Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F7/00—Magnets
  • H01F7/06—Electromagnets; Actuators including electromagnets
  • H01F7/08—Electromagnets; Actuators including electromagnets with armatures
  • H01F7/18—Circuit arrangements for obtaining desired operating characteristics, e.g. for slow operation, for sequential energisation of windings, for high-speed energisation of windings
  • H01F7/1805—Circuit arrangements for holding the operation of electromagnets or for holding the armature in attracted position with reduced energising current
  • H01F7/1816—Circuit arrangements for holding the operation of electromagnets or for holding the armature in attracted position with reduced energising current making use of an energy accumulator
• • 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
• • 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
• • 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
  • F02D2041/2006—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 capacitor
• • 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
  • F02D2041/2058—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit using information of the actual current value
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F7/00—Magnets
  • H01F7/06—Electromagnets; Actuators including electromagnets
  • H01F7/08—Electromagnets; Actuators including electromagnets with armatures
  • H01F7/18—Circuit arrangements for obtaining desired operating characteristics, e.g. for slow operation, for sequential energisation of windings, for high-speed energisation of windings
  • H01F7/1805—Circuit arrangements for holding the operation of electromagnets or for holding the armature in attracted position with reduced energising current
  • H01F7/1816—Circuit arrangements for holding the operation of electromagnets or for holding the armature in attracted position with reduced energising current making use of an energy accumulator
  • H01F2007/1822—Circuit arrangements for holding the operation of electromagnets or for holding the armature in attracted position with reduced energising current making use of an energy accumulator using a capacitor to produce a boost voltage

