WO2024056227A1 - Method for operating a gas injector - Google Patents

Abstract

The invention relates to a method for operating a gas injector of an internal combustion engine, which gas injector injects a gaseous fuel and has a magnetic actuator for operating the gas injector, wherein, in the case of an outlet function in which the gaseous fuel is discharged from the gas injector before the internal combustion engine is shut down in order to still be burnt in the internal combustion engine before the internal combustion engine is finally shut down, the following steps are executed: driving the magnetic actuator in a boost phase (A') comprising continuously increasing a current (I) until the end of the boost phase (A') for the magnetic actuator, and keeping the current (I) constant in an attraction phase (B') of the magnetic actuator at a level which corresponds to a maximum current intensity in the boost phase (A') in order to compensate for a gas pressure, which was reduced during the outlet function of the gas injector, within the gas injector owing to an increased actuator force of the magnetic actuator.

Description

Description

title

Method for operating a gas injector

State of the art

The present invention relates to a method for operating a gas injector of an internal combustion engine when the gas injector is venting before the internal combustion engine is switched off.

Gas injectors are known from the prior art in different designs. One problem with gas injectors that inject a gaseous fuel is that when the internal combustion engine is switched off, despite the gas injector being closed, a leak of the gaseous fuel that is still under high pressure can occur in the gas injector. However, this must be avoided for environmental reasons. Therefore, before the internal combustion engine is finally switched off, the gas injector is operated in a drain function (so-called “purge function”), in which gas that is still under high pressure is released from the gas injector into a combustion chamber of the internal combustion engine and there the internal combustion engine is finally switched off is burned. A connection of the gas injector to a gas storage is already interrupted by additional closing elements. Since the pressure in the gas injector drops during this release function, the gas injector must be designed in such a way that it opens even at low system pressure. Here, a magnetic circuit of a magnetic actuator of the gas injector has been dimensioned in such a way that a sufficient magnetic force is present even at a minimum system pressure that can be achieved. However, this leads to large magnetic actuators, which take up a large installation space, which is larger than the installation space required for the actual injector operation.

Disclosure of the invention The method according to the invention for operating a gas injector of an internal combustion engine with a drain function before switching off the internal combustion engine with the features of claim 1 has the advantage that a magnetic actuator for the gas injector can be designed to be significantly smaller. This saves installation space on the gas injector, which is particularly advantageous for gas injectors that inject directly, since there is little installation space available for the gas injector near a combustion chamber of the internal combustion engine. Furthermore, the gas injector can be manufactured more cost-effectively using a smaller magnetic actuator. This is achieved according to the invention in that during the drain function, in which gaseous fuel is drained from the gas injector into the combustion chamber before the internal combustion engine is finally switched off in order to be burned in the internal combustion engine, in a first step the magnetic actuator is activated in a boost phase takes place in such a way that the current for the magnetic actuator is continuously increased until the end of the boost phase. In a further step, the current for the magnetic actuator is kept constant in a tightening phase, which follows the boost phase. The current is kept constant at a level that corresponds to a maximum current in the boost phase. This makes it possible to open and keep the gas injector open during the venting function of the gas injector despite the reduced gas pressure in the gas injector, since an increased actuator force compensates for the reduced gas pressure during the venting function of the gas injector.

Thus, in the tightening phase, a current level can be increased during the release function in order to compensate for the continuously falling gas pressure during the release function.

The subclaims show preferred developments of the invention.

The increased power requirement in the pick-up phase is preferably provided by a DC/DC converter and/or a boost capacitor. Here, control in the pick-up current phase is preferably carried out with boost voltage. The boost capacitor was charged during normal operation of the internal combustion engine and can therefore provide the increased power requirement for the drain function. More preferably, a length of the tightening phase is reduced in comparison with normal operation of the gas injector, ie, normal injection operation. The background is the longer boost current phase due to a higher boost current level. A switching point from starting current to holding current is preferably stored in the control unit as a constant value. A longer boost current phase therefore results in a shorter pick-up current phase.

More preferably, the current level in the boost phase is increased in comparison to the normal operation of the gas injector. Thus, at the end of the boost phase, a higher current level is achieved than in comparison with normal operation of the gas injector, whereby the current level in the pick-up phase can also be easily maintained at a higher level than in comparison with normal operation.

Alternatively, the current level in the boost phase is kept the same compared to normal operation of the gas injector. Then the higher current level in the pick-up phase is provided, for example, by using the boost capacitor.

