EP3201530A1

EP3201530A1 - Sheathed glow plug

Info

Publication number: EP3201530A1
Application number: EP15766164.6A
Authority: EP
Inventors: Eriko TERASAKI; Eberhard Janzen; Gebro GABRIYEL; Albrecht Geissinger
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-10-02
Filing date: 2015-09-21
Publication date: 2017-08-09
Also published as: JP6405039B2; DE102014220036A1; WO2016050541A1; JP2017527769A

Abstract

The invention relates to an electrically heatable sheathed glow plug (1) with a housing (2), a support tube (3) which is connected to the housing (2), a ceramic heating element (4) which is held in the support tube (3) and which comprises a plus pole (41) and a minus pole (42), and an electrically conductive connection pin (5) which is electrically connected to the plus pole (41) of the ceramic heating element (4) via an electrically conductive contacting element (6). The electrically conductive contacting element (6) can be compressed and is arranged between the connection pin (5) and the plus pole (41) of the ceramic heating element (4), and at least the plus pole (41) of the ceramic heating element (4) and optionally the contacting element (6) as well are arranged in the support tube (3) so as to lie outside of the housing (2).

Description

glow plug

State of the art

The invention relates to a glow plug or glow plug, and more particularly a ceramic glow plug for arrangement in a chamber of an internal combustion engine, such as a pre-vortex or combustion chamber of an air-compressing, self-igniting diesel engine.

In modern motor vehicles and other applications are common

Diesel engines are used compared to gasoline powered ones

Internal combustion engines have a higher efficiency. However, diesel engines often require a cold start aid during the starting process, since in a cold start of a diesel engine problem-free self-ignition of the injected diesel fuel is usually not possible. Even after the start can

Glow plugs are used to cold run the engine and its

Improve exhaust emissions. In addition, different

Fuel qualities minimize the ignitability of the compressed air / diesel mixture. To counteract these effects, located in the combustion chambers of a

Diesel engine normally each at least one electrically heated

Glow plug, also known as GLP (English term "glow plug"), by means of which the diesel engine is preheated in the starting phase Glow plug can have a heating element made of metal or ceramic, also known as glow plug With

Kerosene-powered gas turbines and oil heaters widespread application. In known glow plugs with a ceramic glow plug, the glow plug usually consists of electrically insulating ceramic material in which highly electrically conductive leads and an internal heating conductor can be embedded. The ceramic glow plug, also called ceramic pin, is fixed in a support tube and gas-tight pressed into a glow plug. The electrical contact of the positive pole of the ceramic pin, usually by a at one end of the

Ceramic pin provided contact point of the heating element is provided by a connecting bolt, which is connected via a wire to the positive terminal of the ceramic ceramic pin, and the electrical contact of the negative terminal of the ceramic pin, that is, the ground connection to the engine block via the support tube of the ceramic pin and the Housing made. The described wire connection of the connecting bolt with the positive pole of the ceramic pin of the known glow plugs is usually carried out by a solder joint. Alternatively, a connection between the connecting bolt and positive pole can also be effected by a pressed or soldered metal sleeve. However, a connection by means of the soldered wire or by means of the introduced metal sleeve requires a corresponding stabilization, which is usually carried out by introducing and compacting a powder in the support tube, resulting in a complex manufacturing process.

In order to facilitate a contacting of the connecting bolt with the positive terminal, it is known, for example from DE 103 39 641 A1, to implement a corresponding contacting in a glow plug 9 by a compressible element, as shown in FIG. 3 in a schematic sectional view. The glow plug 9 consists in principle of a connecting pin 91, a heating element in the form of a ceramic pin 92, a rigid metal housing 93 and a plastic sleeve 94. The positive contacting of the ceramic pin 92 takes place here through the connecting pin 91 via a graphite tablet 95 used as an elastic contacting element instead, wherein the positive contact of the ceramic pin 92 and thus also the graphite tablet 95 and the contacting end of the connecting pin 91 within the rigid housing 93 of the glow plug 9, that is in the hollow interior of the housing 93 of the glow plug 9. The ceramic pin 92 is usually made of a more brittle material than the metal housing 93, resulting in excessive stress on the ceramic pin 92, for example, by a force from the side of the ceramic pin 92, which exceeds its strength, usually a breakage of the ceramic pin 92 can lead. The known with glow plugs wire bonding, as described, inter alia, above, therefore requires a complex production, while this must be increasingly soldered, whereby the assembly of the glow plug is difficult and costly. In the known development of a

