Flow-optimised gas injector

Abstract

The present invention relates to a gas injector (1) for injecting a gaseous medium (2), in particular a gaseous fuel. The gas injector (1) comprises: a closing element (3) for opening and closing at least one through-opening (4) at a sealing seat (31); an actuator (5) for actuating the closing element (3); and a blow cap (6) having an outlet opening (61). The blow cap (6) is arranged at an injection-side end (11) of the gas injector (1). The closing element (3) has a top side (32) which is designed to close the through-opening (4). The closing element (3) also has a bottom side (33) which is orientated towards the injection-side end (11) of the gas injector (1). The blow cap (6) has a deflection surface (62) which is designed, when the gas injector (1) is open, to deflect a gas flow (21) in such a way that the gas flow (21) is at least in part directed towards the bottom side (33) of the closing element (3).

Description

[0001] Description

[0002] title

[0003] Flow-optimized gas injector

[0004] State of the art

[0005] The present invention relates to a gas injector for injecting a gaseous medium, in particular a gaseous fuel such as hydrogen or CNG.

[0006] Gas injectors are known from the state of the art in various designs. Due to cost advantages and improved environmental compatibility, gaseous fuels have recently become increasingly popular. Compared to injectors for liquid fuels, the injected gas volume occupies a much larger volume than an equivalent amount of liquid fuel. This results in an increased stroke requirement for a closing element, which is usually actuated by a magnetic actuator. Designing a magnetic circuit using standard materials is very difficult, or sometimes impossible, due to the limited space available. Materials with higher magnetic force are very expensive and sometimes harmful to health (e.g., FeCo).

[0007] Disclosure of the invention

[0008] The inventive gas injector for injecting a gaseous medium, in particular a gaseous fuel, with the features of claim 1 has the advantage that a gas flow in the gas injector is designed by geometric configuration such that the forces acting on a closing element are reduced to a minimum. This reduces the magnetic force of an actuator, which must be selected to keep the injector open, and thus enables the use of cost-effective materials in the magnetic circuit of the actuator. This is achieved according to the invention in that the gas injector has a closing element for opening and closing at least one through-opening on a sealing seat. The closing element is preferably a nozzle needle. Furthermore, an actuator is provided for actuating the closing element. The actuator is preferably a magnetic actuator, but can also be a mechanically or electrically operated actuator, for example.Further preferably, the actuator is configured to actively open the closing element by means of a lifting movement and to keep it open, while the closing element is closed by a spring force. A blow cap is arranged at an inlet-side end of the gas injector and has an outlet opening. The outlet opening is configured to inject the gas from the gas injector, for example, into a combustion chamber. The closing element has an upper side which is configured to close the through-opening, and a lower side which is oriented in the direction of the inlet-side end of the gas injector. The blow cap has a diversion surface which is configured, when the gas injector is in the open state, to divert a gas flow such that the gas flow is at least partially directed towards the underside of the closing element.

[0009] In this way, boundary layer separation on the underside of the closing element is avoided with the help of the diverter surface. By cleverly guiding the flow on the underside of the closing element, a force can be generated on the underside of the closing element which assists the actuator in keeping the injector open. The generated force is preferably a compressive force which points opposite to the closing direction. The actuator therefore requires less force to hold the closing element open, which means that the actuator can be made smaller and more cost-effective. Furthermore, the reduced actuator force required enables greater metering accuracy of the gaseous medium to be injected and a lower holding current requirement. Furthermore, the force generated opposite to the closing direction reduces the final speed when the seat is impacted at the end of the closing process and thus reduces seat closure.

[0010] The subclaims show preferred developments of the invention.

[0011] Preferably, when the gas injector is open, a cross-section of a flow channel between the blow cap and the underside of the closing element is tapered in the direction of the gas flow. As the cross-section decreases in the direction of flow, the velocity of the gas flow at the underside of the closing element increases, and the static pressure in the flow channel decreases. The reduced pressure results in a force directed from the closing element toward its underside, supporting the opening of the closing element and thus reducing the required actuator force.

