EP0995023B1 - Power control circuit for electromagnetic actuator such as an injector or an electrovalve - Google Patents

Abstract

The invention concerns a power control circuit, for powering a coil (7-10) of at least an actuator such as a fuel injector, comprising a positive booster stage connected to a low voltage power source (3), and comprising a capacitor (6) and a self-induction coil (1) designed to accumulate energy, and first switches (4) cyclically closed and opened by a control unit (16) for charging the coil (1) from the source (3) then charging the capacitor (6) from the coil (1); and finally charging several times and successively the coil (1) again before closing the second switches (11-14) to ensure the powering of at least one actuating coil (7-10) by simultaneous discharge of the capacitor (6) and the self-induction coil (1). The invention is applicable for supplying power to electromagnetic actuators such as electrovalves and injectors for internal combustion engine with direct injection.

Description

The invention relates to a circuit for controlling power, for the power supply of a actuating coil of at least one electromagnetic actuator, such as a solenoid valve or a fuel, in particular for internal combustion engine direct injection.

It is known that certain electromagnetic actuators, such as solenoid valves, especially for exhaust gas recirculation systems internal combustion engine of motor vehicles, and fuel injectors for internal combustion engines, include actuator coils or windings to be supplied by strong inrush currents intensity, quick set-up and shutdown, so obtain precise actuation times, in particular specific times of fuel injection by injectors.

Indeed, the proper functioning of an engine injection, at the same time of the power delivered, pollution and consumption, assumes that injectors have a very short response time to both opening and closing, so that the durations of the fuel injection phases by the injectors correspond as precisely as possible to the durations calculated by an electronic control unit and calculation, commonly called engine control computer, which notably controls the injection of fuel, and, if necessary ignition, if necessary, from operating parameters engine speed, such as engine speed, pressure of air to the intake manifold, temperature of the engine cooling, oxygen content in gases which are detected by appropriate detectors.

It is moreover known that electromagnetic injectors are open by the power supply electric from their actuating coil so as to develop a sufficiently intense electromagnetic force on a movable member of the injector, called needle, to spread it, against return springs, against a seat which it is kept applied with sealing by said springs in the closed position.

To obtain rapid actuation, in particular at the opening, of an injector under a supply voltage of its actuating coil that the latter does not not endure permanently as being far superior at the normal supply voltage of this coil from a conventional low voltage power source and direct current, such as a vehicle battery automotive, and while the normal supply voltage must be sufficient to maintain the injector in its opening state after initial quick opening it has already proposed to associate with the order of an injector electromagnetic an energy accumulation stage, which is subject to phase discharge control means initial supply of the actuation coil each injector considered, in order to obtain, in this phase initial, a high inrush current, capable of ensuring a rapid opening of the injector, then, in a phase subsequent, a holding current of reduced intensity by compared to that of the inrush current, and allowing keep the injector open by feeding its coil actuating.

By FR-A-2 425 137, such a circuit has been proposed. power control with energy storage stage by charging a self induction coil connected to the low voltage power source and associated with first switching means controlled upon closing for load the self induction coil, then at the opening at the same time as second switching means, associated with the actuating coil of the electromagnetic actuator and previously opened are ordered at closing, for discharge the self induction coil into the coil of actuation and obtain in the latter the establishment fast of a high inrush current.

In addition to power control circuits with inductive discharge, similar circuits have been proposed capacitive discharge. In particular, we know by FR-A-2 538 942, EP-A-0 548 915 and FR-A-2 735 591 of power control circuits, for power supply electric of an actuating coil of at least one electromagnetic actuator, such as a fuel, circuits including an accumulation stage or booster, connected to a power source direct current at low voltage, such as motor vehicle battery, and comprising a capacitor of energy accumulation, a self induction coil for the accumulation of energy, and of the first means switches, cyclically controlled at closing and at opening by a switching control unit, for ensure in succession at least two consistent sequences each to charge the self induction coil from said power source and then charging the capacitor from the self induction coil and through a diode, and second switching means, controlled by the closing by said control unit to ensure supply of said actuating coil by discharge of said capacitor, to also obtain the establishment fast of a high inrush current.

