GB2236497A

GB2236497A - Apparatus for use in the manufacture of light-alloy pistons for internal combustion engines

Info

Publication number: GB2236497A
Application number: GB9021124A
Authority: GB
Inventors: Siegfried Mielke; Manfred Bordt; Franz Schnaberich; William Coelingh; Emmerich Ottliczky
Original assignee: Kolbenschmidt AG
Current assignee: Kolbenschmidt AG
Priority date: 1989-09-29
Filing date: 1990-09-28
Publication date: 1991-04-10
Also published as: GB9021124D0; DE3932562A1; FR2652526A1

Abstract

Apparatus for use in the manufacture of light-alloy pistons for internal combustion engines, particularly diesel engines, which pistons are made by pressure diecasting and comprise inserts or cores embedded adjacent to the piston head, the piston skirt and/or to the gudgeon pin bosses. The apparatus comprises supporting element(s) for positioning the inserts to be self-supporting in a fixed position in the cavity of the mould. The supporting element(s) may be a wire spring member (1) with recesses (2, 3) which support a salt core (4) for forming a cooling gallery. Alternatively a fibrous insert has recesses receiving a salt core and a male mould punch member (Fig, 3, not shown) has protrusions to steady the core against displacement. <IMAGE>

Description

1 2::E 3 C 4,E:-:) '7- Title: APPARATUS FOR USE IN THE MANUFACTURE OF

LIGHTALLOY PISTONS FOR INTERNAL COMBUSTION ENGINES This invention relates to apparatus for use in the manufacture of light- alloy pistons for internal combustion engines, particularly diesel engines, which pistons comprise inserts to be embedded adjacent to the piston head, the piston skirt and/or to the gudgeon pin bosses and which are made by a pressure diecasting process where the molten material which has been charged into a mould is caused to solidify under high pressure.

In the manufacture of diesel engines, the piston technology must take new developments into account, such as the increase of the ignition pressures and the thermal insulation of the combustion chamber. In addition to structural features, the carrying capacity of the piston materials has been increased and new materials having a lower thermal conductivity have been adopted.

In pressure diecasting, the molten material is charged into a casting mould under a pressure which can be selected as desired, and the molten material is thence used to solidify in the mould under a high pressure in excess of 1000 bars. In this process the strength of the aluminiumsilicon alloys and magnesium alloys generally used in piston manufacture can be raised to the required level. Pressure diecasting is very suitable for making fibre-containing composites because the high casting pressure permits shaped fibrous bodies to be relatively easily penetrated by the molten material. The final pressure in excess of 1000 bars results in an atomic spacing of the molten material and fibres so that the controlled reaction can take place which is required for a good bond between the fibres and the molten material. However, it has been found that it is difficult to provide inserts which are selectively embedded in the piston, such as shaped fibrous bodie;-,, 2 removable cores made of sand, salt or foamed graphite or the like, because it is not possible reliably to position the inserts in the mould cavity so as to avoid damage, so that the charging of the molten material into the mould may be accompanied by a floating or subsiding of the inserts on or in the molten material and/or damage may result during the application of pressure.

DE-C-12 50 605 and DE-C-38 07 986 disclose means for fixing compacted cores of sand or salt to core elements which are intended for use in the casting of pistons for internal combustion engines, or to expansion control elements to be embedded in the piston casting, but said means cannot be used in a pressure diecasting process.

For this reason, it is an object of the present invention to provide for use in the manufacture of light-alloy pistons for internal combustion engines, particularly for diesel engines, which pistons comprise inserts, which are selectively embedded in the piston made by pressure diecasting, an apparatus which is so designed that the inserts can be reliably positioned in the mould without the risk of damage and will not change their position in a radial and/or axial direction in the molten material.

According to the present invention, there is provided an apparatus for use in the manufacture of light-alloy pistons for internal combustion engines, which pistons comprise one or more inserts to be embedded adjacent to the piston head, the piston skirt and/or to the gudgeon pin bosses and which are made by pressure diecasting, with molten material which has been charged into the mould being caused to solidify under high pressure, wherein one or more supporting elements is or are disposed in the cavity of the mould and serve(s) to hold the insert(s) in a self- supporting condition in a fixed position against radial and/or axial movements.

3 In accordance with a preferred feature of the present apparatus, the or each supporting element consists of a wire spring or strip spring element which has bends for receiving the insert(s). In accordance with a further feature of the apparatus, the spring element(s) is(are) secured to the mould by hooking or inserting the ends of the spring element(s) into suitable recesses of the mould. Alternatively, the spring element(s) may be secured to gate means connected to the mould.

For making pistons having a ring carrier, which consists of special austenitic cast iron or of a shaped fibrous body and is embedded in the ring zone, preferably adjacent to the first ring groove, it is desirable to secure the spring element to the ring carrier, which is connected to the mould, and to that end the ends of the spring elements are desirably inserted into suitable recesses of the ring carrier.

The present apparatus can particularly be used to manufacture those lightalloy pistons in which a removable annular core made of sand, salt or foamed graphite and serving to provide a coolant-conducting cavity is to be embedded in the casting on the level of the first ring groove.

It is also possible to provide supporting elements which consists of pinlike projections on the movable half of the mould on the piston head side and which serve axially to position the insert, preferably the core for forming a coolant-conducting cavity, and prevent the insert from floating in the molten material or, if a spring element is used, force the insert into the bends of such spring element. The bores for supplying and withdrawing the coolant to and from the coolant-conducting cavity can desirably be formed in the recesses which have been formed in the cast piston by the action of the pin-like projections.

