EP1139449A1 - Brennstoffeinspritzanlage - Google Patents

Brennstoffeinspritzanlage Download PDF

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Publication number
EP1139449A1
EP1139449A1 EP00107203A EP00107203A EP1139449A1 EP 1139449 A1 EP1139449 A1 EP 1139449A1 EP 00107203 A EP00107203 A EP 00107203A EP 00107203 A EP00107203 A EP 00107203A EP 1139449 A1 EP1139449 A1 EP 1139449A1
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EP
European Patent Office
Prior art keywords
piezoelectric element
voltage
fuel injection
electric power
injection system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00107203A
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English (en)
French (fr)
Inventor
Johannes-Joerg Rueger
Udo Schulz
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Robert Bosch GmbH
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Robert Bosch GmbH
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Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Priority to EP00107203A priority Critical patent/EP1139449A1/de
Publication of EP1139449A1 publication Critical patent/EP1139449A1/de
Withdrawn legal-status Critical Current

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    • 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
    • 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

Definitions

  • the present invention relates to a fuel injection system having a piezoelectric element for controlling the amount of injected fuel into a combustion engine, wherein electric power for driving the piezoelectric element is supplied by an electric power source.
  • the present invention further relates to a method for operating such a fuel injection system.
  • a fuel injection nozzle for example, implemented as a double acting, double seat valve to control the linear stroke of a needle for fuel injection into a cylinder of an internal combustion engine
  • the amount of fuel injected into a corresponding cylinder is a function of the time the valve is open, and in the case of the use of a piezoelectric element, the activation voltage applied to the piezoelectric element.
  • Fig. 8 is a schematic representation of a fuel injection system using a piezoelectric element 2010 as an actuator.
  • the piezoelectric element 2010 is electrically energized to expand and contract in response to a given activation voltage.
  • the piezoelectric element 2010 is coupled to a piston 2015.
  • the piezoelectric element 2010 causes the piston 2015 to protrude into a hydraulic adapter 2020 which contains a hydraulic fluid, for example fuel.
  • a double acting control valve 2025 is hydraulically pushed away from hydraulic adapter 2020 and the valve plug 2035 is extended away from a first closed position 2040.
  • double acting control valve 2025 and hollow bore 2050 is often referred to as double acting, double seat valve for the reason that when piezoelectric element 2010 is in an unexcited state, the double acting control valve 2025 rests in its first closed position 2040. On the other hand, when the piezoelectric element 2010 is fully extended, it rests in its second closed position 2030.
  • the later position of valve plug 2035 is schematically represented with ghost lines in Fig. 8.
  • the fuel injection system comprises an injection needle 2070 allowing for injection of fuel from a pressurized fuel supply line 2060 into the cylinder (not shown).
  • the double acting control valve 2025 rests respectively in its first closed position 2040 or in its second closed position 2030. In either case, the hydraulic rail pressure maintains injection needle 2070 at a closed position. Thus, the fuel mixture does not enter into the cylinder (not shown).
  • the piezoelectric element 2010 is excited such that double acting control valve 2025 is in the so-called mid-position with respect to the hollow bore 2050, then there is a pressure drop in the pressurized fuel supply line 2060. This pressure drop results in a pressure differential in the pressurized fuel supply line 2060 between the top and the bottom of the injection needle 2070 so that the injection needle 2070 is lifted allowing for fuel injection into the cylinder (not shown).
  • An object of the present invention is to increase the accuracy of a fuel injection system.
  • An inventive fuel injection system has at least one piezoelectric element for controlling the amount of injected fuel into a combustion engine, wherein electric power for driving the piezoelectric element is supplied by an electric power source, and wherein the fuel injection system comprises a controllable voltage converter disposed between the piezoelectric element and the electric power source and a control unit for adjusting a current between the electric power source and the controllable voltage converter to a value between 0 ampere and a maximum current.
  • adjusting the current between the electric power sources and the controllable voltage converter to a value between 0 ampere and a maximum current means in particular that the effective value or the amplitude of the current between the electric power source and the controllable voltage converter is adjusted to a value between 0 ampere and a maximum current.
  • Adjusting the current to a value between 0 ampere and a maximum current means in particular that the current is controlled in such a manner that it can be adjusted to more than one of two values, where in particular one value is set to 0 ampere and the other value is set to a value which in particular relates to a maximum value of power which can be necessary to drive the piezoelectric elements. It turns out that the invention is very advantageous as voltage drops between the electric power supply and the controllable voltage converter which occur due to driving the piezoelectric elements are compensated or almost compensated. It turned out that this way a sensor for measuring rail pressure in the fuel supply system provides more accurate measured values resulting in a more precise fuel injection.
