Patent Application
20050029905
The present invention relates to a device for operating electronically driven ultrasonic piezoelectric actuators, and more particularly fuel injectors that have a piezoelectric stage and that are driven by the electronic injection computer of an internal combustion engine in a motor vehicle. It also relates to a method for use of the said device.
More precisely, the problem that the invention is intended to solve is the excitation of piezoelectric cells to cause vibration of the structure of an injector described in French Patent Application No. 99-14548, filed in the name of the Applicant. This type of injector is intended to atomize the fuel very finely into droplets that have the specific size to assure precise dosing and that are sufficiently small to assure complete and homogeneous vaporization of the injected fuel. Such an injector is provided with, among other parts, a cylindrical nozzle fed with fuel and having at its end an injection orifice, and with means for causing cyclic vibration of the nozzle, such as a transducer provided with a piezoelectric ceramic stage, at the terminals of which the electric voltage is varied within a scaling ratio in order to modify its thickness between two extreme positions corresponding to opening and closing of the injector. An injector piezoelectric ceramic is equivalent on the first order to a capacitance having high charging voltage, in excess of one hundred volts. This transducer is driven time-wise and intensity-wise by the engine's electronic control system in order to achieve oscillating opening of the nozzle tip at ultrasonic frequency.
The purpose of the present invention is to generate a high-frequency alternating signal to excite the piezoelectric cells from a direct-current voltage source. In a motor vehicle, the battery or alternator delivers a supply voltage having a value of 12 or 42 volts, which entails stepping up this voltage with a DC-to-DC voltage stepup converter.
To this end, a first object of the invention is a device for operating at least one ultrasonic piezoelectric actuator, which is driven electronically from a control computer and a direct-current voltage source, characterized in that it is provided with a DC-to-DC converter that is fed by the voltage source and that delivers at least one direct-current output voltage between two end terminals, in parallel with which there is connected at least one bridge arm composed of two alternately operable switches in series, the midpoint of the arm being connected alternately to the two output terminals of the DC-to-DC converter via a load composed of at least one actuator in series with a resonance inductor.
According to another characteristic of the invention, the DC-to-DC converter delivers a single direct-current output voltage between the two end terminals, and at least one first bridge arm of the operating device, composed of two alternately operable bridge switches in series, is connected in parallel across the output voltage, the midpoint of the said arm being connected via a load composed of at least one actuator in series with a resonance inductor to the midpoint of at least one second bridge arm, composed of two alternately operable bridge switches and mounted in parallel with the first arm.
According to another characteristic of the invention, wherein the DC-to-DC converter delivers a single direct-current output voltage, the operating device is provided with a first bridge arm, composed of two alternately operable switches and connected in parallel with the output terminals of the converter, the midpoint of the said arm being connected to the midpoint of a second bridge arm, composed of two alternately operable switches and mounted in parallel with the first arm, via a load comprising four actuators in parallel, connected alternately to a resonance inductor.
According to another characteristic of the invention, wherein the DC-to-DC converter delivers a single direct-current output voltage, the operating device is provided with at least one first bridge arm, composed of two alternately operable switches, and with at least two second bridge arms, each composed of two alternately operable switches and mounted in parallel with the first arm between the two end terminals of the converter, such that the midpoint of each first arm is connected to the midpoint of at least one second arm via a load comprising at least one actuator connected to a resonance inductor.
According to another characteristic of the invention, the DC-to-DC converter delivers two direct-current output voltages between a common reference terminal and two end terminals, in parallel with which there is connected at least one bridge arm, composed of two alternately operable switches, the midpoint of the said arm being connected to the reference terminal via a load comprising at least one actuator in series with a resonance inductor.
According to another characteristic of the invention, wherein the DC-to-DC converter delivers two direct-current output voltages, it is provided with four first bridge arms, each composed of two alternately operable bridge switches (P1i, P2i) mounted in parallel between the two end terminals (B1, B2), the midpoint (Ji) of the said arms being connected to the reference terminal (Bo) via a load composed of an actuator (Ii) in series with a resonance inductor (Li).
