JP2001523806A - Method of manufacturing combustion chamber of vehicle / heating machine and combustion chamber manufactured by the method - Google Patents

Abstract

(57) [Summary] A coaxial air supply pipe (10) for supplying combustion air which enters into a circumferential restriction wall (8), an end restriction wall (4) and possibly a combustion chamber (2), and in some cases. In a method for producing a combustion chamber of a burner for a heating machine or for a thermal regenerator of an exhaust gas / particle filter having a lateral tube piece (12) for mounting an ignition device, said combustion chamber (2) or at least It has been proposed to produce the combustion chamber part comprising the circumferential limiting wall (8) and the end face limiting wall (4) from an integral injection-molded part by a metal powder and injection molding method.

Description

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a method for producing a combustion chamber of a heating machine, in particular a burner for a vehicle / heating machine or for a thermal regenerator of an exhaust gas / particle filter, as well as a circumferential limiting wall, an end limiting wall and possibly a combustion chamber. The invention relates to a combustion chamber made by the above-described process, which has a coaxial air supply line for the supply of combustion air entering the chamber and, if appropriate, a lateral tube for mounting the ignition device.

[0002] Combustion chambers of this kind for burners used in the above-mentioned fields of use are known. Known combustion chambers are composed of stamped and bent sheet metal parts, which require considerable expense for joining the individual components, usually by welding or brazing. Said coupling technique generally causes thermal distortion of the combustion chamber, so that the combustion chamber must be readjusted before installation.

According to DE 44 42 425 A1 for economical production,
In particular, it has been proposed to construct the combustion chamber or a part of the combustion chamber as a precision cast part by means of the known lost wax casting method (Wachsausschmelzverfahren). In this method, first, a production model for a wax model having a shape of a precision cast member to be finally produced is produced. The multiple wax models are then connected to a common flow channel and molded into a mold material consisting of ceramic particles with a binder.
During the subsequent casting, the wax model is melted and the mold cavity formed during melting is filled with flowing metal. The mold material is then destroyed for release of the precision cast member.

It is an object of the present invention to maintain the casting principle of the combustion chamber, so that the production of the combustion chamber or a part of the combustion chamber is further improved.

According to the present invention, the object has been attained by a method according to claim 1.

[0006] Further advantageous production methods are described in claims 2 to 7.

Further, the object has been achieved by a combustion chamber manufactured by the method according to the present invention.

[0008] Another advantageous configuration of the combustion chamber is obtained with the features of the other claims.

In other words, the present invention is a method for producing a combustion chamber of a burner for a heating machine or for a thermal regenerator of an exhaust gas / particle filter, wherein the combustion chamber is provided with a circumferential limiting wall, an end face limiting wall and possibly a limiting wall. In the case of a type having a coaxial intake pipe for supplying combustion air which enters into the combustion chamber and possibly a side pipe for mounting an ignition device, the combustion chamber or at least a circumferential restriction wall is provided. The combustion chamber portion comprising the end face limiting wall is manufactured as an integral injection molded member by a metal powder injection molding method.

In particular, the sinterable metal powder / particles are injected by means of an injection device into a prefabricated female mold of the combustion chamber or a part of the combustion chamber. Next, the injection molded body is released from the female mold and the injection molded body is then sintered.

Particularly advantageously, the sinterable metal powder / particles are embedded in a thermoplastic resin used as a binder and a flow aid before injection into the female mold and after injection and from the female mold. After release from the mold and before sintering, it is released or debonded again from the thermoplastic resin.

A quality assurance process can be performed on the sintered injection-molded body of the combustion chamber or of the combustion chamber part after the original production.

As metal for metal powders and particles, preference is given to using steel or steel alloys, in particular austenitic or ferritic special steels, nickel alloy steels, carburized or annealed steels.

[0014] Polar long-chain polyacetals with additives are preferably used as thermoplastics.

[0015] The metal powder / particles are preferably compounded or mixed with a thermoplastic resin (binder) in a volume of 35% to 50% to form granules.

The combustion chamber made according to the present invention is configured as an integral metal injection-molded member in which at least the circumferential limiting wall and the end face limiting wall are injection-molded and sintered.
Is formed.

