DE102014224343A1 - Gas injector with improved thermal properties - Google Patents

Abstract

The present invention relates to a gas injector for injecting a gaseous fuel directly into a combustion chamber (9) of an internal combustion engine, comprising a valve closing element (2) for releasing or closing a passage opening (37), a valve body (3), and a sealing seat (4) between the valve body (3) and the valve closing element (2), wherein the valve body (3) at a combustion chamber end (30) of the valve body (3) comprises a thermal protection device (31). Furthermore, the present invention relates to an injector arrangement with a gas injector according to the invention. Another aspect of the present invention relates to an internal combustion engine which comprises a gas injector or an injector arrangement according to the invention.

Description

State of the art

The present invention relates to a gas injector for injecting a gaseous fuel directly into a combustion chamber of an internal combustion engine. Furthermore, the present invention relates to an injector with a gas injector. Another aspect of the present invention relates to an internal combustion engine that includes a gas injector or injector assembly.

In addition to liquid fuels, gaseous fuels, such as e.g. Natural gas or hydrogen, used. In known Direktinblasenden Gasinjektoren is a problem area, the high thermal load of the gas injector, in particular its valve body. Due to the high thermal load, for example, an elastomer with its limited temperature resistance can not be used as a sealing material. In addition to the good sealing properties of the elastomer and its excellent damping properties during the closing process are advantageous. The latter is particularly important in gas injectors because of the elimination of a load-reducing effect of fluid damping.

Disclosure of the invention

The direct injection gas injector according to the invention for injecting a gaseous fuel directly into a combustion chamber of an internal combustion engine with the features of claim 1 has the advantage that a temperature at the combustion chamber side of the gas injector can be significantly reduced. This is inventively achieved by a thermal protection device on the valve body. Thus, a heat load of other components of the gas injector, in particular the sealing seat and the valve closing element, significantly reduced. Furthermore, it is avoided by the thermal protection device that occurs at too hot areas of the gas injector undesirable glow ignition. For this purpose, the gas injector according to the invention for injecting a gaseous fuel directly into a combustion chamber comprises a valve closing element for releasing or closing a passage opening, a valve body and a sealing seat between the valve body and the valve closing element. According to the invention, the valve body comprises the thermal protection device at a combustion chamber end of the valve body. This also gives the possibility of making the sealing seat of a soft material, e.g. from an elastomer, in particular for outwardly opening gas injectors. Due to the high elastic compliance of such a material with low elastic deformation forces, a gas-tightness of the gas injector can be made possible even with geometric imperfections over a lifetime.

The dependent claims show preferred developments of the invention.

According to a preferred embodiment of the present invention, the thermal protector has a heat dissipation cap having a first heat conduction coefficient which is larger than a heat conduction coefficient of the valve body. Thus, the heat introduced into the combustion side region of the gas injector is efficiently removed, e.g. derived in a cylinder head. Particularly preferably, the heat-conducting cap is made of a metal, in particular aluminum. This makes a light construction possible. Furthermore, the heat conduction cap may preferably be fastened to the valve body by means of a welded connection or a caulking connection. Due to the presence of the heat dissipation cap and its shape, a flow guide and a gas mixture can furthermore be adapted to the customer's individual needs.

Alternatively or additionally, the thermal protection device has a first thermal protection layer with a second coefficient of thermal conduction, which is smaller than the heat conduction coefficient of the valve body and / or smaller than the first heat conduction coefficient of the heat dissipation cap. This serves to reduce or eliminate the heat transfer from the combustion chamber to the valve body and / or the heat dissipation cap. When heat is transferred, it can be dissipated from the heat pipe cap. Thus, a thermal load of the valve body is reduced.

Particularly preferably, the first thermal protective layer is made of ceramic.

Advantageously, the first thermal protection layer is disposed on the heat dissipation cap. In particular, the first thermal protective layer can be arranged on a front side directed toward the combustion chamber. Alternatively or additionally, an inner side of the passage opening along the flow guide may be provided with the first thermal protection layer.

More preferably, the heat dissipation cap on a plate-shaped region, or a plate-shaped base region and a plate-shaped base region disposed on the wall region. Thus, for example, the heat pipe cap can be adapted to different valve body shapes. Furthermore, the heat pipe is adjusted depending on the application.