A second object of the invention is a method for use of a device for operating at least one ultrasonic piezoelectric actuator, composed of a bridge assembly, characterized in that, for operation of a given actuator, the control computer on the one hand causes selection means connected to the said actuator to close and on the other hand, in a first phase, causes a first pair of bridge switches composed of a first switch of a first bridge arm and of a second switch of a second bridge arm to close and simultaneously the second pair formed from the other two switches of the said arms to open and, in a second phase, the said four switches to change over to an inverse position, in such a way as to obtain a sinusoidal voltage at the terminals of the oscillating circuit formed by the said actuator and the associated resonance inductor, these two phases being repeated a specified number of times during the period of functioning of the actuator in order to generate a high-voltage, high-frequency signal at the piezoelectric actuator from the direct-current voltage source.
According to another characteristic of the invention, for operation of a given actuator, the control computer on the one hand causes selection means connected to the said actuator to close and on the other hand, in a first phase, a first switch of a first bridge arm to close and simultaneously the second bridge switch to open and, in a second phase, the said two switches to change over to an inverse position, in such a way as to obtain a sinusoidal voltage at the terminals of the oscillating circuit formed by the said actuator and the associated resonance inductor, these two phases being repeated a specified number of times during the period of functioning of the actuator in order to generate a high-voltage, high-frequency signal at the piezoelectric actuator from the direct-current voltage source.
Other characteristics and advantages of the invention will become apparent upon reading the description of several embodiments of a device for operating a piezoelectric actuator, illustrated by the following figures, wherein:
FIGS. 1 to 6 show the electronic diagram of several embodiments of an inventive operating device, according to a first structure having a DC-to-DC converter that delivers a single output voltage;
FIGS. 7 to 11 show the electronic diagram of several embodiments of an inventive operating device, according to a second structure having a DC-to-DC converter that delivers two output voltages.
For these non-limitative practical examples, elements denoted by like reference numerals on the different figures perform like functions in view of like results.
Since the invention comprises generating a sinusoidal signal having a high voltage greater than one hundred volts and a high frequency greater than ten kilohertz at the piezoelectric cell of each fuel injector of a vehicle from a direct-current source, or in other words the battery, it proposes different topologies of the device for operating an actuator for assuring excitation of the said piezoelectric ceramics through an inductor in order to compose a resonant circuit. These structures are valid for 1 to N injectors, where N is an integral number, preferably equal to 4, 5, 6, 8, 10 or 12. By way of non-limitative example, the number of operated injectors in the description hereinafter is 4.
All the topologies described represent structures having a DC-to-DC converter fed by the direct-current voltage source and delivering one or two direct-current output voltages.
According to a first structure, the DC-to-DC converter has a single output between two end terminals B1 and B2, delivering a direct-current high voltage Vs. As shown by the diagram of a first embodiment in
In the case of an internal combustion engine of a motor vehicle requiring four injectors, the diagram illustrates four piezoelectric ceramic actuators I1, . . . , Ii, . . . , I4, which are mounted in parallel and, according to a first alternative version of the first embodiment, are chosen successively by virtue of an operable selection switch Ki mounted in series with each of them. In the case of injectors having single electrical isolation, or in other words where one of the two electrodes of the piezoelectric cell is connected to the metal frame or to a fixed potential, one of their terminals is connected to the frame. As a function of the piezoelectric injector that must be open during the intervals of activity to assure that the corresponding cylinder of the engine is fed with fuel, switch Ki is operated by a logic signal originating from the injection computer, in order that the high-voltage output vs of the converter is connected to precisely that injector.