  • control unit adjusts the current between the electric power source and the controllable voltage converter based upon a speed of the combustion engine.
  • control unit adjusts the current between the electric power source and the controllable voltage converter based upon the number of cylinders z, in particular based upon the number of cylinders z and the number j of injections per cylinder.
  • the electric power source is a battery.
  • the fuel injection system further comprises a driving circuitry for driving the piezoelectric element, wherein the driving circuitry comprises a buffer capacitor, in particular a buffer capacitor or a bank or capacitors of at least 25 ⁇ F.
  • the buffer capacitor is disposed between the piezoelectric element and the controllable voltage converter.
  • the fuel injection system further comprises a voltage sensor for measuring a voltage across the buffer capacitor.
  • control unit adjusts the current between the electric power source and the controllable voltage converter based upon the voltage across the buffer capacitor.
  • One advantage of the present invention lies in the reduction of the battery voltage fluctuation.
  • Another advantage of the present invention is the substantial increase in the accuracy of the fuel injection system and its independence from the voltage fluctuations.
  • Fig. 1 shows a graph depicting the relationship between activation voltage U and injected fuel volume m E during a preselected fixed time period, for an exemplary fuel injection system using piezoelectric elements acting upon double acting control valves.
  • the y-axis represents volume m E of fuel injected into a cylinder chamber during the preselected fixed period of time.
  • the x-axis represents the activation voltage U applied to or stored in the corresponding piezoelectric element, used to displace a valve plug of the double acting control valve.
  • the activation voltage U is zero, and the valve plug is seated in a first closed position to prevent the flow of fuel during the preselected fixed period of time.
  • the represented values of the activation voltage cause the displacement of the valve plug away from the first closed position and towards the second closed position, in a manner that results in a greater volume of injected fuel for the fixed time period, as the activation voltage approaches U opt , up to the value for volume indicated on the y-axis by m E,max .
  • the point m E,max corresponding to the greatest volume for the injected fuel during the fixed period of time, represents the value of the activation voltage for application to or charging of the piezoelectric element, that results in an optimal displacement of the valve plug between the first and second valve seats.
  • the volume m E of fuel injected during the fixed period of time decreases until it reaches zero. This represents displacement of the valve plug from the optimal point and toward the second closed position of the double acting control valve until the valve plug is seated in its second closed position.
  • the graph of Fig. 1 illustrates that a maximum volume of fuel injection occurs when the activation voltage causes the piezoelectric element to displace the valve plug to the optimal point.
  • the present invention teaches that the value for U opt at any given time for a particular piezoelectric element is influenced by the operating characteristics of the particular piezoelectric element at that time. That is, the amount of displacement caused by the piezoelectric element for a certain activation voltage varies as a function of the operating characteristics of the particular piezoelectric element. Accordingly, in order to achieve a maximum volume of fuel injection, m E,max , during a given fixed period of time, the activation voltage applied to or occurring in the piezoelectric element should be set to a value relevant to current operating characteristics of the particular piezoelectric element, to achieve U opt .
  • Fig. 2 shows a double graph representing a schematic profile of an exemplary control valve stroke, to illustrate the double acting control valve operation discussed above.
  • the x-axis represents time
  • the y-axis represents displacement of the valve plug (valve lift).
  • the x-axis once again represents time
  • the y-axis represents a nozzle needle lift to provide fuel flow, resulting from the valve lift of the upper graph.
  • the upper and lower graphs are aligned with one another to coincide in time, as represented by the respective x-axises.
  • the piezoelectric element is charged resulting in an expansion of the piezoelectric element, as will be described in greater detail, and causing the corresponding valve plug to move from the first closed position to the second closed position for a pre-injection stroke, as shown in the upper graph of Fig. 2.
  • the lower graph of Fig. 2 shows a small injection of fuel that occurs as the valve plug moves between the two seats of the double seat valve, opening and closing the valve as the plug moves between the seats.
  • the charging of the piezoelectric element can be done in two steps: the first one is to charge it to a certain voltage and cause the valve to open and the second one is to charge it further and cause the valve to close again at the second closed position. Between these steps, in general, there can be a certain time delay.
  • a discharging operation is then performed, as will be explained in greater detail below, to reduce the charge within the piezoelectric element so that it contracts, as will also be described in greater detail, causing the valve plug to move away from the second closed position, and hold at a midway point between the two seats.
  • the activation voltage within the piezoelectric element is to reach a value that equals U opt to correspond to an optimal point of the valve lift, and thereby obtain a maximum fuel flow, m E,max , during the period of time allocated to a main injection.
  • the upper and lower graphs of Fig. 2 show the holding of the valve lift at a midway point, resulting in a main fuel injection.