In order to ensure a good thermal connection of the heat dissipation cap to a cylinder head, the heat dissipation cap preferably has a surface structuring on a contact surface, wherein the contact surface is arranged for a contact between the heat dissipation cap and a cylinder head and is arranged on the heat dissipation cap.

Particularly preferably, the surface structuring comprises a knurling. This also reduces a joining force for installing the injector in the cylinder head.

Further preferably, the heat dissipation cap comprises a heat conductor paste applied to a surface of the heat dissipation cap. In particular, the heat conductor paste is introduced into recesses of the knurling of the heat dissipation cap. This enhances heat transfer between the heat dissipation cap and the cylinder head.

By reducing a gap and / or a metallic contact between the heat dissipation cap and the cylinder head, a thermal connection of the heat dissipation cap to a cylinder head is made possible in an advantageous manner.

In addition, it may be advantageous if the valve closing element has a second thermal protection layer with a third coefficient of thermal conduction which is smaller than the heat conduction coefficient of the valve body and / or smaller than the first coefficient of heat conduction of the heat dissipation cap. Thus, a heat input into the combustion-side space of the gas injector, in particular into the valve closing element, can be eliminated or reduced.

Particularly preferably, the first protective layer and the second thermal protective layer are formed from the same material. Thus, a uniform thermal protection layer at a combustion end of the gas injector is possible. This also results in a cost-effective manufacturing process.

Advantageously, with a maximum lift of the valve closing element, a flow cross section between the valve body and the valve closing element is smaller than a flow cross section between the valve closing element and the sealing seat. Since the valve closing element as well as the valve body can be made very precisely, the flow cross sections can be accurately formed. In contrast to a quantitative throttling at the sealing seat, wherein an entire tolerance chain (several geometry tolerances, Hubeinstelloleranz, stroke change by temperature expansion) affects the injected fuel quantity, play according to the invention only the diameter manufacturing tolerances of the valve body and the valve closing element a role. Furthermore, by placing the flow-determining throttle point from the sealing seat into an interior of the gas injector, the throttle point is not mechanically loaded by stops or guides and thus it is wear-free. This results in no change in volume flow over life. Furthermore, thermal expansions and a change in the stroke caused by a thermal expansion do not affect the volume flow or only a slight effect. A detailed geometry of the valve body and the valve closing element before and after the throttle point can be designed to be optimal for a gas supersonic flow.

It is also advantageous if the sealing seat is arranged by a stop region of the valve body with a predetermined distance on the valve body. Thus, the mechanically highly loaded stop area of the valve body is geometrically separated from the sealing point. This allows a small wear on the stop area without the gas injector failing due to leakage. The material of the stop region is preferably hardened and / or coated in order to withstand the high mechanical loads.

Furthermore, the present invention relates to an injector assembly comprising a gas injector for injecting a gaseous fuel into a combustion chamber and a cylinder head with a cylinder head opening, in which the gas injector is arranged, wherein a directed toward the combustion chamber end of the gas injector from a combustion chamber side end of the cylinder head opening with predetermined Distance is arranged in the axial direction of the gas injector. This distance can amount to a maximum of three times the diameter of the cylinder head opening. By displacing the gas injector in a direction opposite to the blowing direction, a dead volume is created, in which a flow velocity is small. Thus, the heat transfer from the hot combustion gases to the valve body and the sealing seat is minimized. In the dead volume combustion preferably takes place, so that no unburned fuel components collect, which could then lead to increased hydrocarbon emissions in the exhaust gas.

Particularly preferably, the injector arrangement has a gas injector according to the invention as described above.

Another aspect of the present invention relates to an internal combustion engine, which has a combustion chamber and an inventive direct injection gas injector or injector assembly according to the invention. Thus, the advantages embodied in relation to the gas injector according to the invention and the injector arrangement according to the invention are associated.

Brief description of the drawings

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings, wherein like or functionally identical parts are designated by the same reference numerals. In the drawing is:

1 a schematic, highly simplified sectional view of an injector with a gas injector in a closed state according to a first embodiment of the present invention,

2 a schematic, highly simplified sectional view of the injector according to the invention the 1 , wherein the gas injector according to the invention is in an open state, and

3 a schematic, highly simplified sectional view of an injector with a gas injector in a closed state according to a second embodiment of the present invention.

