Method for determining a closing time of a gas injector
Patent Information
- Application Number
- EP2024713446
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-03-27
- Filing Date
- 2024-03-19
- Publication Date
- 2026-02-11
AI Technical Summary
Existing methods for determining the closing time of a gas injector in internal combustion engines are impractical due to installation space and cost constraints, leading to inaccurate injection quantities and increased wear and noise from closing bounces, which are exacerbated by the lack of hydraulic damping in gas injectors.
A method using a two-part closing element with a nozzle needle and an anchor bolt actuated by a magnetic actuator, where the closing time is determined by monitoring the voltage curve to identify local maxima and overshoots, and optionally utilizing a damper piston to reduce bounces and improve precision.
Enables precise control of gas injection quantities, reduces closing bounces, and minimizes wear and noise by accurately determining the closing time and adjusting control parameters, such as the magnetic actuator's control duration.
Smart Images
Figure EP2024057265_03102024_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] title
[0003] Method for determining a closing time of a gas injector
[0004] State of the art
[0005] The present invention relates to a method for determining a closing time of a gas injector and to a gas injector configured to carry out the method for determining a closing time.
[0006] Gas injectors are known in various designs from the prior art. When controlling an internal combustion engine, it is advantageous to know the exact closing time of the gas injector. This allows precise injection quantities to be achieved depending on the operating situation of the gas injector. Theoretically, the detection of the closing time of the gas injector is possible using sensors. However, this is only a solution that can be implemented on test benches. In practice, the use of such sensors on a valve needle is not possible due to space and cost reasons. Due to the lack of hydraulic damping compared to injectors for liquid fuels, so-called closing bounce easily occurs. With such closing bounce, the gas injector briefly opens again so that an additional amount of gas is injected. This changes the desired amount of gas to be injected.Such locking bounces also cause additional wear on the sealing seat and loud noises, especially when several locking bounces occur in quick succession.
[0007] Disclosure of the invention
[0008] The inventive method for determining the closing time of a gas injector with the features of claim 1 has the advantage that the closing time of the gas injector can be reliably detected. Thus, with knowledge of the exact closing time of the gas injector, it is possible to specifically adjust the control parameters of the gas injector, for example, the control duration. This allows for a more precise injection quantity. It also allows for targeted reduction of closing bounce.
[0009] This is achieved according to the invention in that the gas injector comprises a two-part closing element with a nozzle needle and an armature bolt that is freely movable in series with the nozzle needle. An armature of a magnetic actuator is firmly connected to the armature bolt in order to actuate the nozzle needle. The nozzle needle releases a sealing seat at a through opening and closes it to inject gas and terminate the injection. A voltage curve of the magnetic actuator is monitored in order to determine a release time of the armature for the closing process, starting from the open position. This is determined based on a local maximum of the voltage curve after the energization of the magnetic actuator has ended. The closing time of the nozzle needle at the sealing seat is defined based on an overshoot of the voltage curve after the release time.Thus, an exact injection end of the gas injector can be determined and used for further control of the gas injector.
[0010] The subclaims show preferred developments of the invention.
[0011] The voltage curve of the magnetic actuator preferably has a local minimum after the local maximum, with the local minimum being determined as the point of maximum acceleration of the closing element. This allows the closing element's return speed to be determined and, if necessary, countermeasures to be taken if the return speed is too high, since high return speeds tend to increase the risk of closing bounce.
[0012] Preferably, a first overshoot is determined as the closing time after the minimum.
[0013] The gas injector further preferably has a damper piston to dampen the closing movement of the closing element before a certain closing time during the closing process. The damper piston is arranged in series with the armature bolt, and the first overshoot of the voltage curve after the closing element's release time is determined as the point at which the armature bolt makes contact with the damper piston. This point in time of contact between the armature bolt and the damper piston occurs before the final closing time of the nozzle needle, since the movement of the nozzle needle is to be dampened before impact with the sealing seat. A second overshoot, after the first overshoot, is determined as the point at which the nozzle needle closes at the sealing seat.
[0014] Preferably, the closing time of the nozzle needle is further determined based on a change in the gradient of the voltage curve, particularly after the local minimum. This allows for an alternative determination of the closing time and thus achieves redundancy in the determination of the closing time.