[0012] Further preferably, the closing element is designed to be rotationally symmetrical. The rotationally symmetrical shape allows the closing element and the sealing seat to be manufactured easily and cost-effectively, for example, on a lathe. Furthermore, the rotationally symmetrical shape seals the closing element evenly and ensures a homogeneous flow around the closing element.

[0013] The closure element and the blow cap are preferably arranged coaxially with each other. Coaxiality refers to a central axis or a rotational axis of the blow cap and the closure element. Thus, the closure element is positioned centrally with respect to the blow cap, allowing the gas to flow evenly from the closure element into the blow flap.

[0014] Preferably, the deflection surface on the blow cap is designed perpendicular to a central axis XX of the closure element. The straight shape of the deflection surface makes it easy to manufacture. Furthermore, the deflection surface enables simple and efficient redirection of an axial gas flow in a radial direction toward the underside of the closure element.

[0015] Alternatively, the deflection surface is preferably concave. The curved shape ensures a smooth redirection of the gas flow and avoids turbulence, which can increase flow resistance along the flow path. Furthermore, the concave deflection surface allows for precise redirection of the gas flow at both low and high flow velocities.

[0016] Further preferably, the diverting surface and the underside of the closing element are designed such that the average flow velocity of the gas flow in the open state is higher at the underside of the closing element than at the injection-side end of the gas injector. Thus, the static pressure at the underside of the closing element is lower than the static pressure at the top of the closing element. The resulting pressure force acts counter to the closing direction of the closing element, so that the force required by the actuator to keep the closing element open is reduced by the inventive design of the flow channel and the through-opening.

[0017] Advantageously, the underside of the closure element has at least one concave surface. The concave surface can be configured to redirect the gas flow toward the injection-side end of the gas injector, thus enabling efficient injection of the gas and reducing flow resistance along the flow path. The redirection also prevents flow paths from opposite ends of the closure element from meeting at the underside of the closure element and forming turbulence.

[0018] Further advantageously, the underside of the closing element has at least one convex surface. The convex surface can be configured to taper the cross-sectional area of ​​the flow channel between the underside of the closing element and the diverting surface along the flow direction, thus reducing the static pressure on the underside of the closing element.

[0019] Particularly preferably, the underside of the closing element has both concave and convex surface elements, which are designed to create defined flow conditions on the underside of the closing element and generate a force in the direction of the opening direction of the closing element. The defined flow conditions on the underside of the closing element reduce periodic pressure oscillations caused by pressure waves between the blow cap and the closing element. This further simplifies the control effort of the gas injector.

[0020] According to a preferred embodiment, the blow cap has multiple outlet openings. This allows the gas injector to inject gas in a targeted manner. Furthermore, the gas can escape from the blow cap with minimal resistance, reducing the backpressure in the blow cap and requiring less force to keep the closure element open.

[0021] Preferably, at least one outlet opening extends at an acute angle from the axial end of the blow cap. According to a further preferred embodiment of the invention, the outlet opening is mounted coaxially at the inlet end of the gas injector in the blow cap.

[0022] Further advantageously, the underside of the closing element is configured to direct the gas flow toward the inlet end of the gas injector. Thus, the gas flow is directed directly toward the outlet opening, which can reduce the pressure in the blow cap and increase the relative force on the closing element in the opening direction.

[0023] Furthermore, the invention relates to an internal combustion engine with a gas injector according to the invention.

[0024] Short description of the drawings

[0025] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0026] Figure 1 is a schematic sectional view of a gas injector according to a first preferred embodiment of the invention,

[0027] Figure 2 is a schematic enlarged partial sectional view of the

[0028] Gas injector in the area of ​​a blow cap according to a second embodiment,

[0029] Figure 3 is a schematic enlarged partial sectional view of the

[0030] Gas injector in the area of ​​the blow cap according to a third embodiment,

[0031] Figure 4 is a schematic enlarged partial sectional view of the

[0032] Gas injector in the area of ​​the blow cap according to a fourth embodiment,

[0033] Figure 5 is a schematic enlarged partial sectional view of the

[0034] Gas injector in the area of ​​the blow cap according to a fifth embodiment, Figure 6 is a schematic enlarged partial sectional view of the

[0035] Gas injector in the area of ​​the blow cap according to a sixth embodiment,

[0036] Figure 7 is a schematic enlarged partial sectional view of the

[0037] Gas injector in the area of ​​the blow cap according to a seventh embodiment, and

[0038] Figure 8 is a schematic enlarged partial sectional view of the

[0039] Gas injector in the area of ​​the blow cap according to an eighth embodiment.