[0017] The combustion chamber may be an evaporator combustion chamber or an air atomizer combustion chamber.

[0018] Furthermore, it is also possible to integrate an advantageously coaxial supply piece into the injection-moulded and sintered one-piece metal injection-moulded part, which supply piece is located in the combustion chamber. It has an air passage opening on the side of the peripheral wall inside the combustion chamber.

Further, an ignition device, an integrated metal injection molded member molded and sintered,
In particular, it is also possible for the glow plug to receive the glow plug to be constructed in one piece, preferably on the side.

[0020] Furthermore, if the flame-holding plate is integrated into an integrated injection-molded and sintered metal injection-molded member, the combustion chamber can be made particularly complex.

Furthermore, a swirl flow generator for generating a swirl flow of the supplied combustion air is at least partially integrated in the injection-molded and sintered integral metal injection-molded member. If so, it can be more complete.

If the air supply line is an integral main component of the metal injection-molded part, the air passage openings through the tube wall can also be produced simultaneously by injection molding, in which case the air The passage openings are equally distributed in the circumferential direction, in particular in the form of sheaves. That is, the air passage openings are not formed by a separate drilling process performed later.

If the combustion chamber is designed as an evaporator combustion chamber, a porous evaporator body in the form of a sintered part, which is preferably arranged on the inner circumferential surface of the circumferential limiting wall, is provided.

The porous evaporator body can also be composed of multiple layers of material with different porosity or multiple single molded parts.

The porous evaporator body itself may be a separate injection molded member made by metal powder injection molding.

The porous evaporator body is advantageously provided with the remainder of the combustion chamber or another combustion chamber component,
In particular, it can be sintered on the inner peripheral surface of the circumferential direction limiting wall and can be fixedly connected.

The metal powder injection molding method is generally known (for example, CM-Pulverspritzguss Gm
bH In-house paper D-88427 Bad Schussenried, Titel: see "Alle reden von MIM"). The method, as is well known, is based on high material costs and required expensive tools (
Based on the in-house papers above, especially in the middle of page 6, see "Nachteile des MIM-Verfahrens") and on the basis of long tooling times (requires repeated tooling corrections), and only from the tool in which the prototype was finally formed Based on the fact that it is possible, 20
It is applicable and economically rational in the case of manufacturing small parts composed of a composite having a weight of not more than g (particularly from the last section on page 5 to the first page on page 6 of the above-mentioned in-house paper).
Section).

In the case of relatively large parts in the range of 100 g, the deformation of the component by the acting gravity is based on the size and shape of the component during sintering, in which the component shrinks by 18% to 25%. Is produced.

However, combustion chambers of the type mentioned at the outset are components of the precision cast construction type having a weight of approximately 200 g. Therefore, a person skilled in the art has hitherto not been able to produce a combustion chamber by means of metal powder injection molding.

The present inventor / applicant has overcome the above-mentioned idea and has a metal injection molding / structure type, so-called MIM / method (Metal Injection Molding = Metal Injection).
It is the first person to foresee and prove the feasibility of producing a combustion chamber of the type described at the beginning in Molding.

According to the present invention, it is apparent that the above-described MIM method is applicable to the combustion chamber according to the general concept, and that the post-processing in the combustion chamber is unnecessary despite the shrinkage of the material during sintering. It became. The component can be produced, for example, with significantly lower wall thicknesses than in precision casting. Another advantage of the process according to the invention for producing combustion chambers (compared to precision casting) is that significantly shorter process times (1 day) are obtained (in the case of precision casting more than 10 days). Process time).

In particular, the following advantages are obtained over precision casting: high process safety, narrow tolerances, low production costs, reduced weight and reduced wall thickness. I do.

The illustrated combustion chamber 2 comprises a substantially flat end face limiting wall 4 that transitions radially outward to the fixed flange 6, and a cylindrical circumferential limiting wall 8 that projects rightward from the end face limiting wall 4 at right angles. It comprises a cylindrical air supply tube 10 projecting rightward at a right angle from the end limiting wall 4 at the center and a receiving tube 12 for receiving an ignition device, preferably a glow plug.