  • the piezoelectric element is discharged to an activation voltage of zero, resulting in further contraction of the piezoelectric element, to cause the valve plug to move away from the optimal position, towards the first closed position, closing the valve and stopping fuel flow, as shown in the upper and lower graphs of Fig. 2.
  • the valve plug will once again be in a position to repeat another pre-injection, main injection cycle, as just described above, for example.
  • any other injection cycle can be performed.
  • Fig. 3 provides a block diagram of an exemplary embodiment of an arrangement in which the present invention may be implemented.
  • Fig. 3 there is a detailed area A and a non-detailed area B, the separation of which is indicated by a dashed line c.
  • the detailed area A comprises a circuit for charging and discharging piezoelectric elements 10, 20, 30, 40, 50 and 60.
  • these piezoelectric elements 10, 20, 30, 40, 50 and 60 are elements in fuel injection nozzles (in particular in so-called common rail injectors) of an internal combustion engine.
  • Piezoelectric elements can be used for such purposes because, as is known, and as discussed above, they possess the property of contracting or expanding as a function of a voltage applied thereto or occurring therein.
  • the reason to take six piezoelectric elements 10, 20, 30, 40, 50 and 60 in the embodiment described is to independently control six cylinders within a combustion engine; hence, any other number of piezoelectric elements might match any other purpose.
  • the non-detailed area B comprises a control unit D and a activation IC E by both of which the elements within the detailed area A are controlled, as well as a measuring system F for measuring system operating characteristics such as, for example, fuel pressure and rotational speed (rpm) of the internal combustion engine for input to and use by the control unit D, according to the present invention, as will be described in detail below.
  • the control unit D and activation IC E are programmed to control activation voltages for piezoelectric elements as a function of operating characteristics of the each particular piezoelectric element.
  • the circuit within the detailed area A comprises six piezoelectric elements 10, 20, 30, 40, 50 and 60.
  • the piezoelectric elements 10, 20, 30, 40, 50 and 60 are distributed into a first group G1 and a second group G2, each comprising three piezoelectric elements (i.e. piezoelectric elements 10, 20 and 30 in the first group G1 resp. 40, 50 and 60 in the second group G2).
  • Groups G1 and G2 are constituents of circuit parts connected in parallel with one another.
  • Group selector switches 310, 320 can be used to establish which of the groups G1, G2 of piezoelectric elements 10, 20 and 30 resp. 40, 50 and 60 will be discharged in each case by a common charging and discharging apparatus (however, the group selector switches 310, 320 are meaningless for charging procedures, as is explained in further detail below).
  • the group selector switches 310, 320 are arranged between a coil 240 and the respective groups G1 and G2 (the coil-side terminals thereof) and are implemented as transistors.
  • Side drivers 311, 321 are implemented which transform control signals received from the activation IC E into voltages which are eligible for closing and opening the switches as required.
  • Diodes 315 and 325 are provided in parallel with the group selector switches 310, 320. If the group selector switches 310, 320 are implemented as MOSFETs or IGBTs, these group selector diodes 315 and 325 can be constituted by the parasitic diodes themselves. The diodes 315, 325 bypass the group selector switches 310, 320 during charging procedures. Hence, the functionality of the group selector switches 310, 320 is reduced to select a group G1, G2 of piezoelectric elements 10, 20 and 30, resp. 40, 50 and 60 for a discharging procedure only.
  • each piezoelectric branch comprises a series circuit made up of a first parallel circuit comprising a piezoelectric element 10, 20, 30, 40, 50 resp. 60 and a resistor 13, 23, 33, 43, 53 resp. 63 (referred to as branch resistors) and a second parallel circuit made up of a selector switch implemented as a transistor 11, 21, 31, 41, 51 resp. 61 (referred to as branch selector switches) and a diode 12, 22, 32, 42, 52 resp. 62 (referred to as branch diodes).
  • the branch resistors 13, 23, 33, 43, 53 resp. 63 cause each corresponding piezoelectric element 10, 20, 30, 40, 50 resp. 60 during and after a charging procedure to continuously discharge themselves, since they connect both terminals of each capacitive piezoelectric element 10, 20, 30, 40, 50, resp. 60 one to another.
  • the branch resistors 13, 23, 33, 43, 53 resp. 63 are sufficiently large to make this procedure slow compared to the controlled charging and discharging procedures as described below.
  • the branch selector switch/branch diode pairs in the individual piezoelectric branches 110, 120, 130, 140, 150 resp. 160 i.e. selector switch 11 and diode 12 in piezoelectric branch 110, selector switch 21 and diode 22 in piezoelectric branch 120, and so on, can be implemented using electronic switches (i.e. transistors) with parasitic diodes, for example MOSFETs or IGBTs (as stated above for the group selector switch/diode pairs 310 and 315 resp. 320 and 325).