Glow plug contact with a graphite tablet 95, as described in DE 103 39 641 A1 as described above, there is also a very rigid structure of the glow plug 9, wherein the contacting of the ceramic pin 92 through the connecting pin 91 on the graphite tablet 95 within the rigid housing 93 is arranged. When mounting such a glow plug 9 in one

Cylinder head of an internal combustion engine, it may happen due to this rigid structure that the ceramic pin 92 is applied by bending careless handling with bending forces, such as snagging the exposed tip of the ceramic pin 92 at the edge of the cylinder head or the like, which can lead to the ceramic pin 92 is not bent but due to its brittleness and the rigid arrangement in the metal housing 93 can easily break off and fall into the combustion chamber. The thus necessary disassembly and reassembly of the cylinder head to remove the broken part of the ceramic pin 92 from the cylinder head leads to a significant delay in the assembly time and the associated undesirable additional costs.

Disclosure of the invention

According to the present invention, an electrically heatable glow plug with the features of claim 1 is proposed, preferably for the cold start aid of a self-igniting internal combustion engine, such as a diesel engine.

Advantageous developments of the invention are characterized by the features of the dependent claims.

Accordingly, the invention comprises an electrically heatable glow plug according to the invention with a housing, also referred to as a plug housing, a supporting tube connected to the housing, a held in the support tube ceramic heating element with a positive pole and a negative terminal, and an electrically conductive terminal bolt, which has an electrically conductive Contacting element with the Positive pole of the ceramic heater is in electrical connection. The support tube is usually a tubular member which may be formed either as a separate part or sometimes as part of a housing of the glow plug. Furthermore, the electrically conductive contacting element is compressible and elastic and is arranged between the connecting bolt and the positive pole of the ceramic heating element, wherein at least the positive pole of the ceramic heating element lying outside of the housing are arranged in the support tube. In the approach according to the invention, consequently, the plus contact is moved out of the housing area into a section of the support tube outside the housing. Preferably, the electrically conductive contacting element is arranged lying outside of the housing in the support tube.

The ceramic heating element of the glow plug according to the invention, also known as glow plug or ceramic pin, consists in principle of electrically insulating ceramic material, for example silicon nitride, in which electrically highly conductive leads and an internal heating conductor can be embedded, as is known from the prior art discussed above. and control function is combined in the heating element. The positive pole is formed by one end of the heating conductor, which is at a held by the rest of the glow plug end of the ceramic

Heating element is exposed, and the negative terminal is formed by a compound of the heat conductor to the outer shell of the heating element, which is connected via the support tube and the housing of the glow plug, which are preferably formed of metal, with the engine block as a ground connection. As already known from the prior art, the ceramic heating element has a free end projecting into the combustion chamber of the internal combustion engine and the end forming the positive pole surface, which usually serves as a positive pole for contacting the heating conductor in the heating element. This means that in the glow plug according to the invention, the positive pole of the ceramic heating element, which is located on the in the support tube

arranged end of the ceramic heating element is located, as well as standing with this in direct contact electrically conductive contacting element are positioned in the support tube, that in the longitudinal direction (axial direction) of the

Sheathed plug outside the housing. According to a development of the glow plug according to the invention, the electrically conductive

Contacting element in communicating end of the electrically conductive Connection bolt to be arranged within the housing. Alternatively, however, this may also be arranged lying in the support tube outside the housing, similar to the positive pole of the ceramic heating element and the electrically conductive contacting element.

More specifically, in the structure of the glow plug according to the invention, the support tube may be partially within the housing, that is arranged in an inner, at least one side open cavity of the housing of the glow plug, at least the positive pole of the ceramic heater or in addition the associated electrically conductive However, contacting element are not positioned within the cavity of the housing but are outside the cavity and thus outside of the housing of the glow plug. Alternatively, the support tube may be attached to the housing so that no part of the support tube is disposed within the housing but instead the support tube is a kind of extension of the housing.

