WO2014202265A1

WO2014202265A1 - Sheathed glow plug for glow temperature control

Info

Publication number: WO2014202265A1
Application number: PCT/EP2014/058664
Authority: WO
Inventors: Albrecht Geissinger; Andreas Reissner; Bruno CERON NICOLAT
Original assignee: Robert Bosch Gmbh
Priority date: 2013-06-21
Filing date: 2014-04-29
Publication date: 2014-12-24
Also published as: EP3011230A1; CN105324610B; CN105324610A; DE102013211789A1

Abstract

The invention relates to a sheathed glow plug (10) for an internal combustion engine (64) of a motor vehicle, comprising a resistor element (16) in the form of a single-material coil (44) and having a defined resistance-temperature coefficient. Said coil is heated up and/or maintained at a defined temperature by means of a dynamically changing drive voltage applied to the resistor element (16).

Description

Description title

Glow plug for annealing temperature control

State of the art glow plugs, also referred to as glow plugs, or based on the English

Term "glow plug" abbreviated to GLP, which are used in internal combustion engines to ignite a fuel-air mixture are preheated in the cold state before their temperature is sufficiently high that it is sufficient for the ignition of the fuel-air mixture For example, after starting to reduce emissions or the like, it may be necessary to continue to operate the glow plugs for some time in order to increase the temperature inside the combustion chamber, whereby the control assumes an electrical glow control device (abbreviated GCU) unit ") in conjunction with an engine control unit, with a short heating time and a controlled afterglow of the glow plug are sought.

A glow plug has to an electrical resistance heater in the form of a

Glow wire, which acts on the cold glow plug in a short period of 1 to 2 seconds with voltage such that reaches a temperature of more than 1000 ° C at the top of the glow plug. Differences are so-called 1 1 volt glow plugs, which are operated with battery or vehicle voltage + and

Quick start glow plugs, also referred to as low voltage glow plugs or "high speed glow plug" (HS GLP), are heated for a limited period of time at a heating voltage of 7 to 12 volts during the preheat phase - Phase "will be the

Voltage reduced to a nominal voltage, which is well below the used

Heating voltage is, for example in a range of 4 to 7 volts. This gives the possibility to adjust or apply the temperature at different engine conditions. The steady-state temperature of the glow plugs, ie the operating temperature, is around 980 ° C. The electric resistance heater generally comprises a combustion chamber-side heating coil and a control coil welded to one end of the heating coil, which are surrounded coaxially in the glow plug by a metallic glow tube or a protective tube as an outer shell. The section of the glow tube protruding into the combustion chamber is usually filled with an electrically insulating filling powder,

For example, magnesium oxide, in which the Wderstandsheizung is embedded. The electrical connection is generally made via a connection pin, which is electrically connected to the control coil and the heating coil. Another end of the heating coil is electrically contacted with the glow tube, via which the current feedback nach0 mass. For example, a connection plug can be attached to the connection bolt

be screwed on.

Accordingly, there are in glow plugs a combination of heating and control coil to a common Wderstandswert before, wherein the heating coil forms the front part of the Glührohres5, the heating zone. The rear part, namely the control coil, has the property that with increasing temperature the resistance increases, i. the control coil has a high positive temperature coefficient (PTC "Positive Temperature Coefficient")

Characteristic). As the resistance value increases, there is a decrease in the current and a defined end temperature is established. Heating and control coil are electrically connected in o series, both coils have positive but different high temperature resistance coefficients. The heating coil, typically made of an iron-chromium-aluminum alloy, has a high electrical resistance at room temperature, which remains almost constant over the operating temperature range. The control coil is usually made of pure nickel or a cobalt-iron alloy or a cobalt-iron-5 nickel alloy, wherein the electrical resistance at room temperature is very low and increases very steeply with increasing temperature.

Furthermore, when the glow plug is activated with an excessive heating voltage, a temperature overshoot occurs, so that after the push phase, a transient

o Temperature course is present until it changes to a stationary one.

