Method for operating a gas injector and gas injector

Abstract

The present invention relates to a method for decelerating a closing element of a gas injector, which is operatively connected to an armature of a magnetic actuator, before the closing process is completed in order to reduce wear on the closing element and on a sealing seat, comprising the steps of detecting an induced current of the armature, which is induced by a movement of the armature during the closing process of the gas injector, creating a second derivative of the induced current of the armature and further monitoring the second derivative, determining a first zero of the second derivative of the induced current of the armature and further monitoring the second derivative, determining a first local minimum of the second derivative in time after the first zero, and when the first local minimum of the second derivative has been found, controlling the magnetic actuator such that a braking force is exerted on the closing element by means of the armature.to reduce the closing speed of the closing element before it impacts the sealing seat and to decelerate the closing element before it impacts the sealing seat.

Description

State of the art

[0001] The present invention relates to a method for operating a gas injector for decelerating a closing element during the closing process and to a gas injector which is configured to carry out the method according to the invention.

[0002] Gas injectors are known in various designs from the prior art. Compared to injectors that operate with liquid fuels, such as gasoline or diesel injectors, gas injectors lack lubrication. This results in increased wear requirements for gas injectors. In particular, the contact zone between a closing element, for example, a valve needle, and a sealing seat is subject to very high wear. To prevent excessive impact on the sealing seat, and the associated wear, especially when the closing element returns to its closed position, it has been proposed to incorporate a damper system filled with hydraulic fluid. However, this results in a large gas injector size, which poses a space constraint, particularly in smaller internal combustion engines, such as those used in vehicles. Disclosure of the invention

[0003] The inventive method for decelerating a closing element of a gas injector, comprising the features of claim 1, has the advantage that, during the closing process of the gas injector, a braking impulse can be applied to the closing element's return movement precisely before it strikes a sealing seat. This results in the closing element striking the sealing seat at a reduced speed, thus reducing wear on the closing element and / or the sealing seat. This can significantly increase the service life of the gas injector. The braking impulse for decelerating the closing element can be achieved without a complex hydraulic and / or mechanical damper assembly. This also results in independence from the ambient temperature at the gas injector, as there is no direct dependence of the damping effect on the viscosity of the fluid in the hydraulic damper assembly.Further advantages of the method according to the invention are the significantly reduced costs and a more flexible design of the braking impulse compared to hydraulic damping. The method according to the invention is also independent of the rail pressure of the gaseous medium to be introduced and / or a combustion chamber backpressure point. Moreover, the installation space of the gas injector can also be reduced, so that, in particular, the installation of the gas injector in small-displacement internal combustion engines, especially internal combustion engines for passenger cars, is possible.

[0004] According to the invention, this is achieved by selectively applying a braking impulse to the closing element before the closing process is completed. In a first step, an induced current in the armature of a magnetic actuator of the gas injector, which actuates the closing element, is detected during the closing process of the gas injector. Subsequently, a second derivative of the induced current of the armature is generated and monitored. Then, a first zero point of the second derivative of the induced current is determined, and the second derivative is monitored further. In the next step, a first local minimum of the second derivative after the first zero point is determined, and once this first local minimum has been determined, the magnetic actuator is controlled such that a braking force is exerted on the closing element by means of the armature.This reduces the closing speed of the locking element and decelerates it before contact with the sealing seat, thus reducing wear during the closing process. To decelerate the locking element, a coil of the magnetic actuator is briefly energized, reducing the speed of the armature and therefore of the locking element in contact with the armature.

[0005] The dependent claims describe preferred embodiments of the invention.

[0006] Preferably, the magnetic actuator is activated immediately after the first local minimum is found, i.e., the activation takes place in the millisecond range, in particular < 5 ms.

[0007] Preferably, the magnetic actuator is controlled such that the closing speed of the closing element is reduced so that the closing element strikes the sealing seat at a speed in the range of 0.20 m / s to 0.25 m / s. In particular, the impact speed of the closing element on the sealing seat is 0.23 m / s.

[0008] The inventive method for decelerating the closing element is preferably implemented without a hydraulic and / or mechanical damper. This significantly reduces the construction costs for the gas injector and, in particular, also reduces the required installation space for the gas injector.

