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
  • 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 device for controlling an ultrasonic piezoelectric injector, electronically controlled, in particular by the injection computer of an internal combustion engine for a motor vehicle. It also relates to a method of implementing the device.
• the control of piezoelectric injectors for automotive applications which is developed by the Applicant in an ultrasonic excitation mode, requires the generation of a high voltage, between 500 and 1000 volts peak-to-peak and modulated between 25 and 50 kHz.
• This type of injectors has the advantage of achieving a good spray of the fuel droplets, with a response time, which is defined between the electrical control and the establishment of the nominal fuel flow, shorter than that of the injectors of the fuel. prior art.
• the device comprises: a first stage E 1, powered by a DC voltage source E, amplifying this voltage E to generate a high DC voltage V b00 st; a second stage E 2 , powered by said high voltage, for generating an alternating current source i R for supplying the injectors I 1 ; a third selection stage E 3 of the piezoelectric injectors to be controlled by an electronic control computer.
• the first two stages carry out the ultrasonic high voltage excitation by means of two so-called hashing transistors T 1 and T 2 and the third selection stage use N selection transistors S in the case of a N cylinder engine, which allows pooling the second hash stage that generates the current source, whose passive components are expensive and occupy a large volume. Moreover, according to this topology, if the response time of the injector at the opening is good, the closing response time is less.
• the control device operates according to an electromechanical resonance principle: the electrical energy sent to the piezoelectric injector is converted into reactive mechanical energy, in the form of stress waves, allowing the nozzle of the injector to open. and passing fuel that is then sprayed into a cylinder.
• the selection switch associated with the injector that was controlled, is open and the energy accumulated in the injector in the form of remaining mechanical waves is again transferred to the switch. selection under important tensions. Said selection switch being open when the injection control is stopped, overvoltages greater than the avalanche voltage of this transistor appear at its terminals and may damage it because the energy absorbed by this switch is then too important. for junctions, which causes their destruction or decreases their life expectancy.
• the document EP1528605 proposes an electronic control device for at least one ultrasonic piezoelectric injector of the type described above, in which an additional branch, connected in parallel with the control circuit of the injectors, comprises a switch and a diode parallel to this switch.
• This branch makes it possible to perform a short circuit of the control circuit of the injectors.
• shorting a resonant circuit means that there is almost no damping.
• a simple short circuit branch is connected in parallel with the injector control circuit, that is to say in parallel with all the injectors.
• Documents DE19945945, DE19709716 and DE1971 1903 propose devices for controlling piezoelectric injectors.
• the object of the invention is therefore to absorb, by dissipating it, the energy stored in an ultrasonic piezoelectric injector at the end of the injection control to protect the selection switch associated with it, and to reduce the time closing the injector.
• the object of the invention is a device for electronically controlling at least one ultrasonic piezoelectric injector, controlled by a control computer and powered by a DC voltage source, comprising: a first amplification stage of said DC voltage delivering a DC high voltage signal; a second stage for generating a charging current of the injectors, composed of an inductance connected to a switching switch and having to produce an oscillating circuit with each piloted injector; a third stage for selecting the injectors to be controlled, comprising a selection switch in series with each injector; characterized in that the third selection stage comprises, for each injector, a damping cell of the residual energy stored in said injector at the end of the injection control, the damping cell comprising a resistor.
• the damping cell is composed of a diode connected in series with the resistor and in the locked direction during the positive half-cycles of the injection control signal, and is arranged in parallel with each injector .
• the damping cell is connected in parallel with the selection switch of the injector.
• the damping cell is composed of a parallel RC circuit, ie the resistance and a capacitance connected in parallel and whose RC value is less than 1/10 of the period of the control signal of the injectors, the value of the resistor being closer to the impedance of the injectors at their resonant frequency.