Embodiments of the invention

The following is with reference to the 1 and 2 an injector arrangement 8th according to a first embodiment of the present invention described in detail.

The injector arrangement 8th includes a gas injector 1 for injecting a gaseous fuel into a combustion chamber 9 and a cylinder head 5 with a cylinder head opening 50 an internal combustion engine, not shown. In the cylinder head opening 50 is the gas injector 1 arranged, with one to the combustion chamber 9 directed finish 10 of the gas injector 1 from a combustion chamber end 51 the cylinder head opening 50 with a first predetermined distance 100 is arranged.

Furthermore, the gas injector includes 1 a valve closing element 2 , a valve body 3 with a passage opening 37 , which the valve closing element 2 releases or closes, and a sealing seat 4 which is between the valve body 3 and the valve closing element 2 is arranged. In 1 is the gas injector 1 in a closed state, the passage opening 37 through the valve closing element 2 is closed. In 2 is the gas injector 1 in a fully opened state, that is, at a maximum stroke of the closing element 2 , shown.

According to the invention, the valve body 3 at a combustion chamber end 30 of the valve body 3 a thermal protection device 31 on.

In particular, the thermal protection device comprises 31 a heat dissipation cap 32 with a first coefficient of thermal conduction. In addition, the thermal protection device 31 a first thermal protection layer 33 with a second coefficient of thermal conductivity. Furthermore, the heat dissipation cap includes 32 a plate-shaped area 34 , which on the valve body 3 through a welded joint 38 is attached.

Furthermore, the valve closing element 2 with a second thermal protection layer 20 provided, which has a third coefficient of thermal conduction.

The first heat conduction coefficient of the heat dissipation cap 32 is larger than a heat conduction coefficient of the valve body 3 , Further, the second heat conduction coefficient of the first thermal protection layer 33 smaller than the heat conduction coefficient of the valve body 3 and smaller than the first heat conduction coefficient of the heat dissipation cap 32 , Advantageously, the third coefficient of thermal conduction of the second thermal protection layer 20 the valve closing element 2 equal to the second coefficient of thermal conduction.

Thus, primarily, a transfer of the resulting heat in the combustion chamber due to the poor heat-conducting properties of the first thermal protection layer 33 and the second thermal protection layer 20 in comparison to the valve body 3 on the valve body 3 prevented. If, despite these protective measures, some of the heat through the first thermal protection layer 33 and the second thermal protection layer 20 This is secondarily via the heat dissipation cap 32 to the cylinder head 5 derived. This can ensure that the valve body 3 and the seal seat 4 not be thermally stressed.

The heat dissipation cap 32 points to a contact surface 36 a surface structuring, not shown, wherein the contact surface 36 arranged for contact between the heat dissipation cap 32 and a cylinder head 5 is and on the heat dissipation cap 32 is arranged. In particular, the surface structuring is designed as a knurling. Not shown depressions of the knurling are provided with a heat conductor paste, whereby the heat transfer between the heat dissipation cap 32 and the cylinder head 5 is increased.

Furthermore, the sealing seat 4 from a stop area 11 of the valve body 3 at a second predetermined distance 200 in the axial direction XX of the gas injector 1 on the valve body 3 arranged. This results in a structural separation between the sealing seat 4 from the stop area 11 of the valve body 3 ,

In 2 is the gas injector 1 shown in an open state, wherein the passage opening 37 from the valve closing element 2 is completely released. This state corresponds to a maximum stroke of the valve closing element 2 , Here is a flow cross section 6 between the valve body 3 and the valve closing element 2 smaller than a flow area 7 between the valve closing element 2 and the seal seat 4 , Thus, an injecting amount of fuel through the flow cross section 6 and not the flow area 7 certainly.