The fixing flange 6 has a circular outer peripheral wall. The air supply pipe piece 10 is a circumferential restriction wall 8
Therefore, an annular chamber is formed between the air supply pipe piece 10 and the circumferential limiting wall 8.

The vertical center axis of the combustion chamber 2 is indicated by reference numeral 14. Air supply pipe piece 1 measured in the axial direction
0 has substantially half the length of the circumferential restriction wall 8. In a cross-sectional view, not shown, the receiving tube piece 12 has an arc-shaped internal shape that extends over approximately 240 °. The partial peripheral wall of the receiving tube piece 12 forms, as it were, a bulge of the circumferential limiting wall 8, where the circumferential limiting wall 8 is interrupted at the point where the receiving tube piece 12 is connected. The receiving tube piece 12 does not reach the end of the circumferential restriction wall 8 rightward. The longitudinal central axis 16 of the receiving tube piece 12 is located slightly outside the circumferential restriction wall 8 and the axis 14
Is parallel to The wall of the air supply pipe piece 10 is distributed circumferentially and
A circular radial air passage opening 18 for combustion air is provided axially side by side in a row.

At the end of the air supply pipe piece 10 on the downstream side as viewed in the flow direction on the right side of the drawing, a large number of webs are continuously distributed in the circumferential direction and provided in the circumferential direction. Between them are formed longitudinal slits which also deflect air radially into the annular chamber.

The upstream end on the left side of the drawing and the downstream end on the right side of the drawing (ie, the starting end of the web)
Then, the air supply pipe piece 10 is open.

All the components of the combustion chamber that have heretofore been required are configured together as an integrated metal powder and injection molded component.

However, it is also possible to manufacture the air supply piece 10 separately and then integrate it with the metal powder and injection molded parts.

A substantially cylindrical air supply casing 20 is connected to the left side of the end face restriction wall 4, and the air supply casing 20 is used to generate a swirling flow that flows into the air supply pipe piece 10. Can be provided. A fan (not shown) that supplies a required overpressure to the combustion air flowing into the air supply casing 20 (schematically illustrated) in the axial direction or the radial direction is connected to the air supply casing 20.

At the downstream end of the air supply pipe 10, a plate curved to the left as a flame holding plate 22 is disposed in contact with the flame holding plate 22, and the plate is a thin rod 24 extending in the central axial direction. And is tightened to the left end face side of the air supply casing 20 through the opening. The thin rod 24 at the left end is guided through the end wall of the air supply casing 20 and is fixed there via a nut 26 screwed there.

The curved flame holding plate is formed from a thin plate. However, it is also possible to associate the flame stabilizer with the metal powder / injection molded part integrally.

As is clear from the drawing, a perforated combustor body 28 is provided on the right side of the end face limiting wall 4 and radially inside the circumferential limiting wall 8. The perforated combustor body 28 is preferably made of sintered metal and is sintered, where appropriate, in particular.
In the illustrated embodiment, the combustor body 28 is formed to be slightly shorter than the circumferential restriction wall 8 when viewed in the axial direction. However, the combustor body 28 may be formed to have the same length as the circumferential restriction wall 8 or may be formed to have the same length. It may be formed longer.

The interior of the receiving tube piece 12 for the ignition device is located inside the combustion chamber 2, that is, the circumferential restriction wall 8.
In the region which transitions into the annular chamber between the air inlet 10 and the air supply piece 10, the perforated combustor body 28 has an opening 30 which is an interruption in the circumferential restriction wall 8 located there. , But may practically have the full size of the interruption.

Further, as is apparent from the drawing, a guide and protection ring 32 is provided which protrudes rightward from the end face restriction wall 4 at right angles into the annular chamber between the circumferential restriction wall 8 and the air supply pipe piece 10. The axial length of the ring 32 is 5% to 30% of the axial length of the air supply pipe piece 10. Furthermore, the ring 32 can advantageously likewise be made in one piece with the metal powder and injection molded part.

Further, a fuel supply hole 34 inclined at an angle of 45 ° is provided at the upper left of the drawing.
In this case, a pipe piece (not shown) can be inserted into the hole 34 by press fitting. In practice, the hole 34 is provided adjacent to the receiving tube 12 for the ignition device, offset circumferentially by 150 ° from the position shown.

