Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/20—Output circuits, e.g. for controlling currents in command coils
  • F02D41/2096—Output circuits, e.g. for controlling currents in command coils for controlling piezoelectric injectors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
  • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
  • H02N2/02—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors
  • H02N2/06—Drive circuits; Control arrangements or methods
  • H02N2/065—Large signal circuits, e.g. final stages
  • H02N2/067—Large signal circuits, e.g. final stages generating drive pulses
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/20—Output circuits, e.g. for controlling currents in command coils
  • F02D2041/2003—Output circuits, e.g. for controlling currents in command coils using means for creating a boost voltage, i.e. generation or use of a voltage higher than the battery voltage, e.g. to speed up injector opening
  • F02D2041/201—Output circuits, e.g. for controlling currents in command coils using means for creating a boost voltage, i.e. generation or use of a voltage higher than the battery voltage, e.g. to speed up injector opening by using a boost inductance
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/20—Output circuits, e.g. for controlling currents in command coils
  • F02D2041/202—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit
  • F02D2041/2024—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit the control switching a load after time-on and time-off pulses
  • F02D2041/2027—Control of the current by pulse width modulation or duty cycle control
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M69/00—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel
  • F02M69/04—Injectors peculiar thereto
  • F02M69/041—Injectors peculiar thereto having vibrating means for atomizing the fuel, e.g. with sonic or ultrasonic vibrations

Definitions

• the present invention relates to a method for controlling an electronically controlled ultrasonic piezoelectric actuator, and more particularly to a piezoelectric stage fuel injector controlled by the electronic injection computer of an internal combustion engine in a vehicle. automobile.
• an ultrasonic injector comprises, inter alia, a cylindrical nozzle supplied with fuel and at the end of which is provided an injection orifice, and means for cyclically vibrating the nozzle, such as a transducer, comprising a piezo ceramic stage.
• a piezoelectric injector ceramic is first-order equivalent to a capacitance whose charging voltage is high, greater than a hundred volts.
• the supply voltage is 12 or 42 volts, which involves increasing this voltage to ensure the charging and discharge of the ceramic.
• transformerless control devices such as the one shown in FIG. 1, which is powered by a DC voltage source E, the vehicle battery for example, whose terminal (B-) is connected to the ground and the terminal (B +) is connected to a first amplification stage of said DC voltage.
• the N injectors Pi of a heat engine are connected in parallel and sequentially controlled by selector switches S 1 each connected in series with an injector P 1 .
• An electronic injection computer sends a control logic signal to each selection switch so that the high voltage output of the voltage booster is applied to the terminals of the selected injector.
• the steering device comprises:
• a second stage ⁇ 2 for generating a current source i r for supplying the injectors Pi and which is powered by the high voltage V b00st generated by the first stage;
• a fourth stage ⁇ 4 for controlling the excitation voltage V pi of the injectors which is not shown in FIG.
• the first stage E 1 for generating a high voltage by amplification of the direct supply voltage E is constituted by a first branch B 1 comprising a first inductor L 1 connected to a switching switch I D i, which can be controlled, with a freewheel diode U 1 , mounted in anti-parallel in the direction of the discharge current of the injector Pi selected to be controlled.
• the inductor L 1 is connected on one side to the terminal (B +) of the voltage source E and on the other side to a terminal of the switch l D i whose other terminal is connected to the terminal ( B-) of the voltage source E.
• a second branch B 2 is connected in parallel to the switch I 01 switching and comprises a rectifier diode D connected to a capacitor C filtering.
• one of the terminals of said diode D is connected to the junction point J 1 of the inductor L 1 and the other switch I 01 and its other terminal is connected to a first terminal of the capacitor C whose second terminal is connected to the terminal (B-) of the voltage source E.
• the first stage S 1 of amplification of the battery voltage E delivers a high voltage V b00St across the filtering capacitor C, which supplies a second stage
• Z 2 consists of a branch mounted between the terminals of said filtering capacitor C and comprising a second inductor L 1 - connected to a second switching switch I D2 . controllable, with an O 2 freewheel diode mounted in antiparallel.
• the inductance L r is determined so as to provide an oscillating circuit with each driven injector, to which it delivers a feed stream i r .
• the injector control method is broken down into at least three sequences, a selection sequence of a piezoelectric actuator P 1 by the switch S 1 , an AC voltage supply sequence of the selected actuator, to which adds an electronic control sequence of the excitation voltage V p , the injectors Pi by regulating the high voltage V bOost generated by the first stage of the control device.
• the computer sends a control signal to control the closing of the selection switch S 1 , so that the piezoelectric actuator can be powered by this AC voltage, and during a first phase of the power supply sequence.