  • the branch selector switches 11, 21, 31, 41, 51 resp. 61 can be used to establish which of the piezoelectric elements 10, 20, 30, 40, 50 or 60 will be charged in each case by a common charging and discharging apparatus: in each case, the piezoelectric elements 10, 20, 30, 40, 50 or 60 that are charged are all those whose branch selector switches 11, 21, 31, 41, 51 or 61 are closed during the charging procedure which is described below. Usually, at any time only one of the branch selector switches is closed.
  • the branch diodes 12, 22, 32, 42, 52 and 62 serve for bypassing the branch selector switches 11, 21, 31, 41, 51 resp. 61 during discharging procedures.
  • any individual piezoelectric element can be selected, whereas for discharging procedures either the first group G1 or the second group G2 of piezoelectric elements 10, 20 and 30 resp. 40, 50 and 60 or both have to be selected.
  • the branch selector piezoelectric terminals 15, 25, 35, 45, 55 resp. 65 may be connected to ground either through the branch selector switches 11, 21, 31, 41, 51 resp. 61 or through the corresponding diodes 12, 22, 32, 42, 52 resp. 62 and in both cases additionally through resistor 300.
  • resistor 300 The purpose of resistor 300 is to measure the currents that flow during charging and discharging of the piezoelectric elements 10, 20, 30, 40, 50 and 60 between the branch selector piezoelectric terminals 15, 25, 35, 45, 55 resp. 65 and the ground. A knowledge of these currents allows a controlled charging and discharging of the piezoelectric elements 10, 20, 30, 40, 50 and 60. In particular, by closing and opening charging switch 220 and discharging switch 230 in a manner dependent on the magnitude of the currents, it is possible to set the charging current and discharging current to predefined average values and/or to keep them from exceeding or falling below predefined maximum and/or minimum values as is explained in further detail below.
  • the measurement itself further requires a voltage source 621 which supplies a voltage of 5 V DC, for example, and a voltage divider implemented as two resistors 622 and 623.
  • a voltage source 621 which supplies a voltage of 5 V DC, for example
  • a voltage divider implemented as two resistors 622 and 623.
  • each piezoelectric element 10, 20, 30, 40, 50 and 60 i.e. the group selector piezoelectric terminal 14, 24, 34, 44, 54 resp. 64
  • the other terminal of each piezoelectric element 10, 20, 30, 40, 50 and 60 may be connected to the plus pole of a voltage source via the group selector switch 310 resp. 320 or via the group selector diode 315 resp. 325 as well as via a coil 240 and a parallel circuit made up of a charging switch 220 and a charging diode 221, and alternatively or additionally connected to ground via the group selector switch 310 resp. 320 or via diode 315 resp. 325 as well as via the coil 240 and a parallel circuit made up of a discharging switch 230 or a discharging diode 231.
  • Charging switch 220 and discharging switch 230 are implemented as transistors, for example, which are controlled via side drivers 222 resp. 232.
  • the voltage source comprises an element having capacitive properties which, in the example being considered, is the (buffer) capacitor 210.
  • Capacitor 210 is charged by a battery 200 (for example a motor vehicle battery) and a DC voltage converter 201 downstream therefrom.
  • DC voltage converter 201 converts the battery voltage (for example, 12 V) into substantially any other DC voltage (for example, 250 V), and charges capacitor 210 to that voltage.
  • DC voltage converter 201 is controlled by means of transistor switch 202 and resistor 203 which is utilized for current measurements taken from a measuring point 630.
  • a further current measurement at a measuring point 650 is allowed by activation IC E as well as by resistors 651, 652 and 653 and a 5 V DC voltage, for example, source 654; moreover, a voltage measurement at a measuring point 640 is allowed by activation IC E as well as by voltage dividing resistors 641 and 642.
  • a resistor 330 (referred to as total discharging resistor), a stop switch implemented as a transistor 331 (referred to as stop switch), and a diode 332 (referred to as total discharging diode) serve to discharge the piezoelectric elements 10, 20, 30, 40, 50 and 60 (if they happen to be not discharged by the "normal" discharging operation as described further below).
  • Stop switch 331 is preferably closed after “normal” discharging procedures (cycled discharging via discharge switch 230). It thereby connects piezoelectric elements 10, 20, 30, 40, 50 and 60 to ground through resistors 330 and 300, and thus removes any residual charges that might remain in piezoelectric elements 10, 20, 30, 40, 50 and 60.
  • the total discharging diode 332 prevents negative voltages from occurring at the piezoelectric elements 10, 20, 30, 40, 50 and 60, which might in some circumstances be damaged thereby.
