This gives a command in particularly precise position.

In one embodiment of the invention, in case of detection of the very low threshold at zero, at least one branch of the bridge is open circuit. The detection of the very low threshold at zero means that the measured intensity is below the very low threshold.

In one embodiment of the invention, in case of detection of the very low threshold at zero, two branches of the bridge are put in open circuit.

Advantageously, the control is performed in variable frequency ripple, for example in modulation of the pulse width.

Advantageously, the actuator acts on a fuel injector.

The invention also proposes an actuating device comprising at least one actuator acting on a fuel injector provided with an actuated part and an electrical component for controlling the displacement of the part actuated so as to oscillate between two positions, a an actuator driving circuit provided with a bridge, and a device for controlling at least one bridge switch, the bridge comprising a DC source connected to first and second terminals of said bridge, the electrical control member being connected between the third and fourth terminals of said bridge, said bridge comprising at least one switch connected between the first and third terminals or between the second and fourth terminals, a measuring element of the current flowing in the electrical control element, characterized by the it comprises a high threshold detector of said current, a low threshold detector of said current, and a very low threshold detector. s of said current flowing in the electrical control unit to determine the moment when this current is canceled in the electrical control member and thus wait until the very low current threshold has been crossed to restart the actuating device .

The invention allows a particularly precise control of the moving part of an injector.

In one embodiment of the invention, the device comprises at most three active switches per controlled injector.

In one embodiment of the invention, the device comprises at most n + 2 active switches for n controlled injectors.

In one embodiment of the invention, the device comprises at most 2n active switches for n controlled injectors.

In one embodiment of the invention, the active switches are MOS transistors.

The very low threshold detector is used to detect the presence of current in the coil. The very low current information delivered by said very low threshold detector makes it possible to better control the amplitude of the ripple.

• la figure 1 est un schéma électrique du dispositif d'actionnement selon un aspect de l'invention;
• la figure 2 est un diagramme temporel du déplacement du dispositif de la figure 1; -
• la figure 3 est un chronogramme des différents signaux du dispositif de la figure 1;
• la figure 4 est une machine d'état du dispositif d'actionnement de la figure 1; et
• les figures 5 à 14 illustrent différentes variantes de pont pouvant être utilisées dans le cadre de l'invention.

The present invention will be better understood on reading the detailed description of some embodiments taken as non-limiting examples and illustrated by the appended drawings, in which:

• the figure 1 is an electrical diagram of the actuating device according to one aspect of the invention;
• the figure 2 is a temporal diagram of the displacement of the device of the figure 1 ; -
• the figure 3 is a chronogram of the various signals of the device of the figure 1 ;
• the figure 4 is a state machine of the actuating device of the figure 1 ; and
• the Figures 5 to 14 illustrate different bridge variants that can be used in the context of the invention.

The invention proposes an actuating device having an electronic topology for controlling an actuator with simplified structure and control. One or two antiparallel diodes are used in a bridge circuit, resulting in a decrease in the number of active switches and a simplification of the control.

As can be seen on the figure 1 , the actuating device 1 comprises a bridge circuit 2, a control unit 3 and a detection unit 4.

The bridge circuit 2 comprises four terminals 5, 6, 7, 8, a DC voltage source 9, for example a battery or a DC AC converter connected to the first and second terminals 5 and 6 of the bridge 2 and provides a voltage keep on going. Alternatively, it can be provided that the source 9 provides a continuous intensity. The electrical control member 10 for controlling the actuator is connected between the third and fourth terminals 7 and 8 of the bridge circuit 5. In electrical terms, the electrical control member 10 is likened to an inductor. A first switch 11 is connected between the first and third terminals 5 and 7 and a second switch 12 is connected between the second and fourth terminals 6 and 8. The bridge circuit 2 may be in the form of an integrated circuit in which MOS transistors are provided which can be used as switches 11 and 12. Other types of switches, such as IGBT transistors, can also be used. The switching of the switches 11 and 12 is controlled via the control unit 3, to which the control terminals of said switches 11 and 12 are connected. The bridge circuit 2 further has first and second diodes 13 and 14. The first diode 13 is connected between the second and third terminals 6 and 7, the cathode of the diode 13 being connected to the third terminal 7. The second diode 14 is connected between the first and fourth terminals 5 and 8, the cathode of the second diode 14 being connected to the first terminal 5.

The use of diodes 13 and 14 simplifies the structure of the control unit 3 and the control method of the switches. The diodes 13 and 14 may be of any suitable type. Diode-mounted MOS transistors are preferably used to facilitate the integration of the electronic control topology and to reduce the cost thereof.