[0040] Embodiments of the invention

[0041] A gas injector 1 according to a first preferred embodiment of the invention is described in detail below with reference to Figure 1.

[0042] As can be seen from Figure 1, the gas injector 1 comprises an elongated housing 7 in a socket 8. The socket 8 can, for example, be part of a cylinder head or an intake manifold. At an inlet-side end 11 of the gas injector 1, a blow cap 6 is arranged coaxially with the housing 7 of the gas injector 1. The blow cap 6 can be connected to the housing of the gas injector 1, for example, via a screw connection or a welded connection.

[0043] Within the housing 7 and the blow cap 6, an elongated closing element 3 is arranged for opening and closing a through-opening 4. The closing element 3 is actuated by an actuator 5, which is arranged at an axial end opposite the blow-in axial end 11.

[0044] The actuator 5 is configured to move the closing element 3 along its central axis X-X. For this purpose, the actuator 5 preferably comprises an electromagnetic stator configured to exert an electromagnetic force on an armature mechanically coupled to the closing element 3. In doing so, the actuator 5 preferably actively opens the closing element 3. By deactivating the actuator 5, the closing element 3 closes automatically, for example, based on a spring force. To open, the actuator 5 must overcome the spring force.

[0045] By means of a lifting movement in the direction of the injection-side end 11, the closing element 3 opens the passage opening 4 and enables a gas flow 21 through the housing 7 of the gas injector 1 to an outlet opening 61 in the blow cap 6 and through the outlet opening 61 out of the gas injector 1. The flow velocity of the gas flow 21 can exceed the speed of sound in the region of the passage opening 4.

[0046] In the open state, the through opening 4 is formed by a gap between an upper side 32 of the closing element 3 and a sealing seat 31 on the housing 7. In the closed state, the upper side 32 of the closing element 3 rests against the sealing seat 31 of the valve body and prevents the gaseous medium 2 from escaping from the gas injector 1. The contact surfaces between the upper side 32 of the closing element 3 and the sealing seat 31 are preferably flat and complementary to one another.

[0047] The closing element 3 comprises an elongated shaft portion connected to the actuator 5. The inlet-side axial end of the closing element 3 is radially widened and thus forms the upper side 32 and a lower side 33, which is oriented in a direction opposite to the upper side 32.

[0048] After the gas flow 21 has flowed radially outward through the through-opening 4, it encounters the blow cap 6 and a diverting surface 62, which is integrated into the blow cap 6. The diverting surface 62 is designed to direct the gas flow 21 radially inward, toward the underside 33. For this purpose, the diverting surface 62 is concave. Furthermore, in the first exemplary embodiment, the diverting surface 62 has an end region 63, the geometric extension of which is at an acute angle a to the central axis XX of the closing element 3 in the open state.

[0049] Between the top side 32 and the bottom side 33, an outer side 34 is arranged at a radially outer end of the closing element 3, which outer side connects the top side 32 and the bottom side 33. In the first exemplary embodiment, the outer side 34 is a cylindrical outer surface which is aligned parallel to the central axis XX of the closing element 3. Via a rounded portion 34a, the outer side 34 merges into the bottom side 33, which is aligned in the direction of the exhaust-side end 11. The bottom side 33 has a concavely curved surface 33a outside the central axis XX. The concavely curved surface 33a forms a central mandrel 35. Due to the concave shape of the bottom side 33, the gas flow 21 is guided axially to the central axis XX in the direction of the exhaust-side end 11.

