Method for operating a gas injector
Patent Information
- Application Number
- EP2023736317
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-09-14
- Filing Date
- 2023-06-29
- Publication Date
- 2025-07-23
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Gas injectors in internal combustion engines face challenges with post-injection due to increased combustion chamber pressure, requiring larger magnetic actuators that occupy excessive space and are costly, especially when the engine load point changes and speed increases.
A method for operating gas injectors involves an improved control strategy during post-injection, where the magnetic actuator's current is continuously increased in a boost phase and maintained at a maximum level in a tightening phase, using a boost capacitor and/or DC/DC converter to provide the necessary force to overcome high combustion chamber pressure, allowing for a smaller actuator design.
This approach enables a significantly smaller magnetic actuator design, saving installation space and reducing costs while ensuring effective post-injection operation even at high combustion chamber pressures, enhancing the gas injector's ability to maintain open during post-injection.
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] title
[0003] Method for operating a gas injector
[0004] State of the art
[0005] The present invention relates to a method for operating a gas injector of an internal combustion engine during a post-injection after a main injection of the gas injector.
[0006] Gas injectors are known in various designs from the prior art. One problem with gas injectors that inject a gaseous fuel is that post-injection should be possible to reduce exhaust emissions and fuel consumption. In particular, when a load point of the internal combustion engine changes with an increase in speed, post-injection should be carried out to enable rapid response, particularly of a turbocharger. A problem with post-injection in direct-injection gas injectors is the increased combustion chamber pressure, since post-injection is usually carried out shortly after the internal combustion engine has reached top dead center. The increased combustion chamber pressure therefore provides an additional closing force on the gas injector, which must also be overcome when post-injection is carried out.To date, the magnetic circuit of a gas injector's magnetic actuator has been dimensioned to ensure sufficient magnetic force even during post-injection. However, this results in large magnetic actuators that require a large installation space, which is larger than the space required for actual injector operation.
[0007] Disclosure of the Invention The method according to the invention for operating an outward-opening gas injector of an internal combustion engine during post-injection into a combustion chamber of 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 directly injecting gas injectors, 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 by using a smaller magnetic actuator. This is achieved according to the invention in that improved control of the gas injector is carried out during the post-injection, which follows a main injection of the gaseous fuel into the combustion chamber.In this case, particularly when the voltage level of the magnetic actuator is constantly high, the magnetic actuator is first controlled in a boost phase 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 pull-in phase which follows the boost phase. The current is kept constant at a level which corresponds to a maximum current intensity in the boost phase. This makes it possible to open and keep the gas injector open during the post-injection of the gas injector despite a high combustion chamber pressure shortly after top dead center of the internal combustion engine, since an increased actuator force compensates for the high combustion chamber pressure during the post-injection of the gas injector.
[0008] This allows a current level to be increased during the pull-in phase during post-injection to provide the force required by the solenoid actuator during post-injection. The force required by the solenoid actuator during post-injection to open the gas injector must overcome the return force of a return spring and the combustion chamber pressure, with the solenoid actuator being supported by the system pressure of the gaseous fuel being injected in the gas injector. This means that the force required by the solenoid actuator to open during post-injection must be greater than the sum of the return force of the spring and the combustion chamber pressure minus the system pressure in the gas injector.
[0009] The subclaims show preferred developments of the invention. Preferably, the boost phase of the post-injection provides the same or higher current level as the main injection, with the increased current requirement in the pickup phase of the post-injection being provided by a boost capacitor and / or a DC / DC converter. The boost current duration of the post-injection is preferably the same or greater than that of the main injection. Thus, a higher pickup current level is preferably achieved during the post-injection compared to the main injection. Preferably, the increased current requirement in the pickup phase is provided by a DC / DC converter and / or a boost capacitor. The boost capacitor was charged during normal operation of the internal combustion engine and can thus provide the increased current requirement during the post-injection.
[0010] Further preferably, the length of the pull-in phase during the post-injection is reduced compared to the main injection of the gas injector. This is possible because the current level is maintained at an increased pull-in current for a longer period during the pull-in phase.
[0011] Preferably, a length of the start-up phase of the post-injection is extended compared to the main injection of the gas injector.
[0012] Further preferably, the current level in the boost phase of the post-injection is increased compared to the main injection of the gas injector. Thus, at the end of the boost phase, a higher current level is achieved than during the main injection of the gas injector, which makes it easy to maintain the current level in the start-up phase of the post-injection at a higher level than during the main injection.
[0013] Alternatively, the current level during the boost phase of the post-injection is kept the same as the main injection of the gas injector. In this case, the higher current level during the start-up phase of the post-injection is provided, for example, by using the boost capacitor.