Further preferably, a length of the boost phase in the drain function is extended in comparison to the normal operation of the gas injector. This means more time is available to achieve a higher absolute current level in the boost phase compared to normal operation.

In order to be able to blow as much gaseous fuel as possible into the combustion chamber during the exhaust function of the gas injector, a holding phase of the gas injector, in which the gas injector is kept open, is preferably extended in comparison to the normal operation of the gas injector.

The present invention further relates to a control device which is set up to carry out the steps of the method according to the invention. The control device preferably carries out the method until a gas pressure in the gas injector corresponds to the ambient pressure. As a result, the gas injector can be kept in the closed position without leakage when the internal combustion engine is switched off. Furthermore, the invention relates to a computer program with a program code which carries out steps of the method according to the invention when the computer program runs on a computer or a corresponding computing unit, for example on a control device according to the invention.

Furthermore, a computer program product is proposed with a computer program according to the invention, which is stored on a machine-readable data carrier or storage medium.

Short description of the drawing

The present invention will be described in detail below with reference to the accompanying drawings. In the drawing is:

Figure 1 is a schematic diagram showing the voltage and the

Current of a magnetic actuator according to the invention and a force curve and a stroke of an armature of the magnetic actuator over time during normal operation of an internal combustion engine,

Figure 2 is a schematic diagram showing the voltage and the

Current of a magnetic actuator according to the invention and a force curve and a stroke of an armature of the magnetic actuator over time during a drain function of an internal combustion engine, and

Figure 3 shows a longitudinal section through a gas injector, which is used for

Implementation of the method according to the invention is set up.

Preferred embodiment of the invention

A preferred exemplary embodiment of the invention is described in detail below with reference to FIGS. 1 to 3. Figure 3 shows an example of a gas injector 1 with a magnetic actuator. The magnetic actuator comprises a magnetic coil 3 for acting on an axially movable armature 2. The armature 2 can be brought into contact with a closing element 4, in particular a valve needle, in order to release an injection cross section at a sealing seat 5. Reference number 8 designates a restoring element of the gas injector. The closing element 4 is held in the closed position shown in Figure 3 by means of a valve spring 7.

When the magnetic coil 3 is energized, a magnetic field is formed, the magnetic force of which moves the armature 2 in the direction of the closing element 4 (arrow 11). An anchor bolt 9 connected to the anchor 2 comes into contact with the closing element 4, so that the closing element 4 is opened against the spring force of the valve spring 7 on the sealing seat 5. The armature 2 is moved up to a stroke stop 6 for the armature, which represents the complete opening state of the gas injector.

To close the gas injector 1, the current supply to the magnetic coil 3 is stopped, so that the restoring element 8 returns the armature 2 to the starting position shown in FIG. At the same time, the valve spring 7 also returns the closing element 4 to the closed position shown in FIG.

The gas injector 1 is an injector that opens to the outside.

Hydrogen or methane or the like is preferably used as the gaseous fuel.

The diagram in Figure 1 shows normal operation of the gas injector 1 for injecting gaseous fuel, in particular hydrogen, directly into a combustion chamber of an internal combustion engine. The gas injector and the magnetic actuator basically go through four phases, namely a boost phase A, a tightening phase B, a holding phase C and a closing phase D.

In Figures 1 and 2, four curves are shown over time t in the four phases. K1 shows the current curve of the current for the magnetic actuator over time. K2 shows the average voltage of the magnetic actuator over time. K3 shows the force curve of the anchor over time and K4 shows the stroke of the anchor over time t. Furthermore, a closing force K5 is shown in Figures 1 and 2, which represents the subtraction of the pressure force of the system pressure in the gas injector from the spring force of the valve spring. This is increased to F1 in normal operation in FIG. 1 and to F2 by F' in the drain operation shown in FIG.

Furthermore, a battery voltage K6 is shown in Figures 1 and 2, which is constant both in normal operation and in discharge operation.

As can be seen from Figure 1, the boost phase A in normal operation of the internal combustion engine ends after time t1, the tightening phase B ends after time t2 has elapsed, the hold phase C ends after time t3 has elapsed and the closing phase D ends after time t4 has elapsed.

Furthermore, in normal operation in Figure 1, the current curve K1 is such that at the end of the boost phase, the current level drops and is then maintained at a constant level 11 in the pick-up phase. As can be seen from Figure 1, the opening process begins, i.e. the closing element is lifted off the sealing seat at the transition between the boost phase A and the tightening phase B. The maximum opening stroke is achieved in the tightening phase B (stroke curve K4).

