Method for mounting a mould for casting a cast part from a metal melt

Abstract

A method for mounting a mould composed of mould parts for casting a cylinder block of an internal combustion engine from a metal melt, includes at least one chill, which forms at least one part section of inner surfaces of a cylinder space of the cylinder block, and is positioned and retained at a wall of one of the mould parts. This method provides for moulds to be mounted with chills provided in a mould cavity. This is achieved by holding the at least one chill in its position at least for a specific duration by magnetic forces, which are exerted by a magnet which is arranged on a side of the wall of one of the mould parts facing away from the at least one chill.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application of International Application No. PCT/EP2007/051294, filed on Feb. 9, 2007, which claims the benefit of and priority to German Patent Application No. DE 10 2006 006 132.2-24, filed on Feb. 10, 2006. The disclosure of the above applications are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to a method for mounting a mould composed of mould parts for casting a cylinder block of an internal combustion engine from a metal melt, in which at least one chill, which forms at least one part section of inner surfaces of a cylinder space of the cylinder block, is positioned and retained at a wall of one of the mould parts.

BACKGROUND OF THE INVENTION

Methods and devices are used on a large technical scale, for example in the motor vehicle industry, in order to manufacture the cylinder blocks of internal combustion engines in large numbers. In this situation, there is a requirement, especially in the area of cylinder barrels, for a fine-grain, metallurgical microstructure to be constructed which will guarantee a high load-bearing capacity. Another example where a particularly fine-grain, rapidly solidifying and tough casting microstructure is required is the area of a cylinder block in which the bearings for the crankshafts are formed.

In order to obtain rapid solidification in the casting microstructure, in particular in the casting of light metal melts, metal inserts are introduced into the mould, referred to as “chills”, which include a highly heat conductive material in order to represent a heat sink, by which comparatively large volumes of heat are drawn within a short period of time from the melt coming into contact with the metal inserts. Accordingly, during the casting of cylinder blocks made of aluminum casting material, chills are arranged in such a way, for example, that they form the cylinder barrels in the block which is being cast. The casting material coming into contact with the chills arranged in this way then cools more rapidly than the melt present in the mould which is further away from the chills, with the result that the desired solidification, characterized by a fine-grain microstructure, takes place in the area of the barrels.

One example of how metal inserts are introduced into moulds as chills is provided in DE 195 33 529 C2. In this patent publication, a method for casting an engine block made of aluminum is described, in which the engine block is cast into a sand mould and its cylinder cavities are formed by chills inserted into the sand mould, wherein these chills consist of a brass material, wherein the brass material has a coefficient of thermal expansion of more than 18×10⁻⁶ K⁻¹, adjusted to suit the coefficient of thermal expansion of the aluminum melt being cast in each case. Although this method may allow for the desired microstructure to be specifically created in the finished cast component, it requires the adaptation of the thermal expansion behavior of the chills when being heated to the coefficient of thermal expansion behavior of the aluminum melt. Furthermore, this method has in practice proved difficult, in certain application situations, for the chills to be removed from the completed casting after solidification of the casting material.

Due to the metal inserts' direct effect on the shape retention of the individual casting, the positioning of the metal inserts must in practice always be exact, even under the rough conditions of a casting plant. This has often proved to be an elaborate procedure if the mould as a core package is composed of several mould parts and metal inserts. The term “core packages” is given to casting moulds which are composed of several casting cores. Casting moulds can be easily assembled from core packages, with which even complex and filigree mould cavities and therefore castings can be formed.

A further problem in connection with the use of metal inserts is derived when, as in the example given in DE 195 33 529 C2, the mould is what is referred to as a “lost mould” which is composed of parts manufactured from a mould material and must be destroyed after the solidification of the melt in order to release the finished casting from the mould. In order to be able to position the metal inserts used for cooling in such moulds in a reliable manner and keep them in position, it is necessary for them to be clamped to the moulds, with the mould material surrounding them, with the result that after solidification of the melts they can only be released from the casting with difficulty.

In order to render the release of the metal inserts easier, it has been common hitherto to provide the metal inserts with a ceramic powder coating, with the intention of reducing the risk of damage to the metal inserts when they are removed from the finished casting. There is not only additional effort and expenditure involved with the application of the coating, this arrangement also has the disadvantage that the heat transfer between the casting metal and the insert is impaired, which reduces the cooling effect.

