Title of Invention

A METHOD AND AN APPARATUS FOR ACTIVATING A SOLENOID VALVE

Abstract

The invention relates to a method and an apparatus for activating a solenoid valve for injecting fuel into an internal combustion engine, the activation phase of the solenoid valve being divided into a pull-in phase (TA), during which a valve needle of the solenoid valve is made to open by a first current intensity (IA) flowing through a magnet coil of the latter, and into a holding phase (T H), during which the valve needle is held in the .open state by a second, lower current intensity (IH) flowing through the magnet coil, and a booster phase (B1) during which a pulsed booster current (IBooST) flows from a booster capacitor charged up to a high voltage (UBOOST) through the magnet coil, being triggered at leaSt once at the beginning of the pull-in phase (TA), and is characterized in that a plurality of booster pulses (B1, B21, B22), the timing of which is freely selectable within the activation phase, are successively triggered during the activation phase of the solenoid valve

Full Text

The invention relates to a method and an apparatus for activating a solenoid valve, in particular for injecting fuel into an internal combustion engine, the activation phase of the solenoid valve being divided into a pull-in phase, during which a valve needle of the solenoid valve is made to open by a first current intensity flowing through a magnet coil of the latter, and into a holding phase/ during which the valve needle is held in the open state by a second, lower current intensity flowing through the magnet coil, and a booster phase, during which a pulsed booster current flows from a booster capacitor charged up to a high voltage or from some other source of current through the magnet coil, being triggered at least once at the beginning of the pull-in phase. A method of this kind and an apparatus of this kind are known from DE 197 46 980 Al filed by Robert Bosch GmbH. The attached Figures 1 and 2 show in the form of signal diagrams the profile of the voltage and the current across or through a magnet coil of an injection valve during an activation phase made up of a pull-in phase TA and a holding phase TH, Figure 1 showing the case where the supply battery has a normal voltage level, e.g. UBATT - 14 V, and Figure 2 showing the case where the supply battery has a voltage level that is too low, the voltage being less than 14 V, for example. According to Figure 1, after the initial maximum current IBOOST brought about by a first booster phase Bi with a large booster voltage UBOOST t^e current reaches a pull-in current level IA, which allows the valve needle of the solenoid valve to operate. It is clear that the booster voltage UBOOST applied to the solenoid valve during the booster phase Bx is much higher than the battery voltage Ui, During the pull-in phase TA, the pull-in current level IA is regulated by applying the battery voltage UBATT a number of times to the magnet coil. The pull-in phase TA is followed initially by a short freewheeling phase or rapid switch-off, during which the current through the magnet coil of the injection valve drops very rapidly and reaches a holding-current level IH, which is regulated to a desired level during the holding phase TH by repeated pulsed application of the battery voltage UBATT* Finally, the holding phase TH is once again followed by a freewheeling phase or rapid switch-off, at the end of which the current through the magnet coil is removed completely. Figure 2 shows the case where the valve needle cannot operate during the pull-in phase TA because the battery voltage is too low UBATT2 (Fig.2)‹ UBATT (Figure 1). It is thus not possible for an adequate pull-in current for the solenoid injection valve to be built up at a given resistance in the circuit, especially when the battery voltage is low. That is to say (I ‹ IA) Figure 2 shows that the current I through the magnet coil drops very rapidly and the control range of the pull-in current regulation system is not reached and hence reliable opening of the solenoid valve is no longer guaranteed. To achieve a good dynamic response from the valve, the level of the current through the injection valve should as far as possible remain at a high level during the entire opening movement, of the valve needle in the pull-in phase TA. A long booster phase over the entire pull-in phase, which is theoretically possible and would produce this high current level, is not advisable because of the high energy drain on the internal booster capacitor. In realistic applications, the booster phase is used to reach a high current level as quickly as possible, a large proportion of the booster energy being converted into eddy currents at the beginning of the pull-in phase TA. In the prior art, the booster phase Bi is discontinued even before the valve needle is completely open under certain operating conditions, and the valve current is driven out of the battery and falls. That is to say that the magnetic force has already fallen back below its maximum value during the actual in-flight phase, i.e. the phase during which the valve needle is in motion. This entails a poor dynamic response of the solenoid valve. Object and advantages of the invention Given the disadvantages of the prior art that have been described above, it is in general terms the object of the invention to utilize the booster energy economically and furthermore to improve the turn-on behaviour of the valve, even where the battery voltage is low. According to an essential aspect of the invention, this object is achieved by virtue of the fact that a plurality of booster pulses are successively triggered during the activation phase of the solenoid valve. In principle, their timing within the activation phase is freely selectable. In a first exemplary embodiment of the invention, it is thus possible, after the first booster pulse triggered at the beginning of the pull-in phase, for a further booster pulse to be triggered before or during the in¬flight phase of the valve needle. According to a second exemplary embodiment, it is possible, after the first booster pulse triggered at the beginning of the pull-in phase, for a further booster pulse to be