Definitions

• the present invention concerns a method for operating an inductive electroactuator control device.
• the present invention can advantageously, but not exclusive, be used to control electroinjectors of a fuel injection system of an internal combustion engine of a motor vehicle, particularly of a common rail injection system of a diesel engine, to which the following description will make specific reference without losing its generality.
• the method ' according to the invention could be applied to other engine types, such as petrol, methane, or LPG engines, or any other type of inductive electroactuators such as, for example, solenoid valves of ABS devices and similar, solenoid valves of variable timing systems, etc.
• engine types such as petrol, methane, or LPG engines
• inductive electroactuators such as, for example, solenoid valves of ABS devices and similar, solenoid valves of variable timing systems, etc.
• each electroinjector in order to control the electroinjectors of a common rail injection system it is customary to supply each electroinjector with a current whose trend over time includes a period of rapid increase up to a first holding value, a first period of oscillating amplitude around the first holding value, a first period of decrease up to a second holding value, a second period of oscillating amplitude around the second holding value, and a second period of rapid decrease until an approximately zero value.
• an electroinjector includes an external body defining a cavity communicating with the outside through an injection nozzle and wherein an axially movable pin is housed to open and close the nozzle, under the opposing thrust of the pressure of the injected fuel, on the one hand, and of a spring and a rod, on the other hand, such rod being placed along the axis of the pin on the side opposite the nozzle, and being operated by an electromagnetically controlled metering valve .
• the exciting current of the electromagnet in the first stage is rather high (first holding value) .
• the rapid increase to the first holding value in the trend of the current is necessary to guarantee sufficient time accuracy about the starting moment of the actuation.
• the high voltage necessary to bring about the rapid increase in the current, in the initial opening stage of the electroinjector is generated by means of a boost circuit configured to raise the voltage supplied by the battery of the motor vehicle and essentially composed of a DC/DC converter, the principle circuit diagram of which is shown in figure 1.
• the DC/DC converter denoted as a whole by 1, has a pair of input terminals connected, in use, to the battery of the motor vehicle, and a pair of output terminals on which it supplies a boost voltage V B oos ⁇ which is greater than the battery voltage V B A and is essentially formed by an inductor 2, a capacitor 3, a controlled electronic switch 4, e.g. a transistor, and a diode 5.
• V B oos ⁇ which is greater than the battery voltage V B A and is essentially formed by an inductor 2, a capacitor 3, a controlled electronic switch 4, e.g. a transistor, and a diode 5.
• the inductor 2 is connected between a first input terminal and a node 6, the diode 5 is connected between the node 6 and a first output terminal, the electronic switch 4 is connected between the node 6 and the second input terminal, and the capacitor 3 is connected between the output terminals .
• the operating principle of the converter is that of cyclically transferring the energy stored in the inductor 2 to the capacitor 3, so as to raise the voltage across it, which constitutes the boost voltage V DO os ⁇ of the converter. This is obtained through an appropriate control of the closing and opening of the electronic switch 4 by means of a control circuit not shown in the figure and functioning in a known way .
• a pulse train is supplied that causes the closing and opening of the electronic switch 4, the repetition of which causes a gradual raising of the voltage across the capacitor 3.
• the raising of the fuel injection pressure would require the use of a considerably larger DC/DC converter compared to that currently used, with a consequent increase in the area taken up by the DC/DC converter 1, the overall dimensions of the control device, and the relative costs .
• the purpose of the present invention is therefore that of identifying a method that allows the generation of the high powers required in the initial stage of the control of the electroinjectors, increased by the raising of the fuel injection pressure, without requiring the use of a dedicated DC/DC converter or, at most, requiring the use of a DC/DC converter of much reduced size.
• figure 1 is a principle circuit diagram of a DC/DC converter
• FIG. 2 is a circuit diagram of an electroinjectors control device
• the idea beneath the present invention is essentially that of using a voltage boost circuit formed, in its simplest embodiment, by only one capacitor, and of recharging this capacitor using one or more non-operating electroinjectors, i.e. which are not involved in an injection of fuel.
• figure 2 contains the circuit diagram of the electroinjectors control device described in the aforesaid European patent of the applicant.
• Figure 2 also shows the circuit diagram of the voltage boost circuit according to the present invention, denoted as a whole by 8.
• the control device denoted as a whole by 10, includes a plurality of control circuits 11, one for each electroinjector 12.
• control circuits 11 are illustrated relating to two electroinjectors 12 belonging to the same main bearings of the engine (not shown) , each of which is represented in the figure with its corresponding equivalent circuit formed by a resistor and an inductor connected in series.
• Each control circuit 11 includes a first and a second input terminal 13, 14, connected to the positive pole and negative pole of the battery 23 of the motor vehicle, which supplies a voltage V BATT whose nominal value is typically 12V; a third and a fourth input terminal 15, 16, connected to a first and a second output terminal of a boost circuit 8 shared by all the control circuits, between which it supplies a boost voltage VB OOS T which is greater than the battery voltage V B ATT, for example 50V; and a first and a second output terminal 19, 20, between which the relative electroinjector 12 is connected.
• each electroinjector 12 connected to the first output terminal 19 of the respective control circuit 11 is typically called the "high side” terminal, whereas the terminal of each electroinjector 12 connected to the second output terminal 20 of the respective control circuit 11 is typically called the "low side” terminal.