  • the load on the battery voltage is as uniform as possible so that the battery voltage fluctuations are minimized.
  • the battery supplies power to the DC/DC converter 201 until the desired voltage is reached (for example, 250V) at which point the battery voltage drops somewhat (for example, 0.5V) below what it would be in an unloaded condition.
  • the desired voltage for example, 250V
  • the battery voltage drops somewhat (for example, 0.5V) below what it would be in an unloaded condition.
  • Such a voltage drop effects the entire electrical system to which the battery is supplying power.
  • Other sensors, and in particular, elements such as those used for rail pressure regulation, exhibit voltage dependence. If the voltage collapses, this effects the accuracy with which those elements operate.
  • the primary side (battery side) current limit of the DC/DC converter 201 is desirable to provide for charging the primary side (battery side) current limit of the DC/DC converter 201 as a function of the operating, or output, side voltage value so that the drive of the DC/DC converter 201 will operate continuously, or almost continuously and provide approximately just enough power to drive the elements 10, 20, 30, 40, 50 and 60.
  • the current limit on the primary side can be updated continuously by way of the SPI in the activation IC E.
  • the control described above could be performed by a converter control unit (not shown, but described in greater detail below) that would determine the energy requirement of the output stage per unit of time from the engine speed, number of cylinders in the engine, number of drive operations, and maximum voltage used for the drive operation. From this energy requirement, the necessary current can be determined by means of a characteristic curve. This is the maximum primary side current wherein the DC/DC converter 201 operates at a fixed frequency. If the primary side current is increased, the converter supplies more power and vise versa.
  • the value can be determined by multiplying the number of cylinders by the number of drive operations per 720° of crankshaft angle. This value is then multiplied by the energy required for charging to the maximum voltage used for the drive operation. This is a function of the efficiency of the DC/DC converter 201, the efficiency of the output stage, and the efficiency of the piezoelectric elements 10, 20, 30, 40, 50 and 60. This product is divided by the engine speed to provide the energy required by the output stage. In order to ensure that the energy required by the output stage is provided reliably, a safety factor can be included (for example, multiplying by 1.1).
  • Charging and discharging of all the piezoelectric elements 10, 20, 30, 40, 50 and 60 or any particular one is accomplished by way of a single charging and discharging apparatus (common to all the groups and their piezoelectric elements).
  • the common charging and discharging apparatus comprises battery 200, DC/DC converter 201, capacitor 210, charging switch 220 and discharging switch 230, charging diode 221 and discharging diode 231 and coil 240.
  • each piezoelectric element works the same way and is explained in the following while referring to the first piezoelectric element 10 only.
  • the selection of one or more particular piezoelectric elements 10, 20, 30, 40, 50 or 60 to be charged or discharged, the charging procedure as described in the following as well as the discharging procedure are driven by activation IC E and control unit D by means of opening or closing one or more of the above introduced switches 11, 21, 31, 41, 51, 61; 310, 320; 220, 230 and 331.
  • activation IC E and control unit D The interactions between the elements within the detailed area A on the one hand and activation IC E and control unit D on the other hand are described in detail further below.
  • any particular piezoelectric element 10, 20, 30, 40, 50 or 60 which is to be charged has to be selected.
  • the branch selector switch 11 of the first branch 110 is closed, whereas all other branch selector switches 21, 31, 41, 51 and 61 remain opened.
  • the charging procedure requires a positive potential difference between capacitor 210 and the group selector piezoelectric terminal 14 of the first piezoelectric element 10.
  • charging switch 220 and discharging switch 230 are open no charging or discharging of piezoelectric element 10 occurs: In this state, the circuit shown in Fig. 3 is in a steady-state condition, i.e. piezoelectric element 10 retains its charge state in substantially unchanged fashion, and no currents flow.
  • charging switch 220 In order to charge the first piezoelectric element 10, charging switch 220 is closed. Theoretically, the first piezoelectric element 10 could become charged just by doing so. However, this would produce large currents which might damage the elements involved. Therefore, the occurring currents are measured at measuring point 620 and switch 220 is opened again as soon as the detected currents exceed a certain limit. Hence, in order to achieve any desired charge on the first piezoelectric element 10, charging switch 220 is repeatedly closed and opened whereas discharging switch 230 remains open.
  • a closed circuit comprising a series circuit made up of piezoelectric element 10, capacitor 210, and coil 240 is formed, in which a current i LE (t) flows as indicated by arrows in Fig. 4a.
  • a current i LE (t) flows as indicated by arrows in Fig. 4a.