[0014] Further preferably, the boost phase during the post-injection is longer than the main injection of the gas injector. This provides more time to achieve a higher absolute current level during the boost phase of the post-injection compared to the main injection.
[0015] In order to be able to inject as much gaseous fuel as possible into the combustion chamber during the post-injection of the gas injector, a holding phase during the post-injection of the gas injector, in which the gas injector is kept open, is preferably extended compared to the main injection of the gas injector.
[0016] Preferably, the holding current level in the holding phase of the post-injection of the gas injector, in which the gas injector is kept open, is the same as or higher than the main injection of the gas injector.
[0017] Preferably, an injection cycle of the internal combustion engine comprises exclusively a main injection and a post-injection. This means that the injection cycle does not include a pre-injection.
[0018] The method according to the invention is further preferably used when a load point of the internal combustion engine changes and in particular when the speed of the internal combustion engine increases.
[0019] Further preferably, the post-injection takes place exclusively after the top dead center of a piston of the internal combustion engine has been reached.
[0020] Furthermore, the present invention relates to a control device which is configured to carry out the steps of the method according to the invention.
[0021] Furthermore, the invention relates to a computer program with a program code which executes 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.
[0022] Furthermore, a computer program product with a computer program according to the invention is proposed, which is stored on a machine-readable data carrier or storage medium. Brief description of the drawing
[0023] The present invention will be described in detail below with reference to the accompanying drawings. In the drawing:
[0024] Figure 1 is a schematic diagram showing the voltage and
[0025] 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 main injection of an internal combustion engine,
[0026] Figure 2 is a schematic diagram showing the voltage and
[0027] 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 post-injection of an internal combustion engine, and
[0028] Figure 3 shows a longitudinal section through a gas injector used for
[0029] Carrying out the method according to the invention.
[0030] Preferred embodiment of the invention
[0031] A preferred embodiment of the invention is described in detail below with reference to Figures 1 to 3.
[0032] 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 numeral 8 denotes a return element of the gas injector. The closing element 4 is held in the closed position shown in Figure 3 by a valve spring 7.
[0033] When the solenoid coil 3 is energized, a magnetic field is created, the magnetic force of which moves the armature 2 toward the closing element 4 (arrow 11). An armature bolt 9 connected to the armature 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 at the sealing seat 5. The armature 2 is moved up to a stroke stop 6 for the armature, which represents the fully open state of the gas injector.
[0034] To close the gas injector 1, the current supply to the solenoid coil 3 is stopped, so that the return element 8 returns the armature 2 to the initial position shown in Figure 3. At the same time, the valve spring 7 also returns the closing element 4 to the closed position shown in Figure 1.
[0035] The gas injector 1 is an outward opening injector.
[0036] Hydrogen, methane, or the like is preferably used as gaseous fuel.
[0037] The diagram in Figure 1 shows a main injection of the gas injector 1 for injecting gaseous fuel, in particular hydrogen, directly into the combustion chamber of an internal combustion engine. The gas injector and the magnetic actuator generally go through four phases: a boost phase A, a pull-in phase B, a hold phase C, and a closing phase D.
[0038] Figures 1 and 2 show four curves plotted against time t in the four phases. K1 shows the current curve for the magnetic actuator over time. K2 shows the voltage of the magnetic actuator over time. K3 shows the force curve of the armature over time, and K4 shows the stroke of the armature over time t.
[0039] Furthermore, Figures 1 and 2 show a closing force K5, which is the sum of the spring force of the valve spring and the counterforce due to the combustion chamber pressure. This is increased by F1 during the main injection in Figure 1 and by F' during the post-injection to F2 shown in Figure 2, since during the post-injection, which is carried out after a piston has reached top dead center in an injection cycle of the internal combustion engine, there is also a high pressure in the combustion chamber, against which an additional opening force must be provided to open the gas injector. Furthermore, Figures 1 and 2 also show a battery voltage K6, which is constant during both the post-injection and the main injection.
[0040] As can be seen from Figure 1, the boost phase A ends during the main injection of the internal combustion engine after the time t1, the pull-in phase B ends after the time t2, the hold phase C ends after the time t3 and the closing phase D ends after the time t4.
[0041] Furthermore, during the main injection 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 pull-in phase. As can be seen from Figure 1, the opening process, i.e., the lifting of the closing element from the sealing seat, begins at the transition between the boost phase A and the pull-in phase B. The maximum opening stroke is reached in the pull-in phase B (stroke curve K4).