In addition to the prior art referred to heretofore, aimed directly at the assembly of moulds from mould parts and cores, a method and device are known from the German Patent Specification 719 454 for the manufacture of cores or mould parts for moulds made of a core compound or mould compound, which allow for a chill to be retained in the individual mould or core box in such a way that it stands reliably in the position intended for it in the individual core or mould part to be produced in each case. For this purpose, the individual chill is initially positioned in the empty mould or core box, wherein in this position it is in contact in each case with an outer wall of the mould or core box. By means of an electromagnet, which is located in a cut-out formed from the outside into the wall concerned of the mould box and exerts its effect through the wall section present between the electromagnet and the chill, the chill is thereafter held in this position. Once the filling of the core compound or mould compound has been completed, the excitation current circuit of the electromagnet is switched off, with the result that the individual mould part or core can be removed from the box in which the chill is incorporated.

SUMMARY OF THE INVENTION

In one aspect, embodiments of the invention provide a method by which moulds can be mounted for casting cylinder blocks with metal inserts provided in a mould cavity.

One embodiment in accordance with the invention provides a method for mounting a mould composed of mould parts for casting a cylinder block of an internal combustion engine from a metal melt, in which at least one chill, which forms at least one part section of inner surfaces of a cylinder space of the cylinder block, is positioned and retained at a wall of one of the mould parts. The at least one chill is held in its position at least for a specific retention duration by means of magnetic forces, which are exerted by a magnet which is arranged on a side of the wall of one of the mould parts facing away from the at least one chill.

This method is suitable for casting light metal melts, for example aluminum-based melts.

In another embodiment in accordance with the invention, the individual chill, which may also be designated hereinafter as a “metal insert”, is held by magnetic forces, which are exerted by at least one magnet arranged in a suitable manner, in the position in the mould provided with regard to its mounting. The chills are themselves magnetically sensitive. Accordingly, the material for the chills is generally ferromagnetic materials, such as iron and its alloys. In particular, chills used in accordance with the invention can be manufactured from economical and wear resistant materials such as cast iron.

In embodiments in accordance with the invention, the magnet body exerting the retaining forces on the individual chill during the mounting procedure is arranged so that the magnet does not interfere with the casting of the metal melt or other mounting procedures. For example, the magnet can be arranged behind the wall at which the at least one metal insert is positioned in such a way that its magnetic forces penetrate through the wall and hold the at least one insert without a direct contact between the at least one insert and the magnet.

In another embodiment in accordance with the invention it is no longer necessary to embed the chills in a mould part in order to hold them. In fact, the chills can be handled separately from the mould parts so that when mounting the mould they can be handled like a mould part. This leads to a distinct simplification of the production process.

Since the chills in embodiments in accordance with the invention do not have to be firmly embedded into a mould part or into the respective cast part any more, when removing a mould produced by embodiments in accordance with the invention there is also no longer the problem of damage caused to the chills or the cast part when demoulding. Therefore, the chills do not have to be coated and the amount of preparation can be reduced. Instead, chills in accordance with the invention held by magnetic forces can be removed easily from the cast part and the mould parts of the mould after casting. This is advantageous particularly when casting cylinder blocks of internal combustion engines, also referred to as “engine blocks”, in which the chills represent the contact surfaces of the cylinders.

Embedding the chills, which is required by the prior art during production of the mould parts by surrounding them with mould material in a mould, is not required by embodiments in accordance with the invention. Due to the fact that the chills are handled separately when the mould is assembled and are held in position by magnetic forces exerted by an individual retaining device, it is possible, in the case of the use of moulds mounted from mould parts formed from mould material, to dispense with the need to coat the chills with a finish, as is required with the conventional procedure in order to guarantee optimum separation of the individual chill from the cast part produced in each case.

A further advantage of embodiments in accordance with the invention is easy integration into already existing systems.

Another embodiment in accordance with the invention makes possible the manufacture of cast components in a simpler and more economical manner than with the prior art. Such embodiment is particularly well-suited for casting light metal melts, for example aluminum melts.

The mould parts from which a mould is composed are preferably manufactured from a mould material which is mixed from a mould basic material and a binder. Basic materials in this situation can be for example sands containing quartz or free of quartz, whereas binders can be both inorganic as well as organic binders. Such embodiment is particularly advantageous if the mould is formed in a known manner as a core package.

The positioning and retaining of at least one chill in the mould can be carried out in another embodiment in accordance with the invention independently of any specific preparation of the particular location at which the metal part is to be arranged. Accordingly, the positioning of the metal part can in each case be carried out at a time which is determined solely by the optimum operational sequence in each case on mounting the individual mould. The magnet used for the retention can be arranged in such a way in the area of the at least one chill which is to be retained that the forces exerted by the magnet will reliably secure the at least one chill.