triggered at the end of or immediately after the in-flight phase of the valve needle. Finally, in accordance with a third exemplary embodiment, it is possible for a further booster pulse or a plurality of further booster pulses to be triggered during the holding phase of the solenoid valve if the voltage of the supply battery is below a particular threshold voltage in this holding phase. The above-described exemplary embodiments of the invention can also be combined with one another. The multiple boosting makes it possible to reduce the energy and the maximum current of the individual booster pulses in comparison with a long single boost at a very high current intensity, A reduced peak current intensity entails lower loading of the bonding islands for integrated circuits, of the hybrid assemblies and a lower capacitance of the booster capacitor. The timing of the build-up of the magnetic force can be varied freely through an appropriate choice of the times of the second and, if appropriate, third booster pulse. This leads to a reduction in eddy-current formation, and the booster energy can be supplied when required by the solenoid valve. This makes it possible to assist the breaking away of the valve needle of the solenoid valve from the lower stop, to speed up the flight of the needle and to suppress impact rebound on the upper stop of the valve needle. Moreover, if the battery voltage is too low and insufficient to drive a sufficiently high current through the high-pressure injection, valve, it is nevertheless possible to raise the current level through the multiple boosting and hence ensure reliable operation of the high-pressure solenoid injection valve. Accordingly the present invention provides a method for activating a solenoid valve, in particular for injecting fuel into, an internal combustion engine, the activation phase of the solenoid valve being divided into a pull-in phase, during which a valve needle of the solenoid valve is made to open by a first current intensity flowing through a magnet coil of the latter, and into a holding phase, during which the valve needle is held in the open state by a second, lower current intensity flowing through the magnet coil, and a booster phase, during which a pulsed booster current flows from a booster capacitor charged up to a high voltage or from some other source of current through the magnet coil, being triggered at least once at the beginning-of the pull-in phase, characterized in that a plurality of booster pulses, the timing of which is freely selectable within the activation phase, are successively triggered during the activation phase of the solenoid valve. Accordingly the present invention also provides an apparatus for activating a solenoid valve, in particular for injecting fuel into an internal combustion engine, which divides the activation phase of the solenoid valve into a pull-in phase, during which a valve needle of the solenoid valve is made to open by a first current intensity flowing through a magnet coil of the latter, and into a holding phase, during which the valve needle is held in the open state by a second, lower current intensity flowing through the magnet coil, and at least once at the beginning of the pull-in phase triggers a booster phase, causing a pulsed booster current to flow from a booster capacitor charged up to a high voltage or from some other source of current through, the magnet coil, characterized in that the apparatus has means for triggering a plurality of booster pulses at selectable times within the activation phase of the solenoid valve. Drawing Exemplary embodiments of the invention are explained below in greater detail with reference to the drawing, in which: Figure 1 shows graphically in the form of a signal timing diagram the usual profile, described above, of the current and voltage through or across a magnet coil of an injection valve in the case of single boosting. Figure 2 shows graphically the case, which has likewise already been described, when the battery voltage falls to too low a level with the known method involving single boosting. Figure 3A shows graphically in the form of a signal-time diagram the profile of the current through a magnet coil in accordance with a first exemplary embodiment of the method according to the invention involving double boosting. Figure 3B shows graphically the deflection of a valve needle during the activation phase of a high-pressure solenoid injection valve, and Figure 3C shows graphically the current and voltage profile against time for a second exemplary embodiment of the invention involving triple boosting. Exemplary embodiments The graphical representation in Figure 3A shows a first exemplary embodiment of the method according to the invention, in which double boosting takes place at a relatively low battery voltage UBATT* That is to say that, after the first booster pulse Bi triggered at the beginning of the pull-in phase TA, a further booster pulse B21 is triggered and, as is immediately evident from a comparison with Figure 3B, which illustrates the deflection X of the valve needle, this takes place during the in-flight phase f of the valve needle. As a result, the fall in the current through the magnet coil plotted in broken lines in Figure 3A, is avoided and the control range of the pull-in current regulating system is thus reached despite the low battery voltage UBATT and reliable opening of the valve is ensured. By means of the double boosting, it is thus possible to keep yp the current level during the pull-in phase TA even when the battery voltage UBATT is low and, as a result, to open the valve reliably. Figure 3C shows a second exemplary embodiment of the activation method according to the invention, in which a third booster pulse B22 is triggered after the second booster pulse B2i, immediately after the in-flight phase, this third booster pulse suppressing rebounding p of the valve needle on the upper stop. According to another exemplary embodiment, not illustrated in the figure, it is possible for a further booster pulse or a plurality of further booster pulses to be triggered during the holding phase TH. if even the holding current IK can no longer be supplied by the battery owing to high resistance