As mentioned above, the combustion chamber can be manufactured as a completely or partially integral metal powder / injection molded part by a metal powder / injection molding method.

The overall production takes place with the following features: Sinterable metal powders and particles, in particular in a prefabricated female mold of the combustion chamber or of the combustion chamber part, using a plastic injection molding machine. Injection of the injection molded body in the female mold Release of the sintered injection molded body from a one-part or multi-part female mold, a so-called injection molding tool.

Thus, according to the MIM method, two known manufacturing technologies are combined, namely injection molding and sintering. Unlike conventional sintering, the MIM method produces a compact body without the application of external force, that is, without pressing, by molecular bonding of extremely fine metal powder and particles. The manufactured body has a density of 95% or more and is far superior in strength to a conventional sintered member.

Furthermore, it is advantageous if the sinterable metal powder / particles are embedded in the thermoplastic resin used as binder and flow aid before injection molding and released or debonded again from the thermoplastic resin after injection molding. It became clear that it was.

The thermoplastic resin is advantageously formed from a polar, long-chain polyacetal and various additives.

The metal powder, preferably a steel or a steel alloy, in particular an austenitic or ferritic special steel, a nickel alloy steel, a carburized or annealed steel, preferably has a volume fraction of 35% to 50%. It is compounded or mixed with a thermoplastic resin, a so-called "binder", and formed into granules, a so-called feedstock.

As in the case of plastic injection molding, the feed can be processed at approximately 150 ° in a very standard automatic extrusion injection molding machine. In this case, the female or injection molding tool of the body to be produced is very important for dimensional stability and surface quality. The high crystalline polyacetal stabilizes the injection molded body so that it can be automatically processed by a robot.

In plastic injection molding, the component is completed, whereas in the case of the MIM method, injection molding only constitutes the first step in the production of the component, the so-called “Gruenling”. Is formed.

In the subsequent decoupling process, the green product is released from the polyacetal, which is only necessary for shaping during the injection process. In this case, the well-known acid instability of polyacetal is utilized. For this purpose, the raw product (along with only the raw product) is introduced into a so-called decoupling furnace in which a nitrogen atmosphere is present. The nitric acid is then pumped into the furnace chamber at a furnace temperature of approximately 140 ° and is immediately vaporized. The acid-containing atmosphere in the furnace chamber thus obtained acts on the components located in the furnace chamber and decomposes the polyacetal into formaldehyde in the form of an acid catalyst. The depolymerization or decoupling action proceeds at a rate of 1 mm / h to 3 mm / h from inside to outside into the component. After the debinding, the so-called blank semi-finished product (Braeunling) is obtained from the unprocessed product, that is to say a component which no longer has a binder component. The gas produced in the method step is combusted without residue by a two-stage torch belonging to the furnace installation.

In the next method step, ie in the sintering step, the component is compressed into a compact body. The sintering takes place in a vacuum furnace lined with molybdenum. Depending on the alloy used, sintering takes place at different temperatures and in different atmospheres (hydrogen or nitrogen). Normally the sintering temperature for metal parts is 1250 °
To 1450 °. The pores created during the debonding are filled during sintering, and the powder particles are baked into a strong, homogenous, compact body. Compaction is based on a diffusion process that proceeds between individual powder particles. The compression causes the green product to shrink to the final finished product size. Sinter shrinkage during sintering is between 18% and 25%, depending on the alloy powder, and must be taken into account by designing the injection molding tool or female mold appropriately large.

After sintering, the component itself manufactured by the MIM method is completed. However, further dimensioning is then performed or the component is subjected to a special quality assurance process.

The unique protective features obtained in the dependent claims are those that have the unique protective features, despite being dependent on the independent claims. Further, features obtained by the items described in the present specification also belong to the protection scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic axial sectional view of an evaporator combustion chamber made according to the present invention.