DE 10 2008 040 971 A1 discloses a method for regulating the temperature of

Glow plug in an internal combustion engine known, in which for each

Shunt plug a mathematical relationship between measured Temperatur5 and measured resistances in a reference operation of the internal combustion engine is recorded. This mathematical relationship is dynamically adjusted over the life of the glow plug. The behavior of the glow plug is measured in a reference mode in air or recorded by expensive and special temperature measuring candles. However, during operation in an engine compartment, an actual temperature of the glow plug differs by the influence of numerous boundary conditions, such as load, speed, outside temperature, diesel particulate regeneration, etc.

DISCLOSURE OF THE INVENTION According to the invention, a glow plug for an internal combustion engine of a

Motor vehicle proposed, comprising an electrical resistance element with a defined Wderstands temperature coefficient and formed as Einstoffwendel. It is further provided that the electrical Wderstandselement is heated by means of a dynamically changing drive voltage and / or maintained at a predetermined temperature. The drive voltage is dependent on a measured

Temperature-dependent resistance changed. The electrical Wderstandselement has a defined, positive Wderstands-temperature coefficient.

The inventive glow plug shows in an operating temperature range of 20 ° C to 1200 ° C preferably a linear behavior of the defined Wderstands- temperature coefficient.

The glow plug according to the invention is based on the detection of the electrical

Resistance of a glow plug, which shows a defined temperature dependence in an operating temperature range of 20 ° C to 1200 ° C. The glow plug comprises an electrical Wderstandselement, designed as a helix, also referred to as Einstoffwendel, which combines the properties of a heating coil and a control coil in a single helix. A material property important for the single-material coil is the specific electrical resistance and its dependence on the temperature.

Suitable materials which show suitable temperature dependencies with respect to the specific electrical resistance are alloys comprising inter alia constituents from a material group (a): niobium, molybdenum, tantalum, tungsten and their alloys and from a material group (b): chromium, nickel, titanium and their alloys. According to the invention, the single-material coil is distinguished by a specific electrical resistance p, which in one embodiment, based on the material group (a), at a temperature of 20 ° C. is 0.1 ₊ 0.06 mQ mm, for example, and with increasing temperature increases, wherein at 1000 ° C, the specific electrical resistance p _a, for example, 0.5 ₊ 0.2 mQ mm.

Alternatively, the specific electrical resistance p _b , based on the material group (b), at a temperature of 20 ° C, for example, 1 ₊ 0, 1 mQ mm and at a temperature of 1000 ° C, the electrical resistivity of the helical material, for example 1, 25 ₊ 0, 1 mQ mm increased.

One example is molybdenum-titanium-zirconium alloys. Another example is nickel-chromium-iron alloys with 19 to 60 wt .-% nickel, 14 to 25 wt .-% chromium, 24 to 58 wt .-% iron and 1 to 2.4 wt .-% aluminum. Another example includes molybdenum or tungsten with up to 3 weight percent lanthanum oxide (La ₂ O ₃ ), up to 3 weight percent thoria (Th0 ₂ ), up to 3 weight percent ceria (CeO ₂ ), bis to 2 wt .-% yttria (Y ₂ 0 ₃ ), up to 30 wt .-% rhenium and up to 50 wt .-% copper (Cu).

A recording of the temperature of the glow plug in the installed state in one

Engine compartment during operation via the electrical resistance of the filament is only possible if the filament is made of a single material, which shows a sufficiently high temperature response over the entire operating temperature range, in particular a range of 20 ° C to 1200 ° C. Thus, the steepest possible increase in the electrical resistance is achieved, which preferably shows a linear behavior. Furthermore, it is necessary that the Einstoffwendel located in the front part of the

Glow plug is located, as these only about 5 mm into a combustion chamber of a

Internal combustion engine protrudes.

Furthermore, a method for operating a glow plug according to the invention is proposed. The inventive method is based on the detection of the electrical

Resistance with a sufficiently high accuracy, which, for example, by an existing Glühzeitsteuergerät with a suitable measuring resistor means

Current measurement with an accuracy of ± 0.02 Ω can be realized. The inventive method for controlling the temperature of a glow plug is based on a defined relationship between temperature and electrical resistance, which can be determined in Einstoffwendeln. A difference in resistance is determined from a measured resistance (R) and an input resistance (R ₀ ). From the determined resistance difference (R - R ₀ ) and the known Wderstands-

Temperature coefficient of the electrical resistance of the material of Einstoffwendel (dR / dT) and a temperature T ₀ at the input resistance (R ₀ ) can now be a

Temperature (T _over ) can be determined according to T _ber = (R-R ₀ ) / (dR / dT) + To (1), which represents an actual temperature.