In power control circuits to capacitive discharge described in the three documents of aforementioned patent, the actuating coil of the electromagnetic actuator directly as a coil self induction for energy accumulation in the floor booster, to simplify the implementation and reduce the cost of such power control circuits.

The problem underlying the invention is to perfect these power control circuits known from so that their energy storage stage can store then discharge more energy than known circuits to be able to actuate electromagnetic actuators requiring great control power, such as electro-magnetic injectors for direct injection of fuel in the combustion chambers of diesel engines or spark ignition engines, in which the injectors are supplied with high pressure fuel and are returned to the closed position by springs of powerful recall, without the control circuits of power of the invention to be much more complex nor much more expensive than known circuits.

To this end, the power control circuit of the invention, of the type presented above and known by three aforementioned patent documents, is characterized in that said self induction coil is separate from said actuation coil, and in that after charging the capacitor and before supplying said coil actuation, said switching control unit controls the closing of said first switching means to charge said self induction coil, so that the closure of said second switching means, said actuating coil is powered by simultaneous discharge of said capacitor and of said self induction coil.

Transfer to the energy actuation coil accumulated in the capacitor and in the inductor induction by simultaneous capacitive and inductive discharges allows current control of the actuating coil with a high peak current established faster that with the power control circuits of the state of the technique. Compared to these, the circuit of power control of the invention is no more complex neither significantly more expensive, and essentially requires a modification of the control mode of the switching means which is provided by the switching control unit. This modification of the command mode is reduced to a modification control software when, advantageously, the switching means include electronic switches, in particular transistorized, controlled by a command logic delivered by the switching control unit, which includes at least one microprocessor or microcontroller.

The circuit of the invention advantageously comprises in addition to the third switching means, interposed between the power source and the self induction coil, and orders; by the closing control unit for ensure the initial charges of the capacitor and the self induction coil, then after closing the second switching means, cyclically controlled at opening and closing to ensure in the coil actuation, a lower intensity holding current to that of the inrush current resulting from the discharge of the capacitor and the self induction coil. Thus, not only the self induction coil and the capacitor are used, as a first step, as reservoir, of energy, restored in a second time to provide high inrush current with rise time very fast, but the self induction coil and the capacitor can, in combination with the third means switches, used for the maintenance of a holding current, thanks to a DC converter structure in direct current which has the advantage of being of low radiation electro-magnetic, because it can work almost resonance, so that the power circuit of the invention can meet electromagnetic emission standards more stringent which will soon be in force, especially for on-board equipment on vehicles automobiles, such as solenoid valves and injectors, especially for direct fuel injection installation.

Advantageously, thanks to the presence of third switching means it is possible after the closing of the second switch means controlling the simultaneous discharge of the capacitor and the inductor induction in the actuating coil, and before the holding current delivery, cyclic control the third switching means at the opening and at the closing by the switching control unit, so maintain the inrush current at an intensity close to that resulting from the simultaneous discharge of the capacitor and from the self induction coil to the actuation coil. This maintenance phase of the inrush current at a level high can thus take place between the initial phase quick establishment of inrush current and phase setting the holding current at a lower level intensity.

To this end, the third switching means are advantageously controlled by the control unit with a variable opening duty cycle to ensure holding current and / or maintaining the inrush current.

In addition, the second switching means are controlled at opening by the control unit, preferably when the actuating coil is traversed by the holding current, so as to quickly cancel the current in this coil, to obtain a brief cut of the current, necessary to obtain good accuracy of actuator operation.

The circuit of the invention is also advantageous by the fact that the booster stage can supply in parallel the actuating coils of at least two actuators electromagnetic, and in particular the coils of all the injectors of an internal combustion engine. In this effect, the second and third switching means can be ordered at closing to obtain a recovery of at least two feed times actuating coils, which allows recoveries to be managed injection duration, with a single power circuit, in the case of applications to injection engines.

In this configuration of collection management actuator actuation times, the third means switches and the self induction coil form a converter which advantageously ensures an increase holding current during these recoveries.

