Method for controlling a gas injector

Abstract

The present invention describes a method for controlling a gas injector (4) with a magnetic actuator (5), comprising the steps of: pre-magnetizing (S1) the magnetic actuator (5) with a pre-magnetizing current (IV), controlling (S2) the magnetic actuator (5) with a boost current (IB) to open a closing element (7), controlling (S3) the magnetic actuator (5) with a holding current (IH) to keep the closing element (7) open, and reducing (S4) the holding current to close the closing element (7). The boost current (IB) is greater than the holding current (IH) and greater than the pre-magnetizing current (IV). Furthermore, the pre-magnetizing current is designed such that the closing element (7) remains closed during pre-magnetizing (S1).

Description

Prior ArtThe present invention relates to a method for controlling a gas injector with a magnetic actuator.Solenoid actuators are used in many injectors for fuel injection into an internal combustion engine (e.g., diesel common rail injectors or injectors for direct gasoline injection). Such an actuator system proven in the Otto and Diesel engines can also continue to be used for future injectors for blowing hydrogen into a hydrogen internal combustion engine.The magnetic actuator is actuated, for example, with a defined current profile. Typically, the armature of the magnetic actuator is first attracted with a high current (boost current) and then held in its energized position with a lower current (holding current). The boost phase is particularly decisive for the energy requirement and thus the power loss at the coil and in the control device, since here operation is performed with high current and a high voltage. The high current requirement in the boost phase results in particular from the fact that the magnetic force is to be built up as quickly as possible in order to be able to operate the magnetic actuator with high dynamics.When using hydrogen in an internal combustion engine, as few changes as possible should be made in comparison with the previous operation with diesel or gasoline. This is critical in particular for gas injectors, since due to the higher volume flow by several orders of magnitude, a gas injector having the same dimensions as an injector for gasoline or diesel is difficult to implement.Disclosure of the InventionThe method according to the invention for controlling a gas injector with a magnetic actuator having the features of claim 1 has the advantage over the related art that the boost phase can be shortened and thus the energy requirement of the gas injector is reduced. This is achieved according to the invention by a method having the features of claim 1 in that the magnetic actuator is premagnetized with a biasing current in a first step. Subsequently, in a second step, the magnetic actuator is activated with a boost current, which leads to the closing element opening. In a third step, the magnetic actuator is actuated with a holding current in order to keep the closing element open. Finally, in a fourth step, the holding current is reduced in order to close the closing element. In this case, the boost current is greater than the holding current and likewise greater than the biasing current. The bias current is furthermore only so high that the closing element remains closed in the first step.Biasing the magnetic actuator has the technical effect that, for opening the closing element, with the same opening dynamics, the activation duration of the magnetic actuator with the boost current and / or the level of the boost current can be reduced. Thus, the current requirement of the gas injector during operation can be reduced. Alternatively, it is possible according to the invention to operate the gas injector at a higher rotational speed with a constant boost current, to design the magnetic actuator for greater magnetic forces or to design the gas injector to be smaller.The dependent claims show preferred developments of the invention.Preferably, the biasing in the first step is limited by a maximum biasing current. It can thus be ensured that during the premagnetization the magnet armature remains closed and the bias current does not assume excessively high values.Alternatively or additionally, the premagnetizing in the first step is preferably limited by a maximum premagnetizing time. The regulation of the premagnetization via the premagnetization time can be implemented simply and cost-effectively. Furthermore, the regulation of the premagnetization by a maximum premagnetization time is resistant to current peaks or voltage peaks.More preferably, a battery provides the bias current. The battery is preferably a secondary battery which is rechargeable. Batteries can provide current to a plurality of electric loads and store electric energy over a long period of time.In a further preferred embodiment of the invention, a capacitor provides the bias current. Capacitors are cost-effective energy stores which can be charged quickly and can provide high currents in a short time.Preferably, the maximum biasing current generates a magnetic force which is as great as a closing force acting on the closing element. Thus, the maximum bias current is just so large that the closing element remains closed in the first step. The higher the bias current, the shorter the magnetic actuator has to be controlled with a boost current in order to open the closing element. Thus, a maximum bias current which is so large that the resulting magnetic force and closing force cancel each other out allows a minimum possible drive time for opening the closing element.Furthermore, the invention describes a gas injector for blowing in a gaseous medium, comprising a closing element which opens and closes a passage opening at a sealing seat, a magnetic actuator for actuating the closing element and a current source for actuating the magnetic actuator. The gas injector is configured to carry out a method according to one of the preceding claims and in particular to blow in hydrogen.Brief Description of the DrawingsAn embodiment of the invention will be described in detail below with reference to the accompanying drawings. In the drawing, the following is: FIG. 1 shows a diagram of the current (I) over time (t) with three schematic current profiles for controlling a gas injector, and FIG. 2 shows a schematic illustration of a gas injector for blowing in a gaseous medium according to a preferred exemplary embodiment.Embodiment of the InventionFIG. 1 shows a diagram of the current (I) over time (t) with three different current profiles. The first current profile 1 is a current profile according to the prior art without bias magnetization. The second current profile 2 and the third current profile 3 show a first and second exemplary embodiment of a method for controlling a gas injector 4.The first current profile 1 according to the prior art is directly controlled with a boost current I B whereby a magnetic force F M is induced in a magnetic actuator 5, which magnetic force is configured to open a closing element 7. After a time t O1 the closing element 7 is completely open and the current is reduced to a holding current I H.The holding current I H is kept constant until the end of an injection process, so that the closing element 7 remains open. At the time t S the holding current I H is reduced to zero, whereupon the closing element 7 closes.The second current profile 2 shows a first exemplary embodiment of a method according to the invention for controlling the gas injector 4. The biasing current I V is so large that under all conceivable boundary conditions the closing element 5 cannot open. The bias current I V first rises sharply and is reduced and maintained at a constant level upon reaching a predetermined value.In a second step, after a maximum biasing time t Vmax has been reached, the biasing current I V is increased to the boost current I B in order to open the closing element 7. As a result of the premagnetization in step 1, the closing element is opened more quickly, with the result that the boost current I B can be reduced to the holding current I H after a time t O2. In this case, due to the shortened opening process, the time t O2 is temporally before the time t O1.The third current profile 3 shows a second exemplary embodiment of a method according to the invention for controlling the gas injector 4. At this time, the bias current I V first rises sharply until it reaches a maximum bias current I Vmax.The maximum bias current I Vmax is so large that the magnetic force F M resulting therefrom and a closing force F S, which acts against the magnetic force F M cancel one another out. The bias current I V is reduced to a predetermined value after reaching the maximum bias current I Vmax and subsequently rises slowly again.Subsequently, in a second step, after a maximum biasing time t Vmax has been reached, the current is increased to the boost current I B until the closing element is opened at a time t O3 and the boost current I B is reduced to the holding current I H. Due to the higher bias current I V in the second exemplary embodiment in comparison with the first exemplary embodiment, the time t O3 is reached before the time t O2.FIG. 2 shows a schematic illustration of the gas injector 4 for blowing in a gaseous medium, such as hydrogen, for example. The gaseous medium is preferably introduced into a combustion chamber of an internal combustion engine.The magnetic actuator 5 is arranged in the gas injector 4. The magnetic actuator 5 preferably comprises a coil and an armature which is connected to the closing element 7. The magnetic actuator 5 is connected to a current source 6 and is controlled via the latter. The power source 6 may be, for example, a battery or a capacitor. As the current flows through the coil, this current generates the magnetic force F M on the armature, which can open the closing element 7 in the opening direction.FIG. 2 shows the closing element 7 in the open state, so that the gaseous medium can flow through the gas injector 4. The gaseous medium can escape from the gas injector 4 at an axial end of the gas injector 4 through a passage opening 8.If no current flows through the coil of the magnetic actuator 5, only a closing force F S, for example by a spring, acts on the closing element 7, whereby the closing element 7 is moved in the direction of a sealing seat 9 and closes the gas injector 4.