• the injector it sends another control signal which controls the closing of the switching switch D2 D2 so that the energy from the high voltage V boost accumulates in the inductance L r by circulation of a current i r in the loop consisting of the filtering capacitor C, the inductance L 2 and the switch l D2 .
• the switch I D2 switching is controlled at the opening, the current i r can not pass through the diode d 2 in non-parallel anti-parallel is forced to flow in the actuator Pi in one direction and then in the other because the inductance L r and the injector Pj are in electrical resonance. Since the value of the inductance L r is a function of the acoustic excitation resonance of the piezoelectric actuator, it is determined so that the inductance L r has the time to charge sufficiently in the first phase so that the excitation voltage V p ⁇ across the injector P 1 , close to 1200 volts, is reached. In addition, the filtering capacitor C is sized to have a very high reactivity to the rise in voltage Vb 00S t-
• the inductance L r is discharged by energy transfer from the inductance L r to the filtering capacitor C, creating a negative current i r in the loop comprising the inductance L r , the filtering capacitor C and the anti-parallel diode d 2 .
• FIGS 2a and 2b which are the temporal representations of the voltage V pi across the injector P 1 and the current i r in the inductance L r , for a high supply voltage V bO constant o the first phase of the supply sequence of the injector, corresponding to the accumulation of energy in the inductance L 1 -, takes place between the times to and U when the current i r in the inductance L r increases from 0 to a maximum value i max .
• the second phase of the sequence takes place between the instants ti and t 3 : first between the instants U and t 2 when the current i r decreases from i max to 0 while the voltage V p ⁇ increases from 0 to a maximum value V pim , close to 1200 Volts, which corresponds to the charge of the injector, and then between the instants t 2 and t 3 from 0 to a negative minimum value i m , n while the voltage V p ⁇ decreases from the maximum value V p ⁇ m to 0, and which corresponds to its discharge.
• the piezoelectric actuator is in electrical resonance with the inductance L r .
• the period of electrical resonance between the piezoelectric actuator and the inductance L 2 corresponding to the second phase of the supply sequence of the actuator, between times t 1 and t 3 , is shorter than the resonance period.
• This acoustic resonance depends on the characteristics of the piezoelectric injector.
• the actual high-voltage supply phase of the injector P between times t 1 and t 3 depends on the value of the inductance L r , the high voltage V t500 St to be reached and the closing time of the switch P, to obtain the voltage V p , necessary.
• the voltage V pi at the terminals of a selected injector P has the form of a sinusoidal pulse when the switch ID2 for switching off the second stage of the control device is controlled at the opening, between U and t 3 .
• This excitation voltage V p , of a piezoelectric injector depends on the following parameters:
• the control device comprises a fourth control stage of this excitation voltage V p ⁇ which will act as follows: the switch I 02 of the second stage is controlled so that at its closure, the inductance L r is charged for a certain time, and when it is opened, the voltage at the terminals of the selected injector describes a sinusoidal pulse.
• the peak value of this voltage V p ⁇ depends on the energy stored in the inductance L r and the high voltage Vb 00 St generated.
• the voltage boost converter generates a periodic high voltage V p ⁇ , greater than a hundred volts, with a high frequency F p ⁇ , greater than ten kHz, for exciting P injectors, ultrasound.
• FIG. 2a is a representation of this electrical resonance in the case where it is theoretical.
• the excitation voltage V p1 passes through an initial transient phase during which its peak value Vp, c can exceed the maximum value V P i m , of 30 at 50%, (FIG. 3) so that, in order not to be damaged, the switches must be sized to withstand this maximum value V plm .
• they are oversized for a transient voltage withstand greater than the voltage required for the excitation of the piezoelectric injectors, which induces a significant cost factor on the switches.
• the object of the invention is to overcome this disadvantage, by proposing several injector control methods for reducing this transient overvoltage at startup.
• the object of the invention is a method for controlling at least one ultrasonic piezoelectric actuator, electronically controlled from a control computer and a DC voltage source, comprising a first stage of amplification of said voltage for generating a high voltage and a second stage, powered by said high voltage, for generating a current source for supplying the injectors associated with selection means controllable by said computer, characterized in that consists in controlling the duty cycle of the control signal of the second feed stage of the injectors, in the initial phase, in order to reduce the energy stored in the resonance inductance of this second stage and consequently the excitation voltage of the injectors .
• the control method consists in reducing the duty ratio of the control signal of the second feed stage of the injectors, in the initial phase, in order to reduce the energy stored in the inductor. resonance of this second stage and therefore the excitation voltage of the injectors.
• the control method consists in imposing, as soon as the first pulse of the initial phase, a cyclic ratio of the control signal of the charge of the inductance, which is equal to the steady-state duty cycle to obtain the voltage peak excitation desired at the terminals of the injectors, so a closing time of the switching switch of the second stage of the injector control device, equal to the duration in steady state.