With the specific arrangement of the positive pole of the ceramic heating element and optionally of the electrically conductive contacting element in the support tube outside the housing, a so-called safe "flexible design" of the glow plug is provided in which the "short" ceramic heating element is held outside the housing in the support tube, whereby it is made possible that with an excessive load of the ceramic heating element by a force from the side of the ceramic heating element, the support tube, which here has a much lower strength than the ceramic heating element absorbs the force by a plastic deformation, without that ceramic heating element is destroyed. Since the electrically conductive contacting element remains flexible even after compression or decompression, a flexible contact between the connecting pin and the positive pole of the ceramic heating element is created by means of the compressible contacting element. This allows a usually coaxial orientation of the ceramic heating element to change to the connecting bolt, that is, that the longitudinal axis of the ceramic heating element to the longitudinal axis of the connecting bolt an angle> 180 ° can take, without the contact between the positive pole of the ceramic heating element and connecting bolt is interrupted. An electrical contact the ceramic heating element through the connecting bolt and thus heating of the ceramic heating element after bending of the support tube including ceramic heating element is therefore further possible. The arranged in the support tube end of the ceramic heating element, which has the positive pole, can thereby a

have frustoconical shape. Alternatively, however, this rear end of the ceramic heating element on which the positive terminal contact surface is located may however also have an end face at an angle of 90 ° to the longitudinal axis of the ceramic heating element, or it may be a cylindrical projection as a projecting one

Pluspolkontaktfläche be provided on this.

According to a further preferred embodiment of the invention

Sheathed plug, the part of the support tube located outside of the housing, in which at least the positive pole of the ceramic heating element and the electrically conductive contacting element are arranged, have a lower resistance moment than a part of the support tube located inside the housing. This can preferably be implemented by an equal or smaller wall thickness of the part of the support tube located outside the housing in comparison to the part of the support tube located inside the housing. The part of the support tube located inside the housing preferably has a wall thickness of 0.88 to 1.4 mm, more preferably 0.93 mm, and the part of the support tube outside the housing preferably has a wall thickness of 0.5 to 0, 8mm, more preferably 0.55mm. Furthermore, the support tube of the

glow plug of the invention consist of a ductile material,

preferably of ferritic or martensitic stainless steel. The strength of the support tube is chosen so that when a force acting on the ceramic heater bending load, the support tube is deformed, the strength of the ceramic heater is not exceeded and the electrical connection between the positive pole of the ceramic heater and the

Connection bolt is maintained by the electrically conductive contacting element. To ensure this it is preferable that the electrically conductive

Contacting element is not materially connected to the positive pole. The electrically conductive contacting element can preferably be positively connected to the positive pole, more preferably by the electrically conductive contacting element between the positive pole of the ceramic heating element and the corresponding end of the connecting bolt, which is aligned within the housing towards the ceramic heating element, is clamped. The electrically conductive contacting element can accordingly be biased by the connecting bolt. The bias of the electrically conductive contacting element or the connecting bolt must also be held by suitable measures in the region of the support tube or the housing, a variety of solutions are conceivable.

Furthermore, the glow plug according to the invention may further comprise a cover component. The lid member may be a gasket forming the cavity of the

Closes housing to keep the ceramic powder in the support tube and to prevent dirt and moisture from entering. Additionally or alternatively, the lid member may be implemented in the form of an electrically insulating sleeve which additionally electrically insulates and mechanically supports the terminal bolt relative to the housing.

The electrically conductive contacting element of the glow plug according to the invention has electrically conductive properties. According to preferred developments of the glow plug according to the invention, the electrically conductive

Contacting of a conductive powder, such as a metal powder, in particular a silver powder, a graphite powder or a conductive ceramic powder, always in solidified form, or from a porous sintered body, preferably from the same materials exist. Alternatively or additionally, the electrically conductive contacting element may have a

Have tablet form. Furthermore, the electrically conductive contacting element may consist of a rolled and / or a compressed metal fabric, wherein the metal fabric is preferably metal wool, and wherein the metal should not oxidize. Examples of such a metal are copper, bronze, brass, steel, stainless steel, silver or nickel. It is also an oxidationsanfälligeres coated, for example, silver-plated or nickel-plated metal fabric used. Alternatively or additionally, the electrically conductive contacting element consist of elastic material, preferably based on graphite. Graphite is preferably used as the material for the electrically conductive contacting element. alternative or in addition, however, the use of other suitable electrically conductive materials is possible.

According to a further preferred embodiment of the invention

Glow plug can be placed inside the support tube between the connecting bolt and the

Support tube may be arranged an insulating sleeve, which preferably electrically isolates the connecting bolt, the electrically conductive contacting element and the positive pole of the ceramic heating element relative to the support tube, the insulating sleeve is preferably made of plastic such as polyimide (PI), polyphenylene sulfide (PPS), polyetheretherketone (PEEK ), or from a temperature-resistant

Fluoro or silicone elastomer or glass silk.