• the boost circuit 8 is formed by a single capacitor 21, so-called “boost”, connected between the first and the second output terminal of the boost circuit 8, and across which is connected a comparator stage with hysteresis 22 supplying at its output a logic signal assuming a first logic level, for example high, when the voltage across the capacitor 21 is greater than a preset upper value, for example 50V, and a second logic level, in this example low, when the voltage across the capacitor 21 is less than a preset lower value, for example 49V.
• Each control circuit 11 also includes a ground line 24 connected to the second input terminal 14 and to the fourth input terminal 16, and a supply line 25 connected to the first input terminal 13 by means of a first diode 26, the anode of which is connected to the first input terminal 13 and the cathode is connected to the supply line 25, and to the third input terminal 15 by means of a first MOS transistor 27, whose gate terminal receives a first control signal Tl, a drain terminal is connected to the third input terminal 15, and a source terminal is connected to the supply line 25.
• Each control circuit 11 also includes a second MOS transistor 28 having a gate terminal receiving a second control signal T2 , a drain terminal connected to the supply line 25, and a source terminal connected to the first output terminal 19; and a third MOS transistor 29 having a gate terminal receiving a third control signal T3, a drain terminal connected to the second output terminal 20, and a source terminal connected to the ground line 24 by means of a sensing stage formed by a sense resistor 31 across which an operational amplifier 32 is connected, generating at its output a voltage which is proportional to the current flowing in the sense resistor 31.
• Each control circuit 11 also includes a second diode 33, so-called “free-wheeling”, having the anode connected to the ground line 24 and the cathode connected to the first output terminal 19; and a third diode 34, so-called “boost”, having the anode connected to the second output terminal 20 and the cathode connected to the third input terminal 15.
• each control circuit 11 can be divided into three distinct stages, characterized by a different trend of the current circulating in the electroinjector 12: a first stage, so-called fast charge or "boost", in which the current rises quickly up to a holding value such as to open the electroinjector 12; a second stage, so-called holding, in which the current oscillates, with a sawtooth trend, around the value reached in the previous stage; and a third stage, so-called fast discharge, in which the current drops quickly from the value reached in the previous stage to a final value, that can be zero .
• V n ⁇ os ⁇ is applied across the electroinjector 12.
• the current flows in the loop including the capacitor 21, the transistor 27, the transistor 28, the electroinjector 12, the transistor 29 and the sense resistor 31, increasing over time in a basically linear manner with a slope V B00ST /L (where L represents the series equivalent inductance of the electroinjector 12). Since V BO os ⁇ is much greater than VBATT, the rise in the current is much more rapid than that which is obtainable with V BATT .
• the transistor 29 is closed, the transistor 27 is open and the transistor 28 is closed and open repeatedly, and therefore across the electroinjector 12 are alternatively applied the battery voltage V BATT (when the transistor 28 is closed) and a zero voltage (when the transistor 28 is open) .
• the current flows in the loop including the battery 23, the diode 26, the transistor 28, the electroinjector 12, the transistor 29, and the sense resistor 31, increasing exponentially over time
• the second case the current flows in the loop including the electroinjector 12, the transistor 29, the sense resistor 31 and the free-wheeling diode 33, decreasing exponentially over time .
• the transistors 27, 28 and 29 are open and therefore, as long as the electroinjector 12 is crossed by current, the boost voltage - V ra0 os ⁇ is applied across the electroinjector 12.
• the current flows in the loop including the capacitor 21, the boost diode 34, the electroinjector 12 and the free-wheeling diode 33, decreasing over time in a basically linear manner with slope - V B oos ⁇ /L. Since V B oos ⁇ is much greater than V BATT/ the decrease in the current is much more rapid compared to that which is obtainable with VBATT.
• the opening and closing of the transistors 27, 28 and 29 are controlled by a timing circuit based on the logic signal supplied by the operational amplifier 32 connected across the sense resistor 31 and indicative of the value of the current flowing in the electroinjector 12, while the duration of the fast discharge stage is ascertained by calculation.
• each control circuit 11 is able to generate advanced "peak and hold" type current profiles of various kinds and complexity, thus allowing the implementation of different fuel injection strategies, each including multiple and close injections.
• Figures 3a-3c show as examples some of the current profiles, relating to a single actuation, that can be generated by each control circuit 11, in which the current circulating in the electroinjector 12 is denoted by I INJ , the fast charge stage is denoted by Stage 1, the holding stage by Stage 2 and the fast discharge stage by Stage 3.
• the recharging of the capacitor 21 of the boost circuit 8 is carried out by making the above described control device 10 function appropriately so as to store electric energy in an electroinjector 12 not involved in a fuel injection and transferring this stored energy to the capacitor 21 of the voltage boost circuit 8.
• the level of the current in the electroinjector 12 during the recharge stage must obviously be less than the minimum current necessary to move the rod of the electroinjector, in such a way as to prevent undesired injections of fuel.
• the transistor 27 is always kept open, the transistor 28 is always kept closed, while the transistor 29 is closed and open repeatedly.
• the current flows in the loop including the battery 23, the diode 26, the transistor 28, the electroinjector 12, the transistor 29 and the sense resistor 31, increasing in an approximately linear manner (at least as long as the value of current is relatively small) with slope V B ⁇ TT jL .
• the time T 0N required to reach the peak current I MAX starting with the value of current I MJ N is given by the following equation:
• the voltage V BATT is across the electroinjector 12 and the electric energy from the battery 23 is transferred to and stored in the electroinjector 12.