  • a closed circuit comprising a series circuit made up of piezoelectric element 10, charging diode 221, and coil 240 is formed, in which a current i LA (t) flows as indicated by arrows in Fig. 4b.
  • the result of this current flow is that energy stored in coil 240 flows into piezoelectric element 10.
  • the voltage occurring in the latter, and its external dimensions increase.
  • charging switch 220 is once again closed and opened again, so that the processes described above are repeated.
  • the energy stored in piezoelectric element 10 increases (the energy already stored in the piezoelectric element 10 and the newly delivered energy are added together), and the voltage occurring at the piezoelectric element 10, and its external dimensions, accordingly increase.
  • charging switch 220 has closed and opened a predefined number of times, and/or once piezoelectric element 10 has reached the desired charge state, charging of the piezoelectric element is terminated by leaving charging switch 220 open.
  • the piezoelectric elements 10, 20, 30, 40, 50 and 60 are discharged in groups (G1 and/or G2) as follows:
  • discharging switch 230 is once again closed and opened again, so that the processes described above are repeated.
  • the energy stored in piezoelectric element 10 decreases further, and the voltage occurring at the piezoelectric element, and its external dimensions, also accordingly decrease.
  • discharging switch 230 Once discharging switch 230 has closed and opened a predefined number of times, and/or once the piezoelectric element has reached the desired discharge state, discharging of the piezoelectric element 10 is terminated by leaving discharging switch 230 open.
  • activation IC E and control unit D on the one hand and the elements within the detailed area A on the other hand is performed by control signals sent from activation IC E to elements within the detailed area A via branch selector control lines 410, 420, 430, 440, 450, 460, group selector control lines 510, 520, stop switch control line 530, charging switch control line 540 and discharging switch control line 550 and control line 560.
  • sensor signals obtained on measuring points 600, 610, 620, 630, 640, 650 within the detailed area A which are transmitted to activation IC E via sensor lines 700, 710, 720, 730, 740, 750.
  • the control lines are used to apply or not to apply voltages to the transistor bases in order to select piezoelectric elements 10, 20, 30, 40, 50 or 60, to perform charging or discharging procedures of single or several piezoelectric elements 10, 20, 30, 40, 50, 60 by means of opening and closing the corresponding switches as described above.
  • the sensor signals are particularly used to determine the resulting voltage of the piezoelectric elements 10, 20 and 30, resp. 40, 50 and 60 from measuring points 600 resp. 610 and the charging and discharging currents from measuring point 620.
  • the control unit D and the activation IC E are used to combine both kinds of signals in order to perform an interaction of both as will be described in detail now while referring to Figs. 3 and 5.
  • control unit D and the activation IC E are connected to each other by means of a parallel bus 840 and additionally by means of a serial bus 850.
  • the parallel bus 840 is particularly used for fast transmission of control signals from control unit D to the activation IC E, whereas the serial bus 850 is used for slower data transfer.
  • the activation IC E comprises: a logic circuit 800, RAM memory 810, digital to analog converter system 820 and cooperator system 830. Furthermore, it is indicated that the fast parallel bus 840 (used for control signals) is connected to the logic circuit 800 of the activation IC E, whereas the slower serial bus 850 is connected to the RAM memory 810.
  • the logic circuit 800 is connected to the RAM memory 810, to the cooperator system 830 and to the signal lines 410, 420, 430, 440, 450 and 460; 510 and 520; 530; 540, 550 and 560.
  • the RAM memory 810 is connected to the logic circuit 800 as well as to the digital to analog converter system 820.
  • the digital to analog converter system 820 is further connected to the cooperator system 830.
  • the cooperator system 830 is further connected to the sensor lines 700 and 710; 720; 730, 740 and 750 and -as already mentioned-to the logic circuit 800.
  • the closing and opening of the charging switch 220 is repeated as long as the detected voltage at measuring point 600 or 610 is below the target voltage. As soon as the target voltage is achieved, the logic circuit stops -the continuation of the procedure.
  • the discharging procedure takes place in a corresponding way: Now the selection of the piezoelectric element 10, 20, 30, 40, 50 or 60 is obtained by means of the group selector switches 310 resp. 320, the discharging switch 230 instead of the charging switch 220 is opened and closed and a predefined minimum target voltage is to be achieved.
  • the timing of the charging and discharging operations and the holding of voltage levels in the piezoelectric elements 10, 20, 30, 40, 50 or 60, as for example, the time of a main injection, can be according to a valve stroke, as shown, for example, in Fig. 2.
  • the fuel injection into the combustion engine 2505 is controlled via the piezoelectric elements 10, 20, 30, 40, 50, and 60, of the circuit within the detailed area A shown in Fig. 4.