ADVANTAGES OF THE INVENTION A glow plug according to the invention has the advantage over the prior art discussed above, due to the use of the flexible, electrically conductive contacting element, that no wires are used for contacting between the connecting bolt and the ceramic heating element of the glow plug, whereby a soldering of wires between these

Components becomes unnecessary and thus the entire manufacturing process is cheaper. Further, in known glow plugs, as described above, in a mechanical external action to a release or breakage between the ceramic heating element and its negative contact region

or its plus contact area come, which are usually connected to each other by soldering or the like. By using the

compressible elastic, electrically conductive contacting element, which is not materially connected to the positive pole of the ceramic heating element, a direct force on the contact surfaces between the ceramic heating element and negative contact region or positive contact region can be prevented or at least mitigated so that it does not lead to a loss of contact

Delamination occurs between these areas of the ceramic heating element. Furthermore, by the inventive solution with the outside of the housing arranged contacting the positive pole of the ceramic heating element destruction of the ceramic heating element by acting on this potential Bending forces weakened or completely avoided. The above-mentioned contacting of the positive pole of the ceramic heating element by the flexible contacting element is connected according to the invention with the described "flexible design" to a new overall solution.

Further advantages and preferred embodiments of the invention will become apparent from the following description of the figures.

Brief description of the drawings

Show it

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

preferred embodiment of the invention;

FIG. 2 is a schematic sectional view of a front part of FIG. 1

shown glow plug in an enlarged view; and

Figure 3 is a schematic sectional view of a glow plug with flexible

Contact element according to the prior art.

Preferred embodiment of the invention

1 shows a schematic sectional view of a glow plug 1 according to a preferred embodiment of the invention, and FIG. 2 shows a schematic sectional view of a front part of the glow plug 1 according to the present invention shown in FIG.

The glow plug 1 according to the invention consists of a housing 2, an associated support tube 3, a ceramic heating element or glow plug 4, which called a positive pole 41, also called positive contact region, and a negative terminal 42, also referred to as negative contact region 42, an electrically conductive

Connecting bolt 5 and an electrically conductive contacting element 6 in the form of a graphite tablet. The ceramic heating element 4 with its positive pole 41 and Negative pole 42, the contacting element 6 and a standing with the contacting element 6 in electrical connection end 51 of the connecting bolt 5 are arranged in an insulating sleeve 7, which electrically isolates the contacting element 6 and the end 51 of the connecting bolt 5 with respect to the support tube 3 to a short circuit between positive pole 41 and negative pole 42 to avoid. At the other

End 52 of the connecting bolt 5, which of the ceramic heating element 4th

is pointing the way, and more precisely on a contact portion 53 for making electrical contact with the connecting bolt 5, also known as glow plugs of the prior art, a round plug 81 is plugged, with the

Contact area 53 is in electrical contact. Furthermore, an insulating disk 82 made of an electrically non-conductive material, preferably plastic, as well as a seal 83 is arranged between circular connector 81 and housing 2 or connecting bolt 5. The support tube 3, in the preferred embodiment, towards the

Combustion tapered hollow cylinder shape, in which a wall thickness towards the combustion chamber is also lower. A part of the support tube 3 with a thicker

Wall thickness is here pressed into the housing 2 and optionally welded or soldered to this, in order to achieve a firm connection between the housing 2 and support tube 3. Alternatively, the support tube 3 only in the housing. 2

be welded. A transition region between support tube 3 and housing 2 is provided in Figure 2 with a dashed line, which marks the transition between these components. In the preferred embodiment, as shown in Figures 1 and 2, the contacting element 6, which is arranged clamped within the support tube 3 between positive pole 41 of the ceramic heating element 4 and the end 51 of the connecting bolt 5, in an overall arrangement outside the housing 2, ie in Figure 2 below the dashed line, and thus in the part of the support tube 3 with a tapered diameter and thin wall thickness of 0.5 to 0.8 mm, more precisely 0.55 mm, compared to that located within the housing 2 Part of the support tube 3 with a wall thickness of 0.88 to

1, 4mm, more precisely 0.93mm.