[0009] Furthermore, the present invention relates to a gas injector comprising a control unit configured to carry out the method according to the invention.

[0010] The gas injector preferably includes an outwardly opening closing element.

[0011] The gas injector preferably comprises a mechanical return element, in particular a spring, to return the closing element from an open position to a closed position. An actuator of the gas injector's magnetic actuator then acts against the closing force of the spring to decelerate the closing element.

[0012] The gas injector is particularly preferably configured to introduce gaseous hydrogen into an internal combustion engine. In particular, the gas injector is configured to introduce the gaseous medium directly into a combustion chamber of an internal combustion engine (direct injection).

[0013] The present invention can thus, by means of a mechatronic quantity found in the injector current signals of the gas injector, which can describe the impact of the closing element on the sealing seat with very good accuracy, control the closing element in such a way that the closing element can be selectively decelerated shortly before impact on the sealing seat. drawing

[0014] An embodiment of the invention is described in detail below with reference to the accompanying drawing. The drawing shows: Fig. 1 a schematic diagram showing a stroke of the closing element and an indicated current through a moving armature during the closing process over time, according to the present invention, Fig. 2 a schematic diagram showing the second derivative of the indicated current of Fig. 1 and shows the indicated current over time t according to the present invention, Fig. 3 and Fig. 4 schematic diagrams, which correspond to the diagrams in the Fig. 1 and Fig. 2 correspond to, in the case of a premature braking impulse, Fig. 5 and Fig. 6 schematic diagrams that illustrate the Fig. 1 and Fig. 2 correspond to, in the case of a braking impulse that is too late and Fig. Figure 7 shows a schematic diagram illustrating the induced current by movement of the armature during the closing process and the closing speed of the closing element. Preferred embodiments of the invention

[0015] The following refers to the Fig. 1 to 7 describe in detail a method for braking a closing element of a gas injector and a gas injector according to a preferred embodiment of the invention.

[0016] The gas injector is specifically designed for the direct injection of hydrogen into the combustion chamber of an internal combustion engine.

[0017] The gas injector comprises a magnetic actuator with a coil, an inner pole, and an armature. The armature is operatively connected to a closing element, in particular a valve needle.

[0018] Actuating the magnetic actuator moves the armature, thus bringing the closing element of the gas injector into an open position. This allows the injection of a gaseous medium.

[0019] The closing element is preferably returned to the closed starting position by means of a spring element.

[0020] The gas injector is preferably an outwardly opening gas injector.

[0021] To minimize wear between the closing element and the sealing seat in which the closing element seals the gas injector during operation, the invention provides for a braking impulse by controlling the magnetic actuator, which generates a speed of the armature and thereby a closing speed of the closing element, which is in operative connection with the armature. The braking impulse decelerates the closing element to a predetermined speed, so that the impact of the closing element on the sealing seat does not cause wear on the sealing seat or the closing element.

[0022] The impact velocity is preferably between 0.20 m / s and 0.25 m / s, and particularly preferably 0.23 m / s.

[0023] In the inventive method, an induced current of the armature is detected in a first step during the closing process of the gas injector. This is possible because an armature moving in the magnetic field of the magnetic actuator induces a change in the current signal of a magnetic circuit of the magnetic actuator. This induction leads to a change in the current signal, which can then be further processed.

[0024] After detecting the current induced by the movement of the armature during the closing process, a second derivative T of the current induced by the armature movement is created and monitored. This second derivative T of the current signal I after time t is in Fig. 1 represented by curve T. In Fig. Figure 1 also shows a curve H, which shows a stroke h over time t, and a curve S, which represents the current induced by the armature.

[0025] In Fig. 1. Point A represents the point of impact where the closing element meets the sealing seat and the gas injector is closed (stroke h = 0).

[0026] In Fig. 2 is represented by the curve T in the diagram shown as the second derivative of the current I induced by movement of the armature at the closing element over time t in addition to the curve S of the induced current.

[0027] As from Fig. As can be seen in Figure 2, the second derivative T has a first zero at point B. The curve T of the second derivative exhibits a first local minimum C after the first zero at B. As can be seen from Figure 2, the second derivative T has a first local minimum C. Fig. As can be seen in 2, the sign of the second derivative T changes at the first local minimum C.