In an embodiment, an opening (i.e. aperture) may be formed in one of the mould parts at the wall of which the at least one chill is positioned, into which the magnet is introduced. With this arrangement of the wall of the individual mould part, the magnet used to retain the at least one chill can be moved into close proximity to the at least one chill in order to facilitate the mounting process. In particular, when casting engine blocks of which the barrels are represented by chills, it can be of advantage for this arrangement if the mould part is designed in a mandrel shape with a blind hole aperture, into which the magnet is introduced. With this formation of the mould part concerned, a plurality of chills can be arranged next to one another on the outer surface of one of the mould parts, so that they form in common the inner shape of the individual cylinder and are held jointly by a magnet arranged in the central blind hole aperture.

Another embodiment in accordance with the invention is of importance for practical application, wherein the at least one chill is held in its position by means of the magnet until a further mould part is arranged which then holds the at least one chill in its position, by positive and/or non-positive fit. With this embodiment of the invention, the at least one chill is held in its position by mould parts mounted after its positioning without magnetic forces being required for this. A further advantage of this method is that the position of the at least one chill in the mould can be exactly defined by the other parts of the mould which come into contact with the at least one chill in positive and/or non-positive fit. The retention of the at least one chill by magnetic forces therefore serves, in this embodiment of the invention, only for as long as needed to bridge a situation, undefined with regard to the retaining of the at least one chill in the mould, until the individual chill is held in its position by a further mould part, without the need for any further retention forces to be exerted by a separate retaining device.

In general, all magnets are suitable for the application of the magnetic forces used for the retaining of the at least one chill in accordance with the invention provided the magnets can produce a sufficiently strong magnetic field. Thus, for example, in another embodiment in accordance with the invention, permanent magnets can be provided in order to apply the retaining forces in the manner in accordance with the invention onto the individual chills.

However, if particularly powerful forces are to be applied, and at the same time a particularly precise control of the magnetic retaining forces needs to be achieved, then an electromagnet is particularly well-suited. Electromagnets not only allow for an exact adjustment of the strength of the magnetic field generated by them in each case, but it is also possible with them, in a simple manner, by switching the electric power on and off, to determine precisely the time period within which the magnetic forces are applied on the individual chill in embodiments in accordance with the invention. For this purpose, for example, electromagnets comprising coils can be considered. The magnetic field from such electromagnets can be controlled proportionally to the strength of the current conducted through the coils.

Another embodiment in accordance with the invention provides for the manufacture of a cylinder block of an internal combustion engine including a light metal melt, such as an aluminum or magnesium melt, wherein at least one part section of the inner surfaces of the individual cylinder space of the cylinder block can be formed by one or more chills.

Another embodiment in accordance with the invention provides for application in a fully-automatic device for assembling a mould in which devices such as robots are provided for the handling of the mould parts. Devices in accordance with the invention can position precisely the at least one chill because the retention of this metal insert in its particular position by the magnet is assured, for which no integral joining of the at least one chill to one of the mould parts is required.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter on the basis of drawings representing exemplary embodiments. These show in diagrammatic form:

FIG. 1 A first mould part in a section along the section line A shown in FIG. 3,

FIG. 2 The mould part represented in FIG. 1 in a side view, and

FIG. 3 The mould part represented in FIGS. 1 and 2 in a section along the section line B shown in FIG. 2.

DESCRIPTION

The mould part 1 formed as a single piece is a constituent part of a mould not further represented here for casting a cylinder block for a combustion engine from a melt including an aluminum casting alloy. It is manufactured in an inherently known manner from a mould material which is mixed from a mould sand as the basic mould material and a binder and has a basic section 2, which carries a mandrel section 3 projecting upwards and substantially cylindrical in shape.

The mandrel section 3 has a casing surface 4 which is subdivided by four radially projecting ribs 5 into four part sections. Included in the area of the transition of the mandrel section 3 into the basic section 2 of the mould 1 is a circumferential groove 6 formed into the upper face surface 7 of the basic section running around the mandrel section 3 aligned substantially at right angles to the circumferential surface 4 of the mandrel section 3.

In another embodiment not represented in the Figures, the mandrel section can also have a casing surface, which is divided by radially projecting ribs into two, three or more part sections. In addition the ribs can be designed in contrast to the shape having parallel side walls represented in the Figures conically in cross-section tapering or broadening out. In another embodiment, the mandrel section can also have a casing surface which is not subdivided by additional ribs. In this case the casing surface is entirely surrounded by the chill which is to be accommodated in each case.

With the embodiment represented in the Figures a blind hole aperture 9 is additionally formed into the casting part 1, going outwards from the lower face surface 8 of the basic section 2, opposite the upper face surface 7, wherein this blind hole aperture 9 extends from the face surface 8 of the basic section 2 as far as the closure wall 10 of the mandrel section 3, forming the face side of the mandrel section 3. The diameter of the blind hole aperture 9 in this situation is adapted to the outer diameter of the mandrel section 3 in such a way that only one wall 11 with a low wall thickness is present between the inner faces of the blind hole aperture 9 and the casing surface 4, this wall 11 being sufficient to guarantee the required shape stability of the mandrel section 3.