Claims

Method for controlling a gas injector (4) with a magnetic actuator (5), comprising the steps of: - premagnetizing (S1) the magnetic actuator (5) with a premagnetizing current (I V), - controlling (S2) the magnetic actuator (5) with a boost current (I B), in order to open a closing element (7), - controlling (S3) the magnetic actuator (5) with a holding current (I H), in order to keep the closing element (7) open, and - reducing (S4) the holding current (I H), in order to close the closing element 7), wherein the boost current (I B) is greater than the holding current (I H), - wherein the boost current (I B) is greater than the biasing current (I V), and - wherein the closing element (7) is closed during the biasing (S1).Method according to claim 1, wherein the biasing (S1) is limited by a maximum biasing current (I Vmax).Method according to one of the preceding claims, wherein the premagnetising (S1) is limited by a maximum premagnetising time (t Vmax).Method according to one of the preceding claims, wherein a battery provides the bias current (I V).Method according to one of Claims 1 to 3, wherein a capacitor provides the bias current (I V).Method according to one of the preceding claims, wherein the maximum biasing current (I Vmax) generates a magnetic force (F M) which is equal to a closing force (F S). acting on the closing element (7).Gas injector (4) for blowing in a gaseous medium, in particular hydrogen, comprising: - a closing element (7) which opens and closes a passage opening (8) at a sealing seat (9), - a magnetic actuator (5) for actuating the closing element (7) and - a current source (6) for actuating the magnetic actuator (5), - wherein the gas injector (4) is configured to carry out a method according to one of the preceding claims.

Images