Method for valve actuation and gas injection valve

Abstract

The invention relates to a method for valve actuation (64) of a gas injection valve (10) for introducing a gaseous fuel for combustion into a combustion chamber of an internal combustion engine; the invention also relates to a gas injection valve (10).

Description

[0001] Method for valve actuation and gas injection valve

[0002] Description introduction

[0003] The invention relates to a method for valve actuation according to claim 1. Furthermore, the invention relates to a gas injection valve.

[0004] German patent DE 102021 200689 A1 describes a gas injection valve for injecting a gaseous fuel, which has a closing element that is movable between a closed and an open state. A braking device is arranged in a lubricant chamber, which is sealed off from the gas flow and filled with oil, to decelerate the closing element during a return process from the open to the closed state.

[0005] The object of the present invention is to make the actuation of a gas injection valve more reliable, precise, and gentle. The service life of the gas injection valve is to be increased. The components of the gas injection valve are to be better protected against overload. The gaseous fuel is to be discharged as precisely and in as small a metered manner as possible.

[0006] At least one of these problems is solved by a valve actuation method with the features of claim 1. This allows the closing movement of the valve element to be dampened more reliably and precisely. Wear of the gas injection valve caused by excessive contact speeds of the valve element during the closing movement can be reduced. The actuating force can support the braking effect of the braking device on the valve element during the time window without placing increased demands on the accuracy of the control of the electrical operating parameter of the actuating element.

[0007] This allows the braking device to be designed for the weakest case of the required braking force, and, depending on the specific closing time requirement, the electrical operating parameter can be adjusted as a flexible means of influencing the overall braking effect.

[0008] The gas injection valve can be located in a vehicle. The internal combustion engine can provide power to propel the vehicle. Fuel can be introduced by blowing or injecting it.

[0009] The gaseous fuel is preferably hydrogen. The combustion engine is preferably a hydrogen engine.

[0010] The fuel can be introduced directly into the combustion chamber or indirectly into the combustion chamber, in particular by direct introduction into a supply channel leading to the combustion chamber, for example a suction pipe.

[0011] The outlet opening can be the only outlet opening of the gas injection valve for introducing the gaseous fuel for combustion in the combustion chamber.

[0012] The valve element can be made of multiple parts. It can include a valve needle and a valve disc rigidly connected to it. The valve element can be displaceable along an axial direction to change the valve position.

[0013] The closing force can be generated by a spring force of a return spring coupled to the valve element and a pressure force from an external gas pressure, in particular of the gaseous fuel, acting on the valve element.

[0014] The actuating device can comprise a magnetic coil with a coil and a magnetic armature that is movable relative to it, or it can be connected to the actuating element. The actuating element can be the magnetic armature of the magnetic coil. The electrical operating variable can be applied to the coil and move the magnetic armature. The electrical operating variable can be an electrical voltage and / or an electrical current. The electrical operating variable can be adjusted by pulse-width modulation.

[0015] The time window can extend at least until or shortly before the completion of the closing movement. The time window can be the period during which the braking force is greater than zero. The sum of the actuating force and the braking force during the time window can be greater than the closing force over a time interval within the time window that includes a specific point in time.

[0016] In a preferred embodiment of the invention, it is advantageous if the maximum braking force during the time window is the total maximum braking force during a single operation of the gas injection valve. This allows the maximum braking force to be concentrated in the time window during which the maximum braking effect, particularly immediately after completion of the closing movement, is to be achieved. In a specific embodiment of the invention, it is advantageous if the maximum actuating force during the time window is less than the total maximum actuating force during a single operation of the gas injection valve. The maximum actuating force during operation of the gas injection valve can be present in the open position.

[0017] In a preferred embodiment of the invention, it is advantageous if the fluid-dynamic braking device comprises a braking element coupled to the valve element. This braking element is subjected to a differential pressure dependent on the flow of gaseous fuel through a fluid channel and is converted into a braking force acting on the valve element. The braking element can be displaceable along the axial direction. The braking element can modify the cross-sectional area of ​​at least one channel section of the fluid channel leading from the gas injection valve to the outlet opening to allow flow of gaseous fuel. This modification can depend on the position of the valve element. The braking force can act on the braking element when gaseous fuel flows through the fluid channel and can depend on the cross-sectional area of ​​the channel section.

