DE102019115924A1 - Injection nozzle for an internal combustion engine in a motor vehicle - Google Patents

Abstract

, vorzugsweise mehr als $5\frac{\text{W}}{\text{m}\times \text{K}},$

aufweist.

The invention relates to an injection nozzle (100) for an internal combustion engine in a motor vehicle, comprising a metallic fuel duct (101), a heating element (103) and an insulating element (102), the insulating element (102) running around the fuel duct (101) and between the fuel duct (101) and the heating element (103) is arranged, the heating element (103) being arranged circumferentially around the insulating element (102), and the insulating element (102) being designed to be electrically insulating, the insulating element (102) having a coefficient of thermal conductivity from more than $3\frac{\text{W.}}{\text{m}\times \text{K}},$

, preferably more than $5\frac{\text{W.}}{\text{m}\times \text{K}},$

having.

Description

The present invention relates to an injection nozzle according to the preamble of claim 1.

It is known from the prior art to heat injection nozzles near an outlet opening for the fuel so that the fuel is heated shortly before it enters the combustion chamber. This is done primarily in order to achieve thorough mixing of the fuel with oxygen. The fuel should at least partially evaporate before it enters the combustion chamber in order to obtain a homogeneous gaseous fuel-oxygen mixture.

From the U.S. 5,159,915 A an injection nozzle with a metallic fuel channel is known. A ceramic insulating element is arranged around the fuel channel and is intended to electrically insulate the fuel channel from a coil arranged around the insulating element. The coil is used to induce eddy currents in the fuel duct and thus heat the fuel duct. The ceramic also serves to prevent the fuel duct from radiating heat to the outside.

In contrast, the present invention is based on the object of creating an injection nozzle with a fuel channel that can be heated better. In addition, such a motor vehicle and such a method are to be created.

This object is achieved by an injection nozzle according to claim 1, by a motor vehicle according to claim 9 and by a method according to claim 10. Embodiments of the invention are given in the dependent claims.

The injection nozzle includes a metallic fuel passage, a heating element and an insulating element. The fuel channel can be designed so that fuel flows through it into a combustion chamber of an internal combustion engine of a motor vehicle. The insulating element is arranged circumferentially around the fuel channel between the fuel channel and the heating element. The heating element is arranged circumferentially around the insulating element. The insulating element is designed to be electrically insulating. This can mean in particular that a current flowing through the heating element does not reach the fuel duct. The fuel channel can in particular define a fuel flow direction and be designed to allow circulating circular flows in a plane perpendicular to the fuel flow direction.

vorzugsweise mehr als $5\frac{\text{W}}{\text{m}\times \text{K}},$

aufweist. Durch diesen relativ hohen Wärmeleitkoeffizienten wird erreicht, dass in dem Heizelement erzeugte Wärme über das Isolierelement zum Kraftstoffkanal geleitet wird. Das Isolierelement dient also lediglich der elektrischen Isolierung und nicht der thermischen Isolierung.According to the invention it is provided that the insulating element has a coefficient of thermal conductivity of more than $3\frac{\text{W.}}{\text{m}\times \text{K}},$

preferably more than $5\frac{\text{W.}}{\text{m}\times \text{K}},$

having. This relatively high coefficient of thermal conductivity ensures that heat generated in the heating element is conducted to the fuel duct via the insulating element. The insulating element is only used for electrical insulation and not for thermal insulation.

During operation, an alternating current can be passed through the heating element, which on the one hand induces eddy currents in the fuel duct and thus heats the fuel duct, as is known from the prior art. In addition to this, the heating element is also heated by the alternating current. Due to the relatively good thermal conductivity of the insulating element, this heat is at least partially passed on to the fuel duct and thus also contributes to the heating of the fuel duct.

According to one embodiment of the invention, the insulating element can consist of ceramic and / or a composite material. The composite material can preferably comprise a metal oxide. Such a composite material is particularly advantageous because it is electrically insulating and thermally conductive.

According to one embodiment of the invention, the composite material can comprise ZnO, Ti ₂ O ₅ and / or Ta ₂ O ₅ . These materials are particularly suitable for producing a thermally conductive and electrically insulating composite material.

According to one embodiment of the invention, the composite material can comprise a ceramic.