• it is embedded in a motor vehicle, whose engine is controlled in particular by an electronic injection computer, which drives the ultrasonic piezoelectric injectors.
• the first stage Ei of amplification of the direct voltage E comprises a first branch in parallel of the voltage source B, composed of a first inductance Li connected to a switching switch Ti with a freewheel diode mounted in antiparallel.
• a second branch is connected in parallel with the switching switch Ti and comprises a rectification diode D connected to a filtering capacitor Ci at the terminals of which this first stage delivers a high voltage V b00 st which supplies a second stage E 2 .
• It consists of a first branch, comprising a second inductor L 2 connected to a second switching switch T 2 with a diode d 2 freewheel mounted anti-parallel, and a second branch in parallel with said transistor T 2 and constituted by a second capacitance C 2 of impedance matching.
• the inductance L 2 is determined in order to produce a circuit, resonant with each injector I, selected and controlled, to which it delivers a current i r of supply.
• Each piezoelectric injector I 1 is connected to a switch S 1 selection, controllable by an electronic control computer, for example the injection computer of the engine of a vehicle.
• a switch may for example be a MOS type transistor, or a bipolar type with an IGBT insulated gate with a diode mounted in antiparallel.
• the invention consists in inserting, in the selection stage, a damping cell of the residual energy stored in each injector at the end of the injection control, in order to protect it from the large overvoltages caused on its terminals by the opening of the switch S, selection associated with it.
• the damping cell has a resistor.
• the damping cells are each mounted in parallel with a piezoelectric injector.
• the control stage comprises a damping cell A, arranged in parallel with each injector I, and composed of a diode D, connected in series with the resistor R 1 .
• the diode D 1 is mounted in the blocked direction during the positive half cycles of the injection control signal.
• the damping cell A 1 associated with it When controlling the injection by a selected injector, the damping cell A 1 associated with it is inactive because the voltage across the diode D 1 is negative, so it is blocked and no current flows.
• the opening of the selection switch S 1 corresponding to the selected injector I 1 causes significant overvoltages at its terminals in the form of positive oscillations. negative.
• the damping cell A 1 closes the negative half-waves of these overvoltages, which correspond to positive overvoltages on the "cold point" F of the injector, connected to the selection switch S 1 , because its diode D 1 is then passing.
• the RD cell bypasses the injector at the end of the injection on the positive half-waves between the point F and the ground, which are capable of destroying the selection switch S 1 .
• the damping cells A 1 each associated with the different injectors connected in parallel, fulfill two functions: they protect the selection transistors S 1 against overvoltages on the one hand by short-circuiting the injectors and absorb by their resistance R 1 much of the residual energy stored in the injectors.
• the damping cells are each mounted in parallel with a piezoelectric injector.
• the damping cells are each mounted in parallel with the selection switch; the damping cell A 'connected in parallel with the selector switch S is composed of a parallel RC circuit, that is to say the resistor R' and a capacitor C connected in parallel.
• This solution makes it possible to size the amount of energy absorbed after each injection and the characteristic damping times of the injector.
• the value of the RC product of the resistance by the capacitance must be less than 1/10 of the period T of the control signal of the injectors, which is therefore the period of the peak values of the excitation voltage V p ⁇ .
• the value of the resistor R ' must be close to the impedance of the injector at its resonant frequency, under typical conditions of use.
• the damping cells with a resistance of the control device of the ultrasonic piezoelectric injectors have the advantage of damping the overvoltages resulting from the residual oscillations of the injectors at the end of the injection, in particular those which are greater than the voltage of the isolation of the selector switch, without damping the control voltages during the injection.
• certain variants allow a rapid dissipation of the residual energy and thus a closure of the injector in a sufficiently short time.

Landscapes

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

Applications Claiming Priority (2)

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Family Cites Families (7)

• 2006
  • 2006-05-24 FR FR0604727A patent/FR2901575B1/fr active Active
• 2007
  • 2007-05-23 EP EP07766086A patent/EP2024627A1/de not_active Withdrawn
  • 2007-05-23 WO PCT/FR2007/051313 patent/WO2007135339A1/fr not_active Ceased

Non-Patent Citations (2)

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