4 The present apparatus will be particularly useful in the manufacture of a light-alloy piston, which is preferably cast with the piston head facing downwardly and which comprises a shaped fibrous body, which is to be inserted into the mould and constitutes the piston head or the rim of the combustion chamber recess in the piston head, and which piston also comprises a ring carrier, which is connected to the mould and embedded in the piston casting adjacent to the ring zone, preferably adjacent to the first ring groove, and an annular core, which is embedded in the casting on the level of the first ring groove and lies on the shaped fibrous body and is made of sand, salt or foamed graphite and serves to form a coolantconducting cavity and is removable from the cast piston, and is formed by the pin-like projections into a mating annular groove in the shaped fibrous body.

In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings, which illustrate diagrammatically and by way of example two embodiments thereof, and in which:- Figure 1 is a side elevation of a supporting element for a core, Figure 2 is a sectional view of a mould, and Figure 3 is a sectional view of another mould.

Referring now to Figure 1, there is shown a spring wire element 1, which has two bends 2, 3, into which an insert has been inserted which consists of a core 4 of water-soluble salt. The core 4 is intended to define an annular coolant-conducting cavity in the piston in the region behind the first annular groove.

Figure 2 shows a mould 5,6 into which molten material has been charged. The wire spring element 1 and the salt core 4 connected to the spring element 1 have been inserted in the mould by hooking the free ends of the wire spring element 1 into bores formed in a ring carrier 7, which consists of austenitic special cast iron. As a result, the salt core 4 is held reliably and without damage as molten material is charged into and pressurised in the cavity 8 of the mould 5, 6.

Figure 3 is a sectional view showing another mould 9, 10 and molten material charged into said mould. A shaped fibrous body 11 lies on the bottom of the stationary mould half 9 and in a properly designed annular groove 13 supports a removable salt core 12 so as to prevent radial displacement of the salt core 12. The salt core 12 is to be embedded in the light-alloy piston in the region behind the first ring groove to be cut into the ring carrier 16. Pin-like projections 14, 15 are attached to the movable top half 10 of the mould and force the salt core against the shaped fibrous body 11 to prevent the salt core from floating in the molten metal. A recess formed in the inside surface of the cast piston 17 by means of each of the pin-like projections 14, 15 will be formed with bores for supplying and withdrawing coolant to and from the coolantconducting cavity.

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Claims

CLAIMS:

Apparatus for use in the manufacture of light- alloy pistons for internal combustion engines, which pistons comprise one or more inserts to be embedded adjacent to the piston head, the piston skirt and/or to the gudgeon pin bosses and which are made by pressure diecasting, with molten material which has been charged into the mould being caused to solidify under high pressure, wherein one or more supporting elements is or are disposed in the cavity of the mould and serve(s) to hold the insert(s) in a self-supporting condition in a fixed position against radial and/or axial movements.
2. Apparatus according to Claim 1, wherein the or each supporting element consists of a wire spring or strip spring element, which is formed with bends for receiving the insert(s).
3. Apparatus according to Claim 2, wherein the spring element(s) is(are) secured to the mould.
4. Apparatus according to Claim 2, wherein the spring element(s) is(are) secured to gate means which are connected to the mould.
5. Apparatus according to Claim 3 or 4, wherein the ends of the spring element(s) is(are) inserted into suitable shaped recesses of the mould or of the gate means connected to the mould.
6. Apparatus according to Claim 4 or 5, wherein, for making a light-alloy piston having a ring carrier which consists of special austenitic cast iron or of a shaped fibrous body and is embedded in the ring zone, the insert(s) is(are) secured to the ring carrier by one or 7 more spring elements by which the insert(s) is(are) positioned to be self- supporting.
7. Apparatus according to any one of Claims 1 to 6, wherein the insert consists of a core, which is made of sand, salt or foamed graphite and is removable from the cast light-alloy piston and serves to form a coolantconducting cavity.
8. Apparatus according to any one of Claims 1 to 7, wherein the supporting elements comprise pin-like projections which are secured on the piston head side to a movable half of the mould and serve axially to position an insert which consists of a core for forming a coolant- conducting cavity.
9. The use of the apparatus according to Claim 8 for the manufacture of a light-alloy piston which is to be cast with the piston head facing downwardly and which comprises a shaped fibrous body which is to be inserted into the mould and constitutes the piston head or the rim of the combustion chamber recess in the piston head, and which piston also comprises a ring carrier, which is connected to the mould and embedded in the piston casting adjacent to the ring zone, and an annular core, which is embedded in the casting on the level of the first ring groove and lies on the shaped fibrous body and is made of sand, salt or foamed graphite and serves to form a coolant-conducting cavity and is removable from the cast piston and is forced by the pin-like projections into a mating annular groove in the shaped fibrous body.
10. The use of the apparatus according to Claim 8, wherein the core is forced into an annular groove of the shaped fibrous body.

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11. Apparatus for use in the manufacture of lightalloy pistons for internal combustion engines substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.
12. A light-alloy piston which has been pressure die cast using the apparatus claimed in any one of Claims 1 to 8 and 11.

Published 1991 at Me Patent Office. State House. 66171 High Hoiborn. London WC1 R 47P. Further copies Tnay be obtained frorn Sales Branch. Unit 6. Nine Mile Point Cwmfelinfach, Cross Keys. Newport. NP1 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent.