Auxiliary device for controlling a motor with piezoelectric injectors

Abstract

The invention relates to an auxiliary device (30) for controlling a motor, the device comprising first and second connection terminals (32, 34) for connecting the device between an output of the ECU (10) and a piezoelectric actuator (12); a discharge stage (36) at the second terminal (34) for discharging the actuator; an electronic switch (38) between the first and second terminals in order to connect or disconnect the ECU and the piezoelectric actuator; a simulation stage (40) connected to the first terminal (32) in order to simulate, for the ECU, connection to the piezoelectric actuator; a microcontroller (46) configured to resume control of the actuator by acting programmatically on the discharge stage, the electronic switch and the simulation stage. The simulation stage comprises a boost converter (48). The microcontroller controls the boost converter so as to reproduce behavior of the piezoelectric actuator.

Description

DP.FRTE.0003 / PC 1 SUPPLEMENTARY ENGINE CONTROL DEVICE FOR INJECTORS PIEZOELECTRIC Technical Field

[0001] In general, the invention relates to a supplementary device for controlling an internal combustion engine. Technological background

[0002] The state of the art includes complementary engine control devices that supplement a car's original equipment and enable improved performance in terms of power, engine torque, responsiveness, and / or harmful emissions (CO2, NOx). X (e.g., soot, etc.) This is referred to as automotive "personalization" (or "tuning").

[0003] Document DE 198 36 113 describes, for example, an additional engine control device connected to the fuel injection valves. This allows the injection durations determined by the original engine control unit to be extended, resulting in an increased quantity of fuel injected. A similar device is described in document DE 198 37 060.

[0004] Document EP 2 143 917 describes an additional engine control device that is connected between the original engine control unit and the fuel injection system. This additional device intercepts the signals sent by the original engine control unit to the fuel injection system and replaces them with signals that define modified fuel quantities if the engine speed exceeds a certain threshold. Specifically, above a certain engine speed, the amount of fuel defined by the additional device is reduced compared to that predicted by the original control unit. The resulting effect of this intervention is that the driver experiences less dynamic behavior from the car at high engine speeds. This naturally encourages the driver to shift gears and adopt a more economical, and therefore more environmentally friendly, driving style.

[0005] Document EP 2957752 A1 describes a supplementary motor control device comprising a microcontroller, non-volatile memory, an interface unit, an analog input, and an analog output. The interface unit can connect the microcontroller to a computer bus and allows the microcontroller DP.FRTE.0003 / PC 2 listens to data on the bus. The analog input is connected to the microcontroller via an analog-to-digital converter and is used to connect the supplementary device to a probe. The analog output is connected to the microcontroller via a digital-to-analog converter and is used to connect the supplementary device to an analog input of the original engine control unit. The microcontroller is designed to listen to data on the bus, calculate a correction to a signal applied to the analog input based on a map stored in memory, and output a corrected signal to the analog output. This corrected signal corresponds to the signal applied to the analog input but includes the correction.

[0006] Tampering with the injector control signals can cause problems because the original control unit must at least temporarily be disconnected from the injectors and reconnected to replacement loads so that it does not detect an error.

[0007] Publication WO 2007 / 134353 A1 relates to a device for controlling a piezoelectric actuator of an injection nozzle for an internal combustion engine, comprising a control unit that cyclically controls a charging circuit and a discharging circuit for the piezoelectric actuator. A capacitive replacement load, electrically replicating the piezoelectric actuator and connected to a charging stage, an additional discharging stage for the piezoelectric actuator, and a switch controlled by a control circuit are used. The switch connects the replacement load or the piezoelectric actuator to the discharging circuit controlled by the control unit.Depending on at least one parameter that varies according to the load applied to the motor, the control circuit can decouple the piezoelectric actuator from the discharge circuit by acting on the switch and can then discharge the piezoelectric actuator with a delayed effect by acting on the additional discharge stage. When the piezoelectric actuator is decoupled from the discharge circuit, the discharge expected by the control unit is simulated using the replacement load. This load must therefore be recharged after being discharged by the discharge circuit controlled by the control unit. DP.FRTE.0003 / PC 3

[0008] It has been observed that using the device from publication WO 2007 / 134353 A1 in a modern internal combustion engine can result in the control unit going into error mode and preventing starting. General description

[0009] A supplementary engine control device better suited for modern cars is proposed. Such a supplementary engine control device comprises a first and a second connection terminal for connecting the supplementary engine control device between an output of the original engine control unit (hereafter referred to as "ECU," "ECU" being the acronym for the English term "engine control unit") intended for driving a piezoelectric actuator and said piezoelectric actuator; a discharge stage connected to the second connection terminal for discharging said piezoelectric actuator; an electronic switch between the first and second terminals for connecting or disconnecting the ECU and said piezoelectric actuator; a simulation stage connected to the first connection terminal for simulating to the ECU the connection with said piezoelectric actuator;a microcontroller connected to said discharge stage, to the electronic switch and to the simulation stage, the microcontroller being configured to take over the control of said piezoelectric actuator by acting programmatically on the discharge stage, on the electronic switch and on the simulation stage.; The simulation stage includes a boost converter connected to the microcontroller, and the microcontroller is configured to control the boost converter so as to reproduce a behavior (in terms of voltage and / or current observable on the first terminal) of said piezoelectric actuator, in particular a behavior (voltage and / or current observable on the first terminal) expected by the ECU.

[0010] Preferably, the complementary motor control device includes several channels configured in this way, so as to be able to drive several piezoelectric actuators in parallel. DP.FRTE.0003 / PC 4

[0011] The supplementary device can be interposed between the ECU and the piezoelectric actuators, intercepting the control signals from the ECU and replacing them with modified (corrected) control signals. The corrections or modifications applied by the microcontroller may depend on input data, such as data monitored on a data bus (e.g., data relating to engine speed, accelerator pedal position, and / or oil temperature, etc.), and on a map stored in memory. The corrections or modifications may also depend on other parameters obtained from analog lines to which the supplementary device is connected. The supplementary device modifies the control of the piezoelectric actuators, such as injection durations, resulting in different engine behavior.

[0012] The supplementary engine control device according to the invention allows for a more faithful reproduction of the voltage and / or current signal expected by the ECU at its output when it applies a control signal to the piezoelectric actuators. Consequently, the risk of the ECU detecting a malfunction and entering error mode is significantly reduced. The supplementary engine control device is particularly suitable for integration into a vehicle whose ECU monitors for certain signatures in the voltage and / or current signal or performs advanced diagnostics on this signal. It should be noted that the proposed solution can be adapted to different types of vehicles by programming the microcontroller and / or the boost converter.Therefore, thanks to the boost converter, the problem of reproducing the behavior of the piezoelectric actuator can be reduced to programming and will not present any particular difficulty depending on the type of vehicle.

[0013] The supplementary motor control device may include a current sensor and / or a voltage sensor arranged to measure the current entering the first terminal and / or the voltage across the first terminal. In this case, the current sensor and / or voltage sensor are connected to the microcontroller to transmit the current and / or voltage measurements.

[0014] The microcontroller can be configured to control the boost converter so as to adjust the current entering the first terminal or the voltage at the first terminal according to the behavior of the piezoelectric actuator. In this way, the current DP.FRTE.0003 / PC 5 entering the first terminal or the voltage at the first terminal can be varied in such a way that an ECU monitoring this / these parameter(s) can be fooled.

[0015] Preferably, the complementary motor control device includes non-volatile memory connected to the microcontroller, which has access to data stored in the memory, e.g., one or more maps. The microcontroller and the memory (and possibly other components) can be integrated on the same chip, thus forming a system-on-a-chip (SoC).

[0016] The complementary motor control device may include an interface unit configured to connect the microcontroller to a computer bus (e.g., a PT-CAN bus), enabling the microcontroller to listen for data on said bus and, optionally, to transmit data on said bus.

[0017] The microcontroller is preferably configured to take over the control of said piezoelectric actuator by opening the electronic switch (at determined times), discharging said piezoelectric actuator by the discharge stage in a delayed or advanced manner, and controlling the boost converter so as to adjust the current entering the first terminal or the voltage at the first terminal to the behavior that the piezoelectric actuator would have if it were directly connected to the ECU output intended to control it.

[0018] The microcontroller can, e.g., be configured to control the boost converter so as to produce, at the time the ECU attempts to discharge the piezoelectric actuator, a voltage ramp that resembles the voltage ramp that the piezoelectric actuator would produce if it were directly connected to the ECU.

[0019] In some embodiments, the microcontroller can be configured to control the boost converter to produce a simulated needle-closing signal. The needle-closing signal can consist of a characteristic voltage change at the moment the injector is fully closed. More generally, the microcontroller can be configured to control the boost converter to produce any characteristic signal (signature) whose occurrence is monitored by the ECU.

[0020] According to a preferred embodiment of the invention, the simulation stage includes an electronic switch, controlled by the microcontroller, arranged between the first DP.FRTE.0003 / PC 6 connection terminals and the boost converter to connect the boost converter to the first terminal when the electronic switch between the first and second terminals is open. The simulation stage may also include a diode between the boost converter and the electronic switch arranged between the first connection terminal and the boost converter. The simulation stage may also include a filtering capacitor in parallel with the boost converter. Brief description of the drawings

[0021] Other features and characteristics of the invention will become apparent from the detailed description presented below, by way of illustration, with reference to the accompanying drawings which show: Fig. 1: an engine control unit (ECU) connected to a piezoelectric actuator; Fig. 2: the current I and the voltage U at the output of the ECU as a function of time t during a pilot cycle of a main injection; Fig. 3: Diagram of a complementary engine control device according to an embodiment of the invention connected between an ECU and a piezoelectric actuator; Fig. 4: the diagram of figure 3 during the charging phase of the piezoelectric actuator; Fig. 5: the diagram of figure s when the charging phase is complete and the piezoelectric actuator is under high voltage; Fig. 6: the diagram of figure 3 during the phase where the ECU tries to discharge the piezoelectric actuator; Fig. 7: the diagram of figure s, during the phase where the ECU tries to partially charge the piezoelectric actuator; Fig. 8: the diagram of figure 3, during the phase where the complementary device actually discharges the piezoelectric actuator; Fig. 9: the diagram of figure 3, during the diagnostic phase; Fig. 10: the diagram of figure 3, during the diagnostic phase, when the complementary device generates a signal to close the injector needle; DP.FRTE.0003 / PC 7 Fig. 11: the diagram of figure 3, during the final phase of the cycle where the ECU tries to discharge the piezoelectric actuator. Detailed description

[0022] Figure 1 schematically shows an engine control unit (ECU) 10 connected to a piezoelectric actuator 12 of an internal combustion engine injector. Depending on certain input parameters 22, such as the accelerator pedal position and engine speed, the ECU 10 controls (among other things) the piezoelectric actuators of the injectors.

[0023] The ECU 10 includes a charging circuit 14 for charging the piezoelectric actuator 12 and a discharging circuit 16 for discharging it. The charging circuit 14 includes a current source 14a and a switch 14b, controlled by a controller 18. The discharging circuit 16 includes a switch 16a, controlled by the controller 18, for connecting the driven terminal of the piezoelectric actuator 12 to ground. The ECU 10 controls fuel injection by charging and discharging the piezoelectric actuator 12 at specific times during the engine cycle and for precise durations, which are determined by the amount of fuel to be injected and the fuel pressure.

[0024] The illustrated ECU includes a voltage sensor 20 measuring the voltage on the driven terminal of the piezoelectric actuator 12.

[0025] Figure 2 schematically shows the current I and voltage U at the ECU output as a function of time t during a main injection control cycle. The piezoelectric actuator 12 is charged by the ECU 10 when switch 14b is closed (phase A). To limit the amplitude of the charging current, the controller 18 can apply a pulse-width modulation (PWM) signal to switch 14b. The injector normally opens when the voltage reaches a threshold value typically between 120V and 200V. Once the piezoelectric actuator 12 is charged, the ECU cuts off the current supply by opening switch 14b. The voltage at the controlled terminal of the piezoelectric actuator 12 remains approximately constant as long as the controlled terminal is open (phase B). The injector remains open during this time. To close the injector, ECU 10 closes switch 16a.To limit the amplitude of the discharge current, the controller 18 applies a pulse-width modulated signal (signal. DP.FRTE.0003 / PC 8 PWM (Pulse Width Modulation) results in a series of openings and closings of switch 16a over a short period. The voltage at the driven terminal of the piezoelectric actuator 12 decreases according to a ramp (phase C). When the mechanical force of the piezoelectric actuator is no longer sufficient to keep the injector open, it closes after a short delay depending on the injector's mechanical / hydraulic design.

[0026] The ECU of a modern combustion engine can perform a partial discharge of the piezoelectric actuator, so that a residual voltage is maintained at the driven terminal, e.g., 40 V. Alternatively, the ECU can perform a complete discharge immediately followed by a partial charge (e.g., to the aforementioned 40 V) of the piezoelectric actuator (phase D in Figure 2). After the discharge or partial charge, the driven terminal of the piezoelectric actuator can again be opened. The piezoelectric actuator is partially expanded, and the pressure variations to which it is subjected generate mechanical stresses that result in voltage variations detectable at the ECU 10 by the voltage sensor 20 (phase E). The voltage variation 24 allows for precise detection of the mechanical closure of the injector needle.This strategy is used by some modern ECUs, particularly when performing pre-injections and / or post-injections. For engine operation, precise detection of needle closure is less critical during primary injections, but some ECUs detect the presence of the mechanical needle closure signature. The absence of this signature can then trigger an error mode and illuminate the "check engine" light. At the end of the primary injection cycle, the ECU discharges the piezoelectric actuator (phase F).

[0027] Document WO 2007 / 134353 A1 explains how the duration of the main injection can be increased using an additional device interposed between the ECU and the actuators. However, the document does not explain how to perform a partial charge or discharge of the piezoelectric actuator, nor how to prevent the ECU from detecting the absence of certain signatures in the voltage signal.

[0028] Figure 3 schematically shows how an additional engine control device 30 according to an advantageous embodiment of the invention is connected to the ECU 10. The additional device 30 (or additional control unit) comprises a first connection terminal 32 and a second connection terminal DP.FRTE.0003 / PC 9 34 to connect the additional motor control device 30 between an output of the ECU 10 intended for the control of a piezoelectric actuator 12 and the controlled terminal of the latter.

[0029] The device 30 further includes a discharge stage 36 connected to the second connection terminal 34 for discharging the piezoelectric actuator, an electronic switch 38 between the first and second terminals 32, 34 for connecting or disconnecting the ECU 10 from the piezoelectric actuator, a simulation stage 40 connected to the first connection terminal 32 for simulating the connection of the piezoelectric actuator 12 to the ECU 10, a current sensor 42 arranged to measure a current entering the first terminal, and a voltage sensor 44 arranged to measure a voltage at the first terminal 32. The device 30 further includes a microcontroller 46 connected to the discharge stage 36, the electronic switch 38, the simulation stage 40, the current sensor 42, and the voltage sensor 44.The microcontroller 46 is configured to (temporarily) control the piezoelectric actuator 12 by acting programmatically on the discharge stage 36, on the electronic switch 38 and on the simulation stage 40.

[0030] The simulation stage 40 includes a boost converter 48 controlled by the microcontroller 46, and an electronic switch 50, also controlled by the microcontroller 46, arranged between the first connection terminal 32 and the boost converter 48. A filter capacitor 52 is arranged in parallel with the boost converter 48 between ground and the electronic switch 50. The simulation stage 40 further includes a diode 54 between the boost converter 48 and the electronic switch 50. The microcontroller 46 can close the electronic switch 50 to connect the boost converter 48 and the filter capacitor 52 to the first terminal 32 when the electronic switch 38 between the first and second terminals 32 and 34 is open, i.e., when the ECU 10 is disconnected from the piezoelectric actuator 12.

[0031] The complementary device 30 includes a non-volatile memory 56 connected to the microcontroller 46. The memory 56 may be integrated into the microcontroller 46 or be a separate component. The memory 56 may be used for storing maps and / or firmware. DP.FRTE.0003 / PC 10

[0032] The microcontroller 46 includes a connection 58 to the CAN bus (acronym for the English term "controller area network") internal to the motor (this is referred to as the "CAN powertrain" or "PT-CAN").

[0033] The supplementary device 30 is configured to modify the control of the piezoelectric actuators. The modification depends on the maps stored in the memory 56 and, according to a preferred embodiment of the invention, concerns only the main injections. Any pre- and / or post-injections are therefore not changed. Such a case will be presented later by way of illustration. However, according to other embodiments of the invention, the supplementary device could be configured to modify any pre- and / or post-injections.