In the case of injectors having piezoelectric cells with double isolation, or in other words where the two electrodes of each cell are isolated from the metal frame, it is also possible to invert injectors Ii and selection switches Ki in the oscillating circuit of the actuator. As shown by the diagram of a second version of the first embodiment in
The functioning of this operating circuit is as follows, as a function of the operation of the different switches. In a first phase, the operating signal transmitted by the injection computer on the one hand causes selection switch Ki connected to the chosen injector Ii, to close and on the other hand a first pair of bridge switches composed of a first switch P2 of the first arm and of a second switch P3 of the second arm to close simultaneously, thus connecting midpoint J1 of the first arm to terminal B2 of converter C and midpoint J2 of the second arm to terminal B1 thereof. Simultaneously, the second pair formed by the other two switches of the said arms is operated such that these switches open. During this time interval, the voltage v2 at the terminals of the resonant circuit composed of resonance inductor L and actuator Ii is positive, with a maximum value equal to +Vs. Then, in a second phase, the signal operates switches P3 and P2 such that they open and simultaneously operates the two switches P1 and P4 such that they close, thus connecting midpoint J1 of the first arm to terminal B1 of converter C and midpoint J2 of the second arm to terminal B2 thereof. Thus voltage v2 at the terminals of the resonant circuit becomes negative, with a maximum value equal to −Vs. These two phases are repeated a large number of times during the injection period, which ranges from 100 μs to 8 ms. Voltage vci at the terminals of injector Ii is then a high-voltage, high-frequency sinusoidal signal, oscillating between a maximum value and a minimum value. The injection computer then successively operates the other injectors Ii mounted in parallel, in the order specified for the functioning of an internal combustion engine.
According to a second embodiment, illustrated by the diagram of
The functioning of the operating device is as follows. For excitation of injector I1, the computer first causes the means for selection of the injector, or in other words relay R1, to turn off relative to injector I1 when relay R2 is in off position, and also causes switch K1 to close and switch K2 to open for the purpose of connecting actuator I1 to resonance inductor L. Then it simultaneously causes, in a first phase, bridge switch P2 of the first arm to close and bridge switch P3 of the second arm to open, while the other switches P1 and P4 are open. In a second phase, the computer causes the four switches to change over to the inverse position. Thus the voltage vc1 at the terminals of actuator I1 is a sinusoidal signal oscillating between the extreme values +Vs and −Vs, while the three other injectors do not receive any voltage. The duration TKi of closing of each selection switch corresponds to the injection time, which can vary between 100 μs and 5 ms for a four-injector engine. The period TPi of the sinusoidal signal v2 at the terminals of the oscillating circuit formed by the actuator and the associated resonance inductor depends exclusively on the structure of the injectors, the resonance frequency FPi varying between 10 kHz and 1 MHz.
Since relay R2 is already in off position, the excitation of actuator I3 is achieved by opening selection switch K1 and closing switch K2, so that the voltage v2 at the terminals of the oscillating circuit composed of inductor L and injector I3 causes resonance thereof. The voltage signal vc3 at the terminals of injector I3 is a high-voltage, high-frequency sinusoidal signal between the following instants.
Since the switching of a relay from off position to on position takes longer than the opening or closing of a switch, the computer causes first relay R1 to switch to on position for the purpose of being able to excite injector I2 in the following instant. Then relay R1 is switched to on position while relay R2 is still switched to off position relative to injector I3, and simultaneously switch K2 is closed while switch K1 is open. And so on for the four actuators.
As in the foregoing, it is possible in an alternative embodiment to invert the position of the actuators with that of the selection means when they have double galvanic isolation, such that one of their terminals is connected directly to the inductor.
According to a third embodiment, illustrated in the diagram of
In the precise case of
In an alternative version of this embodiment, the load connecting the midpoint of the first arm to that of one of the second arms mounted in parallel is composed of two actuators mounted in parallel, such as I1 and I2, I3 and I4, and each connected to an operable selection switch Ki, where i is an integral number varying from 1 to 4, itself connected to a resonance inductor Li.
The functioning of this operating device depends on the injection computer, which successively acts on the relays or the selection switches in such a way that the voltage obtained from voltage source B is sufficient to achieve excitation, by an alternating square-wave voltage, of the oscillating circuit that is formed by injector Ii and the associated resonance inductor and is driven by the computer.
The fourth embodiment, illustrated in
The functioning of the device is driven by the injection computer which, before exciting an actuator Ii, for example, operates switch P2 of the first arm and switch P1i of the second arm connected to actuator Ii, such that they close and simultaneously operates switch P1 of the first arm and switch P4i of the second arm such that they open in a first phase, then in a second phase it inverts the operation of the said switches to deliver an exciting voltage to the oscillating circuit composed of actuator Ii and its associated resonance inductor Li. These two phases are repeated a specified number of times during the injection period.