According to the invention, the control of the electrical resistance element, designed as Einstoffwendel, in connection with a Glühzeitsteuergerät or a

Engine control unit realized by software. Through the procedure, the glow time control device can be adapted to the respective glow plugs by means of a so-called teach-in phase. In particular, an initial temperature (Ti) of the respective

Glow plugs at a certain voltage level (Ui) determined, which corresponds to an initial resistance (R ^

Increased voltage level (U ₂ ) and read the set temperature (T ₂ ), wherein a resistance (R ₂ ) is determined. Thus, the resistance temperature coefficient of the particular glow plug used can be determined.

In a further development of the method according to the invention, a limit value of

Temperature or a target temperature deposited in the software of Glühzeitsteuergerätes or in a higher-level control unit, which prevents overheating of the glow plug in the engine compartment.

Advantages of the invention

The solution according to the invention provides a heating device for regulating or controlling the temperature in an internal combustion engine, which provides the heating element in front of a

Overheating or melting reliably protects, since the determination of

Drive voltage across the measured electrical resistance with high accuracy occurs. In particular, can be dispensed with a control coil, whereby the production the heating element is significantly cheaper and easier. Thus, both the required annealing function can be met, as a fast heating rate and maintaining a stationary temperature once reached. Advantageously, the measured electrical resistance increases with the temperature of

Single-material coil, with a control by means of the drive voltage in response to the rising measured resistance. Accordingly, the PTC behavior of the heating element made of a uniform material complements with a dynamically changed drive voltage for controlling or controlling a glow plug.

The constant monitoring of the electrical resistance of the heating element or the Einstoffwendel allows control of the annealing temperature, which are adjusted by adjusting the drive voltage to different engine conditions. Accordingly, it is not necessary to take into account for the exact determination of the temperature in the engine compartment permanently values with respect to the combustion characteristics of the internal combustion engine, for example, the speed of the internal combustion engine, the amount of in the

Internal combustion engine injected fuel, the exhaust gas recirculation, the supply air temperature, the exhaust gas temperature and the regeneration status of the diesel particulate filter. Advantageously, the robustness of the glow plug is increased, but also by the constant monitoring of the electrical resistance is an opportunity to detect the aging of a glow plug and, if necessary, to detect a malfunction in a timely manner. Advantageously, the temperature is dependent on a measured electrical

Resistance determined. The measured electrical resistance forms a

reliable output value for the calculation of the temperature and provides a

Reliable basis for the regulation or control of the temperature of the glow plug. This approach eliminates the need for applications using a thermocouple as a metering plug, reducing material costs and process costs.

A controlled annealing system generally provides increased protection of the glow plug, increasing service life and promoting combustion efficiency in the combustion chamber. In addition, more stable combustion in the combustion chamber of a combustion engine can be achieved by a constant temperature, wherein improved exhaust gas values and a lower need for exhaust aftertreatment can be achieved.

Brief description of the drawings

Further advantages and embodiments of the device and the method according to the invention are illustrated by the drawings and explained in more detail in the following description.

Show it:

Figure 1 is a schematic cross-sectional view of a glow plug according to the

State of the art;

Figure 2 is a detail of a schematic cross-sectional view of a glow plug according to the invention;

Figure 3 is a specific electrical Wderstand - temperature diagram for

Materials of a heating element;

Figure 4 is a schematic diagram of the arrangement of a glow plug in a

Internal combustion engine;

According to the prior art, FIG. 1 shows a cross-sectional view of a glow plug 10.

