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
• • 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
  • F02D2041/2013—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 voltage source
• • 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
  • F02D2041/2031—Control of the current by means of delays or monostable multivibrators

Definitions

• the invention relates to a method and a device for controlling switching electromagnets, in particular in injection valves according to the preambles of the independent claims.
• the fuel is supplied to the combustion chamber of the engine via electrically controlled injection valves.
• the fuel metering and the map ignition take place here via a central computer system, which calculates system data from various measurement values supplied by sensors and supplies corresponding pulse-width-modulated control signals to an electromagnet of the valve.
• Air flow meters, cooling water temperature meters, air inlet temperature meters, which measure the inlet temperature of the air at the entrance to the combustion chamber, air temperature meters, revolution markers, speed sensors and throttle clap switches serve as sensors.
• the admixture of the fuel in the 'air flow during Ansaug vides the associated cylinder brings the best technical results.
• the pulse-width modulated control pulses are also emitted by the process computer.
• the ratio between the amount of fuel and the above-mentioned duty cycle of the pulse duration-modulated signals or the injection angle should be as constant as possible.
• the characteristic curves should be as linear as possible in the ideal state and should have the same value for the metered fuel amount for all engine speeds for a given injection angle.
• the main components of conventional electric injection valves are the nozzle part with the nozzle assembly, the winding of the electromagnet, the magnetic core, the armature, the return spring and the housing with force. material line connections.
• the return spring pressing against the nozzle assembly with such a force that the injection valve is reliably closed.
• the movement distance of the armature and thus of the associated nozzle assembly is mechanically limited by a disc.
• the current in the winding of the electromagnet increases linearly until the core saturates and is now only limited by the series resistor of the injection valve 1 or the resistance of the winding wire.
• the field strength in the electromagnet is proportional to the product of the current and the number of turns divided by the length of the magnetic path.
• the parameters for optimal control of the electromagnets have a diametrical course.
• a large inductance is required for a given mechanical force in order to keep the current low and not to require complex control circuits.
• the armature is removed from the core in the switch-on moment and therefore, owing to the degressive field density as a function of the distance, a considerably higher field strength for the movement of the armature is required than in the steady state.
• the magnetic energy in the winding of the electromagnet which reached its maximum at the moment of switching off, must be reduced. If the dismantling takes place quickly, high voltage peaks are the result. If the degradation is damped, the counter-EMF causes a switch-off delay.
• the switch-on delay due to the time-linear current rise and the switch-off delay due to the stored magnetic energy are the two main disturbance parameters which are responsible for non-linear relationships in fuel metering.
• the invention is based on the object of specifying a method and a device of the type in question, with which in particular the switch-on and switch-off delay of switched electromagnets, in particular in electrically controlled injection valves, can be reduced in such a way that the switching characteristics are as optimal as possible fen.
• the guiding principle of the invention is to be seen in this, by means of a specific control circuit without change or change in the component switched by the electromagnet component 1 to see specific parameters and to reduce or eliminate the two above-mentioned interference parameters and thus to ensure the operation of the component in the permissible characteristic field.
• the switching characteristics show approximately the desired horizontal displacement.
• the electromagnet for example of an injection valve, is consciously overridden with an initial pulse of high voltage amplitude within a defined and, in particular, very short time frame, independent of the duty cycle, due to the short time of the initial pulse.
• the windings of the electromagnet are not thermally overloaded.
• the unregulated supply voltage is transformed to a regulated high voltage level, which generally corresponds to a multiple of the supply voltage.
• the anchor moves very quickly in this way into the other position, which, for. B. it is the open position of an egg n Spritzventi 1.
• the current rise is practically linear.
• the switching movements of the armature can also be clearly reproduced over time.
• the electromagnet is provided with only a minimum energy necessary for securely holding the armature, which is preferably done by a minimal and preferably constant holding current.
• Overriding in the switch-on phase improves the switch-on delay by about a power of ten.
• the switch-on override takes place with high voltages, which are between 40 and 80 V for injection valves in motor vehicles. These voltages cannot be reached in vehicle electrical systems, so that they have to be generated in separate circuit stages. A preferred way of doing this is to convert the vehicle electrical system voltage
• the switch-off delay is reduced since only a small amount of magnetic energy has to be dissipated.
• the initial pulse of high voltage amplitude can in principle be generated in several ways using the vehicle electrical system voltage available in motor vehicles.
• the generation of the initial pulse would be similar to realizing the generation of the ignition pulse.
• this solution is not recommended, since currents of approx. 20 amperes would then occur on the primary side in a corresponding pulse transformer.
• the necessary reinforced cross sections of the supply lines and large filter capacities are also disadvantageous.