  • the rotational speed of the combustion engine 2505 is measured and fed into a fuel correction unit 2506.
  • the fuel correction unit 2506 comprises a frequency analyzer which evaluates the frequency of the rotational speed.
  • the fuel correction unit 2506 calculates a fuel correction value ⁇ m E upon this frequency analysis for each individual cylinder o the combustion engine 2505.
  • the configuration shown in Fig. 6 also comprises a fuel volume calculation unit 2507 calculating a desired fuel volume m E .
  • the desired fuel volume is added to the fuel volume correction value ⁇ m E via an adder 2508.
  • the sum of the desired fuel volume m E and the fuel volume correction value ⁇ m E is fed into a fuel metering unit 2509.
  • the fuel metering unit calculates the time a voltage has to be applied to the piezoelectric elements 10, 20, 30, 40, 50 and 60, to inject fuel into the combustion engine 2505.
  • the fuel correction unit 2506, the adder 2508, the fuel volume calculation unit 2507, and the fuel metering unit 2509 are implemented in the control unit D.
  • Time signals to signaling when a voltage has to be applied to the piezoelectric elements 10, 20 ,30, 40, 50 and 60, to inject fuel into the combustion engine 2505 are transferred from the fuel metering unit 2509 to the activation IC E via the parallel bus 840.
  • the online correction value K o is calculated by an online optimization unit 2510.
  • the online optimization unit 2510 calculates the online correction value K o based upon the fuel correction value ⁇ m E calculated by the fuel correction unit 2506.
  • an embodiment of the present invention provides for charging the primary-side current limit of the DC/DC converter 201 as a function of the engine speed so that the drive of the DC/DC converter 201 is substantially uniform. Otherwise, there could be a gap in the voltage consistency supplied to the piezoelectric element. If the desired voltage is not attained, the piezoelectric element will not be properly charged resulting in an inaccurate fuel injection.
  • the DC/DC converter 201 will operate substantially continuously to provide just enough power for driving the piezoelectric elements. According to this embodiment, power is not provided directly from the battery, rather from a buffer capacitor which is in turn fed from the battery through a DC/DC converter 201.
  • battery 200 is connected to DC/DC converter 201 which supplies power to buffer capacitor 210.
  • Activation IC E contains therein a threshold frequency value for the capacitor 210 of, for example, 10 Amp.
  • the duty cycles of the elements must be readjusted as frequently to ensure the desired average current. If the readjustment does not take place frequently or completely the fuel injection quantity will be affected.
  • the feedback is minimized by determining the energy requirement of the output stage as a function of time, engine speed, number of cylinders, number of drive operations and the maximum voltage used for the drive operation. This value can be calculated from the engine's operating parameters that are supplied to control unit D shown in Fig. 3 and the result is communicated with the activation IC E.
  • the output of the DC/DC converter 201 can be controlled and updated with the most recent engine performance requirements by way of the SPI in the activation IC E. In this manner, the DC/DC converter is continuously providing voltage to the buffer capacitor 210, which in turn attends to charging the piezoelectric elements.
  • the data comprising the characteristic curve can be compiled under laboratory conditions and stored, for example, in the RAM memory module 810.
  • Such characteristic curve correlates data for energy requirement to DC/DC current.
  • the value for the frequency is constant and can be stored in the activation IC E.
  • the energy requirement establishes the maximum primary-side current wherein the DC/DC converter 201 operates at a fixed frequency and vice versa.
  • Fig. 7 represents an embodiment of the present invention for reducing voltage fluctuations in systems having piezoelectric elements.
  • the number of cylinders z is multiplied (using a multiplier 7055) by the number j of injections per cylinder.
  • the outcome is then multiplied (using a multiplier 7050) by an energy value S.
  • the energy value S is determined by obtaining the maximum voltage U max as normalized by the energy required for charging U max .
  • Reference number 7045 denotes a characterizing curve depicting the relationship between activation voltage U and the energy S needed to charge the piezoelectric element 10.
  • Such data can be compiled from laboratory measurement and stored in RAM memory 810. The result, denoted as S z in Fig.
  • the DC/DC converter's primary side current I DC/DC,min is multiplied (using a multiplier 7075) by a safety factor e.
  • a safety factor e of 1.1 is exemplary and it would be within the scope of the present invention to apply other values that satisfy the safety factor requirement.
  • the result of the multiplication, I* DC/DC is a desired value for the current between the battery 200 and the DC/DC-converter 201.
  • the DC/DC converter 201 supplies more power and vice versa. This enables the buffer capacitor to stay charged continuously throughout the engine's operation while substantially eliminating voltage fluctuations.
  • data relating to engine speed n, number z of cylinders and number j of injections per cylinder can be measured by the measuring system F.