[Explanation of symbols]

2 combustion chamber, 4 end face limiting wall, 6 fixing flange, 8 circumferential limiting wall,
10 air supply piece, 12 receiving piece, 16 longitudinal center axis of receiving piece, 18
Air passage opening, 20 air supply casing, 22 flame holding plate, 24 rod,
26 nut, 28 evaporator body, 30 opening, 32 protective ring,
34 holes

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission Date] October 20, 1999 (Oct. 20, 1999)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

15. The evaporator according to claim 8, wherein the perforated evaporator body is formed as a separate injection-molded part manufactured by a metal powder injection molding method. Chamber combustion chamber.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] December 3, 1999 (1999.12.3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 8

[Correction method] Change

[Correction contents]

Claims (18)

[Claims] 1. A method for producing a combustion chamber of a burner for a heating machine or for a thermal regenerator of an exhaust gas / particle filter, the combustion chamber comprising a circumferential limiting wall (8), an end face limiting wall (4) and A coaxial air supply line (10) for the supply of combustion air, possibly entering the combustion chamber (2), and possibly a side tube (12) for mounting the ignition device.
The combustion chamber (2) or at least the combustion chamber part comprising the circumferential limiting wall (8) and the end face limiting wall (4) is integrally injection-molded by a metal powder injection molding method. A method for manufacturing a combustion chamber of a burner, which is manufactured as a molded member. 2. The sinterable metal powder / particles are injected by means of an injection device into a prefabricated female mold in the combustion chamber or part of the combustion chamber, and then the injection-molded body is released from the female mold. The method of claim 1 wherein the injection molded body is then sintered. 3. The sinterable metal powder / particles are embedded in a thermoplastic resin used as a binder and a flow aid before injection into the female mold, after injection and after release from the female mold. The method according to claim 2, wherein the thermoplastic resin is released or debonded again before sintering. 4. The process as claimed in claim 1, wherein a quality assurance process is performed on the sintered injection-molded body of the combustion chamber or of the combustion chamber part. 5. The steel as claimed in claim 1, wherein the metal for the metal powders / particles is steel or a steel alloy, in particular austenitic or ferritic special steel, nickel alloy steel, carburized steel or annealed steel. The production method according to any one of the preceding claims. 6. The process according to claim 3, wherein a polar long chain polyacetal having an additive is used as the thermoplastic resin. 7. A metal powder / particle is compounded or mixed with a thermoplastic resin (binder) in a volume of 35% to 50% to form granules.
The method according to any one of claims 3 to 6. 8. The device according to claim 1, wherein at least the circumferential limiting wall and the end face limiting wall are formed as an integral injection-molded and sintered metal injection-molded part. A combustion chamber at least partially manufactured by the process according to any one of the preceding claims. 9. The combustion chamber according to claim 8, wherein the combustion chamber is an evaporator combustion chamber or an air atomizer combustion chamber. 10. An integrated injection-molded and sintered metal injection-molded part, which is preferably constructed in one piece with a coaxial air supply line (10), the air supply line being combustible. 10. The combustion chamber according to claim 8, wherein the combustion chamber protrudes into the chamber and has an air passage opening on the peripheral wall side inside the combustion chamber. 11. A side receiving tube (12) for receiving an ignition device, in particular a glow plug, in an injection-molded and sintered integral metal injection-molded part.
11), wherein the combustion chamber is integrated. 12. The flame-retardant plate (22) integrated in an integral injection-molded and sintered metal injection-moulded part. Combustion chamber. 13. A swirl flow generator for generating a swirl flow of the supplied combustion air is at least partially integrated in an integral injection-molded and sintered metal injection-molded member. 13. The combustion chamber according to any one of claims 8 to 12, wherein 14. Combustion chamber according to claim 10, wherein the air passage openings (18) are equally distributed in the circumferential direction, in particular in the form of sheaves. 15. A porous evaporator body (28) is provided in the form of a sintered part, which is preferably arranged on the inner peripheral surface of the circumferential limiting wall (8). 15. The combustion chamber according to any one of claims 8 to 14, wherein 16. The method as claimed in claim 8, wherein the porous evaporator body comprises a plurality of material layers having different porosity or a plurality of single-piece parts. Combustion chamber. 17. The porous evaporator body (28) is formed in the form of a separate injection-molded part manufactured by a metal powder injection molding method.
The combustion chamber according to any one of the preceding claims. 18. The combustion chamber according to claim 15, wherein the porous evaporator body is sintered to the remainder of the combustion chamber or to another combustion chamber component.