• la figure 1 est un schéma synoptique du circuit de l'invention pour l'alimentation en parallèle des bobines d'actionnement de quatre injecteurs d'un moteur à combustion interne de véhicule à injection directe,
• la figure 2 est un chronogramme représentant les évolutions de la tension Vout à la borne commune du condensateur et de la diode de charge et du courant iL de la bobine de self induction en fonction de la commande logique des premiers moyens commutateurs pendant la phase de charges successives du condensateur,
• la figure 3 est un chronogramme représentant schématiquement l'évolution du courant i dans une bobine d'injecteur et la commande logique des seconds et troisièmes moyens commutateurs pour l'entretien du courant d'appel puis l'obtention du courant de maintien, jusqu'à la coupure du courant dans cette bobine,
• la figure 4 représente des chronogrammes montrant en superposition l'évolution respectivement du courant i dans une bobine d'injecteur et de la tension V aux bornes de cette bobine, en fonction de la commande logique des premiers moyens commutateurs pendant la phase de décharge,
• la figure 5 représente l'évolution du courant iL dans la bobine de self induction pendant la décharge, et
• la figure 6 représente des chronogrammes montrant l'évolution des courants i1 et i2 dans le cas du recouvrement des alimentations de deux bobines d'injecteur, ainsi que le courant iL dans la bobine de self induction en fonction des commandes logiques des premiers et troisièmes moyens commutateurs en phase de recouvrement.

Other advantages and characteristics of the invention will emerge from the description given below, without limitation, of an exemplary embodiment described with reference to the appended drawings in which:

• FIG. 1 is a block diagram of the circuit of the invention for the parallel supply of the actuating coils of four injectors of an internal combustion engine of a direct injection vehicle,
• FIG. 2 is a timing diagram representing the changes in the voltage Vout at the common terminal of the capacitor and the charging diode and of the current iL of the self-induction coil as a function of the logic control of the first switching means during the charging phase of the capacitor,
• FIG. 3 is a timing diagram schematically representing the evolution of the current i in an injector coil and the logic control of the second and third switching means for maintaining the inrush current and then obtaining the holding current, up to when the current is cut in this coil,
• FIG. 4 represents timing diagrams showing in superposition the evolution respectively of the current i in an injector coil and of the voltage V at the terminals of this coil, as a function of the logic control of the first switching means during the discharge phase,
• FIG. 5 represents the evolution of the current iL in the self-induction coil during the discharge, and
• FIG. 6 represents timing diagrams showing the evolution of the currents i1 and i2 in the case of the overlapping of the supplies of two injector coils, as well as the current iL in the self-induction coil as a function of the logic commands of the first and third means switches in recovery phase.

The power control circuit of Figure 1 includes a self induction coil 1 connected by a end in series with a switch 2 connected to the terminal "+" from a DC power source 3 at low voltage Vbat, which is the battery of a motor vehicle, whose terminal "-" is earthed. By his other end, coil 1 is connected in parallel to another switch 4, connected to ground, and via a diode 5, on the one hand to a terminal of a capacitor 6, whose other terminal is connected to ground, and, on the other hand, with four actuator actuator coils 7, 8, 9 and 10, which are connected in parallel with each other, and each of which is connected to ground via one respectively of four power switches 11, 12, 13 and 14, the overvoltage at the terminals of each coil of injector 7 to 10 being limited, for example to around 80V, by a Zenner diode 15 in parallel on the switch 11, 12, 13 or 14 corresponding.

A capacitor 17, with a value of about 0.5 µF at about 5 µF, and a reverse diode 18 are each mounted in parallel on switch 2, and diode 18 can be the diode integrated in a MOS type switching transistor channel P constituting the switch 2. Similarly, a diode reverse 19 is connected in parallel on switch 4, and this diode can be the integrated diode of a transistor N-type MOS switching device constituting the switch 4.

All switches 2, 4, 11, 12, 13 and 14 are solid state electronic switches controlled by opening and closing by control signals low and high level logic delivered by a unit of switching logic control 16 with microprocessors or microcontrollers, and which is connected to each of the switches ordered through a command line.