According to one embodiment of the invention, the insulating element can have a specific electrical resistance of more than 10 ⁷ Ω × cm, preferably more than 10 ¹⁰ Ω × cm.

According to one embodiment of the invention, the fuel channel can consist of a para- or ferromagnetic material. This is advantageous in order to heat the fuel duct by induced eddy currents. For example, the fuel channel can be made of steel, preferably a non-purely austenitic stainless steel.

According to one embodiment of the invention, the fuel channel can consist of a material with a magnetic permeability of more than 5, preferably more than 10.

According to one embodiment of the invention, the heating element can be arranged helically. In the context of this description, this is understood in particular to mean that the heating element can have a plurality of turns which are arranged around a longitudinal axis and are connected to each other. The turns can have the same distance from the longitudinal axis. The longitudinal axis preferably runs within the fuel channel.

The helical arrangement is advantageous for the heating function of the heating element, in particular eddy currents can be induced particularly well in the fuel channel.

The heating element is preferably made of a material that is more electrically conductive than the material of the fuel channel. The heating element can for example consist of a metal or a metal alloy.

For example, the heating element can consist of copper, aluminum, tungsten or an alloy of at least two of these materials.

The motor vehicle according to claim 9 comprises an internal combustion engine and an injection nozzle according to one embodiment of the invention.

In the method according to claim 10, the heating element is first heated by passing an alternating electrical current, preferably with a frequency of more than 10 kHz, through it. Heat is transferred from the heating element to the fuel duct via the insulating element. In addition, eddy currents are induced in the fuel duct by the alternating current. The eddy currents can in particular circle perpendicularly around a fuel flow direction defined by the fuel channel.

• 1 eine schematische Längsschnittansicht einer Einspritzdüse nach einer Ausführungsform der Erfindung;
• 2 ein schematisches Ersatzschaltbild, anhand dessen das elektrische Verhalten der Einspritzdüse aus 1 erklärt wird;
• 3 ein schematisches Diagramm der Impedanz des Heizelements der Einspritzdüse aus 1 in Abhängigkeit von einer Wechselstromfrequenz; und
• 4 ein schematisches Diagramm einer Phasenverschiebung des durch das Heizelement der Einspritzdüse aus 1 geleiteten Wechselstroms.

Further features and advantages of the present invention will become clear on the basis of the following description of preferred exemplary embodiments with reference to the accompanying figures. The same reference symbols are used for the same or similar components and for components with the same or similar functions. It shows

• 1 a schematic longitudinal sectional view of an injection nozzle according to an embodiment of the invention;
• 2 a schematic equivalent circuit diagram, on the basis of which the electrical behavior of the injection nozzle 1 is explained;
• 3 Figure 8 is a schematic diagram of the impedance of the injector heater element 1 as a function of an alternating current frequency; and
• 4th Figure 3 is a schematic diagram of a phase shift of the injector heater element 1 conducted alternating current.

The injector 100 includes a metallic fuel passage 101 , an insulating element 102 and a heating element 103 . The fuel duct 101 defines a fuel flow direction so that the fuel can exit from the injector through one end into a combustion chamber of a motor vehicle. The insulating element 102 is all around the fuel duct 101 arranged and electrically isolated from the heating element 103 around the insulating element 102 is arranged and has several turns. The fuel duct 101 , the insulating element 102 and the heating element 103 are arranged concentrically around a geometric longitudinal axis, which is centered within the fuel channel 101 runs.

The fuel duct 101 consists of a para- or ferromagnetic material such as steel. Its electrical conductivity can be lower than that of the heating element 103 . The heating element 103 can be made of copper, aluminum or tungsten. The insulating element 102 is an electrical insulator, but thermally conductive. It can for example consist of a composite material made of a ceramic and a metal oxide.

In operation, an alternating current is passed through the heating element 103 directed. On the one hand, the alternating current heats the heating element 103 . This heat gets through the insulating element 102 to the fuel duct 101 directed. On the other hand, the alternating current induces eddy currents in the fuel duct 101 , which preferably circle vertically around the direction of fuel flow. These eddy currents heat the fuel duct 101 additionally.