• there is high electromagnetic interference radiation. Semiconductors that can withstand high peak currents would have to be used as circuit breakers. Overall, a complicated control with high circuit complexity is required.
• electrolytic capacitors are only of limited suitability for such pulse applications, e.g. B. due to their high volume, their unfavorable Temperaturver ⁇ behavior and poor electrical switching behavior due to the inductance.
• Favor 't is therefore held by means of a fast, a transformer having a transducer storage capacitor continuously on a high state of charge, to write a triggered by the control circuit Wegvor ⁇ direction its charge pulse-like manner to the injector.
• a semiconductor is used as the circuit breaker. This solution is considerably simpler and less expensive than the ones mentioned above.
• a certain amount of energy is required to switch the electromagnet through quickly using the high voltage start pulse. Since a relatively high intermediate voltage is made available with the aid of the storage capacitor, only relatively small currents occur in the windings of the electromagnet, the values being between 2 to 4 times the continuous load current and no thermal excess due to the short-term nature of the initial pulse load on the winding of the electromagnet. Given a predetermined permissible charge on the storage capacitor, a considerably smaller capacitance is permissible, which is of the order of a few microfarads. Such capacitors are available inexpensively in a polypropylene design. This type of capacitor has an extremely good pulse behavior, so that overall better values can be achieved than with electrolytic capacitors. The capacitor is charged relatively slowly by the fast converter and then gives off its charge to the respective electromagnet when switched through.
• a constant current source 1 e is preferably used to provide the low holding energy for the electromagnet. If several electromagnets are activated one after the other, e.g. B. the electromagnets of injectors of an engine, the converter, the switching device and the constant current source e can be used together for all injectors of an engine. A separate circuit breaker is then available for each injection valve. This solution simplifies the control circuit considerably, since a separate control circuit is not necessary for each injection valve.
• these injection valves are not modified in terms of design, so that existing control circuits can also be converted in the sense of the invention.
• the basic frequency of the egg ni spri z es i. H. the frequency at which the injection valve no longer opens despite a control signal has been raised significantly.
• the amount of fuel added can be dispensed in a single cycle instead of in several portions as in the prior art.
• ninjection valve 1 show a much better linear Course as those of conventionally controlled injection valves.
• FIG. 1 shows a schematic block circuit diagram of a device according to the invention for controlling a plurality of injection valves
• FIG. 2 shows diagrams for the control voltage, the current profile through an electromagnet of the injection valve and for the injection quantity, in each case plotted over time, on the one hand for conventional control and on the other hand for control of an injection valve 1 according to the invention;
• 3 shows two characteristic diagrams for the injection quantity per time versus the speed of an internal combustion engine per minute with the injection angle as parameters, specifically a characteristic diagram for conventionally controlled and another characteristic diagram for injection valves 1 controlled according to the invention; 4a and b diagrams for the calculated errors in percent in the fuel metering with conventional control or control according to the invention of an injection valve 1.
• the injection system has a plurality of electromagnetically actuated injection valves 2a to 2n, each with an electromagnet 3a to 3n, which are controlled with the aid of a computer 4 with control signals modulated by pulse duration, the computer using this control signal in a conventional manner on the basis of measured values calculated, which are delivered by several sensors.
• the control signals of the computer 4 are fed via a pulse shaper 5 to a pulse source 6, the output pulses of which are fed via a circuit breaker 7a to 7n for each injector to the associated electromagnet 3a to 3n, between the feed lines to the respective electromagnets 3a to 3n, a filter network 17a to 17n is also provided in order to reduce peak values of the supplied signals.
• the circuit breakers are controlled via a decoder 8, which in turn receives control signals from the computer 4.
• a data converter 9 controlled by the computer 4 is also provided, which is connected to the pulse shaper 5 and the decoder 8.
• the pulse source 6 is with an input terminal 10 to the voltage U of an electrical system of a motor vehicle and with another input terminal 11 to a basic potential, for. B. mass. With the input terminal 10 in a first branch of the pulse source 6 a direct voltage / Gl ei chwoodswandl er 12 and a pulse switch 13 and in another branch parallel to it a constant current source 14 connected. A filter capacitor or a capacitor arrangement 15 is also provided between the input terminals 10 and 11. A storage capacitor 16 is located between the basic potential connected to the input terminal 11 and a connection point between the converter 12 and the pulse switch 13.
• the DC / DC voltage converter 12 converts the on-board voltage U from z. B. 12 V in a higher voltage of z. B. 80 V around.
• a transformer with a primary winding of. 9 turns and a secondary winding of 72 turns are provided.
• a demagnetization winding with 12 windings is also provided on the primary side.
• the computer 4 outputs a control signal based on the measured values calculated by the sensors to the pulse shaper 5 and the data converter 9 and also a marking signal to the decoder 8.
• the corresponding signal switches 7a to 7n of the individual injection valves are sent with the marking signal 2a to 2n and closed for the time period specified by the pulse-width-modulated control signal.
• the pulse shaper 5 in turn controls the pulse switch 13, which thereby closes a predetermined time period, in this case 250 ⁇ sec.