Coil 1, for example having a coefficient self-induction from about 10 µH to about 50 µH, is a energy storage coil. The capacitor 6, by example with a capacity between 1 and 10 µF, is a capacitor of a technology other than chemical, of preferably for storing capacitive energy and for ensure energy transfer from the self induction coil 1 to at least one injector coil 7 to 10.

Switch 4 is cyclically controlled at the closing and opening by unit 16 to ensure, when switch 2 is closed, the coil load 1, for a time varying from approximately 20 μs to approximately 100 μs, when switch 4 is closed, then to ensure the charging of the capacitor 6 through the diode 5, by transfer of inductive energy from coil 1, when switch 4 is open. Switch 2 is also ordered to close by unit 16 during a time from about 10 µs to about 70 µs, to ensure the load of coil 1, then in a later phase explained below, switch 2 is controlled so cyclic at closing and opening by unit 16 for maintain the current at a determined value, about 3 to 5 A, in at least one of the injector coils 7 to 10 supplied by closing the switch 11 to 14 correspondent. Indeed, each of the switches 11 to 14 is intended to ensure the conduction of the coil of injector 7 to 10 corresponding. Diode 5 is for function of avoiding the discharge of the capacitor 6 by the switches 2 and 4 when closed.

All the switches 11 to 14 being open, the circuit operation sequencing, controlled by unit 16 is as follows: closing switches 2 and 4 causes the load of the coil 1, traversed by a current iL which increases linearly from 0 to about 15 A for a time of about 20 µs to about 100 µs. The opening switch 4 causes the capacitor 6 to charge by energy transfer from coil 1 to the capacitor 6, through diode 5. The voltage across the capacitor 6 grows along an exponential curve, at the same time that a current peak occurs. This sequence comprising a charge of coil 1 followed by a charge of capacitor 6 is renewed a certain number of times up to charge capacitor 6 at a voltage of 80 V about. This sequence of successive charges is shown in Figure 2, whose curves (a) and (b) represent the voltage Vout at point A of the circuit of FIG. 1, which is at the common terminal to capacitor 6 and to the diode 5, and the current iL in the coil 1, depending on the logic control of switch 4 (curve (c)), the switch 2 being closed and therefore passing during this phase. The circuit, in which the coil 1, the switch 4, the diode 5 and the capacitor 6 constitute a booster stage, is then waiting until a moment before the closure of at least one of the switches 11 to 14 for supply at least one injector coil 7 to 10. Just before ordering an injector, switch 4 is closed, as shown in figure 4, to charge again the coils 1. Then one of the injector switches, by example switch 11 is closed, while switch 2 remains closed and switch 4 is open (see Figures 3 and 4), so that a simultaneous discharge of coil 1 and capacitor 6 into the coil injector 7, traversed by an intense inrush current, which reaches 15 to 20 A after a time of 30 to 50 µs, and corresponds to the sum of the currents resulting from the discharge capacitive of capacitor 6 and the inductive discharge of coil 1. This rapid establishment of an inrush current intense is visible on the curves of Figures 3 and 4.

Maintenance of the inrush current is then ensured by cyclic control of switch 2 to adjust the current in the injector coil 7 at a desired value and varying between 15 and 20 A as shown in Figure 3. The control unit 16 cyclically controls the switch 2 with a variable aperture duty cycle, which is then lowered to decrease the current to an intensity of 3 to 5 A approximately, then keep it around this value to ensure a holding current of the injector in its coil 7.

Finally, stopping the current in the injector coil 7 is obtained by controlling the opening of the switch 11, resulting in the rapid cancellation of the current (Figure 3).

During the simultaneous discharge of the capacitor 6 and from coil 1 in coil 7, the current iL in the coil 1 evolves as shown in figure 5.