[0042] During the post-injection of the gas injector shown in Figure 2 after the main injection of the internal combustion engine has taken place, the current curve K1 is such that in the boost phase A' a continuous increase in the current up to point II' is achieved. This current value IT is maintained throughout the entire pickup phase B' during the post-injection. As a comparison between Figure 1 and Figure 2 shows, the current level in the pickup phase B' during the post-injection is significantly higher than in the pickup phase B of Figure 1 during the main injection. In this case, the pickup current phase B' is preferably controlled with the boost voltage rather than with the battery voltage as in Figure 1 during the pickup phase B.
[0043] In particular, there is no reduction in the current level in the activation phase B' during the post-injection of the gas injector. Furthermore, the absolute value IT is greater than the value 11 during the main injection 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 dimensioned such that all relevant operating points of the gas injector can be served during the main injection (Figure 1). In the case of the post-injection of the internal combustion engine, power reserves are available that are sufficient for the necessary injections during the post-injection.
[0044] Thus, the energy reserves from the DC / DC converter and / or the boost capacitor are used for the control shown in Figure 2 to increase the current level (curve K1 in Figure 2 in the pull-in phase B').
[0045] As can also be seen from the comparison between Figure 1 and Figure 2, the pull-up phase B' during post-injection (t2'-tT) is shorter than the pull-up phase B during main injection (t2-t1). In contrast, the boost phase A' during post-injection is longer than during main injection due to the higher boost current level 11', which is shown in Figure 2 by the time t1' compared to the time t1 during main injection.
[0046] The higher current level 11 'during post-injection also provides an increased opening force of the magnetic actuator, which can be seen by comparing the force curves K3 between Figure 1 and Figure 2. This compensates for the missing force component for opening the gas injector during post-injection due to the high combustion chamber pressure in the gas injector. In the holding phase C, C' and the closing phase D, D' during post-injection and main injection, all four curves K1, K2, K3 and K4 are again the same. If necessary, however, the holding current level in the holding phase C' can be increased in order to counteract the increased closing forces K5 in Figure 2.
[0047] Thus, by using the boost voltage for the pull-in current control in the pull-in phase B', a higher average voltage and thus a higher pull-in current IT for the post-injection can be achieved. This allows for higher magnetic forces from the magnetic actuator, which enable the gas injector to open at high combustion chamber pressures.
[0048] The described embodiment shows a control variant with increased boost current at the end of boost phase A'. However, control variants are also conceivable in which the current profile in boost phase A' during post-injection is the same as during main injection, and then the compensation by the magnetic force is only realized in the pull-in phase B' with increased current.
Claims
Claims 1 . A method for operating an outwardly opening gas injector of an internal combustion engine, which injects a gaseous fuel and has a magnetic actuator for actuating the gas injector, wherein the following steps are carried out during a post-injection, in which the gaseous fuel is injected into a combustion chamber after a main injection: Controlling the magnetic actuator in a boost phase (A') with a continuous increase of a current (I) until the end of the boost phase (A') for the magnetic actuator, and Keeping the current (I) constant in a pull-in phase (B') of the magnetic actuator at a level corresponding to a maximum current in the boost phase (A') in order to compensate for an increased back pressure in the combustion chamber during the post-injection of the gas injector by an increased actuator force of the magnetic actuator.
2. Method according to claim 1, wherein in the boost phase (A') of the post-injection an equal or higher current level is present as in the main injection, and wherein in particular the increased current requirement in the pickup phase (B') of the post-injection 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 start-up phase (B') of the post-injection is reduced in comparison with the main injection of the gas injector.
4. Method according to one of the preceding claims, wherein a length of the start-up phase (B') of the post-injection is extended in comparison with the main injection of the gas injector. Method according to one of the preceding claims, wherein the current level in the boost phase (A') of the post-injection is increased compared to the main injection of the gas injector. Method according to one of claims 1 to 4, wherein the current level in the boost phase (A') of the post-injection remains the same compared to the main injection of the gas injector. Method according to one of the preceding claims, wherein a length of the boost phase (A') of the post-injection is extended compared to the main injection of the gas injector. Method according to one of the preceding claims, wherein a holding phase (C') of the post-injection of the gas injector, in which the gas injector is kept open, is extended compared to the main injection of the gas injector.Method according to one of the preceding claims, wherein the holding current level in the holding phase (C') of the post-injection of the gas injector, in which the gas injector is kept open, is the same as or higher than the main injection of the gas injector. Control unit configured to carry out steps of a method according to one of the preceding claims. Computer program with program code that carries out steps of a method according to one of claims 1 to 9 when the computer program runs on a computer or a corresponding computing unit, for example on a control unit. Computer program product with a computer program according to claim 11, which is stored on a machine-readable data carrier or storage medium.