[0015] Further preferably, the change in the gradient of the voltage curve with a temporal offset is used to determine the closing time of the nozzle needle. Due to the inertia of the signal, particularly in conjunction with the use of a damper piston, there is a temporal offset, which is preferably constant and is taken into account during the evaluation. When using the damper piston, the signal change is not initiated by a hard impact, but by the damped contact of the closing element with the damper piston.
[0016] Further preferably, a comparison of the detected closing time with a stored target closing time is performed, and if a detected closing time deviates from the target closing time, a change in the control of the gas injector occurs. Preferably, the change in the control occurs by changing the control duration of the magnetic actuator during operation.
[0017] Further preferably, a damper stroke, which is a return path of the closing element from the first contact of the closing element with the damper piston to the contact of the nozzle needle with the sealing seat, is in a range from 50 pm to 250 pm. Preferably, an overstroke of the armature bolt, which is a difference between a maximum stroke of the armature bolt and a maximum stroke of the nozzle needle, is in a range from 150 pm to 800 pm.
[0018] Preferably, the damper stroke is smaller than the overstroke of the anchor bolt.
[0019] Furthermore, the present invention relates to a gas injector configured to carry out the method according to the invention.
[0020] Short description of the drawings
[0021] The present invention will be described in detail below with reference to the accompanying drawings. In the drawing:
[0022] Figure 1 is a schematic sectional view of an inventive
[0023] Gas injector in a fully open state,
[0024] Figure 2 is a schematic sectional view of the gas injector of Figure 1 during the closing process of the gas injector,
[0025] Figure 3 is a schematic sectional view of the gas injector of Figure 1 in a state in which a nozzle needle seals against a sealing seat,
[0026] Figure 4 is a schematic representation of current I and voltage U of a magnetic actuator of the gas injector over an entire opening and closing cycle,
[0027] Figure 5 is a schematic diagram showing three diagrams of
[0028] Current, needle stroke and voltage on top of each other to explain the inventive method according to the embodiment and
[0029] Figure 6 is a schematic representation of the armature stroke and the
[0030] Voltage in the area of a closing point of the gas injector with and without a damper piston. Preferred embodiment of the invention
[0031] The invention according to a preferred embodiment is described in detail below with reference to Figures 1 to 6.
[0032] Figure 1 shows schematically a gas injector configured to carry out the method according to the invention.
[0033] The gas injector 1 comprises a two-part closing element 2. The closing element 2 comprises a nozzle needle 20 and an armature bolt 21. The nozzle needle 20 seals against a sealing seat 7 on a housing component 70. The armature bolt 21 is fixedly connected to an armature 30 of a magnetic actuator 3.
[0034] The magnetic actuator 3 further comprises a coil 31 and a magnetic return element 32.
[0035] The gas injector 1 has a housing 9 in which the components of the gas injector are accommodated.
[0036] The nozzle needle 20 and the armature bolt 21 are arranged in series and are freely movable in an axial direction XX of the gas injector 1. The armature bolt 21 rests loosely against the nozzle needle 20.
[0037] The nozzle needle 20 is returned from the open position to the closed position by means of a first return element 5, which is arranged between the housing component 70 and a spring plate on the nozzle needle 20.
[0038] The gas injector 1 further comprises a damper piston 4, which is fixedly connected to a stationary guide component 40 connected to the housing 9.
[0039] A gas flow 10 runs through the interior of the gas injector 1, with corresponding through-openings provided in the guide component 40 and the armature 30. Figure 1 shows the fully open state of the gas injector, in which the nozzle needle 20 is lifted from the sealing seat 7 and completely exposes a through-opening 70. The gas injector 1 of this exemplary embodiment is an outward-opening gas injector. Starting from the fully open state shown in Figure 1, the current supply to the magnetic actuator 3 is interrupted to terminate the injection. As a result, the nozzle needle 2 and the armature bolt 21, which is loosely arranged on the nozzle needle 20, move in the direction of arrow A due to the restoring force of the restoring element 5 (see Figure 1).