Inserted into the blind hole aperture 9 is an electromagnet 12, which is secured to the free end of a rod 13. The rod 13 with the electromagnet 12 is part of a device, not further represented in the Figures, for the retaining of metal parts 14, 15, 16, 17, which are put into use as chills by a device not represented in the Figures for positioning at the casing surface 4 of the mandrel section 3.

The rod 13 with the electromagnet 12 can be moved from a position of rest by means of an adjustment device likewise not represented in the Figures, in which the electromagnet 12 is outside the blind hole aperture 9, into the operational position represented in FIG. 1, in which the electromagnet 12 is fully introduced into the blind hole aperture 9. The supply of the electromagnet 12 with electrical energy is effected by a control device, not represented in the Figures, which supplies electrical energy to the electromagnet 12 when the chills 14-17 are positioned, in order to retain them in position.

The height of the chills 14-17 is adapted to the height of the mandrel section 3. In this context the chills in each case have on their upper and lower narrow sides a web 18, 19, projecting upwards and downwards respectively, wherein the lower web 18 engages in the groove 6, so that the chills 14-17 are held in that location in positive fit. At the same time, the chills 14-17 are cambered in such a way that they are located flush with the section of the casing surface 4 of the mandrel section 3 allocated to them in each case. At the same time, the width of the chills 14-17 is adjusted to the width of the sections of the casing surface 4 in such a way that the sections of the casing surface 4 are filled completely by the chills 14-17 located flush with them.

The chills 14-17 are cast as grey cast iron from a cast iron alloy, known under the designation GG20 (as per DIN 1691).

As soon as the chills 14-17 are positioned in the sections of the casing surface 4, the electromagnet 12 is charged with electrical energy. The magnetic field which is then generated by the electromagnet 12 acquires the chills 14-17, and holds them in position at the casing surface 4 of the mandrel section 3.

Next, other parts, not shown in the Figures, of the mould, not shown in the Figures, are mounted. One of the mould parts, not shown in the Figures, has a groove-shaped mounting into which, after positioning of the mould part concerned, the rib 19 engages, wherein the groove-shaped mounting is formed at the upper end of the chills 14-17, such that the chills 14-17 are then also held in positive fit at their upper end. As soon as this state is attained, the energy supply to the electromagnet 12 can be switched off and the rod 13 with the electromagnet 12 can be withdrawn from the blind hole aperture 9.

On casting the cylinder block in the mould, assembled by using the mould 1 and the chills 14-17, the chills 14-17 form the barrels of one of the cylinders of the cylinder block. In this case, the chills 14-17 form a heat sink, which ensures that the aluminum melt coming into contact with the chills 14-17 solidifies rapidly and forms a fine-grain microstructure.

REFERENCE FIGURES

• 1 Mould part
• 2 Basic section
• 3 Mandrel section
• 4 Casing surface of the mandrel section 3
• 5 Ribs of the mandrel section 3
• 6 Groove
• 7 Upper face surface of the basic section 2
• 8 Lower face surface of the basic section 2
• 9 Blind hole aperture
• 10 Closure wall of the mandrel section 3
• 11 Wall of the mandrel section 3
• 12 Electromagnet
• 13 Bar
• 14-17 Chills
• 18, 19 Webs

Claims

1. Method for mounting a mould composed of mould parts for casting a cylinder block of an internal combustion engine from a metal melt, in which at least one chill, which forms at least one part section of inner surfaces of a cylinder space of the cylinder block, is positioned and retained at a wall of one of the mould parts, wherein

the at least one chill is held in its position at least for a specific retention duration by means of magnetic forces, which are exerted by a magnet which is arranged on a side of the wall of one of the mould parts facing away from the at least one chill.

2. Method according to claim 1, wherein an aperture is included at the wall of one of the mould parts of which the at least one chill is positioned, into which the magnet is introduced.

3. Method according to claim 2, wherein one of the mould parts is formed in mandrel shape with a blind hole aperture, into which the magnet is introduced.

4. Method according to claim 1, wherein the at least one chill is held in its position by means of the magnet until a further mould part is arranged which then holds the at least one chill in its position by positive and/or non-positive fit.

5. Method according to claim 1, wherein the magnet is an electromagnet.

6. Method according to claim 1, wherein the magnet is a permanent magnet.

7. Method according to claim 1, wherein the metal melt is a light metal melt.

8. Method according to claim 7, wherein the metal melt is a melt includes aluminum.