[0018] The braking element can reduce the cross-sectional area of ​​the channel section during the closing movement. The braking element can reduce the cross-sectional area of ​​the channel section more significantly the closer the valve element gets to the closed position from the open position. This allows the braking force to increase as the valve element approaches the closed position.

[0019] The braking element can reduce the channel cross-section of the channel section continuously, abruptly, or stepwise, or initially continuously and then stepwise or abruptly, or vice versa, or alternately.

[0020] In a preferred embodiment of the invention, it is advantageous if the valve element is coupled to the valve element via a spring element, and the braking force is exerted on the valve element via the spring element. The spring element can be a helical spring. The spring element can be composed of several individual springs. The spring element can be arranged concentrically to the axial direction. The spring element can be arranged between the brake element and the valve element such that, at least during a closing movement of the valve element, a braking force from the brake element acts on the valve element via the spring element. The spring force of the spring element can counteract the braking force during the closing movement. The spring element can limit the maximum braking force on the brake element.When the maximum braking force is reached, the brake element can be deflected relative to the valve element against the spring force, thereby changing the channel cross-section until the spring force corresponds to the maximum braking force and a force equilibrium is established between the spring force and the braking force.

[0021] A preferred embodiment of the invention is advantageous in which the actuating element is actuated by the electrical operating variable for at least a significant portion of the closing movement to initiate the actuating force on the valve element. The braking effect can thus be independent of a precise switch-on and switch-off time of the electrical operating variable during the closing movement. The actuating element can be actuated by the electrical operating variable throughout the entire closing movement. The exact time for the start of actuation of the actuating element during the closing movement to initiate an actuating force on the valve element that generates a braking effect can be irrelevant, since the maximum actuating force during the time window is smaller than the minimum closing force within that time window.

[0022] In a preferred embodiment of the invention, it is advantageous if the electrical operating parameter is evaluated during the closing movement and, depending on the evaluation, a closing time is recorded as the duration of the entire closing movement. The use of an electrical operating parameter that acts primarily during the closing movement, and in particular continuously during the closing movement, is especially well suited for investigating the closing movement. The electrical operating parameter can be set by using current control or by employing a fixed control frequency without control. Evaluating the magnetic properties requires knowledge of the electrical behavior of the actuating device, which is not constant over the actuating stroke.For example, in current control, the valve movement leads to a change in the current controller frequency, which contains information about characteristic points of the closing movement.

[0023] A preferred embodiment of the invention is advantageous in which the electrical operating parameter during the closing movement is adjusted depending on the detected closing time of a preceding closing movement. This allows the closing time to be varied during operation by adjusting the electrical operating parameter to the specific requirements, and in particular beyond the use of a characteristic curve. This allows, for example, the compensation of manufacturing tolerances and changes in properties due to wear. The electrical operating parameter can be reduced if the desired closing time is shorter than the detected closing time. Conversely, the electrical operating parameter can be increased if the desired closing time is longer than the detected closing time.

[0024] In a specific embodiment of the invention, it is advantageous if the time window occupies less than half the duration of the entire closing movement. The braking force can thus be effective only partially during the closing movement. Furthermore, within the scope of the invention, a gas injection valve with the features of claim 10 is proposed to solve at least one of the aforementioned problems.

[0025] Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations.

[0026] Character description

[0027] The invention is described in detail below with reference to the illustrations. These show, in detail:

[0028] Figure 1: A cross-section of a gas injection valve in a special embodiment of the invention.

[0029] Figure 2: A time diagram for a closing movement of a gas injection valve in a further special embodiment of the invention.

[0030] Figure 3: A time diagram during the execution of a method for valve actuation in a special embodiment of the invention.

[0031] Figure 1 shows a cross-section of a gas injection valve in a specific embodiment of the invention. The gas injection valve 10 is arranged for introducing a gaseous fuel, in particular hydrogen, for combustion in a combustion chamber of an internal combustion engine, especially a hydrogen engine, and comprises a housing 12, an outlet opening 14 for venting the hydrogen from the housing 12, and a fluid channel 16 within the housing 12 leading to the outlet opening 14 for the flow of hydrogen. The fluid channel 16 is connected to an inlet opening 18 of the gas injection valve 10, which connects to a supply channel that provides the hydrogen to the gas injection valve 10 at a predetermined fluid pressure.