[0034] Figures 4 to 11 illustrate the sequence of a main injection, the duration of which is modified by the supplementary device 30. The insets in the lower left of each figure show the current (I) and voltage (U) at the output of the ECU 10 (solid lines) and the current and voltage at the controlled terminal of the piezoelectric actuator (dashed lines). The phase under discussion is indicated by a dashed area.

[0035] During the first phase (Figure 4) of a main injection control cycle, the ECU 10 supplies current to the piezoelectric actuator 12 to charge it. The direction of the current is indicated in Figures 4 to 11 by double arrows. Switch 14b is closed, controlled by a PWM signal to limit the current amplitude (e.g., between 5 and 10 A). Switch 16a is open. The auxiliary device 30 keeps switch 38 closed during this phase. When the voltage reaches a threshold value, the ECU 10 cuts off the current by opening switch 14b. The microcontroller 46 measures the voltage reached using the voltage sensor 44.

[0036] When the piezoelectric actuator 12 is charged to the operating voltage (Figure 5), the microcontroller 46 of the complementary device 30 closes the switch 50 so as to charge the filter capacitor 52, sets the voltage of the boost converter 48 to the operating voltage which has been measured, and opens the switch 38 when the filter capacitor 52 is charged. DP.FRTE.0003 / PC 11

[0037] When the ECU 10 requests injector closure, it closes switch 16a, or controls it via a PWM signal to limit the discharge current. At this stage (Figure 6), with switch 38 open, the piezoelectric actuator 12 remains charged and fuel injection continues. The discharge circuit 16 of the ECU 10 thus draws current from the filter capacitor 52 and the boost converter 48. The microcontroller 46 drives the boost converter 48 to produce a voltage ramp similar to that produced during the discharge of the piezoelectric actuator 12 in the situation shown in Figure 1 (without the additional device 30). In the illustrated case, the ECU 10 performs a complete discharge immediately followed by a partial charge to a diagnostic voltage (Figure 7). As the ECU 10 is at this stage disconnected from the piezoelectric actuator 12 (switch 38 being open), it charges the filtering capacitor 52.Thanks to diode 54, the boost converter 48 can remain passive during this time. The voltage ramp measured by ECU 10 corresponds to the expected behavior.

[0038] The auxiliary device 30 discharges the piezoelectric actuator 12 after a certain time by closing the discharge stage switch 39 (Figure 8). More specifically, the microcontroller 46 applies a PWM signal to the switch 39 to limit the discharge current. This discharge remains invisible to the ECU 10, since the switch 38 is open at this stage. It should be noted that the discharge of the piezoelectric actuator 12 by the auxiliary device 30 can, in principle, occur at any time as long as the switch 38 is open. The microcontroller 46 can therefore close the injector earlier or later than intended by the ECU 10, regardless of the cycle phase it is in.

[0039] When the filter capacitor 52 is charged to the diagnostic voltage, the ECU 10 reduces the injected current. When the microcontroller 46 detects that the current entering the first terminal 32 returns to 0 (or falls below a certain threshold), it measures the voltage at the first terminal 32 and stores it (Figure 9). Then, the microcontroller 46 controls the boost converter 48 so that it produces the signature of the injector needle closing, e.g., a small increase in voltage 24, which the ECU can detect (Figure 10).

[0040] To end the diagnostic phase, ECU 10 opens switch 14b and closes switch 16a, respectively controlling it with a PWM signal to limit the DP.FRTE.0003 / PC 12 discharge current. The microcontroller 46 detects that the discharge is initiated by the ECU 10 by monitoring (using the current sensor 42) the current coming out at the first terminal and controls the boost converter 48 so as to achieve the voltage ramp expected by the ECU 10.

[0041] The supplementary device 30 can therefore be interposed between the ECU and the piezoelectric actuators, intercepting the control signals emanating from the ECU and substituting modified (corrected) control signals. The corrections or modifications applied by the supplementary device 30 may depend on input data, e.g., data monitored on a data bus (e.g., data relating to engine speed, accelerator pedal position, and / or oil temperature, etc.), and on a map stored in memory. The corrections or modifications may also depend on other parameters obtained on analog lines to which the supplementary device is connected. The supplementary device modifies the control of the piezoelectric actuators, e.g., the injection durations, resulting in different engine behavior.

