EP0735247B1 - Method for mounting and for finishing a powder metal valve seat - Google Patents

Abstract

The method concerns mounting and finish shaping of valve seat ring blanks produced by powder metallurgy, with this operation taking in their working position in a seat at the beginning of a gas channel in the cylinder head of an internal combustion engine made of a light alloy. The method is characterised by the fact that a ring blank (1) produced by powder pressing and sintering is introduced with a clearance into a bore by means of a roller tool (4), is then radially expanded by rolling until it is held by the bore wall, and possesses the required dimensions and density. The ring blank (1) is compacted by means of a roller set (6) with a cylindrical envelope to produce finish dimensions corresponding to the wall of the gas channel. A second roller set (8) with a conical envelope on the rolling tool (4) produces further compacting of the ring material, and a valve seat on the free internal edge of the ring with a given angle (45 or 60 deg.). Alternatively, the rolling tool is provided with additional profiled rollers to achieve the required compacting, and to produce given main and auxiliary seating surfaces.

Description

The invention relates to a method for Assembly and finishing of Valve seat rings prefabricated using powder metallurgy according to the preamble of claim 1.

Valve seat rings manufactured using powder metallurgy known for years. They are in the cylinder head of Otto engines suitable for operation with leaded and unleaded fuel as well suitable for gas and diesel engines. The required Density of use for low-wear operation is necessary, is generated by axial pressing. The valve seat rings thus prefabricated must then elaborate to be ground with tight dimensional tolerance be shrunk into the bore of the cylinder head to be able to. Even after installation, there are more chips Edits required. First, the Valve seat and then the transition Valve seat ring / gas channel machined. Such a manufacturing process is e.g. known from US-A-4,896,638.

The known technique of manufacturing and assembling Valve seat rings based on powder metallurgy time consuming and costly. So there is initially a wide variety of press tools Tool parts. In addition, the relatively high Number of different operations a lot Handling work arises and in the individual processes little opportunities for simplification or Improvements exist, so a noteworthy one Achieve cost reduction.

The invention seeks to remedy this. She is pursuing the goal of the production process in manufacturing and assembly of valve seat rings significantly simplify, especially in that a Reduction in total time and therefore one considerable savings in manufacturing costs can be achieved is.

According to the invention, this object is achieved in a process for assembly and finishing of valve seat rings prefabricated by powder metallurgy according to claim 1.

Unlike the previously known method, the new process of the prefabricated valve seat ring with the help of a known roller burnishing tool Installation in the mounting hole in the cylinder head radial expansion to finished dimensions with usage density condensed. The main advantages of such a process are fewer production and assembly operations, less use of materials and significantly lower costs. Further advantages are discussed below.

Advantageous further refinements of the inventive method are in the Subclaims described.

In the method according to the invention, the prefabricated valve seat ring first with the Rolling tool fed to the mounting hole and then expanded. In cases where the finished valve seat with its inner surface aligned with the wall of the gas duct, the Ring body according to the invention with a set of rollers cylindrical envelope contour to that of the cylindrical Finished dimensions adapted to the wall of the gas duct. The rolling process is carried out by rotation simultaneous spread of those on the circumference Rolling by setting the cone of the roller burnishing tool carried out. The expansion gives the valve seat ring in the mounting hole form-fitting hold. At the same time with the transition also becomes condensing Valve seat ring / gas channel processed by roller burnishing.

According to an advantageous development of the invention is then using a roller burnishing tool provided second set of rollers with tapered Wrapping contour on the free inner edge of the Annular body of the valve seat under a predetermined Angle of z. B. 45 ° or 60 ° by rolling simultaneous further compression of the material generated. Side seats can also be used Rolling are formed. When generating The valve seat ring in receives seat and side seats this area of use density.

The method according to the invention offers the others Advantage that valve seat rings are easier than before a contoured inner surface can be produced, the lateral surface also opposite the gas channel can protrude. For this purpose, according to the invention a roller burnishing tool with a roller set Profile roles applied and the pre-made Valve seat ring after feeding into the location hole first expanded and in one operation Finished dimension with the desired contoured Inner surface compressed.

Another advantageous development of the invention is that the prefabricated ring body during the radial expansion even after contact closure the wall of the receiving bore initially in Rotation is offset, being by the resulting heating of the parts Friction weld connection is created.

In addition to the advantages mentioned, the invention offers other important advantages such as less material, no disposal of chips, the cylinder head does not have to be heated, the valve seat rings do not have to be supercooled and the rolling results in comparison for machining surfaces with high Load share.

In valve construction, roller burnishing tools are being installed already used by steel seat rings. Here becomes a finished in terms of its state of use Seat ring by radial expansion into the bore of one Fitting made of gray cast iron. Any Post-processing of the steel ring such as compacting or Deformation is not carried out here.