The glow plug 10 illustrated in FIG. 1 includes, inter alia, a substantially hollow-cylindrical glow tube 12 which is connected to a housing 14. In the glow tube 12 is an electrical resistance element 16, which comprises a control coil 18 and a downstream, with the control coil 18 generally welded heating coil 20. The substantially spirally formed Wderstandselement 16 is disposed coaxially with the glow tube 12 and preferably completely embedded in a filling powder 22 for mechanical stabilization and for electrical insulation. The filling powder 22 may be, for example, magnesium oxide (MgO). The control coil 18 and the heating coil 20 are electrically connected to each other via a contact pad 24, wherein they are connected in series. A lower end of the heating coil (not designated) is electrically connected by means of a contact point 26 with a Glührohrendabschnitt 28. A likewise not designated end of the control coil 18 is electrically conductively connected by means of a further contact point 30 with a substantially cylindrical connecting bolt 32. The connecting bolt 32 is made of an electrically conductive metallic

Material made. The contact points 24, 26, 30 may be formed as welding points. On the connecting bolt 32, a cap-shaped round plug 34 is screwed, which is also made of a highly conductive electrical material. By means of the

Rundsteckers 34 is an electrical connection of the glow plug 10 to a

Power distribution of an electrical supply system, not shown

Motor vehicle created, which is connected, for example, with the positive pole of a battery and / or a generator. The return to the ground via the contact point 26, the glow tube 12, the conductive housing 14 connected thereto and - in a non-illustrated engine block - screwed housing threaded portion 36. The electrical insulation against the housing 14 is, inter alia, arranged below the circular connector 34 disc-shaped Insulation disc 38 and a subsequently positioned, frusto-conical housing seal 40. Another, disc-shaped

Glührohrabdichtung 42 is provided in the region of the glow tube 12. The housing seal 40 and the glow tube seal 42 are made of an electrically insulating,

made of temperature-resistant material, wherein in addition to the electrical insulation function, a coaxial attachment of the connecting bolt 32 and the control and heating coil 18, 20 is ensured within the glow tube 12 and the housing 14. variants

FIG. 2 shows a detailed view of an embodiment of the glow plug 10 according to the invention. In Fig. 2, a tip of the glow plug 10 is shown, which projects into a combustion chamber, not shown, of an internal combustion engine. The glow plug 10 also includes the glow tube 12, which comprises a filament substantially coaxially, which is formed according to the embodiment of the invention as Einstoffwendel 44. The single-material coil 44 combines properties of the heating coil 20 and the control coil 18 of FIG. 1 and is also referred to as a heating element. Furthermore, the Einstoffwendel 44 embedded in the glow tube 12 in the electrically insulating filling powder 22. FIG. 2 also shows the radiator seal at 42. The

Single-material coil 44 comprises a glow wire which is made of a uniform material and fulfills functions of the heating coil 20. The used uniform material of

Single-material coil 44 has a resistor with PTC behavior.

FIG. 3 shows a specific electrical resistance (p) temperature (T) diagram of uniform materials suitable for the single-material coil 44. FIG. 3 shows courses of the specific electrical resistance (p in mQ mm) with increasing temperature (T in ° C), where with 46 a range of a course of the specific electrical resistance p with increasing temperature of a material group (a) and with 48 a range of History of the specific Wderstands p with increasing temperature of a material group (b) is characterized. It can be seen that the specific electrical resistances of the material groups (a) and (b) increase with increasing temperature, wherein the specific electrical resistance values are in a range of values, bounded in each case by an upper line 50, 52 and a lower line 56, 58. Furthermore, a temperature range 60 can be seen from FIG. 3, in which the sheathed-element glow plug 10 according to the invention is used. The limits of the temperature range 60 are chosen such that on the one hand a sufficient annealing temperature can be achieved and on the other hand overheating of the glow plug 10 is avoided. The material groups (a) and (b) differ by the absolute values of the specific electrical resistance (p) and their temperature response, or the course of the specific electrical resistance with increasing temperature. The material group (a), which comprises a uniform material for the Einstoffwendel 44, for example, characterized by a lower electrical resistivity at a temperature of 0 ° C compared to the material group (b), wherein the temperature rise and thus the temperature coefficient is higher , Suitable materials for a single-material coil 44 include in the material group (a): niobium, molybdenum, tantalum and tungsten and their alloys and in the material group (b): chromium, nickel and titanium and their alloys.

FIG. 4 generally shows an annealing system 1. The glow plug 10 protrudes into a combustion chamber 62 of an internal combustion engine 64, for example, a diesel engine. The glow plug 10 is on the one hand connected to a Glühzeitsteuergerät 66 and on the other hand leads to a vehicle electrical system voltage 68, the glow plug 10 with a voltage controls. The glow time controller 66 is connected to an engine controller 70, which in turn leads to the engine 64.

