WO2007000367A1

WO2007000367A1 - Sheathed-element glow plug

Info

Publication number: WO2007000367A1
Application number: PCT/EP2006/062142
Authority: WO
Inventors: Jens Schneider; Christoph Kern
Original assignee: Robert Bosch Gmbh
Priority date: 2005-06-27
Filing date: 2006-05-09
Publication date: 2007-01-04
Also published as: DE102005029837A1; EP1899647A1

Abstract

The invention relates to a sheathed-element glow plug (1) which is designed to be fitted into a chamber of an air compression type, self-igniting internal combustion engine. Said sheathed-type glow plug (1) comprises a heating body (2) and a housing (4), whereby the heating body (2) protrudes at least partially into the housing (4). A protective body (20), which seals the interface between the heating body (2) and the housing (4) and which sectionally surrounds the heating body (2), is provided. An intermediate chamber (21), which is formed between the protective body (20) and the heating body (2), is filled with at least one filling material (31, 36). The filling material (31, 36) ensures a certain temperature insulation, such that a sensor (37), which is used to measure the combustion pressure or similar, can be arranged inside the protective body (20).

Description

glow plug

The invention relates to a glow plug for arrangement in a chamber of an internal combustion engine. Specifically, the invention relates to a glow plug for air compressing, self-igniting internal combustion engines.

From DE 100 30 924 Al a glow plug for arrangement in a combustion chamber of an internal combustion engine is known. The known glow plug has a rod-shaped radiator, which is partially surrounded by a housing of the glow plug. The radiator is designed as a ceramic heater and has a first current-carrying layer, a second current-carrying layer and an insulating layer. The insulating layer serves to isolate the first current-carrying layer of the second current-carrying layer, wherein at the combustion chamber end of the radiator, a heating element is provided which connects the two current-carrying layers. By applying an electrical voltage to the two current-carrying layers, a current flow is generated by the heating element, which leads to the heating of the radiator. The known from DE 100 30 924 Al known glow plug is mounted in a bore of the internal combustion engine, wherein the rod-shaped heater is partially within a combustion chamber side portion of the bore during operation of the internal combustion engine. During the operation of the internal combustion engine, combustion residues, in particular soot, settle in this intermediate space. At the interface between the rod-shaped radiator and the housing, this may result in the penetration of combustion residues. In addition, in the disassembly of the known glow plug, the problem that, if necessary, considerable forces act on the rod-shaped radiator due to the fixed in the gap combustion residues when loosening the glow plug.

Advantages of the invention

The glow plug according to the invention with the features of claim 1 has the advantage that the rod-shaped radiator is protected from mechanical stress. In addition, in the glow plug according to the invention a reliable sealing of an interior of the glow plug in relation to the chamber of the internal combustion engine, in particular the combustion chamber, given.

The measures listed in the dependent claims advantageous refinements of the claim 1 glow plug are possible.

It is advantageous that the protective body has an opening at a chamber-side end, through which the radiator protrudes into the chamber, that a cross section of the opening is slightly larger than a cross section of the radiator and that the protective body surrounds the radiator without contact in the region of the opening. As a result, the protective body rests without contact on the rod-shaped heating element at the chamber-side end. Mechanical stresses of the preferably metallic protective body are thereby not transmitted to the radiator, whereby a mechanical load on the radiator is prevented. This is particularly advantageous for a ceramic heater. In addition, the penetration of larger dirt particles in the space between the protective body and the radiator is prevented by the contact-free concerns.

Advantageously, the filling material is arranged in a chamber-side part of the protective body to the radiator. The filler may consist of a high temperature resistant ceramic fiber, a molded body, a high temperature resistant ceramic paper or a similar filler. In the chamber-side part of the protective body may also be provided a mixture of said filling materials. The filling material in the chamber-side part prevents the penetration of relatively large particles of dirt that have passed through the opening at the chamber-side end of the protective body. In addition, the filling material ensures a certain temperature insulation in the chamber side part to a certain extent

To achieve temperature gradients in the chamber-side part of the protective body.