[0032] The gas injection valve 10 is shown here in a closed position 22 and further comprises a valve element 24 which can be moved by changing the valve position, thus altering the opening cross-section of the outlet opening 14. To change the valve position, the valve element 24 can change a valve stroke H by displacement along an axial direction 20 and has a valve disc 26 that closes the outlet opening 14 and a valve needle 28 connected to the valve disc 26. A closing force Fc acts on the valve element 24 in the direction of the closed position 22. This closing force is composed of a restoring force 29 (at least one restoring spring 30), a contact force 32 acting on the valve element 24 due to an external contact pressure, and a pressure force 34 acting on the valve element 24 in the direction of the open position, depending on the fluid pressure of the gaseous fuel.

[0033] Furthermore, an actuating device 36 is arranged with an actuating element 38, which is coupled to the valve element 24 for changing the valve position depending on the actuating element 38. The actuating device 36 comprises a solenoid coil 40 with a coil 42 and a magnetic armature 44 forming the actuating element 38. The magnetic armature 44 is displaceable depending on an electric current in the coil 42. The valve element 24 is movably coupled to the magnetic armature 44, in particular fixedly connected, and the valve position depends on the position of the magnetic armature 44.

[0034] The gas injection valve 10 comprises a fluid-dynamic braking device 46 for braking a closing movement 48 of the valve element 24, which changes the valve position from an open position towards a closed position 22. The braking device 46 comprises a braking element 54 coupled to the valve element 24 via a spring element 50 and whose cross-sectional area of ​​at least one channel section 52 of the fluid channel 16 can be changed depending on the valve position. When hydrogen flows through the fluid channel 16, a braking force Fb acts on the braking element 54, counteracting the closing movement 48 of the valve element 24. The channel section 52 is located in the area of ​​the braking element 54.A differential pressure, dependent on the channel cross-section of channel section 52 during hydrogen flow, between an upstream first side and a downstream second side of the brake element 54 facing the outlet opening 14, causes the braking force Fb at the brake element 54. The brake element 54 reduces the channel cross-section of channel section 52 more during the closing movement 48 the closer the valve element 24 gets to the closed position 22 shown here, starting from the open position.

[0035] The fluid channel 16 of channel section 52 is formed between the brake element 54 and a housing wall 60 of the housing 12. In the area of ​​the brake element 54, the contour of the housing wall 60 defines the course of the fluid channel 16 and thus also the dependence of the reduction of the channel cross-section of channel section 52 on the valve position and thus also the braking force Fb.

[0036] The brake element 54 is coupled to the valve element 24 for the transmission of the braking force Fb to the valve element 24 via the spring element 50. The spring element 50 is, for example, designed as a coil spring and is arranged between the brake element 54 and the valve element 24 such that, during a closing movement 48 of the valve element 24, a braking force Fb of the brake element 54 acts on the valve element 24 via the spring element 50.

[0037] The spring element 50 limits the braking force Fb on the brake element 54 by allowing the brake element 54 to deflect against the spring force of the spring element 50 relative to the valve element 24 as the braking force Fb increases, particularly after overcoming a preload force of the spring element 50. This deflection alters the channel cross-section in such a way that a force equilibrium is established between the spring force of the spring element 50 and the braking force Fb. The brake element 54's deflection is limited in one direction by a stop 62.

[0038] Figure 2 shows a time diagram of the closing movement of a gas injection valve in a further specific embodiment of the invention. The diagram depicts the time course of the channel cross-section K, the opening cross-section A, the valve stroke H, the differential pressure pd, and the braking force Fb. As the closing movement of the valve element begins at time tO, when the opening cross-section A reaches its maximum Amax and the valve stroke H reaches its maximum Hmax, the opening cross-section A and the valve stroke H decrease linearly.If, at time t1, the channel cross-section K is abruptly reduced from a first channel cross-section K1 to a smaller second channel cross-section K2 due to the movement of the braking element relative to the wall, coupled with the closing movement, a first differential pressure pd1 arises as the fluid flows through the channel with the existing opening cross-section A. This differential pressure pd decreases as the opening cross-section A decreases. The braking force Fb acts due to this differential pressure pd, decreasing proportionally to the differential pressure pd from a maximum braking force Fbmax at time t1. This allows the closing movement to be slowed down by the braking force Fb of the braking element.