According to the fifth embodiment of the inventive operating device, illustrated by the diagram of
For actuators having double galvanic isolation, it is possible according to another version of the topology to invert the position of the actuators with that of the selection means.
To function, the injection computer operates the relay or switch corresponding to the actuator to be excited, such as I1, and then, in a first phase, operates a bridge switch P2 of the first arm connecting a terminal of the said actuator to terminal B2 of the converter such that it closes, and also operates bridge switch P3 of the second arm connecting the other terminal of the said actuator to terminal B1 of the converter such that it closes. In a second phase, the operation of the switches is inverted to obtain a periodic signal for excitation of the oscillating circuit composed of the actuator and its resonance inductor. These two phases are repeated a large number of times during the injection period.
According to a second structure of the invention, the device for operating an ultrasonic piezoelectric actuator is provided with a DC-to-DC converter that delivers two direct-current output voltages vs1, vs2 between a common reference terminal Bo and two end terminals B1, B2, in parallel with which there is connected at least one bridge arm, composed of two alternately operable switches, the midpoint of the said arm being connected to reference terminal Bo by a load comprising at least one actuator in series with a resonance inductor. The three terminals B0, B1, B2 may or may not be mounted at floating potential relative to the battery.
According to the version of
According to another version, illustrated by the diagram of
The functioning of this operating circuit according to the first version of
According to another version of this embodiment, illustrated in
According to a third embodiment of this second structure, illustrated in
According to an essential characteristic of the invention, selection switches K of the actuators can be operated bidirectionally current-wise, and for that purpose can be constructed from two semiconductors mounted in series or in parallel. For example, they can be two transistors of the MOSFET type mounted in series.
Selection relays R of the actuators are of the monostable electromechanical type and have a break contact and a make contact.
As far as bridge switches P and P are concerned, if they are placed directly on the output side of the DC-to-DC converter, they are of the MOSFET, transistor or IGBT type, provided a diode is connected in anti-parallel manner in the latter case.
In all embodiments, the load inductor composing a resonant circuit with an injector is designed in such a way as to achieve the maximum resonance at the exciting frequency.
A second object of the invention is a method for use of a device for operating at least one ultrasonic piezoelectric actuator, such as described for the different foregoing topologies with the manner in which they function.
According to the first structure of the operating device, in which the DC-to-DC converter has a single output between two end terminals B1 and B2 and delivers a direct-current high voltage Vs, the method is characterized in that, for operation of a given actuator, the control computer on the one hand causes selection means connected to the said actuator to close and on the other hand, in a first phase, causes a first pair of bridge switches composed of a first switch of a first arm and of a second switch of a second arm to close and simultaneously the second pair formed from the other two switches of the said arms to open and, in a second phase, causes the said four switches to change over to an inverse position, in such a way as to obtain a sinusoidal voltage at the terminals of the oscillating circuit formed by the said actuator and the associated resonance inductor, these two phases being repeated a specified number of times during the period of functioning of the actuator in order to generate a high-voltage, high-frequency signal at the piezoelectric actuator from the direct-current voltage source.
According to the second structure of the device for operating an ultrasonic piezoelectric actuator, which is provided with a DC-to-DC converter that delivers two direct-current output voltages vs1, vs2 between a common reference terminal Bo and two end terminals B1, B2, the method is characterized in that, for operation of a given actuator, the control computer on the one hand causes selection means connected to the said actuator to close and on the other hand, in a first phase, causes a first bridge switch of a first arm to close and simultaneously the second switch to open and, in a second phase, causes the said two switches to change over to an inverse position, in such a way as to obtain a sinusoidal voltage at the terminals of the oscillating circuit formed by the said actuator and the associated resonance inductor, these two phases being repeated a specified number of times during the period of functioning of the actuator in order to generate a high-voltage, high-frequency signal at the piezoelectric actuator from the direct-current voltage source.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01/15125 | Nov 2001 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR02/04013 | 11/22/2002 | WO |