Advantageously, a further filling material is provided, which consists of a temperature-resistant powder and which is arranged in the chamber distant part of the protective body to the radiator. The temperature-resistant powder ensures the seal against relatively small Dirt particles that have passed the filler in the chamber side part. In addition, the further filling material ensures a further thermal insulation of the chamber distant part of the protective body.

Advantageously, a sensor for measuring a physical quantity is arranged in a chamber-distant part of the protective body. By the filling material in the chamber near part and by a certain proportion of the other filling material in the chamber distant part of a temperature insulation of the sensor or a temperature gradient for the sensor is ensured with respect to a prevailing in the chamber temperature at which ensures trouble-free operation of the sensor and destruction of the sensor is prevented. The sensor can be configured as a temperature measuring sensor for measuring the temperature of the heating element and / or the temperature in the chamber, in particular in a combustion chamber. The influence of the filling material and optionally of a further filling material can be taken into account by a mathematical correction variable. The sensor can also be used for pressure measurement or for measuring an ionic current of the combustion gases. Furthermore, a plurality of sensors, which are optionally accommodated in a housing, can be used for the combined measurement of the variables mentioned. Further, depending on the desired application, other physical quantities, especially within the framework of a test bench measurement, can also be measured by the sensor.

drawing

A preferred embodiment of the invention is explained in more detail in the following description with reference to the accompanying drawings. It shows: Fig. 1 shows an embodiment of a glow plug according to the invention in a schematic sectional view.

Description of the embodiment

Fig. 1 shows an embodiment of a glow plug 1 in a schematic sectional view. The glow plug 1 can be configured in particular as a glow plug 1 for an air-compressing, self-igniting internal combustion engine. A radiator 2 of the glow plug 1 protrudes in operation with its chamber-side end 3 at least partially into a chamber of the internal combustion engine. The radiator 2 can protrude in vor- and swirl chamber in vor- and swirl chamber engines and in engines with direct injection into the combustion chamber of the engine. However, the glow plug 1 according to the invention is also suitable for other applications.

The glow plug 1 has a simplified illustrated housing 4, which receives the radiator 2 and is closed at one end with an element 5. The housing 4 of the glow plug 1 is preferably formed of a metallic material. The rod-shaped heater 2 is formed in the illustrated embodiment as a ceramic heater 2. However, the radiator 2 may also have a metallic glow tube or be configured in another way.

The rod-shaped heating element 2 has a first current-carrying layer 6, a second current-carrying layer 7 and an electrically insulating insulating layer 8 arranged between the current-carrying layers 6, 7. At the Chamber-side end 3, the current-carrying layers 6, 1 are connected to one another at a tip 9 of the radiator 2. The current-carrying layers 6, 1 and the insulating layer 8 also form a circumferential, cylindrical projection 10, which serves for fastening of the radiator 2 in the housing 4. This attachment is shown in simplified form in FIG.

At a chamber-distal end 11 of the radiator 2, which is arranged opposite to the chamber-side end 3, an electrically conductive contact element 12 is connected to the second current-carrying layer 7. The contact element 12 is connected via an electrical line 13 to the positive contact of an electrical connection 14. Furthermore, a contact element 15 is connected to the first current-carrying layer 6, which is connected via an electrical line 16 to the negative contact of the electrical connection 14. When applying an operating voltage to the electrical connection 14, a current flows through the current-carrying layers 6, 7 and the tip 9 of the radiator 2, whereby the radiator 2 heats up due to the heating of the tip 9 to the chamber-side end 3 of the radiator 2 flowing past To warm up the air.

The glow plug 1 can be arranged in a combustion chamber of the internal combustion engine. From the chamber-side end 3 penetrate during operation of the internal combustion engine gases and particles to the glow plug 1. There is a risk that the gases or particles penetrate into an interior 17 of the housing 4 of the glow plug 1. There is also the risk that dirt particles settle on the radiator 2, wherein at a considerable deposition of dirt sticking of the radiator 2 in the opening of the Internal combustion engine, in which the glow plug 1 is screwed, can take place. In a disassembly of the glow plug 1 then considerable forces can act on the radiator 2, whereby the radiator 2 can be damaged and optionally breaks, optionally with parts of the glow plug 1 remain in the chamber of the engine, which is undesirable.