The detection assembly 4 comprises a current probe 15 mounted on a power line arranged between the fourth terminal 8 and the electrical control member 10. Of course, the current probe 15 could also be mounted between the third terminal 7 and the electrical control unit 10. The detection assembly 4 also comprises three comparators 16, 17 and 18, for example in the form of operational amplifiers, each having a first input connected to the output of the current probe 15 and an output connected to a specific input of the control unit 3. The second input of each comparator 16, 17, 18 is connected to a specific voltage reference 19, 20, 21, respectively, each providing a reference of high level, low level and very low level, respectively.

In the application of the method to an internal combustion engine injector, it is particularly desirable to carry out a control sequence of the actuator as a function of time between a shutter position of the injector and an injection setpoint position. . The needle can be moved initially from the shutter position to the injection setpoint position with a maximum amplitude, and then move alternately with a small amplitude of _alt , and this, periodically. The needle can subsequently be returned to the closed position or maintained at the injection setpoint position. It can also be provided that the reciprocating movement does not immediately follow the movement towards the injection setpoint position and that the needle is maintained for a certain duration at the injection setpoint position.

Such a sequence may correspond either to an injection sequence or to a sequence prior to the injection. In particular, it is possible for the injection setpoint position to be an open position of the needle in the case where the reciprocating displacement is used during the injection. It can also be provided that the injection setpoint position is a closed position and that the reciprocating movement with respect to the injection setpoint position is generated just before the opening of the needle.

On the figure 3 are illustrated timing diagrams of different control signals applied by the control unit 3 and signals applied across the electrical control member 10. The electrical control member 10 is electrically assimilated to an inductor. The continuous electrical source 9 applies a continuous potential. The voltage level applied to the gate of the transistors forming the switches 11 and 12 corresponds to their switching position.

During a first phase, the switches 11 and 12 are open and the current in the electrical control member 10 is zero. In a second phase, the switch 11 is closed, its transistor being turned on. The current then begins to grow. In a third phase, the comparator 18 detects that the very low threshold is reached. The switch 12 is closed. In a third phase, the switches 11 and 12 remain closed and the comparator 17 detects that the low current threshold is reached. The current continues to grow substantially linearly. In the next phase, the comparator 16 detects that the high current threshold is reached. The control unit 3 controls the opening of the switch 11, which causes the conduction of the diode 13. The current in the electrical control member 10 decreases. In the next phase, the comparator 17 detects that the current has reached the threshold of low levels. The control unit 3 then controls the closing of the switch 11, which causes a growth of the current in the electrical control member 10 and the blocking of the diode 13. The last two phases can then be repeated a number of times.

As illustrated, the order of end of control actuation occurs in a current decay phase in the electrical control member 10, the switch 11 is open and the switch 12 is closed. Upon receipt of an end of actuation command, the control unit 3 controls the opening of the switch 12, which causes the conduction of the diode 14, the diode 13 is already in conduction. The current in the electrical control member 10 then decreases sharply. The comparator 17 detects the downward crossing of the low level threshold. Then, the comparator 18 detects the downward crossing of the very low level threshold.

The different states of the device are illustrated on the figure 4 . At state 0, switches 11 and 12 are open. The device goes to state 1 as soon as it is switched on. If an error is detected, the transition to state 5 is controlled. In state 1, switches 11 and 12 are closed. In the event of a stop, the device goes to state 4. In the event of an error, the device goes to state 5. If the crossing of the low threshold DSB is detected, the device switches to state 2. At state 2, switches 11 and 12 are closed. In the event of a stop, the device goes to state 4. In the event of an error, the device goes to state 5. If the high threshold DSH is detected, the device goes to state 3 In state 3, the switch 11 is open and the switch 12 is on. If the DSB low level threshold is detected, the The device switches back to state 2. In the event of a stop, the device switches to state 4. In the event of an error, the device switches to state 5. In state 4, switches 11 and 12 are open. In case of detection of crossing the low threshold very low DSTB, the device goes to state 0. In case of error, the device goes to state 5. In state 5, the switches 11 and 12 are open. The device returns to state 0 on receipt of an initialization signal. The detection of the very low threshold makes it possible to identify the moment when the current in the coil has canceled after the end of the on command of the device. It can thus be expected that the very low current threshold has been crossed to then restart the device. This avoids operating errors, which increases the reliability and robustness of the device.

The invention makes it possible to precisely control the movement of the actuator, which makes it possible to better cut the jet of fuel in the case of an injector and to improve the fuel atomization during the injection.

