EP1805404A1

EP1805404A1 - Method for monitoring a control circuit and actuating device

Info

Publication number: EP1805404A1
Application number: EP05815531A
Authority: EP
Inventors: Eugenio Macua; Christophe Ripoll
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2004-10-18
Filing date: 2005-10-18
Publication date: 2007-07-11
Also published as: FR2876741A1; KR20070068360A; US20080262696A1; WO2006042998A1; FR2876741B1; JP2008517200A; JP4689676B2; US7747376B2

Abstract

The invention concerns a method for monitoring a control circuit of an actuating device (1) provided with at least one actuator including an actuated part and an electric member controlling (10) the movement of the actuated part, the control circuit comprising a bridge (2), the controlling electric member being connected in said bridge. The method includes steps which consist in: powering the bridge (2), producing at least one measurement signal (15) representing the position of the actuated part, selectively interrupting conduction in at least one branch of the bridge (2) in accordance with the measurement signal to maintain same substantially in an operating zone defined between a low threshold and a high threshold during a phase activating the controlling electric member (10) and wherein: conduction is interrupted in at least one branch so as to place the controlling electrical member (10) in short-circuit via two branches of the bridge (2) when the measurement signal reaches at least one specific threshold above the low threshold.

Description

Method for controlling a control circuit and an actuating device

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 the 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 times taken to open or close the needles are still too high, about 1 to 2 ms, which prevents to distribute properly the injection over the entire opening time of the valve. In addition, the minimum opening time, which determines the minimum amount of fuel that can be injected, is still too great for some operating points of the engine.

Known needle injectors also have injection ports of relatively large diameters to enable 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 unvaporized 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 in the transient for lack of knowledge of the amount of fuel that actually enters the corresponding combustion chamber. This phenomenon of wall wetting is one of the important causes of high pollutant emissions during cold engine starts.

Moreover, with a conventional needle injector, when the needle opens when the needle begins to leave its seat, a bull e of liquid is formed which disappears when the needle is completely lifted, the flow of fluid then regularizing.

This change in the nature of the flow renders impossible any precise control of the instantaneous flow rate of the injector.

Some have tried to solve these different problems by developing injectors using piezoelectric actuators to maneuver the needle so as to lower the duration of opening and closing 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 drops in the fuel jet coming out 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-2801346 describes a fuel injection device for an internal combustion engine equipped with an injector comprising a nozzle supplied with fuel and at the end of which is provided an injection orifice, means for placing fuel. in cyclic vibration of the nozzle such as a transducer controlled in duration and intensity by the engine control electronic system, and shutter means biased by elastic 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; vibrating the nozzle and shutter means ensuring the ejection of a predetermined amount of fuel.

The document FR-A-2 846 808 describes an actuator device provided with an actuator, an electronic actuator control topology comprising a bridge circuit with a source. continuous between the first and second terminals of the circuit, the actuator being connected between the third and fourth terminals 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 driving method of a control circuit is intended for an actuating device provided with at least one actuator having an actuated part and an electric control member for moving the actuated part, the control circuit comprising a bridge, the electrical control member being connected in said bridge. The method comprises the steps of: supplying the bridge generating at least one measurement signal representative of the position of the actuated part selectively interrupt the conduction in at least one branch of the bridge as a function of the measurement signal to maintain it substantially in a zone defined between a low threshold and a high threshold during an activation phase of the electrical control member and wherein: the conduction is interrupted in at least one branch so as to place the electric control member in short position; circuit via two branches of the bridge when the measurement signal reaches at least a determined threshold above the low threshold.

It is thus possible to obtain a stream of shape close to a sinusoid in the electrical control element. In one embodiment of the invention, the electrical control device is placed in short circuit when the measurement signal reaches or exceeds said determined threshold.

In one embodiment of the invention, the electrical control device is placed in short circuit when the measurement signal passes below said determined threshold.

In one embodiment of the invention, the electrical control device is placed in short circuit when the measurement signal reaches the high threshold.

In one embodiment of the invention, the electrical control device is placed in short circuit when the measurement signal passes an intermediate threshold situated between the high threshold and the low threshold.

In one embodiment of the invention, the conduction is interrupted in at least one branch as a function of a time base signal.

In one embodiment of the invention, the conduction is interrupted in at least one branch so as to apply the power supply to the terminals of the electrical control unit so that the measurement signal reaches the operating zone when the signal if it is below the low threshold and the time base signal indicates a unit of time.

In one embodiment of the invention, the conduction is interrupted in at least one branch so as to apply the power supply to the terminals of the electrical control unit so that the measurement signal reaches the low threshold when the signal of The measurement is in the operating area and the time base signal indicates a unit of time.

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:

FIG 1 is an electrical diagram of the actuating device according to one aspect of the invention; 005/050861

FIG. 2 is a time diagram of the displacement of the device of FIG. 1;

FIG. 3 is a timing diagram of the various signals of the device of FIG. 1; FIG. 4 is a state machine of the actuating device of FIG. 1; and

- Figure 5 is a timing diagram of the current in the actuator.