To remedy these problems, the glow plug 1 has a metallic protective body 20, which surrounds the radiator 2 in sections. Between the protective body 20 and the radiator 2, a gap 21 is formed. As a result, there may be a spacing of, for example, 1 mm to 5 mm between an inner wall 22 of the protective body 20 and an outer side 23 of the heating body 2. At the chamber distal end of the protective body 20 is guided substantially to the radiator 2 and at a chamber-side end 24 of the protective body 20 is also guided substantially to the radiator 2, so that there is a substantially closed space 21. In this case, the end wall 25 of the protective body 20 at the chamber-side end 24 has an opening 26, so that the protective body 20, in particular the wall 25, slightly spaced from the outside 23 of the radiator 2 or contactless abuts against the outside 23 of the radiator 2 in order not to transfer the mechanical stresses of the metallic protective body 20 that occur during the considerable temperature fluctuations to the radiator 2. The conclusion of the chamber-side end 24 between the wall 25 and the radiator 2 can be made with a given through the opening 26 air gap, as shown in FIG. 1, but also without an air gap. Within a chamber-side part 30 of the protective body 20, a filling material 31 is arranged in the intermediate space 21. The filling material 31 preferably fills the chamber-side part 30 at least substantially completely between the inner wall 22 of the protective body 20 and the outer side 23 of the radiator 2. The ring and stuffing box formed thereby may be formed of a filling material 31 formed of high temperature resistant ceramic fibers. As the ceramic fiber, a fiber of alumina, especially the alpha modification of A12O3, can be used. The filling material 31 may also consist of a shaped body. Furthermore, the filling material 31 may also comprise a high temperature resistant ceramic paper. There are also other high temperature resistant materials for the filler 31 conceivable. In addition, the chamber-side part 30 of the protective body 20 may also be filled up by a combination of a plurality of said filling materials 31.

At the chamber-side part 30 of the protective body 20, a chamber-remote part 32 of the protective body 20 connects. The chamber-distant part 32 is in a front part 33, which connects directly to the chamber-side part 30, a rear part 34 which is adjacent to the chamber-side end 24 of the protective body 20, and a central part 35, which is between the front part 33rd and the rear part 34 is divided. The intermediate space 21 of the chamber-distant part 32 of the protective body 20 is filled with a further filling material 36. The additional filling material 36 consists of a temperature-resistant powder. The further filling material 36 may be formed from a packing of ceramic powder, in particular of MgO, glass powder or fibers, in particular ceramic fibers of A12O3. The additional filling material 36 ensures a seal against smaller particles that can pass through the filling material 31.

In addition, given by the filling material 31 in the chamber-side part 30 and the further filling material 36 in the front part 33 of the chamber distant part 32, a certain temperature insulation of the central part 35 of the chamber distant part 32 of the protective body 20. In the middle part 35, therefore, a sensor 37 can be arranged, which can be operated reliably due to the temperature insulation and is protected from destruction by the action of heat. The sensor 37 may be formed as a sensor for pressure measurement and constantly, that is, both during operation of the glow plug 1 and when not operating the glow plug 1, the pressure in the chamber

Internal combustion engine, in particular the combustion pressure in the combustion chamber of the internal combustion engine, measure. The sensor 37 can also be designed as a sensor for temperature measurement in order to measure the temperature of the heating body 2 and / or the temperature in the chamber, in particular the combustion chamber temperature of the combustion chamber. The sensor 37 may also be configured as a sensor for measuring an ion current in order to measure the ion current generated by the combustion gases. This ion current, which may be in the range of some rtiA, can be measured as a current flow through the radiator 2 when the glow plug 1 is out of operation.

The intermediate space 21 between the sensor 37 and the inner wall 22 of the protective body 20 is also filled in the middle part 35 with the further filling material 36 in order to achieve a certain temperature insulation for the sensor 37 from the outside as well. The provided in the rear part 34 of the gap 21 of the protective body 20 further filler 36 serves to further improve the sealing of the interior 17 relative to the chamber of the internal combustion engine.