With the equivalent circuit in 2 represents the resistance R _w the electrical resistance of the heating element 103 because of which the heating element 103 heats up when the alternating current passes through the heating element 103 is directed. The resistance R _km represents the magnetic losses when using a ferromagnetic material for the fuel duct 101 is used. This is especially true when using steel for the fuel duct 101 to be observed. The inductance L _km provides the magnetic coupling of the fuel duct 101 with the heating element 103 represent. The resistances R _Ke represent the induced electrical currents in the fuel duct 101 The inductance L _s takes into account magnetic stray fields. In particular, these are magnetic fields of the induced currents and the heating element that do not overlap with one another. They increase the necessary supply voltage, but do not lead to the heating of the fuel duct 101 . They increase with the distance from the heating element 103 from the fuel duct 101 and with decreasing magnetic permeability of the material of the fuel channel 101 . The desired heating of the fuel duct 101 is achieved by induced currents, which in the equivalent circuit through the resistors R _Ke flow.

The measured impedance 300 of the heating element 103 depends on the frequency of the alternating current. The higher the frequency, the higher the measured impedance 300 . Theoretically this results for the heating element 103 the history 301 where the impedance increases proportionally to the frequency. The measured impedance 300 deviates from this course 301 due to the in the fuel passage 101 induced eddy currents. The deviation begins to increase substantially at a frequency of 10 kHz and increases with increasing frequencies.

In the 4th measured phase shift shown 400 des through the heating element 103 conducted alternating current also depends on the frequency. Here, too, there is a deviation in the measured phase shift 400 from the theoretical phase shift 401 by the induction of eddy currents in the fuel duct 101 . The deviation begins to increase significantly at a frequency of approximately 800 Hz and increases with increasing frequencies.

The eddy currents in the fuel duct 101 generated heat depends on the deviation of the measured impedance 300 from the theoretical impedance 301 and the measured phase shift 400 from the theoretical phase shift 401 from. At frequencies above 10 kHz, these deviations are particularly large, so that at these frequencies in the fuel channel 101 a lot of heat is generated by the eddy currents.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 5159915 A [0003]

Claims (10)

Injection nozzle (100) for an internal combustion engine in a motor vehicle, comprising a metallic fuel duct (101), a heating element (103) and an insulating element (102), the insulating element (102) running around the fuel duct (101) and between the fuel duct (101) ) and the heating element (103) is arranged, wherein the heating element (103) is arranged circumferentially around the insulating element (102), and wherein the insulating element (102) is designed to be electrically insulating, characterized in that the insulating element (102) has a coefficient of thermal conductivity of more than $3\frac{\text{W.}}{\text{m}\times \text{K}},$

preferably more than $5\frac{\text{W.}}{\text{m}\times \text{K}},$

having. The injection nozzle (100) Claim 1 , characterized in that the insulating element (102) consists of ceramic and / or a composite material, the composite material preferably comprising a metal oxide. Injection nozzle (100) according to one of the two preceding claims, characterized in that the composite material comprises ZnO, Ti ₂ O ₅ and / or Ta ₂ O ₅ . Injection nozzle (100) according to one of the three preceding claims, characterized in that the composite material comprises a ceramic. Injection nozzle (100) according to one of the preceding claims, characterized in that the insulating element (102) has a specific electrical resistance of more than 10 ⁷ Ω × cm, preferably more than 10 ¹⁰ Ω × cm. Injection nozzle (100) according to one of the preceding claims, characterized in that the fuel channel (101) consists of a para- or ferromagnetic material. Injection nozzle (100) according to one of the preceding claims, characterized in that the fuel channel (101) consists of a material with a magnetic permeability of more than 5, preferably more than 10. Injection nozzle (100) according to one of the preceding claims, characterized in that the heating element (103) is arranged helically. Motor vehicle, comprising an internal combustion engine and an injection nozzle (100) according to one of the preceding claims. Method for heating fuel in an injection nozzle (100) according to one of the Claims 1 to 8th , wherein the method comprises the following steps: - heating the heating element (103) by an electrical alternating current, preferably with a frequency of more than 10 kHz, is passed through, with heat from the heating element (103) via the insulating element (102) to Fuel passage (101) is transmitted; and - induction of eddy currents in the fuel channel (101) by the alternating current.

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