Different variants of the bridge circuit 2 can be envisaged. On the figure 5 , the bridge circuit is identical to that of the figure 1 but the controls of the switches 11 and 12 are reversed. On the figure 6 , the diode 14 is removed. On the figure 7 , the diode 13 is removed and the controls of the transistors 11 and 12 are reversed as in the figure 14 . On the figure 8 , the transistor 12 is replaced by a conductive connection or permanently maintained in the on state. The diode 14 is also suppressed. In the embodiment illustrated on the figure 9 , the switch 12 is replaced by a conductive connection or permanently maintained in the on state, the diodes 13 and 14 being present. In the embodiment illustrated on the figure 10 , the controls of the transistors 11 and 12 are reversed and the transistor 12 is permanently maintained in the on state or replaced by an electric wire connected between the terminals 5 and 6. The embodiment of the figure 11 gets closer to the one shown on the figure 10 , except that the diode 13 is removed and replaced.

In the embodiment illustrated on the figure 12 the bridge circuit 2 comprises three identical subassemblies 22, 23 and 24, each similar to the bridge circuit illustrated in FIG. figure 1 . We can thus order three injectors from the same source electric. In the embodiment illustrated on the figure 13 , the three subassemblies 22 to 24 are devoid of diode 14. The subassemblies 22 and 23 are devoid of switch 12 replaced by an electric wire, while the subassembly 24 is provided with a switch 12.

In the embodiment illustrated on the figure 14 , the subassemblies 22 to 24 have a switch 12 and a diode 13 common. There is no diode 14. Only the switch 11 is specific to each subassembly 22 to 24.

It is therefore understood that, according to the variants, the structure of the bridge arrangement can be simplified for the sake of economy, or on the contrary performed more completely for better control of the current and a limitation of overvoltages.

Claims (9)

1. Method for driving a circuit for controlling an actuation device (1) furnished with at least one actuator acting on a fuel injector having an actuated part and an electric control member (10) for moving the actuated part so as to oscillate between two positions, the control circuit comprising a bridge (2), the electric control member (10) being connected in the said bridge (2), the method comprising the steps consisting in supplying the bridge circuit (2) with a direct-current signal, producing at least one measurement signal representative of the position of the actuated part, selectively controlling the conduction in at least one branch of the bridge (2) according to the measurement signal, the step of production of the measurement signal comprising the comparison of the measured intensity respectively with a high threshold (DSH), with a low threshold (DSB) and with a very low threshold (DSTB) in order to determine the moment when the current in the electric control member (10) is zero and thus wait until the very low current threshold (DSTB) has been exceeded in order to reactivate the actuation device (1), and the generation of the measurement signal as a function of the result of the comparison.
2. Method according to Claim 1, wherein at least one branch of the bridge (2) is placed in closed circuit, if the measured intensity is greater than the very low threshold (DSTB).
3. Method according to Claim 1 or 2, wherein two branches of the bridge (2) are placed in closed circuit, if the measured intensity is greater than the very low threshold (DSTB).
4. Method according to any one of the preceding claims, wherein the driving is carried out in variable-frequency ripple.
5. Method according to any one of the preceding claims, wherein the actuator acts on a fuel injector.
6. Actuation device (1) comprising at least one actuator acting on a fuel injector provided with an actuated part and an electric control member (10) for moving the actuated part so as to oscillate between two positions, a circuit for driving the actuator provided with a bridge (2) and a device (3) for driving at least one switch (11, 12) of the bridge (2), the bridge (2) comprising a direct-current source (9) connected to a first terminal (5) and a second terminal (6) of the said bridge (2), the electric control member (10) being connected between the third terminal (7) and fourth terminal (8) of the said bridge (2), the said bridge (2) comprising at least one switch (11) connected between the first terminal (5) and third terminal (7) or between the second terminal (6) and fourth terminal (8), an element (15) for measuring the current flowing in the electric control member (10), characterized in that it comprises a high threshold detector (DSH) (16) of the said current, a low threshold detector (DSB) (17) of the said current, and a very low threshold detector (DSTB) (18) of the said current flowing in the electric control member (10) in order to determine the moment when this current is cancelled out in the electric control member (10) and thus wait until the very low current threshold (DSTB) has been exceeded in order to reactivate the actuation device (1).
7. Device according to Claim 6, characterized in that it comprises at most three active switches (11, 12) per controlled injector.
8. Device according to Claim 6 or 7, characterized in that it comprises at most n+2 active switches (11, 12) for n controlled injectors.
9. Device according to Claim 6 or 7, characterized in that it comprises at most 2n active switches (11, 12) for n controlled injectors.

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