[0042] The complementary motor control device 30 more accurately reproduces the voltage and / or current signal that the ECU expects at its output when it applies a control signal. Consequently, the risk of the ECU detecting a malfunction and entering error mode is significantly reduced. It should be noted that the complementary device 30 can be placed in a passive operating mode, in which it simply allows the control signals emitted by the ECU 10 to pass through. Such an operating mode can be used to analyze and / or record the evolution of the current and voltage during one or more injection cycles. This analysis or recording can then be used by the microcontroller 46 to simulate the behavior of the piezoelectric actuator using the simulation stage 40.

[0043] The switches of the complementary motor control device 30 preferably include insulated gate field-effect transistors, e.g. metal-oxide-semiconductor field-effect transistors, better known by the English acronym "MOSFET".

[0044] While specific embodiments have just been described in detail, those skilled in the art will appreciate that various modifications and alternatives to these- DP.FRTE.0003 / PC 13 may be developed in light of the overall teaching provided by this disclosure of the invention. Therefore, the specific arrangements and / or methods described herein are intended to be given solely by way of illustration, without any intention of limiting the scope of the invention, which is determined by the extent of the related claims.

Claims

DP.FRTE.0003 / PC 14 Demands 1. Supplementary motor control device, comprising a first and a second connection terminal for connecting the supplementary motor control device between an ECU output intended to drive a piezoelectric actuator and said piezoelectric actuator; a discharge stage connected to the second connection terminal for discharging said piezoelectric actuator; an electronic switch between the first and second terminals for connecting or disconnecting the ECU and said piezoelectric actuator; a simulation stage connected to the first connection terminal for simulating to the ECU the connection with said piezoelectric actuator;a microcontroller connected to said discharge stage, to the electronic switch and to the simulation stage, the microcontroller being configured to take over the control of said piezoelectric actuator by acting programmatically on the discharge stage, on the electronic switch and on the simulation stage; in which the simulation stage includes a boost converter connected to the microcontroller, the microcontroller being configured to control the boost converter so as to reproduce a behavior, in terms of voltage and / or current observable on the first terminal, of said piezoelectric actuator, namely to control the boost converter so as to adjust the current entering the first terminal or the voltage at the first terminal to the behavior of said piezoelectric actuator.; 2. The complementary motor control device as claimed in claim 1, comprising a current sensor and a voltage sensor arranged to measure a current entering the first terminal and a voltage at the first terminal respectively, the current sensor and the voltage sensor being connected to the microcontroller.

3. The complementary motor control device according to any one of claims 1 to 2, comprising a non-volatile memory connected to the microcontroller, the microcontroller having access to data stored in the memory. DP.FRTE.0003 / PC 15 4. The complementary motor control device according to any one of claims 1 to 3, comprising an interface unit configured to connect the microcontroller to a computer bus, enabling the microcontroller to listen for data present on said bus and, optionally, to transmit data on said bus.

5. The complementary motor control device according to any one of claims 1 to 4, wherein the microcontroller is configured to take over the control of said piezoelectric actuator by opening the electronic switch, discharging said piezoelectric actuator through the discharge stage in a delayed or advanced manner, and controlling the boost converter so as to adjust the current entering the first terminal or the voltage at the first terminal to the behavior that the piezoelectric actuator would have if it were directly connected to the ECU output intended to control it.

6. The complementary motor control device according to claim 5, wherein the microcontroller is configured to control the boost converter so as to produce, at the time when the ECU attempts to discharge the piezoelectric actuator, a voltage ramp.

7. The complementary motor control device according to claim 5 or 6, wherein the microcontroller is configured to control the boost converter so as to produce, the imitation of a needle closing signal.

8. The complementary motor control device according to any one of claims 1 to 7, wherein the simulation stage includes an electronic switch, controlled by the microcontroller, arranged between the first connection terminal and the boost converter to connect the boost converter to the first terminal when the electronic switch between the first and second terminals is open.

9. The complementary motor control device according to claim 8, wherein the simulation stage includes a diode between the boost converter and the electronic switch arranged between the first connection terminal and the boost converter. DP.FRTE.0003 / PC 16 10. The complementary motor control device according to any one of claims 1 to 9, wherein the simulation stage includes a filtering capability in parallel with the boost converter.

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