• the control method consists of increasing the duty ratio of the control signal of the first stage of generation of a high voltage, during the initial phase, from a determined minimum value to a maximum value necessary for to obtain, in the steady state, a high supply voltage necessary for excitation of the injectors, and thus to vary the high supply voltage, during the initial phase, by a value lower than that required at the steady state until the latter, to control the charging current of the resonance inductance and the peak value of the excitation voltage, in the initial phase, which does not exceed the value required in steady state.
• control method consists in applying an initial voltage across each selected injector, in the initial driving phase, obtained by precharging the capacity of said injectors, either by controlling the switching switch or by controlling the switches of said injectors.
• FIGS. 4a, 5a, 6a and 7a the temporal variations of the excitation voltage resulting respectively from the four methods according to the invention
• FIGS. 4b, 5b, 6b and 7b the temporal variations of the control signal of the second stage of the injector control device, respectively following the four methods according to the invention
• FIGS. 4c, 5c, 6c and 7c show the temporal variations of the high voltage delivered by the injector control device, respectively following the four methods according to the invention
• FIGS. 4d, 5d, 6d and 7d the temporal variations of the excitation current delivered by the injector control device, respectively following the four methods according to the invention.
• the control method of the piezoelectric actuators consists, in order to control this excitation voltage V p , of an injector, to control the duty cycle of the control signal V C2 of the injector supply stage, either of the switching switch I D2 , the duty cycle being equal to the conduction time divided by the period T of the signal.
• the method consists in particular in reducing its conduction time, or closing time, in the initial phase so that, during this closing, the inductance L 1 - is charged for a shorter time, thus stores less energy and that when it is opened, the excitation voltage V pi at the terminals of the selected injector describes a sinusoidal pulse of peak value V p , c less than or equal to that of the maximum value V p ⁇ m of the excitation voltage in the steady state.
• this first method consists in reducing the closing time D f of the switching switch I D 2 of this second stage, powered by a high DC voltage V b00S t (FIG. 4c), causing less current i r flowing in inductance L r ( Figure 4d), which is thus less charged, so that at the opening of said switch I D2 , the excitation voltage V pi will be lower than steady state.
• the first pulses of the excitation voltage V P V P i have a peak value determined ⁇ c, less than the maximum peak value m i V p supported by the switches.
• the closing time D.sub.i of said switch I D2 is thus determined to be less than the closing time D.sub.F necessary, in steady state, to excite the ultrasonic piezoelectric injectors.
• the closing time is gradually increased to the established speed, the frequency F kl of the excitation voltage signal remains constant except for the first pulses.
• the piloting method of the piezoelectric actuators consists in imposing, from the first pulse of the initial phase (FIG.
• a duty cycle ratio of the inductance load control signal L r which equals the steady-state duty cycle to obtain the peak excitation voltage intended to the terminals of the injectors, in other words a closing time D f , of the switching switch I 02 of the second feed stage of the injectors which is equal to the duration D f8 in steady state.
• This charge duration of the inductance by the current i r is obtained by knowing the instant of the zero crossing of this current i r in the inductance L 1 - (FIG. 5d), this duration being determined by calibration or established by knowledge of the system.
• the first pulses of this excitation voltage V p ⁇ have a peak value V peak determined, lower than the maximum peak value V p ⁇ supported by the switches in steady state, for a high supply voltage Vb. 00S t constant ( Figure 5c).
• the driving method of the piezoelectric actuators consists in increasing the duty ratio of the control signal of the first generation stage of a high voltage, during the initial phase, from a minimum value determined to a value the maximum necessary to obtain, in steady state, a high supply voltage V boO st necessary for the excitation of the injectors.
• the method varies the high supply voltage V bO o s t. during the initial phase, by a value lower than that required at the steady state up to the latter, as shown in FIG. 6c, which makes it possible to control the charging current i r of the resonance inductor L r (FIG. 6d).
• the control method consists in applying an initial voltage V pii across the terminals of each selected injector, in the initial driving phase, as shown in FIG. 7a, without varying the duty cycle of the control signals of the first two so stages of the switching switch I D2 , as shown in Figure 6b.
• This initial voltage V pll across the injectors is obtained by precharging the capacity of each of them, either by controlling the switching switch ID 2 or by controlling the switches S 1 of the injectors.
• control method can combine these different variants simultaneously.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fuel-Injection Apparatus (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

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• 2004
  • 2004-12-14 FR FR0413277A patent/FR2879255B1/fr not_active Expired - Fee Related
• 2005
  • 2005-12-07 WO PCT/FR2005/051051 patent/WO2006077295A1/fr active Application Filing
  • 2005-12-07 EP EP05824392A patent/EP1828583A1/de not_active Withdrawn

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