[0040] As the closing process continues, the armature bolt 21 comes into contact with the damper piston 4, which is pressed into the position shown in Figures 1 and 2 by a second return element 6. The armature 30 has moved away from a stroke stop 8, against which the armature rests when the gas injector is fully open. This is indicated in Figure 2 by arrow B. Since the gas injector is still partially open in the state shown in Figure 2, gas continues to be injected into the combustion chamber 11.
[0041] Figure 3 shows the fully closed state of the gas injector, in which the nozzle needle 20 seals against the sealing seat 7. As a result, no more gas is injected into the combustion chamber 11. Since the armature pin 21 continues to move after the nozzle needle 20 reaches the sealing seat due to the speed of movement of the nozzle needle 20 and the armature pin 21 during the closing process, this results in further movement of the armature pin 21 and the damper piston 4 after an initial contact C (see Figure 2) between the armature pin 21 and the damper piston 4, which is indicated in Figure 3 by the arrow D. This dampens the armature pin and the armature 30, which significantly contributes to reducing closing bounce.
[0042] In order to achieve the most precise injection quantities possible during an injection process, the method according to the invention is now implemented. By means of the method according to the invention, a closing time of the nozzle needle 20 can be detected very precisely. In particular, during the closing process of the gas injector, any changes to the valve dynamics, in which possible influencing factors include, for example, an inlet pressure of the gas to be injected, a cylinder pressure in the combustion chamber, and / or any friction that occurs, can be detected by the method according to the invention, and any resulting change in the injection quantity can be compensated for by a targeted adjustment of control parameters, in particular a control duration of the magnetic actuator. The method for determining a closing time of the gas injector 1 is described in particular with reference to Figures 4 to 6.
[0043] To determine the closing time, a voltage curve G is monitored over time t during an injection cycle. The schematic diagram in Figure 4 shows the voltage U over time t and, correspondingly, a current I over time t during an injection cycle. At time t0, the current supply to the magnetic actuator 3 is stopped, causing the voltage to drop abruptly and then, without movement of the closing element 2, theoretically increasing exponentially, which is represented in Figure 4 by the dashed line G'. In practice, the voltage signal during the closing process follows the solid line G in Figure 4 due to the voltage induced by the lifting movement.
[0044] Figure 5 shows again the voltage curve G in the area of the process of closing the gas injector, a needle stroke H and the current I over time t.
[0045] As can be seen in Figure 5 from curve N for the needle closing movement, due to inertia, the closing process only begins slightly after time t0, at which the current supply to the magnetic actuator 3 is terminated. The nozzle needle 20 has reached the sealing seat 7 at time t1, thus ending the injection. N1, N2, and N3 are schematically depicted as three closing bouncers of the nozzle needle 20 after the closing time.
[0046] After the current supply to the magnetic actuator 3 is terminated, the voltage curve G exhibits a local maximum M1, which is followed in time by a local minimum M2. At the local minimum M2, the closing element 2 has reached its maximum acceleration during the reset process.
[0047] As shown in Figure 6, monitoring the voltage curve G enables the determination of the closing time of the nozzle needle 20 at the sealing seat 7 based on a first overshoot 51 of the voltage curve G after the release time.
[0048] Due to the presence of the damper piston 4, an initial contact C can also be detected from the voltage curve G (see Figure 5). Since the armature bolt 21 detaches from the nozzle needle 20 when the gas injector closes as soon as the nozzle needle 20 reaches the sealing seat 7, an overstroke 13 occurs (see Figure 3). Due to this overstroke 13, the armature bolt 21 moves further, but the acceleration by the first return element 5 is completely eliminated. This leads to a sudden change in the speed of the armature bolt 21, which can be detected from the voltage curve G. This is indicated in Figure 6 by the overshoot 52.
[0049] Thus, in the temporal sequence, the first overshoot 52 forms the first contact and the second overshoot 51 the closing time t1.