To ignite the fuel-air mixture, the glow plug 10 is preheated in a push phase, which lasts 1 to 2 seconds, by the application of a voltage, or an overvoltage. In the existing, not shown in Figure 4, electrical

Resistance element 16 of the glow plug 10, the electrical energy is converted into heat, so that the temperature at the top of the glow plug 10 rises steeply. The fuel-air mixture is conducted past the hot tip of the glow plug 10 and heats up. Connected with the intake air heating during the compressor stroke of the internal combustion engine 64, the ignition temperature of the fuel-air mixture is achieved.

Claims

Claims 1. Glow plug (10) in an internal combustion engine (64) of a motor vehicle, comprising an electrical resistance element (16) with a defined resistance temperature coefficient, designed as a single-material coil (44), characterized in that the electrical resistance element (16) by means of a dynamically changing

Control voltage is heated and / or kept at a predetermined temperature.

2. Glow plug (10) according to claim 1, characterized in that the electrical resistance element (16), designed as a single-material coil (44), has a positive, defined resistance temperature coefficient.

3. Glow plug (10) according to claim 1 or 2, characterized in that the positive defined resistance temperature coefficient shows linear behavior in a temperature range from 20 ° C to 1200 ° C.

4. Glow plug (10) according to one of claims 1 to 3, characterized in that the electrical resistance element (16) at a temperature T of 20 ° C

specific electrical resistance p _a of 0.1 ± 0.07 mQ mm and at a temperature T of 1000 ° C has a specific electrical resistance p _a of 0.5 ± 0.2 mQ mm.

5. Glow plug (10) according to claim 4, characterized in that the electrical resistance element (16) is made of a material selected from one

Material group (a), comprising molybdenum, niobium, tantalum, tungsten and their alloys, or a material group (b), comprising chromium, nickel and titanium and their alloys.

6. Glow plug (10) according to claim 4, characterized in that the electrical resistance element (16) is made of a material which has a molybdenum-titanium

Zirconium alloy includes.

7. Glow plug (10) according to claim 4, characterized in that the electrical resistance element (16) is made of a material which contains molybdenum or tungsten and up to 3% by weight of lanthanum dioxide or up to 3% by weight of thorium dioxide or up to to 3 weight % cerium dioxide or up to 2% by weight of yttrium oxide or up to 30% by weight of rhenium or up to 50% by weight of copper or a combination of several of these additional elements.

8. Glow plug (10) according to one of claims 1 to 3, characterized in that 5 the specific resistance element (16) at a temperature T of 20 ° C

specific electrical resistance p _b of 1 ± 0.1 mQ mm and at a temperature T of 1000 ° C has a specific electrical resistance p _b of 1.25 ± 0.1 mQ mm.

9. Glow plug (10) according to claim 8, characterized in that the electrical resistance element (16) is made of a material comprising a nickel-chromium-iron alloy with a nickel content of 15 to 60% by weight and / or a Chromium content of 12 to 27% by weight and/or an iron content of 24 to 58% by weight and/or an aluminum content of 0.1 to 10% by weight. 5 10. Methods for operating a glow plug

(10) according to one of claims 1 to 9 in an internal combustion engine (64) of a motor vehicle, wherein on an electrical resistance element (16), designed as a single-material coil (44) with a defined resistance temperature coefficient, a dynamically changing control voltage depending on a measured temperature-dependent resistance is present, the electrical resistance element (16) being heated and/or at a predetermined level

temperature is maintained.

1 1. The method according to claim 10, characterized in that from one

Initial temperature and a measured electrical resistance of the electrical

5 resistance element (16) and an initial resistance, a resistance difference is determined, which is related to the resistance temperature coefficient in order to calculate an actual temperature of the electrical resistance element (16).

12. The method according to claim 11, characterized in that the actual temperature is compared with 0 of a target temperature, whereby if the target temperature is exceeded

The control voltage is reduced and if the temperature falls below the target temperature

Control voltage to the electrical resistance element (16) is increased.

13. The method according to one of claims 1 to 12, characterized in that relevant parameters are read in to characterize the glow plug (10) before the start of the method.