• the charge of the storage capacitor 16 is supplied to the electromagnetic 3a in a pulsed manner via the circuit breaker 7a during this period. Due to this short-term high voltage pulse, the respective injection valve becomes only one opened with a slight switch-on delay of approximately 0.25 msec.
• a constant holding current is fed from the constant atom source 1 e 14 to the respective electromagnet 3a to 3n, which holds the injection valve in the open position. If the circuit breaker 7a is opened when the control signal drops, the injection valve is moved back into the closed position by a compression spring (not shown here), this taking place with only a slight delay.
• a predetermined quantity of fuel determined by the duration of the control signal is injected from the injection valve.
• FIG. 2 shows a signal diagram for conventional control of an injection valve on the left-hand side, and a signal diagram for control of the same injection valve 1es according to the invention on the right-hand side.
• the top line a shows part of a pulse duration module of the control voltage supplied by the computer.
• Line b for the conventional control shows that the current profile through the electromagnet increases linearly until the current reaches a value at which the armature of the electromagnet overcomes the force of the compression spring in the injection valve and the injection valve is thereby opened.
• the delay time between the first edge of the control voltage and the start of the opening is approximately 2 msec.
• the switching current then rises further and falls with the end flank of the control voltage. At this moment the closing movement of the armature begins, which is initiated by the compression spring of the injection valve 1.
• the injection valve is completely closed again after a short delay. This cycle is repeated according to the course of the control voltage.
• the sudden discharge of the storage capacitor 16 causes the current through the electromagnet of the respective injection valve to increase very rapidly and already reaches the switching current value after a delay time of approximately 0.25 msec, so that the injection valve is opened.
• the opening process started shortly before, due to the high current values.
• currents of up to 3 amperes flow in the primary winding of the respective electromagnet in the injection valve. Due to the short time duration of 250 microseconds, however, non-lead this to 'a thermal overloading of the winding.
• the constant current source 14 supplies a small holding current which holds the armature of the respective electromagnet 3a to 3n in the open position of the valve.
• this holding current is. much lower than the switching current required to initiate the switching of the valve. With the end flank of the control voltage then only needs . the magnetic energy in the electromagnet, which is also low due to the low holding current, is reduced, so that the valve is closed again after a very short delay.
• the instantaneous value of the field strength is the relevant parameter for opening the injection valve 1.
• This instantaneous value is a function of the time constant, ie the ratio ses between the inductance and the resistance as well as the supply voltage.
• the switch-on delay is therefore a function of these three variables. While the supply voltage is a constant in a control according to the prior art, it is a variable according to the invention, with the aid of which the switch-on delay also becomes variable.
• the values for the switch-on and switch-off delay can be optimized by appropriate dimensioning of the amplitude of the initial pulse and its duration.
• the amount of injection in a conventional control system differs significantly from the course of the control voltage due to the long delay time when the injection valve 1 is switched on. Since the delay time when switching on is constant regardless of the course of the control voltage, it is obvious that there is no proportionality between the time course of the control voltage and the time course of the injection quantity. In contrast to this, according to the invention, the short delay time when switching on ensures an approximately optimal proportionality between the time course of the injection quantity and the control voltage.
• a characteristic diagram for the flow rate per unit of time is plotted against the engine revolution per minute with the injection angle as a parameter in a conventional control and with broken lines in a control according to the invention Ei n Spritzventi 1 it shown. It can clearly be seen that with injection at angles of up to 144 °, the characteristic curves drop with conventional control in the direction of higher speeds and only with an injection wave your hand! rise from 162 ° above about 4000 revolutions per minute. The desired linear, horizontal course is not achieved. It can be seen that, however, this is approximately the case for all the characteristic curves in the case of a control according to the invention. The characteristic curves have good linearity, which gives the advantages mentioned above.
• FIG. 4a shows the theoretically determined error in percent in fuel metering in a conventional control of an injection valve with a determined switch-on delay of 2 msec
• FIG. 4b the error in percent in fuel metering when controlling the same injector according to the invention , each with the injection angle as a parameter.
• This error is mainly due to the switch-on delay of the injection valve. It is seen that the error in a conventional An 'control even at low revolutions per minute considerable values which during this error tion at a erf ndungswashen Ansteue ⁇ is substantially smaller and assumes only for low injection angle to about 40 ° noticeable .Werte.

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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)

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ID=6335430

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Citations (6)

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• 1987
  • 1987-09-07 DE DE19873729954 patent/DE3729954A1/de active Granted
• 1988
  • 1988-09-01 EP EP88114289A patent/EP0306839A1/de not_active Ceased
  • 1988-09-01 WO PCT/DE1988/000538 patent/WO1989002523A1/de unknown

Patent Citations (6)

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