Fig. 1

einen zugeführten Ventilsitzring vor dem Expandieren,

Fig. 2

ein Rollierwerkzeug in Verbindung mit einem expandierten Ventilsitzring,

Fig. 3

eine weitere Arbeitsstellung des Rollierwerkzeugs der Fig. 2,

Fig. 4

ein Rollierwerkzeug mit einem zweiten Rollensatz mit Profilrollen,

Fig. 5

ein Rollierwerkzeug mit einem einzigen Rollensatz mit Profilrollen und

Fig. 6

den Zustand des Rollierwerkzeugs der Fig. 5 am Ende des Bearbeitungsvorgangs.

The invention is explained in more detail below on the basis of exemplary embodiments shown schematically in the drawing. The individual figures show sections of a receiving bore at the end of a gas channel as sections in a radial plane. It shows:

Fig. 1

a supplied valve seat ring before expanding,

Fig. 2

a roller burnishing tool in connection with an expanded valve seat ring,

Fig. 3

another working position of the roller burnishing tool of FIG. 2,

Fig. 4

a roller burnishing tool with a second roller set with profile rollers,

Fig. 5

a roller burnishing tool with a single roller set with profile rollers and

Fig. 6

5 at the end of the machining process.

Fig. 1 illustrates a prefabricated Ring body 1 within a receiving bore 2 of a Cylinder head 3 before its further processing. The ring body 1 is supplied with a per se known roller burnishing tool, which is not shown in FIG. 1 is indicated. By setting the cone with the ring body 1 becomes the roller of the rolling tool held.

In Fig. 2 the ring body 1 is expanded and on Fit dimension compressed. From the burnishing tool 4 is the Head shown with the cone 5 on its Scope of a roller set 6 with a cylindrical Wrapping contour carries. The rolling process will by the rotation of the tool 4 at the same time Spreading of the rollers 6 located on the circumference Instead of the cone 5 performed. The expanding gives the ring body 1 a positive hold in the Location hole 2. After expanding the transition ring body 1 / gas channel 7 also worked.

The assembly of the ring body 1 can also be as follows be performed. By an appropriate Control of the cone 5 can when starting Contact of the ring body 1 with the wall the receiving bore 2 an initial further rotation of the ring body 1 for heating the material the mounting hole 2 and thus to one Friction welded connection with a positive fit of the Guide ring body 1.

For the final creation of the actual one The head of the roller burnishing tool 4 contains the valve seat a second roller set 8 with a tapered Wrapping contour. By moving the head axially comes the second set of rollers 8 on the free inner edge of the ring body 1 for use. With this second roller set 8, the valve seat 9 under an angle of z. B. 45 ° with further compression of the material rolls.

4 is a head of a roller burnishing tool 4 a modified version with regard to second set of roles, in which the Rollers 10 are designed as profile rolls Seating and side seats in one step to be able to roll.

Another embodiment of a head of a The roller burnishing tool 4 is shown in FIGS. 5 and 6 illustrated. In this embodiment the arranged on the cone 5 roles as Profile rollers 11 formed. It is for the Surface of the rollers 11 selected such a profile, that after expanding the ring body 1 Valve seat ring is formed, one against the Gas channel 7 protruding contoured inner surface having. In the one shown in Fig. 6 Embodiment has the inner surface 12 in essentially a funnel-shaped constriction Course, the transitions rounded at the edges are. Such a valve seat ring is also in one Rolling operation to the desired one Finished dimension compressed.

Claims (8)

1. A method of fitting and finishing valve seat rings prefabricated by powder metallurgy, in their position of use in a receiving bore intended for same at the beginning of a gas duct in the cylinder head of internal combustion engines comprising light metal alloys, for example on an Al-basis, characterised in that a respective ring body (1) which is prefabricated by powder pressing and sintering is introduced with play into a bore (2) by means of a rolling tool (4), then radially expanded by rolling until positively lockingly held to the wall of the bore, and compacted to the finished size with its operational density.
2. A method according to claim 1 characterised in that the ring body (2) is compacted by a roller set (6) with a cylindrical envelope contour to the finished size which is matched to the cylindrical wall of the gas duct (7).
3. A method according to claim 2 characterised in that at the same time as the compacting operation the valve seat ring/gas duct transition is also processed by rolling.
4. A method according to claim 2 or claim 3 characterised in that, by means of a second roller set (8) with a conical envelope contour, provided on the rolling tool (4), the valve seat is produced at the free inside edge of the ring body (1) at a predetermined angle of for example 45° or 60° by rolling with simultaneous further compacting of the material.
5. A method according to claim 2 or claim 3 characterised in that, by means of a second roller set with profile rollers (10), provided on the rolling tool (4), seat surfaces and secondary seat surfaces are produced on the ring body (1) by rolling with simultaneous further compacting of the material.
6. A method according to claim 1 characterised in that the ring body is compacted with a roller set with profile rollers (11) to a finished size with a contoured internal peripheral surface (12).
7. A method according to claim 6 characterised in that an internal peripheral surface (12) which projects with respect to the wall of the gas duct (7) is produced.
8. A method according to one of claims 1 to 7 characterised in that during the radial expansion the ring body (1) is also initially caused to rotate after coming into contacting relationship with the wall of the bore and a frictional welded join is produced by the resulting rise in temperature of the parts.

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