With a single power circuit according to the invention, it is possible to simultaneously control the supply of two injector coils such as 7 and 8 for example. In effect, the booster stage comprising the coil 1, the diode 5, the switch 4 and the capacitor 6, supplies parallel the injector coils 7 to 10. Switch 2 and the two switches for example 11 and 12 of the two injector coils 7 and 8 to be supplied with recovery, are controlled upon opening by the control unit 16 of so as to ensure this recovery of feeding times. Curves (a) and (b) in Figure 6 show the currents i1 and i2 in the injector coils 7 and 8 after the two time-shifted switch 4 closures - see curve (d) - to load coil 1 just before shifted closings of switches 11 and 12, which are at the origin of currents i1 and 12. The charges of coil 1 resulting from the closings of switch 4 are visible on the curve (c) of figure 6, representing the current iL in this coil 1. Finally, the switch 2 command with a variable duty cycle after the openings of the switch 4 (see curve (e) in figure 6) allows maintaining the inrush current then obtaining the inrush current maintenance. For coil 7, there is an increase in the holding current i1 supplied by the converter constituted by coil 1 and switch 2, by a factor of 2, as shown on curve (a) of figure 6, during the recovery period, which begins at establishment of current i2 (closing of switch 12) and ends at the cut (not shown in Figure 6) of the current i1 (when switch 11 is opened).

Claims (8)

1. Power control circuit for supplying electric current to an actuating coil (7-10) of at least one electromagnetic actuator such as a fuel injector for an internal-combustion engine, the circuit comprising a booster stage connected to a low-voltage DC power supply (3) such as a vehicle battery and including a capacitor (6) for energy storage, an inductance coil (1) for energy storage and first switching means (4) of which the closure and opening are controlled cyclically by a switch control unit (16) to produce a succession of at least two sequences in each of which the inductance coil (1) is charged by said power supply (3) then the capacitor (6) is charged by the inductance coil (1) via a diode (5), and including second switching means (11-14) of which the closure is controlled by said control unit (16) to supply said actuating coil (7-10) by discharging said capacitor (6), characterised in that said inductance coil (1) is distinct from said actuating coil (7-10) and in that, after charging the capacitor (6) and before supplying said actuating coil (7-10), said switch control unit (16) controls the closure of said first switching means (4) to charge said inductance coil (1) such that, on closure of said second switching means (11-14), said actuating coil (7-10) is supplied by the simultaneous discharging of said capacitor (6) and of said inductance coil (1).
2. Power control circuit according to claim 1, characterised in that it additionally comprises third switching means (2) which are interposed between said power supply (3) and said inductance coil (1) and of which the closure is controlled by said control unit (16) to bring about the initial charging of said capacitor (6) and of said inductance coil (1) then, after closure of said second switching means (11-14), the opening and closure of said third switching means (2) are controlled cyclically to produce, in said actuating coil (7-10), a holding current which is weaker than the cut-in current produced by the simultaneous discharging of said capacitor (6) and of said inductance coil (1).
3. Power control circuit according to claim 2, characterised in that, after closure of said second switching means (11-14) to control the simultaneous discharging of the capacitor (6) and of the inductance coil (1) into the actuating coil (7-10) and before delivery of said holding current, the opening and closure of said third switching means (2) are controlled cyclically by said control unit (16) to maintain the cut-in current at a strength close to that produced by the simultaneous discharging of the capacitor (6) and of the inductance coil (1) into the actuating coil (7-10).
4. Power control circuit according to either of claims 2 and 3, characterised in that the third switching means (2) are controlled by said control unit (16) with a variable make-break ratio to produce said holding current and/or to maintain said cut-in current.
5. Power control circuit according to any of claims 1 to 4, characterised in that the opening of the second switching means (11-14) is controlled by said control unit (16) to rapidly cancel the current supplying the actuating coil (7-10) .
6. Power control circuit according to any of claims 1 to 5, characterised in that the switching means (2, 4, 11-14) comprise electronic switches which are driven via a logic control output by said switch control unit (16) which comprises at least one microprocessor or microcontroller.
7. Power control circuit according to any of claims 2 to 6, characterised in that the booster stage (1, 4, 5, 6) supplies, in parallel, the actuating coils (7-10) of at least two electromagnetic actuators, and the closure of said second (11-14) and third (2) switching means is controlled to produce an overlap of the periods for supplying at least two actuating coils (7-10).
8. Power control circuit according to claim 7, characterised in that the third switching means (2) and the inductance coil (1) form a converter which increases the holding current during an overlap of the periods for supplying at least two actuating coils (7-10).

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