[0028] The first zero B and the first local minimum C thus define a feature m as a mechatronic quantity which exactly describes the impact of the locking element on the sealing seat.

[0029] A control unit of the gas injector can now generate a braking pulse by briefly energizing the magnetic actuator, thereby decelerating the armature and thus also the locking element connected to the armature. This prevents the locking element from impacting the sealing seat too forcefully.

[0030] Thus, according to the invention, if the first zero B and the first subsequent local minimum C have been detected ( Fig. 2) The magnetic actuator is controlled in such a way that a braking force is exerted on the locking element by means of the armature. This reduces the closing speed of the locking element and decelerates the locking element before it impacts the sealing seat.

[0031] For better understanding, the following are used as a comparison in the Fig. 3 and Fig. Four schematic diagrams are shown, which correspond to the diagrams in the Fig. 1 and Fig. 2 correspond, whereby in the Fig. 3 and Fig. Figure 4 shows premature braking. This does not sufficiently reduce the impact speed of the locking element, which can lead to wear on the locking element and / or the sealing seat. The impact point A also shifts later in time.

[0032] In the Fig. 5 and Fig. 6, which schematically the Fig. 1 and Fig. 2, where braking is shown too late, the impact A occurs at too high a speed because the braking impulse to reduce the closing speed of the locking element occurred too late. This can cause so-called bounces P, which in Fig. Figure 5 is shown schematically. Since the closing element of such rebound devices briefly lifts off the sealing seat again, an additional, undesirable amount of gas is injected, which can have negative effects on the combustion process in the internal combustion engine or lead to undesirable increased fuel consumption. The impact point A shifts forward in time.

[0033] In Fig. Figure 7 shows the impact velocity V over time t represented by curve 10 and the magnitude of the local minimum C over time t.

[0034] The present invention thus enables a method and a gas injector in which a damping function is achieved by a targeted braking impulse before the closing element engages the sealing seat. No hydraulic and / or mechanical damping devices are required. This allows, in particular, a reduction in the size of the gas injector.

[0035] The method according to the invention is preferably integrated into control software for controlling the gas injector. This allows the present invention to be implemented very simply and cost-effectively.

Claims

[1] Method for decelerating a closing element of a gas injector, which is in operative connection with an armature of a magnetic actuator, prior to the termination of the closing process in order to reduce wear on the closing element and on a sealing seat, comprising the steps: - Detecting an induced current of the armature, which is induced by a movement of the armature during the closing process of the gas injector, - Creating a second derivative T of the induced current of the armature and further monitoring of the second derivative, - Determining a first zero B of the second derivative T of the induced current of the armature and further monitoring of the second derivative, - Determining a first local minimum C of the second derivative T after the first zero B, and - when the first local minimum C of the second derivative T has been found, the magnetic actuator is controlled in such a way that a braking force is exerted on the closing element by means of the armature in order to reduce the closing speed of the closing element before it impacts the sealing seat and to decelerate the closing element before it impacts the sealing seat. [2] Method according to claim 1, wherein the actuation of the magnetic actuator after finding the first local minimum C takes place immediately after finding the first local minimum C, in particular within 5 ms. [3] Method according to one of the preceding claims, wherein the closing speed of the closing element is reduced such that the closing element strikes the sealing seat at a speed in the range of 0.20 m / s to 0.25 m / s. [4] Method according to claim 3, wherein the closing speed of the closing element is reduced to 0.23 m / s when striking the sealing seat. [5] Method according to one of the preceding claims, wherein the braking of the closing element is carried out without a hydraulic damper and / or without a mechanical damper. [6] Gas injector comprising a control unit configured for carrying out a method according to any one of claims 1 to 5. [7] Gas injector according to claim 6, wherein the gas injector comprises an outwardly opening closing element, in particular a valve needle. [8] Gas injector according to claim 6 or 7, further comprising a mechanical return element, in particular a spring, wherein the mechanical return element returns the closing element from an open position to a closed position. [9] Gas injector according to any one of claims 6 to 8, wherein the gas injector is configured for injecting hydrogen. [10] Gas injector according to one of claims 6 to 9, wherein the gas injector is configured for directly injecting a gaseous medium into a combustion chamber of an internal combustion engine.

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