GB2335253A

GB2335253A - A piston having a cooling chamber and ring carrier cast simultaneously

Info

Publication number: GB2335253A
Application number: GB9904787A
Authority: GB
Inventors: Peter-Klaus Esser
Original assignee: Federal Mogul Burscheid GmbH
Current assignee: Federal Mogul Burscheid GmbH
Priority date: 1998-03-07
Filing date: 1999-03-02
Publication date: 1999-09-15
Also published as: DE29823552U1; FR2775627A1; GB9904787D0

Abstract

A method of making a piston 1 comprises the steps of placing a ring carrier 4 in a casting mould 7, the ring carrier 4 being held in supporting engagement with the sides of the mould 7, fixing a soluble core 3 to a plurality of studs 5 extending from the ring carrier 4 and then casting the piston 1. After cooling the soluble core 3 is washed out through bore holes leaving a cooling channel in the piston 1. The core 3 may be attached to the studs by a bayonet-type connection (figure 3).

Description

2335253 Method of making a piston for internal combustion engines This

invention relates to a method of making a piston for internal combustion engines, with a surrounding annular cooling channel in the piston head at the level of the uppermost ring groove, the cooling channel being formed using a dissolving core in a casting mould, as well as a ring carrier cast into the ring groove.

High performance pistons of internal combustion engines are often cooled by the engine lubricating oil, in that the oil is fed through various channels and bores into the region of the inside of the piston head. The ring groove for the uppermost piston ring is subjected to the highest temperature stresses and is therefore provided with a ring carrier in Diesel engines as reinforcement. The reinforcement consists of a metal which is resistant to abrasion.

A cast light metal piston for internal combustion engines is disclosed in DE 4 438 703 Al, in which a metal tube is cast into the piston head as a cooling channel. The ring carrier is also cast in.

In order to cast in both components these are usually previously annealed. The ring carrier is moreover previously dipped into an aluminium alloy, in order to create an intimate bond with the cast metal. In order that the position of the metal tube shall not alter while it is cast in, retaining pins have to be used, which hold the tube in position. The ring carrier is held by separate devices. Retaining pins have the disadvantage that the pins alter their position in large production runs after several production cycles, which makes placement of the metal tube difficult.

In order to avoid this problem cooling channels have already been made with soluble cores of salt, which are held in the mould without retaining pins. DE 19 649 363 Al discloses a method in which the soluble core is clamped in the hollow space of the mould. The soluble core is so designed to this end that it projects radially outwardly and thus simultaneously forms a groove for the ring carrier to be fitted later in a separate working step. It is not possible to cast in the ring carrier simultaneously in this way.

The invention is based on the object of providing a method of making a piston for internal combustion engines in which the use of retaining pins-is obviated while cooling channels and ring carriers are nevertheless cast in in one working step and the cooling effect of the cooling channel is improved at the same time.

This object is met according to the invention by the characterizing features of claim 1. Advantageous arrangements of the invention appear from the dependent claims.

The method according to the invention provides the possibility of arranging the soluble core and the ring carrier in the same plane. The result is better dissipation of heat through the cooling channel. Moreover the studs projecting into the cooling channel have a positive effect on the heat removal, since they are bathed in oil. The connection effected between the ring carrier and the soluble core is designed as a screw connection and can thus be automated in a simple way by means of a suitable device.

The invention is shown in the drawings with reference to one embodiment and is explained in more detail below. In the drawings:

Fig. 1 is a view of a piston according to the invention in the casting mould, Fig. 2 is a plan view of a ring carrier with the soluble core, Fig. 3 is a section III-III in Fig. 2.

A preferred embodiment of a piston 1 for internal combustion engines is shown in Fig. 1. The piston 1 shown in the casting mould is initially a blank after removal from the mould and has to be further machined. The further machining steps necessary to the function of the piston are not explained in detail in what follows. only the manufacture of the cooling channel and the ring groove is described.

The piston 1 (shown in chain-dotted lines) is made from an aluminium alloy in a mould 7 with a plurality of mould parts 2, 2', 2''. The illustrated soluble core 3 and the ring carrier 4 are pre-heated before the casting. The ring carrier 4 is so constructed that it can be quickly attached by means of a bayonet-type connection to the soluble core, which can be made of.salt for example. To this end three fixing elements in the form of studs 5 are provided on the inner periphery of the ring carrier, which can be engaged in recesses 6 of the soluble core 3 by relative rotation. The quick-connect attachment (Fig. 3) is an important feature of the manufacturing method and facilitates the method according to the invention.

The ring carrier 4 consisting of a cast iron alloy or other alloy harder than the remainder of the piston must be dipped into an aluminium melt before being cast in, in order to create a good bond to the casting material. The ring carrier 4 thus sheathed completely in an Al layer is placed in the casting mould 7 and held in position. This can be through suitable features on the mould parts 2, 2'' of the casting mould for example. Only after introducing the ring carrier.4 is the connection of the soluble core 3 to the ring carrier 4 effected, in that the soluble core 3 is fitted so as to engage its recesses 6 with the studs 5 and is then turned.

The soluble core 3 is connected in this way to the ring carrier 4, without additional retaining pins being necessary.

After the casting operation, suitable bores are drilled in the piston to enable the soluble core to be washed out. Following removal of the soluble core 3 a cooling channel is created, into which the studs 5 of the ring carrier 4 project and are thus bathed in the oil of the engine, whereby the heat dissipation is improved, the engine oil circulating through the bores through which the soluble core was washed out.

Claims

3.

A method of making a piston for internal combustion engines, with a surrounding annular cooling channel in the piston head at the level of the uppermost ring groove, the cooling channel being formed using a soluble core in a casting mould, as well as a ring carrier cast into the ring groove, characterized in that the ring carrier (4) in fitted in the mould (7) and held in position and, after fitting the ring carrier (4) the soluble core (3) is fixed on a plurality of fixing elements of the ring carrier (4), and in that-the fixing elements are cast in together with the ring carrier (4) and the soluble core (3).

A method according to claim 1, characterized in that the ring carrier (4) has radially inwardly projecting fixing elements on the inner peripheral surface, which are formed as studs, which can be engaged in corresponding recesses (6) of the soluble core, so that the soluble core (3) is held concentric with the ring carrier (4).

A method according to claims 1 and 2, characterized in that three studs (5) offset by 120' are provided.

4. A method according to claims 1 to 3, characterized in that the studs (5) are connected to the ring carrier (4) in one piece.

A piston for internal combustion engines with a surrounding annular cooling channel in the piston head at the level of the uppermost ring groove, the cooling channel being formed by use of a soluble core (3) in a casting mould (7), as well as a cast in ring carrier (4) in the ring groove, produced by the method according to claims 1 to 4, characterized in 1 that the ring carrier (4) has studs (5) on the inner peripheral surface extending radially into the cooling channel.

6. A piston according to claim 5, characterized in that the studs (5) extend approximately into the middle of the cooling channel.

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