The connection of the protective body 20 to the housing 4 can be done by a circumferential weld in the area 38.

The glow plug 1 ensures good mechanical protection of the ceramic heater 2 through the tubular protection body 20 and the filling materials 31, 36 or the powder pack. In an eventual breakage of the radiator 2 also a complete removal during disassembly of the glow plug 1 is ensured from the chamber. In particular, it is prevented that the radiator 2 or part of the radiator 2 falls into the chamber of the internal combustion engine. Furthermore, the protective body 20 ensures protection against thermal shock. Another advantage is the mechanically and thermally protected space in the middle part 35 for the sensor 37, which may be arranged relatively close to the chamber-side end 3. The measurement data of the sensor 37 can be output to a terminal 40 via an electrical lead 39 led through the rear part 34 of the chamber-distant part 32 of the gap 21. If necessary, the energy for operating an active sensor 37 can also be supplied via the line 39 or a corresponding line.

As material for the filling materials 31, 36, in particular for the filling material 31, for example, fibers of A1203 or of yttrium-stabilized zirconium (YSZ), shaped bodies of magnesium silicate, magnesium aluminum silicate or a fire-resistant insulating material, especially from Fire resistance class R90, and / or a heat-resistant high temperature resistant ceramic paper serve. As material for the filling materials 31, 36, in particular for the filling material 36, for example mica (mica denotes a group in the monoclinic crystal system of crystallizing silicate minerals), in particular KA12 [(OH, F) | AlSi3O10], alpha-A1203, which in Form of fibers in different thickness, length and processing can be used and is generally temperature resistant up to about 1900 ° C, and / or MgO, for example in the form of a powder pack, which is temperature resistant to about 2800 ° C serve.

The invention is not limited to the embodiment described.

Claims

R. 311221ROBERT BOSCH GMBH, 70442 Stuttgart claims

1. glow plug (1) for arrangement in a chamber of an internal combustion engine with a rod-shaped radiator (2) and a housing (4), wherein the radiator (2) partially from the housing (4) protrudes, characterized in that one with the housing (4) connected protective body (20) is provided, which surrounds the radiator (2) in sections, that between the protective body (20) and the radiator (2), a gap (21) is formed and that the intermediate space (21) with at least one Filling material (31, 36) is at least partially filled.

2. glow plug according to claim 1, characterized in that the filling material (31, 36) seals a transition region of an interior space (17) of the housing (4) to the chamber.

3. glow plug according to claim 1 or 2, characterized in that the protective body (20) has, at a chamber-side end (24), an opening (26) through which the heating body (2) projects into the chamber.

4. glow plug according to claim 3, characterized in that a cross section of the opening (26) is slightly larger than a cross section of the radiator (2) and that the protective body (20) surrounds the radiator (2) in the region of the opening (26) without contact ,

5. glow plug according to one of claims 1 to 4, characterized in that the filling material (31) in a chamber-side part (30) of the protective body (20) to the radiator (2) is arranged.

6. glow plug according to claim 5, characterized in that the filling material (31) made of high temperature resistant fibers, in particular of ceramic fibers exists.

7. glow plug according to claim 5, characterized in that the filling material (31) consists of a molded body.

8. sheathed plug according to claim 5, characterized in that the filling material (31) consists of a high temperature resistant ceramic paper.

9. glow plug according to one of claims 5 to 8, characterized in that a further filling material (36) is provided, which consists of a temperature-resistant powder, and in that the further filling material (36) is arranged in a chamber-distant part (32) of the protective body (20) around the heating body (2).

10. glow plug according to one of claims 1 to 9, characterized in that in a chamber distant part (32) of the protective body (20) is arranged a sensor (37) for measuring a physical quantity.

11. glow plug according to claim 10, characterized in that the sensor (37) as a sensor (37) for pressure measurement, as a sensor (37) for measuring temperature or as a sensor (37) for measuring an ion current is configured.