By the gas injector according to the invention 1 There are a lot of advantages. In particular, by the thermal protection device 31 of the valve body 3 as well as the second thermal protection layer 20 the valve closing element 2 can be a temperature especially in the combustion area of the gas injector 1 be reduced. Thus, a thermal load of the valve body 3 and the sealing seat 4 be avoided. Resetting the gas injector 1 in the cylinder head opening 50 also contributes to the reduced thermal load of the valve body 3 and the sealing seat 4 at. This along with resetting the seal seat 4 As a result, the sealing seat 4 can be formed of a soft material. This is particularly advantageous because a soft material has very good sealing properties and damping properties. In the gas injector according to the invention 1 and the injector arrangement according to the invention also enables a consistent separation of functions. For example, the sealing, the determination of the static flow rate, the absorption of the mechanical loads, the spray or mixture formation as well as the absorption and the dissipation of the thermal loads by different components of the gas injector 1 provided. This causes a more cost-effective structure and a fail-safe operation of the gas injector 1 ,

The gas injector 1 of the second embodiment in 3 is fundamentally different from the gas injector 1 of the first embodiment in that the heat dissipation cap 32 a plate-shaped base area 34 and one at the plate-shaped base portion 34 arranged wall area 35 having. Thus, the contact surface 36 between the heat dissipation cap 32 and the cylinder head 5 formed larger, whereby a heat transfer is increased to the cylinder head. Further, the heat dissipation cap 32 through a caulking connection 39 on the valve body 3 attached.

It should be noted that the foregoing embodiments are for illustrative purposes only and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

Claims (11)

Gas injector for injecting a gaseous fuel directly into a combustion chamber ( 9 ) of an internal combustion engine, comprising: - a valve closing element ( 2 ) for releasing or closing a passage opening ( 37 ), - a valve body ( 3 ), and - a sealing seat ( 4 ) between the valve body ( 3 ) and the valve closing element ( 2 ), - wherein the valve body ( 3 ) at a combustion chamber end ( 30 ) of the valve body ( 3 ) a thermal protection device ( 31 ). Gas injector according to claim 1, wherein the thermal protection device ( 31 ) a heat dissipation cap ( 32 ) having a first heat conduction coefficient which is greater than a heat conduction coefficient of the valve body ( 3 ). Gas injector according to one of the preceding claims, wherein the thermal protection device ( 31 ) a first thermal protective layer ( 33 ) having a second coefficient of thermal conduction, which is smaller than the heat conduction coefficient of the valve body ( 3 ) and / or less than the first coefficient of thermal conduction of the heat dissipation cap ( 32 ). Gas injector according to claim 3, wherein the first thermal protective layer ( 33 ) on the heat dissipation cap ( 32 ) is arranged. Gas injector according to one of claims 2 to 4, wherein the heat dissipation cap ( 32 ) a plate-shaped area ( 34 ), or a plate-shaped base region ( 34 ) and one at the plate-shaped base area ( 34 ) arranged wall area ( 35 ) having. Gas injector according to one of claims 2 to 5, wherein the heat dissipation cap ( 32 ) at a contact surface ( 36 ) has a surface structuring, wherein the contact surface ( 36 ) arranged for a contact between the heat dissipation cap ( 32 ) and a cylinder head ( 5 ) and on the heat dissipation cap ( 32 ) is arranged. Gas injector according to one of claims 2 to 6, wherein the valve closing element ( 2 ) a second thermal protection layer ( 20 ) having a third coefficient of thermal conduction, which is smaller than the heat conduction coefficient of the valve body ( 3 ) and / or the first heat conduction coefficient of the heat dissipation cap ( 32 ). Gas injector according to one of the preceding claims, wherein at a maximum lift of the valve closing element ( 2 ) a flow cross-section ( 6 ) between the valve body ( 3 ) and the valve closing element ( 2 ) smaller than a flow cross-section ( 7 ) between the valve closing element ( 2 ) and the sealing seat ( 4 ). Injector assembly comprising a gas injector ( 1 ) for injecting a gaseous fuel into a combustion chamber ( 9 ) and a cylinder head ( 5 ) with a cylinder head opening ( 50 ), in which the gas injector ( 1 ), one to the combustion chamber ( 9 ) end ( 10 ) of the gas injector ( 1 ) from a combustion chamber end ( 51 ) of the cylinder head opening ( 50 ) in the axial direction (XX) at a predetermined distance (XX) 100 ) is arranged. Injector assembly according to claim 9, comprising a gas injector ( 1 ) according to one of claims 1 to 8. Internal combustion engine, comprising a combustion chamber ( 9 ) as well as a gas injector ( 1 ) according to one of claims 1 to 8 or an injector arrangement ( 8th ) according to one of claims 9 or 10.

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