• the current flows in the loop including the battery 23, the diode 26, the transistor 28, the electroinjector 12, the boost diode 34 and the capacitor 21, decreasing in a basically linear manner with a slope
• the mean recharge current towards the capacitor 21 generated 10 by each electroactuator engaged in the aforesaid recharging operations can be obtained simply by multiplying the charge regenerated at each pulse by the frequency of the recharge pulses :
• the power delivered towards the capacitor 21 from an electroinjector 12 when it is in the recharge stage can be obtained by multiplying the value of the recharge current by 20 the boost voltage V B oos ⁇ :
• the transistor 28 is always kept on during the recharge stage 25 so that maximum efficiency is obtained. In fact, in this manner, also during the stage in which the transistor 29 is open and the energy is transferred from the electroinjector 12 to the capacitor 21, the current flows through the battery, which therefore continues to supply energy.
• the stages of electric energy storage in the electroinjector 12 and of transfer to the capacitor 21 of the energy stored in the electroinjector 12 are repeated until the voltage across the capacitor 21 exceeds the aforesaid upper limit (50V) .
• the recharge stage When it is necessary to carry out an injection on an electroinjector 12 engaged at the time in recharge operations, the recharge stage is interrupted in advance, by simultaneously opening the transistors 27, 28 and 29 (similar to that which occurs during the fast discharge) , so as to cancel the current in the electroinjector 12 before carrying out the injection in the exact moment required.
• the recharge stage can be resumed, but not before a certain amount of guard time has passed from the end of the injection, so as not to disturb the closing stage of the electroinjector.
• each injection corresponds to a partial discharge of the capacitor 21, it is necessary that upon completion of a series of consecutive injections the V BO os ⁇ voltage is kept above the specified lower limit for the electroinjector 12.
• the size of the capacitor 21 is therefore based on the voltage drop caused by a single injection and the number of consecutive injections that can be carried out.
• the passage from the storage stage of electric energy in the electroinjector 12 to the transfer stage of the energy stored from the electroinjector 12 to the capacitor 21 can be carried out by implementing a control strategy that can be broadly defined as "closed loop” and in which the passage from one stage to another takes place based on the current flowing in the electroinjector 12, or a control strategy that can be broadly defined as "open loop” and in which the passage from one stage to another takes place in a timed manner.
• the closed loop control strategy envisages the measurement, in the energy storage stage in the electroinjector 12, of . the current flowing in the electroinjector 12 used in the recharge, the comparison of the latter with an upper threshold value, and the interruption of the energy storage stage when the current flowing in the electroinjector 12 exceeds this upper threshold value. Since during this stage the current flowing in the electroinjector 12 also circulates in the sense resistor 31, the value of such current is ascertained on the basis of the output voltage of the operational amplifier 32 connected across the sense resistor 31.
• the end of this stage is calculated mathematically as a function of the values of the electronic components in the loop in which the current circulates, of the voltage in this loop (V BATT - V RO os ⁇ ) , and of the lower limit that one wishes the current to reach.
• the open loop control strategy instead envisages the mathematical calculation of the duration of the storage and transfer stages of electric energy as a function of the values of the electronic components in the loops in which the current circulates in both stages, of the voltages in such loops (V BAT ⁇ in the storage stage and V B A T T - V BO os ⁇ in the transfer stage), and of the upper and lower limits that one wishes the current to reach.
• the adopted control strategy is open loop and the lower limit that one wishes the current to reach is zero, between a stage of energy transfer and the subsequent energy storage stage a certain amount of time is waited so as to be certain that the current has actually reached the zero value and thus avoiding the dangerous phenomena of upwards drift of the mean value of the current.
• Figure 4a shows as an example the trend over time of the current ITN J circulating in the electroinjector 12 during the recharge stage of the capacitor 21, denoted as a whole by Stage 4, in which the aforesaid lower limit is zero.
• Figure 4a also denotes by ⁇ t the waiting time that elapses between a stage of energy transfer and the subsequent stage of energy storage to avoid the drift of the mean value of the current.
• Figure 4b shows, as an example, a different trend over time of the current I IN j circulating in the electroinjector 12 during the recharge stage of the capacitor 21, which differs from that shown in figure 4a in that the aforesaid lower limit is different from zero and therefore no waiting time ⁇ t is waited.
• the recharge of the capacitor is carried out on the one hand by regenerating, in the fast discharge stage, the electric energy stored, during the previous fast charge and holding stages, in an electroinjector involved in an injection of fuel, and on the other hand using the electric energy stored in the inductor 2 of the DC/DC converter 1 of figure 1.
• the recharge of the capacitor 21 is carried out using the electric energy purposely stored in an electroinjector 12 not involved in an injection of fuel, in a moment which is separate from the fuel injection carried out by means of the same electroinjector 12.
• the closed loop control strategy described previously through which one controls the passage between the stages of energy storage and transfer, could be modified in such a way as to also accomplish the passage from the stage of energy transfer to the energy storage stage based on the measurement of the current flowing in the electroinjector instead of being based on the calculation of a time interval.

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Cited By (6)

Citations (6)

• 2003
  • 2003-08-05 IT ITTO20030609 patent/ITTO20030609A1/it unknown
• 2004
  • 2004-08-04 WO PCT/EP2004/051707 patent/WO2005014992A1/en active Application Filing

Patent Citations (6)

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