in the circuit. The activation method illustrated in the figure is preferably carried out by an apparatus for activating a solenoid valve for injecting fuel into an internal combustion engine, which divides the activation phase of the solenoid valve into a pull-in phase, during which a valve needle of the solenoid valve is made to open by a first current intensity flowing through a magnet coil of the latter, and into a holding phase, during which the valve needle is held in the open state by a second, lower current intensity flowing through the magnet coil, and which triggers a booster phase at least once at the beginning of the pull-in phase, allowing a pulsed booster current to flow from a booster capacitor charged to a high voltage or from some other source of current through the magnet coil, and which has means for triggering a plurality of booster pulses at selectable times within the activation phase of the solenoid valve. These triggering means can be connected to measuring means' for measuring at least the pull-in current intensity IA, the holding current intensity IH, the battery voltage UBATT of the supply battery, the booster voltage UBOOST and the booster current intensity IBOOST• Apart from assuring the operation of a high-pressure injection valve at low battery voltage by triggering a plurality of booster pulses and thereby raising the current level, thus ensuring that the high-pressure injection valve is opened or held open reliably, the method according to the invention thus allows more economical and variable usage of the booster energy since the multiple boosting reduces eddy-current formation and makes booster energy available when required. This makes it possible to assist the breaking away of the valve needle from its lower stop, to speed up the flight of the needle and to suppress impact rebound on the upper stop of the valve needle. By means of the multiple boosting, the energy or maximum current of the individual booster pulse can be reduced, as a comparison between Figures 1 and 2, which illustrate conventional single boosting, shows. This makes it possible to reduce the peak loads on the bonding islands for the integrated circuits and the hybrid assemblies and to reduce the capacitance of the booster capacitor. WH CLAIM : 1. A method for activating a solenoid valve, in particular for injecting fuel into an internal combustion engine, the activation phase of the solenoid valve being divided into a pull-in phase (TA), during which a valve needle of the solenoid valve is made to open by a first current intensity (IA) flowing through a magnet coil of the latter, and into a holding phase (TH), during which the valve needle is held in the open state by a second, lower current intensity (IH) flowing through the magnet coil, and a booster phase (Bi), during which a pulsed booster current (IBOOST) flows from a booster capacitor charged up to a high voltage (UBOOST) or from some other source of current through the magnet coil, being triggered at least once at the beginning of the pull-in phase (TA), characterized in that a plurality of booster pulses (Bl3 B2i, B22), the timing of which is freely selectable within the activation phase, are successively triggered during the activation phase of the solenoid valve. 2. The method as claimed in claim 1, wherein, after the first booster pulse (Bi) triggered at the beginning of the pull-in phase (TA), a further booster pulse (Bj) is triggered before or during the in-flight phase of the valve needle. 3. The method as claimed in claim 1 or 2, wherein, after the first booster pulse (Bi) triggered at the beginning of the pull-in phase (TA), a further booster pulse (B22) is triggered at the end of or immediately after the in-flight phase of the valve needle. 4. The method as claimed in any one of the preceding claims, wherein a further booster pulse or a plurality of booster pulses is or are trigger during the holding phase (TH) of the solenoid valve if the voltage (UBATT) of the supply battery is below a particular threshold voltage in this phase. 5. An apparatus for activating a solenoid valve, in particular for injecting fuel into an internal combustion engine, which divides the activation phase of the solenoid valve into a pull-in phase (TA), during which a valve needle of the solenoid valve is made to open by a first current intensity (IA) flowing through a magnet coil of the latter, and into a holding phase (TH), during which the valve needle is held in the open state by a second, lower current intensity (IH) flowing through the magnet coil, and at least once at the beginning of the pull-in phase (TA) triggers a booster phase (Bt), causing a pulsed booster current (IBOOST) to flow from a booster capacitor charged up to a high voltage (UBOOST) ºr from some other source of current through the magnet coil, characterized in that the apparatus has means for triggering a plurality of booster pulses (Bi, B21, B22) at selectable times within the activation phase of the solenoid valve. 6. The apparatus as claimed in claim 5, wherein the activation means are connected to measuring means for measuring at least the pull-in current intensity (IA), the holding current intensity (IH), the battery voltage (UBATT) of a supply battery, the booster voltage (UB00ST), and the booster current (IBOOST)• 7. A method for activating a solenoid valve, substantially as hereinabove described and illustrated with reference to figures 3A to 3C of the accompanying drawings. 8. An apparatus for activating a solenoid valve, substantially as hereinabove described and illustrated with reference to figures 3A to 3 C of the accompanying drawings.

Documents:

abs-in-pct-2001-1619-che.jpg

in-pct-2001-1619-che-abstract.pdf

in-pct-2001-1619-che-claims filed.pdf

in-pct-2001-1619-che-claims granted.pdf

in-pct-2001-1619-che-correspondnece-others.pdf

in-pct-2001-1619-che-correspondnece-po.pdf

in-pct-2001-1619-che-description(complete)filed.pdf

in-pct-2001-1619-che-description(complete)granted.pdf

in-pct-2001-1619-che-drawings.pdf

in-pct-2001-1619-che-form 1.pdf

in-pct-2001-1619-che-form 26.pdf

in-pct-2001-1619-che-form 3.pdf

in-pct-2001-1619-che-form 5.pdf

in-pct-2001-1619-che-other documents.pdf

in-pct-2001-1619-che-pct.pdf