In the exhaust function of the gas injector shown in Figure 2 before the internal combustion engine is finally switched off, the current curve K1 is such that a continuous increase in the current up to point IT is achieved in the boost phase A '. This current value I is maintained in the let-off function throughout the entire tightening phase B'. As a comparison between Figure 1 and Figure 2 shows, the current level in the boost phase A 'or in the tightening phase B' in the let-down function is significantly higher than in the boost phase A or in the tightening phase B of Figure 1 in normal operation.

In particular, there is no reduction in the current level in the pick-up phase B 'in the exhaust function of the gas injector. The absolute value IT is also greater than the value 11 in normal operation at the end of the boost phase. This can be achieved by dimensioning a DC/DC converter and/or a boost capacitor. The DC/DC converter and the boost capacitor are like this dimensioned so that all relevant operating points of the gas injector can be served in normal operation (Figure 1). If the internal combustion engine is switched off and the purge function is then required, power reserves are available which are sufficient in the purge function for the few necessary injections, usually at a lower speed than in normal operation.

Thus, the energy reserves from the DC/DC converter and/or the boost capacitor are used for the control shown in FIG. 2 to increase the current level (curve K1 in FIG. 2 in the pick-up phase B').

As can also be seen from the comparison between FIG. 1 and FIG. 2, the tightening phase B 'in draining operation (t2'-tT) is shorter than the tightening phase B in normal operation (t2-t1). On the other hand, the boost phase A' in drain operation is larger than in normal operation due to the higher boost current level, which is shown in Figure 2 by the time tT compared to the time t1 in normal operation.

The higher current level IT in the draining operation also provides an increased opening force of the magnetic actuator, which can be seen by comparing the force curves K3 between FIG. 1 and FIG. 2. This allows the missing force component of the gas pressure to open the gas injector due to the falling gas pressure in the gas injector to be compensated for. In the holding phase C, C' and the closing phase D, D' in the draining operation and in normal operation, all four curves K1, K2, K3 and K4 are the same again.

Thus, by using the boost voltage for the starting current control in the starting phase B, a higher average voltage and thus also a higher starting current IT can be made possible. This means that higher magnetic forces are possible through the magnetic actuator, which compensate for the reduced opening pressure forces of the gaseous fuel to be injected.

In the exemplary embodiment described, a control variant with increased boost current is shown at the end of the boost phase A'. However, control variants are also conceivable in which the current curve in the boost phase A' in the let-off mode is the same as in normal operation and then the compensation is only realized by the magnetic force in the pick-up phase B' with increased current.

Claims

Expectations 1. A method for operating a gas injector of an internal combustion engine, which blows in a gaseous fuel and has a magnetic actuator for actuating the gas injector, with a drain function in which the gaseous fuel is released from the gas injector before the internal combustion engine is switched off in order to still be in the internal combustion engine To be burned before the internal combustion engine is finally switched off, the following steps are carried out: Controlling the magnetic actuator in a boost phase (A') with a continuous increase in a current (I) until the end of the boost phase (A') for the magnetic actuator, and Keeping the current (I) constant in a tightening phase (B') of the magnetic actuator at a level that corresponds to a maximum current intensity in the boost phase (A') in order to reduce the gas pressure within the gas injector during the release function of the gas injector by increasing the actuator force of the magnetic actuator to balance. 2. The method according to claim 1, wherein the increased power requirement in the pick-up phase (B ') is provided by a boost capacitor and / or a DC / DC converter. 3. Method according to one of the preceding claims, wherein a length of the tightening phase (B ') is reduced in comparison with normal operation of the gas injector. 4. Method according to one of the preceding claims, wherein the current level in the boost phase (A ') is increased in comparison to the normal operation of the gas injector. 5. The method according to any one of claims 1 to 3, wherein the current level in the boost phase (A ') remains the same compared to the normal operation of the gas injector. 6. Method according to one of the preceding claims, wherein a length of the boost phase (A ') is extended in comparison to the normal operation of the gas injector. 7. The method according to any one of the preceding claims, wherein a holding phase (C ') of the gas injector, in which the gas injector is kept open, is extended in comparison to the normal operation of the gas injector. 8. Control device which is set up to carry out steps of a method according to one of the preceding claims. 9. Computer program with a program code that carries out steps of a method according to one of claims 1 to 7 when the computer program runs on a computer or a corresponding computing unit, for example on a control device. 10. Computer program product with a computer program according to claim 9, which is stored on a machine-readable data carrier or storage medium.