The invention provides an actuating device having an electronic control topology of 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 in FIG. 1, the actuating device 1 comprises a bridge circuit 2, a control unit

3 and a detection assembly 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 power 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 1 1 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 can be in the form of an integrated circuit in which are provided the transistors of MOS type that can be used as switches 1 1 and 12. Other types of switches, such as IGBT transistors, can also be used. The switching of the switches 1 1 and 12 is controlled via the control unit 3, to which the control terminals of said switches 1 1 and 12 are connected. The bridge circuit 2 further has first and second diodes 1 3 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 method of controlling 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 detecting unit 4 comprises a current probe 15 mounted on a power line disposed between the fourth terminal 8 and the electrical control member 10. Bi, of course, the current probe 15 could also be mounted between the third terminal 7 and the electrical control member 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 sensor current 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, low and very low, respectively. In the application of the method to an internal combustion engine injector, it is particularly desired to perform 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 _aU , 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.

FIG. 3 illustrates the timing diagrams of various control signals applied by the control unit 3 and signals applied across the electrical control unit 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, an order of operation comes (signal F) and switches 11 and 12 are closed, by turning on the corresponding transistor. The current then begins to grow. In a third phase, the comparator 18 detects that the very low threshold is reached. 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 slowly. In the next phase, the control unit 3 receives a clock signal H and controls the opening of the switch 12, resulting in a rapid decay of the current I which must then pass through the diodes 13 and 14.

Then, the comparator 17 detects that the current has reached the low level threshold. The control unit 3 then controls the closing of the switch 12, which causes a slow decay of the current in the electrical control member 10. The two slow decay phases have similar decay slopes. In the following phase, the control unit 3 receives a clock signal H and controls the closing of the switch 11, hence a growth of the current I. The comparator 17 detects that the current exceeds the threshold low level. The comparator 16 detects that the current exceeds the high level threshold. The control unit 3 then controls the opening of the switch 11. The last four 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 in FIG. 4. In state 0, the 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 7 is controlled. In state 1, switches 11 and 12 are closed. In the event of a stop, the device switches to state 6. In the event of an error or a clock signal H, the device switches to state 7. In case of detection of crossing the low threshold DSB the device goes to state 2. In state 2, switches 11 and 12 are closed. In the event of a stop, the device switches to state 6. In the event of an error or of a clock signal H, the device goes to state 7. If the high threshold DSH is detected, the device device goes to state 3. In state 3, the switch 11 is open and the switch 12 is on. In the event of a stop, the device goes to state 6. In case of error, the device goes to state 7. In case of clock signal H, the device goes to state 4. In state 4, switches 11 and 12 are open. In the event of detection of the low level threshold DSB down, the device goes to state 5. In case of stop, the device goes to state 6. In case of error, the device switches to state 7. In case of clock signal H, the device returns to state 2. At state 5, switch 11 is open and switch 12 is on. In the event of a stop, the device switches to state 6. If an error occurs, the device switches to state 7. In case of clock signal H, the device returns to state 1.

In state 6, switches 11 and 12 are open. In case of detection of crossing the very low threshold DSTB down, the device goes to state 0. In case of error, the device goes to state 7.

In the state 7, 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. In FIG. 5, the current waveform 1 is illustrated with high, low and intermediate three-level control. An additional comparator 19 is shown in dotted line in FIG. 1 to detect the intermediate current threshold. The waveform of the current is then close to a sinusoid.

Claims

1 -Procédé of piloting a control circuit of an actuating device provided with at least one actuator having an actuated part and an electrical component for controlling displacement of the actuated part, the control circuit comprising a bridge, the electrical control member being connected in said bridge, the method comprising the steps of: supplying the bridge to produce at least one measurement signal representative of the position of the actuated part - selectively interrupting the conduction in at least one branch of the bridge as a function of the measurement signal to maintain it substantially in an operating zone defined between a low threshold and a high threshold during an activation phase of the electrical control element and in which: - the conduction is interrupted in at least one branch so as to place the electrical control device short-circuited by means of two branches of the bridge when the measurement signal reaches at least one determined threshold above the low threshold.

2-Process according to claim 1, wherein the electrical control member is placed in short circuit when the measurement signal reaches or exceeds said determined threshold.

3-A method according to claim 1 or 2, wherein the electrical control member is placed in short circuit when the measurement signal passes below said determined threshold. 4-Method according to one of the preceding claims, wherein the electrical control member is placed in short circuit when the measurement signal reaches the high threshold. 5-Method according to one of the preceding claims, wherein the electrical control member is placed in short circuit when the measurement signal passes an intermediate threshold between the high threshold and the low threshold. 6-Method according to one of the preceding claims, wherein the conduction is interrupted in at least one branch according to a time base signal. 7-Method according to one of the preceding claims, wherein the conduction is interrupted in at least one branch so as to apply the power to the terminals of the electrical control member so that the measurement signal joins the operating zone when the measurement signal is below the low threshold and the time base signal indicates a unit of time.

8-Method according to one of the preceding claims, wherein the conduction is interrupted in at least one branch so as to apply the power to the terminals of the electrical control member so that the measurement signal reaches the low threshold when the measurement signal is in the operating area and the time base signal indicates a unit of time.