[0050] At the blow-out end 11, the outlet opening 61 is integrated into the blow cap 6, through which the gaseous medium 2 can escape from the gas injector 1. The outlet opening 61 is arranged laterally of the central axis XX and is aligned at an acute angle ß to the central axis XX. Thus, the gas stream 21 can be blown out of the gas injector 1 in a laterally directed manner.

[0051] Due to the greater curvature of the diverting surface 62 in the axial overlap area between the diverting surface 62 and the underside 33 of the closing element and the orientation of the diverting surface 62 toward the underside 33, the cross section between the diverting surface 62 and the underside 33 is tapered in the direction of the gas flow 21. Based on the Bernoulli equation, the velocity of the gas flow 21 increases due to the cross-sectional taper, and the static pressure decreases. This results in a pressure force F in the direction of the injection-side end 11 and thus in the opening direction of the closing element 3. Thus, the actuator 5 needs to apply less force to open and keep the closing element 3 open, which allows it to be designed smaller and / or cheaper materials can be used.

[0052] Figure 2 shows a detailed view of the blow cap 6 and the closing element 3 of a gas injector 1 according to the second embodiment of the invention.

[0053] The second embodiment differs from the first embodiment in the shape of the diverting surface 62, the shape of the underside 33 of the closing element 3 and in the position and orientation of the outlet opening 61.

[0054] In the second embodiment, the diverting surface 62 is a flat surface oriented perpendicular to the central axis XX of the closing element 3. Thus, it directs the gas flow radially inward, toward the central axis XX. The end region 63 is formed as a rectangular edge.

[0055] The underside 33 of the rotationally symmetrical locking element has a conical surface in the radially outer region of the central axis XX, adjacent to the outer side 34. This conical surface transitions in the direction of the central axis XX, first into a concavely curved surface 33a and then into a convexly curved surface 33b. The convexly curved surface 33b ends perpendicular to the central axis XX and forms a mandrel 35.

[0056] The outlet opening 61 is arranged coaxially to the central axis XX of the closing element 3 in the center of the blow cap 6.

[0057] Figure 3 shows a detailed view of the blow cap 6 and the closing element 3 of a gas injector 1 according to the third embodiment of the invention.

[0058] The third embodiment differs from the first embodiment in the shape of the underside 33 of the closing element 3 and in the position, number and orientation of the outlet opening 61.

[0059] The underside 33 of the closing element 3 is a flat surface arranged perpendicular to the central axis XX. Thus, the underside 33 of the closing element 3 is easy to manufacture. The diverting surface 62 is concavely curved, as in the first embodiment, so that the flow cross-section of the gas flow 21 tapers between the diverting surface 62 and the underside 33.

[0060] At the injection-side end 11 of the gas injector 1, three outlet openings 61 are shown in the sectional view. A central outlet opening 61 is arranged coaxially to the central axis XX. The two additional outlet openings 61 are arranged on both sides, at an acute angle ß to the central axis XX, next to the central outlet opening 61 in the blow cap.

[0061] Figure 4 shows a detailed view of the blow cap 6 and the closing element 3 of a gas injector 1 according to the fourth exemplary embodiment of the invention. The fourth exemplary embodiment differs from the first exemplary embodiment only in the shape of the underside 33 of the closing element 3. In the fourth exemplary embodiment, the underside 33 of the closing element 3 has a single concavely curved surface 33a. The underside 33 intersects the center line XX perpendicularly. The radius of curvature of the underside 33 is larger than the radius of curvature of the diverting surface 62, so that the flow cross-section between the underside 33 and the diverting surface 62 tapers and the static pressure on the underside 33 is reduced.

[0062] Since the locking element 3 in the fourth embodiment does not have a pin, it requires little material and is lightweight. Due to the low weight of the locking element 3 in the fourth embodiment, opening and closing movements can be performed more dynamically.

[0063] Figure 5 shows a detailed view of the blow cap 6 and the closing element 3 of a gas injector 1 according to the fifth embodiment of the invention. The fifth embodiment differs from the first embodiment only in the shape of the underside 33 of the closing element 3.