  • the data is then transmitted to control unit D and thereafter to activation IC E.
  • the primary side current of the DC/DC converter 201 i.e. the current between the DC/DC converter 201 (controllable voltage converter) is continuously updated by the activation IC E.
  • Other information such as the characteristic curve depicting the characteristic curve 7045 between maximum voltage U max and energy s needed to charge a piezoelectric element and the characteristic curve 7070 can be stored, for example, in RAM 810.
  • the desired value I* DC/DC for the current between the battery 200 and the DC/DC-converter 201 is adjusted via the transistor switch 202.
  • the embodiments of the present invention provide a means for obtaining the maximum primary side current at which the DC/DC converter 201 operates at a fixed frequency. If the primary side current is increased, the DC/DC converter 201 supplies more power to the buffer capacitor 210. Conversely, if the primary side current is decreased, the DC/DC converter 201 supplies less power.

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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)
EP00107203A 2000-04-01 2000-04-01 Brennstoffeinspritzanlage Withdrawn EP1139449A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP00107203A EP1139449A1 (de) 2000-04-01 2000-04-01 Brennstoffeinspritzanlage

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP00107203A EP1139449A1 (de) 2000-04-01 2000-04-01 Brennstoffeinspritzanlage

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EP1139449A1 true EP1139449A1 (de) 2001-10-04

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004022957A1 (de) * 2002-09-03 2004-03-18 Robert Bosch Gmbh Verfahren zum betrieb einer brennkraftmaschine
DE102005001282A1 (de) * 2005-01-11 2006-07-20 Siemens Ag Aktorvorrichtung

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4749897A (en) * 1986-03-12 1988-06-07 Nippondenso Co., Ltd. Driving device for piezoelectric element
EP0371469A2 (de) * 1988-11-30 1990-06-06 Toyota Jidosha Kabushiki Kaisha Apparat zum Antreiben eines piezoelektrischen Elements zum Öffnen oder zum Schliessen eines Ventilteils
US5036263A (en) * 1988-11-09 1991-07-30 Nippondenso Co., Ltd. Piezoelectric actuator driving apparatus
EP0379182B1 (de) 1989-01-18 1994-04-13 Toyota Jidosha Kabushiki Kaisha Einrichtung zur Ansteuerung eines piezoelektrischen Elements für das Schliessen und Öffnen eines Ventilglieds
DE19729844A1 (de) 1997-07-11 1999-01-14 Bosch Gmbh Robert Kraftstoffeinspritzvorrichtung
DE19742073A1 (de) 1997-09-24 1999-03-25 Bosch Gmbh Robert Kraftstoffeinspritzvorrichtung für Brennkraftmaschinen
GB2334164A (en) * 1998-02-10 1999-08-11 Bosch Gmbh Robert A drift-compensated piezoelectric fuel injector actuator

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4749897A (en) * 1986-03-12 1988-06-07 Nippondenso Co., Ltd. Driving device for piezoelectric element
US5036263A (en) * 1988-11-09 1991-07-30 Nippondenso Co., Ltd. Piezoelectric actuator driving apparatus
EP0371469A2 (de) * 1988-11-30 1990-06-06 Toyota Jidosha Kabushiki Kaisha Apparat zum Antreiben eines piezoelektrischen Elements zum Öffnen oder zum Schliessen eines Ventilteils
EP0371469B1 (de) 1988-11-30 1995-02-08 Toyota Jidosha Kabushiki Kaisha Apparat zum Antreiben eines piezoelektrischen Elements zum Öffnen oder zum Schliessen eines Ventilteils
EP0379182B1 (de) 1989-01-18 1994-04-13 Toyota Jidosha Kabushiki Kaisha Einrichtung zur Ansteuerung eines piezoelektrischen Elements für das Schliessen und Öffnen eines Ventilglieds
DE19729844A1 (de) 1997-07-11 1999-01-14 Bosch Gmbh Robert Kraftstoffeinspritzvorrichtung
DE19742073A1 (de) 1997-09-24 1999-03-25 Bosch Gmbh Robert Kraftstoffeinspritzvorrichtung für Brennkraftmaschinen
GB2334164A (en) * 1998-02-10 1999-08-11 Bosch Gmbh Robert A drift-compensated piezoelectric fuel injector actuator

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004022957A1 (de) * 2002-09-03 2004-03-18 Robert Bosch Gmbh Verfahren zum betrieb einer brennkraftmaschine
DE102005001282A1 (de) * 2005-01-11 2006-07-20 Siemens Ag Aktorvorrichtung
DE102005001282B4 (de) * 2005-01-11 2007-02-15 Siemens Ag Aktorvorrichtung

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