[0050] Since the overshoot 52 occurs first due to the initial contact between the armature bolt 21 and the damper piston 4, which occurs before the sealing seat 7 is reached, the overshoot 51 for reaching the sealing seat 7 cannot always be reliably detected on the voltage curve G, since the overshoot 52 may not have completely decayed yet. In this case, as an alternative, a change in the gradient of the voltage curve G between a first gradient S1 and a second gradient S2 can be added to the detection of the closing time. However, due to the inertia of a signal, the change in gradient may have a small, constant temporal offset T between the time t1 of needle closing and the time tT detected by the change in gradient. This offset T is taken into account when determining the closing time (see Figures 5 and 6).Figure 6 also shows the stroke of the anchor bolt Ah.
[0051] As is clear from Figure 5, the needle closing movement N and the corresponding overshoots 51, 52 in the voltage curve G are clearly visible. Thus, the two times of initial contact C of the nozzle needle 20 with the armature pin 21 and the closing of the nozzle needle 20 at the sealing seat 7 can be reliably detected. If the closing time deviates from a target closing time, appropriate countermeasures can be taken in the control of the gas injector, for example, by adjusting the control duration of the magnetic actuator.
[0052] In Figure 6, dashed lines G' also show the determination of a
[0053] Closing time of a gas injector without a damper element is shown. As can be seen in the voltage diagram over time t in Figure 6, the first overshoot 51 'II after the local maximum M1 and the local minimum M2 is shown in the voltage curve G. Accordingly, the needle stroke H diagram shows the needle closing movement N' in dashed lines, which then ends at time t1 'by the closing of the nozzle needle at the sealing seat 7.
Claims
Claims 1 . Method for determining a closing time of a gas injector (1) which comprises a two-part closing element (2) with a nozzle needle (20) and an anchor bolt (21) which is freely movable on the nozzle needle (20), • wherein an armature (30) of a magnetic actuator (3) is firmly connected to the armature bolt (21) in order to actuate the nozzle needle (20), • wherein the nozzle needle (20) opens and closes a through-opening (70) at a sealing seat (7) in order to inject gas, • wherein a voltage curve (G) of the magnetic actuator (3) is monitored in order to determine, starting from an open position of the gas injector (1), a release time point of the armature (30) based on a local maximum (M1) of the voltage curve (G) after termination of energization of the magnetic actuator (3) and • wherein the closing time of the nozzle needle (20) at the sealing seat (7) is determined based on an overshoot (51) of the voltage curve (G) after the release time point.
2. Method according to claim 1, wherein the voltage curve (G) has a local minimum (M2) after the local maximum (M1), wherein the local minimum (M2) is determined as a point of maximum acceleration of the closing element (2).
3. The method according to claim 2, wherein a first overshoot is determined as the closing time after the minimum (M2).
4. Method according to one of claims 1 or 2, wherein the gas injector (1) further comprises a damper piston (4) to dampen the closing movement of the closing element (2) during the closing process, wherein the damper piston (4) is arranged in series with the armature bolt (21) and wherein a first overshoot (52) of the voltage curve (G) after the release time of the closing element (2) as contact of the armature bolt (21) with the damper piston (4) and a second overshoot (51) is determined after the first overshoot (52) as the closing time of the nozzle needle (20) at the sealing seat (7).
5. Method according to one of the preceding claims, wherein the closing time of the nozzle needle (20) is also determined based on a change in a gradient (S1, S2) of the voltage curve (G).
6. The method according to claim 5, wherein the change in the slope (S1, S2) with a time offset (T) is used to determine the closing time of the nozzle needle (20).
7. Method according to one of the preceding claims, wherein a comparison of the detected closing time with a stored target closing time is carried out and, if the detected closing time deviates from the target closing time, a change in the control of the gas injector (1) takes place.
8. The method according to claim 7, wherein the change in the control of the gas injector (1) is carried out by changing a control duration of the magnetic actuator (3).
9. Method according to one of claims 4 to 8, wherein a damper stroke, which is a return path of the closing element from a first contact with the damper piston (4) to the contact of the nozzle needle (20) on the sealing seat (7), is smaller than an overstroke of the armature bolt (21), which is a difference between the maximum stroke of the armature bolt (21) and a maximum stroke of the nozzle needle (20), which is the movement of the armature bolt (21) after closing the gas injector (1) on the sealing seat (7).
10. The method of claim 9, wherein the damper stroke is approximately one-third of the overstroke. 11 . Gas injector (1) arranged to carry out a method according to one of the preceding claims.