[0039] Figure 3 shows a time diagram for the execution of a method for valve actuation in a specific embodiment of the invention. It illustrates various states during the actuation of a gas injection valve. Actuation begins at time t0, starting from a previously closed gas injection valve, with the actuation of an actuating element by applying an electrical operating parameter, here an electric current I, which from time t1 onwards is adjusted to a constant initial current value 11 by pulse width modulation. A closing force Fc acts on the valve element during this process.As the current I increases, the actuating force Fa of the actuating element, which acts on the valve element in the direction of the opening cross-section A, also increases until a time t2, from which the current I, which was initially set higher to overcome self-induction of the actuating device, is set to a lower second current value I2, with which the actuating force Fa also decreases.

[0040] Even before time t2, the valve element begins to move from the closed position due to an increasing valve stroke H, until the open position is reached at time t3, where the valve stroke H is at its maximum. From time t4 onwards, when the open position is still present, the current I can assume the second current value I2, which is lower than the first current value 11, because the actuating force Fa required to maintain the open position requires less energy and therefore a lower current I due to a reduced air gap in the solenoid coil.

[0041] The closing force Fc gradually increases as the external contact pressure on the valve element increases in the direction of the opening position.

[0042] The procedure for actuating valve 64 is explained below. From time t5, the closing movement of the valve element is initiated electrically by reducing the current I by applying an electrical reversing voltage to the coil of the solenoid until it is zero at time t6. This also reduces the actuating force Fa until it equals the closing force Fc at time t7. From time t6, the current I is adjusted to a third current value I3 to assist in a braking effect on the valve element in the direction of the opening position.

[0043] The valve element begins to move from the open position to the closed position at time t8, causing the valve stroke H to decrease again. The current I begins to increase due to the armature movement. This increase can be detected electrically and indicates the start of the closing movement at time t8 of the valve element. During a time window W, lasting from time t9 during the closing movement until time t11, when the open position is reached, and lasting less than half the duration of the entire closing movement, a braking force Fb acts on the valve element in the direction of the open position via the braking device. The braking force Fb and the actuating force Fa add up to a total counterforce Fs.The maximum actuating force Famax and the maximum braking force Fbmax during the time window W are individually smaller than the minimum closing force Fc within the time window W, but at least at one point in time t10 within the time window W, their combined force is greater than the closing force Fc. This allows the valve element to be braked electrically by the actuating force Fa in conjunction with the fluid-dynamic braking device. However, neither braking effect alone is sufficient to overcome the closing force Fc. Therefore, controlling the actuating device to support the braking effect with the actuating force Fa is simpler and less sensitive to tolerances.

[0044] The maximum braking force Fbmax during the time window W is the total maximum braking force during operation of the gas injection valve. Furthermore, the maximum actuation force Famax during the time window W is less than the total maximum actuation force during operation of the gas injection valve.

[0045] Here, the exemplary use of a constant control frequency of the current I leads to an increase in the current I due to the change in the inductance of the actuator's coil. This increase corresponds to time t8, the start of the closing movement caused by the displacement of the actuator. When the actuator reaches its end position, a constant current I is again established at the previous level. The inflection point between the rise and fall of the current I at time t11 indicates the completion of the closing movement.

[0046] The closing time Ts can be measured as the time difference between time t8 and time t11. The electrical operating parameter during the closing movement, used to build up a braking effect, can then be adjusted, for example, depending on the measured closing time Ts of a preceding closing movement. Reference symbol list