For as long as possible continuous maintenance of the electrical contact between positive terminal 41 and terminal pin 5, more specifically between positive terminal 41 and end 51st of the connecting bolt 5, the contacting element 6 must be under tension, wherein the contacting element 6 is elastic in the preferred embodiment for this purpose. When mounting the glow plug 1 according to the invention, the connecting bolt 5 is pressed into the support tube 3, so that the contacting element 6 is biased. With such an arrangement of the contacting element 6 within the support tube 3 outside the housing 2, it is possible that one in Figures 1 and 2 from the side of the ceramic heating element 4 or on the

Supporting tube 3 acting compressive force, which may occur, for example, by a careless installation of the glow plug 1 in a diesel engine, is intercepted by the fact that the support tube 3 plastically deformed without breaking off or tearing. The support tube 3 consists for this purpose of a ductile material whose strength and geometry is set so that when a lateral load of the heating element 4, the yield strength is exceeded first, but not the

Bending strength of the ceramic, ie a material such as ferritic or martensitic stainless steel. This can be achieved that the support tube 3 bends and absorbs the externally applied bending force, wherein the contacting element 6, which may be elastic for this purpose, followed by a bending position change and a possible change in shape follows and thereby an electrical contact between Positive pole 41 and the end 51 of the connecting bolt 5 maintains. This allows an electrical connection within the glow plug 1 even when bent by

improper use can be ensured.

As a field of application for such a design glow plug are still more

Areas of application of the above-described support tube arrangement conceivable, such as for a fuel heater such as an ethanol heater in a Flex-start system or the like.

Claims

claims

1 . Electrically heated glow plug (1) with

a housing (2),

a support tube (3) connected to the housing (2),

a ceramic heating element (4) held in the support tube (3) with a positive pole (41) and a negative pole (42), and

an electrically conductive connecting bolt (5) which is in electrical connection via an electrically conductive contacting element (6) to the positive pole (41) of the ceramic heating element (4), wherein the electrically conductive contacting element (6) is compressible and between the connecting bolt (5 ) and the positive pole (41) of the ceramic heating element (4) is arranged,

characterized in that

at least the positive pole (41) of the ceramic heating element (4) outside of

Housing (2) lying in the support tube (3) are arranged.

2. glow plug (1) according to claim 1, wherein the positive pole (41) of the ceramic heating element (4) and the contacting element (6) outside of the housing (2) lying in the support tube (3) are arranged.

3. glow plug (1) according to claim 1 or 2, wherein one with the electrically conductive contacting element (6) in communication end (51) of the electrically conductive connecting bolt (5) within the housing (2) is arranged.

4. glow plug (1) according to one of the preceding claims, wherein a part of the support tube (3) located outside of the housing (2), in which at least the positive pole (41) of the ceramic heating element (4) and the electrically conductive

Contacting element (6) are arranged, a lower resistance moment than a within the housing (2) located part of the support tube (3).

5. glow plug (1) according to any one of the preceding claims, wherein the support tube (3) consists of a ductile material, preferably of a ferritic or martensitic stainless steel.

6. glow plug (1) according to any one of the preceding claims, wherein the electrically conductive contacting element (6) is not materially connected to the positive pole (41) of the ceramic heating element (4), wherein the electrically conductive contacting element (6) preferably non-positively with the positive pole (41) of the ceramic heating element (4) is connected.

7. glow plug (1) according to any one of the preceding claims, wherein the electrically conductive contacting element (6) consists of conductive powder or a porous sintered body.

8. glow plug (1) according to any one of the preceding claims, wherein the electrically conductive contacting element (6) has a tablet form.

9. glow plug (1) according to any one of the preceding claims, wherein the electrically conductive contacting element (6) consists of a rolled and / or pressed metal fabric, wherein the metal fabric is preferably metal wool.

10. glow plug (1) according to any one of the preceding claims, wherein the electrically conductive contacting element (6) consists of elastic material, preferably based on graphite.

1 1. Shunt plug (1) according to one of the preceding claims, wherein the electrically conductive contacting element (6) is biased by the connecting bolt (5).

12, glow plug (1) according to any one of the preceding claims, wherein within the support tube (3) between the terminal bolt (5) and the support tube (3) an insulating sleeve (7) is arranged, preferably the connecting bolt (5), the electrically conductive Contacting element (6) and the positive pole (41) of the ceramic Heating element (4) opposite the support tube (3) electrically insulated.