[0064] In the fifth embodiment, the underside 33 of the closing element 3 has a single convexly curved surface 33a. Due to the convex curvature, the flow cross-section between the diverting surface 62 and the underside 33 tapers more sharply than, for example, in the fourth embodiment. The convexly curved surface 33b in the fifth embodiment advantageously directs the gas flow 21 toward the injection-side end 11.

[0065] Figure 6 shows a detailed view of the blow cap 6 and the closing element 3 of a gas injector 1 according to the sixth embodiment of the invention. The sixth embodiment comprises a closing element 3 according to the first embodiment. In contrast to the first embodiment, the deflection surface is flat and oriented perpendicular to the central axis XX. Furthermore, the outlet opening 61 is arranged coaxially to the central axis XX.

[0066] Figure 7 shows a detailed view of the blow cap 6 and the closing element 3 of a gas injector 1 according to the seventh embodiment of the invention. The seventh embodiment comprises a closing element 3 according to the third embodiment. In contrast to the third embodiment, the deflection surface is flat and oriented perpendicular to the central axis XX. Furthermore, the seventh embodiment has only one outlet opening 61 coaxial with the central axis XX.

[0067] Figure 8 shows a detailed view of the blow cap 6 and the closing element 3 of a gas injector 1 according to the eighth embodiment of the invention. The eighth embodiment comprises a closing element 3 according to the fourth embodiment. In contrast to the fourth embodiment, the deflection surface is flat and oriented perpendicular to the central axis XX. Furthermore, the outlet opening 61 is arranged coaxially to the central axis XX.

Claims

Claims 1. Gas injector (1) for injecting a gaseous medium (2), in particular a gaseous fuel, comprising • a closing element (3) for releasing and closing at least one through-opening (4) on a sealing seat (31), • an actuator (5) for actuating the locking element (3), and • a blow cap (6) with an outlet opening (61), • wherein the blow cap (6) is arranged at an injection-side end (11) of the gas injector (1), • wherein the closing element (3) has an upper side (32) which is designed to close the through opening (4), • wherein the closing element (3) has a bottom side (33) which is oriented in the direction of the injection-side end (11) of the gas injector (1), and • wherein the blow cap (6) has a diversion surface (62) which is designed to divert a gas flow (21) in an open state of the gas injector (1) such that the gas flow (21) is directed at least partially in the direction of the underside (33) of the closing element (3).

2. Gas injector (1) according to claim 1, wherein in an open state of the gas injector (1) a cross section of a flow channel between the blow cap (6) and the underside (33) of the closing element (3) is tapered in the flow direction of the gas flow (21).

3. Gas injector (1) according to one of the preceding claims, wherein the closing element (3) is rotationally symmetrical.

4. Gas injector (1) according to claim 3, wherein the closing element (3) and the blow cap (6) are arranged coaxially to one another.

5. Gas injector (1) according to one of claims 3 and 4, wherein the diverting surface (62) is designed perpendicular to a central axis (XX) of the closing element (3).

6. Gas injector (1) according to one of claims 1 to 4, wherein the diverting surface (62) is concave.

7. Gas injector (1) according to one of the preceding claims, wherein an average flow velocity of the gas flow (21) in the open state at the underside (33) of the closing element (3) is higher than at the injection-side end (11) of the gas injector (1).

8. Gas injector (1) according to one of the preceding claims, wherein the underside (33) of the closing element (3) has at least one concavely curved surface (33a).

9. Gas injector (1) according to one of the preceding claims, wherein the underside of the closing element (3) has at least one convexly curved surface (33b).

10. Gas injector (1) according to one of the preceding claims, wherein the blow cap (6) has a plurality of outlet openings (61).

11. Gas injector (1) according to one of the preceding claims, wherein at least one outlet opening (61) extends at an acute angle a away from the axial end of the blow cap (6).

12. Gas injector (1) according to one of the preceding claims, wherein at least one outlet opening (61) is coaxially attached to the blow-in end (11) of the gas injector (1) on the blow cap (6).

13. Gas injector (1) according to one of the preceding claims, wherein the underside (33) of the closing element (3) is arranged to direct the gas flow in the direction of the injection-side end (11) of the gas injector (1).

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