[0047] 10 Gas injection valve

[0048] 12 cases

[0049] 14 Outlet opening

[0050] 16 Fluid channel

[0051] 18 Entrance opening

[0052] 20 Axial direction

[0053] 22 Closing position

[0054] 24 Valve element

[0055] 26 valve plates

[0056] 28 Valve needle

[0057] 29 Restoring force

[0058] 30 Return spring

[0059] 32 Contact force

[0060] 34 compressive force

[0061] 36 Actuating device

[0062] 38 Actuating element

[0063] 40 magnetic coil

[0064] 42 coil

[0065] 44 magnetic anchors

[0066] 46 Brake device

[0067] 48 Closing movement

[0068] 50 spring element

[0069] 52 Canal section

[0070] 54 Brake element

[0071] 60 Housing wall

[0072] 62 stops

[0073] 64 Methods for valve actuation A Opening cross-section

[0074] Amax maximum opening cross-section Fa actuation force

[0075] Famax maximum actuation force Fb braking force

[0076] Fbmax maximum braking force

[0077] FC closing force

[0078] Fs counterforce

[0079] H Valve stroke

[0080] Hmax maximum valve lift

[0081] I current

[0082] K Channel cross-section

[0083] K1 first channel cross-section

[0084] K2 second channel cross-section

[0085] pd differential pressure

[0086] pd1 first differential pressure

[0087] Ts closing time

[0088] W Time window

Claims

Patent claims 1. Method for actuating (64) a gas injection valve (10) for introducing a gaseous fuel for combustion in a combustion chamber of an internal combustion engine, comprising the steps Providing the gas injection valve (10) comprising an actuating device (36) which can be actuated depending on an electrical operating parameter (I) and which has a movable actuating element (38), a valve element (24) coupled to the actuating element (38) which is movable to change an opening cross-section (A) of an outlet opening (14) for the discharge of the gaseous fuel by changing a valve position between an opening position with maximum opening cross-section (Amax) and a closed position (22) with closed outlet opening (14) and a fluid dynamic braking device (46) for braking a closing movement (48) of the valve element (24) that changes the valve position from the open position to the closed position (22), wherein at least within a time window (W) during a closing movement (48) of the valve element (24) from the open position to the closed position (22) caused by a closing force (Fc) on the one hand, the actuating element (38) exerts an actuating force (Fa) in the direction of the opening position on the valve element (24) by adjusting the applied electrical operating parameter (I) and On the other hand, the fluid dynamic braking device (46) exerts a braking force (Fb) in the direction of the opening position on the valve element (24), wherein at least the maximum actuating force (Famax), in particular also the maximum braking force (Fbmax), are each during the time window (W) smaller than the smallest closing force (Fc) in the time window (W), but at least at one time within the time window (W) are in total greater than the closing force (Fc).

2. Method for valve actuation (64) according to claim 1 , characterized in that the maximum braking force (Fbmax) during the time window (W) is the total maximum braking force during one operation of the gas injection valve (10).

3. Method for actuating the valve (64) according to claim 1 or 2, characterized in that the maximum actuating force (Famax) during the time window (W) is smaller than a total maximum actuating force during an operation of the gas injection valve (10).

4. Method for valve actuation (64) according to one of the preceding claims, characterized in that the fluid dynamic braking device (46) has a braking element (54) coupled to the valve element (24), on which a differential pressure (pd) dependent on a flow of the gaseous fuel in a fluid channel (16) acts and which the braking element (54) converts into the braking force (Fb) acting on the valve element (24).

5. Method for valve actuation (64) according to claim 4, characterized in that the valve element (24) is coupled to the valve element (24) via a spring element (50) and the braking force (Fb) is exerted on the valve element (24) via the spring element (50).

6. Method for valve actuation (64) according to one of the preceding claims, characterized in that the actuating element (38) is actuated at least largely during the closing movement (48) by the electrical operating variable (I) to introduce the actuating force (Fa) onto the valve element (24).

7. Method for valve actuation (64) according to one of the preceding claims, characterized in that the electrical operating variable (I) is evaluated during the closing movement (48) and, depending on the evaluation, a closing time (Ts) is recorded as the duration of the entire closing movement (48).

8. Method for valve actuation (64) according to claim 7, characterized in that the electrical operating parameter (I) is set during the closing movement (48) depending on the detected closing time (Ts) of a preceding closing movement (48).

9. Method for actuating the valve (64) according to one of the preceding claims, characterized in that the time window (W) occupies less than half of the time duration (Ts) of the entire closing movement (48).

10. Gas injection valve (10) for introducing a gaseous fuel for combustion in a combustion chamber of an internal combustion engine and for carrying out a method for valve actuation (64) according to one of the preceding claims, configured and comprising a case (12), an outlet opening (14) for the discharge of the gaseous fuel from the housing (12), a valve element (24) coupled to the actuating element (38), which is displaceable to change an opening cross-section (A) of an outlet opening (14) for the discharge of the gaseous fuel by changing a valve position between an opening position with maximum opening cross-section (Amax) and a closed position (22) with closed outlet opening (14) and a fluid dynamic braking device (46) for braking a closing movement (48) of the valve element (24) that changes the valve position from the open position to the closed position (22) and an actuating device (36) which can be operated depending on an electrical operating parameter (I) and which has a movable actuating element (38).

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