A CYLINDER LINER AND METHOD FOR ITS PRODUCTION

Abstract: A light metal, e.g. aluminium alloy, cylinder liner (10) is produced by squeeze forming to incorporate woven glass fibre strengthening elements (18) in the metal matrix of the liner during the squeeze forming operation. Said elements (18) are shaped to extend into radially outwardly projecting flanges (12, 14) and/or over the full length of the liner to provide enhanced strength and stiffness.

Description: A CYLINDER LINER AND METHOD FOR ITS PRODUCTION This invention relates to cylinder liners for internal comhustion engines wherein the liners are formed of a light metal such as an aluminium alloy. Aluminium alloy cylinder liners are generally designed for use in aluminium alloy engine " blocks in lieu of the conventional cast iron or steel cylinder liners. The use of an aluminium alloy liner provides a significant weight saving to the engine as a whole; for example on a typical four-cylinder petrol engine the weight saving for the liners alone could approximate three kilogrammes. Other advantages * of the use of aluminium alloy for cylinder liners are that there is a significant reduction or elimination of differential thermal expansion between the block and the liner (thus simplifying gasket sealing) and between the liner and the piston (thus allowing smaller cold clearances); there is also an increased heat exchange allowing improved engine performance. However, an aluminium alloy liner formed as a dimensional copy of a conventional cast iron liner which it is to replace, would not be acceptable as it would be lacking in both the necessary mechanical strength and stiffness. Thus, where aluminium alloy liners have been utilised they have of necessity been formed of a much thicker material section than is the case with a cast iron liner; hence the potential saving in liner weight has not been fully realised. Proposals have been made to achieve the desired mechanical strength by producing alloy liners by powder metallurgy; the alloy being aluminium-silicon and including inter-metallic compounds for example as disclosed in GB-A-2 131 457. It has also been proposed to produce a cylinder liner with improved anti-scuffing and anti-abrasion properties by a method disclosed in GB-A-1 567 328 wherein fibres are incorporated into and throughout an aluminium matrix by what is described as a high pressure solidification casting method. In this said disclosure, the fibres are distributed through the whole of the cast cylinder liner. It is an object of the present invention to provide a light metal cylinder liner which may be manufactured to provide the requisite strength and stiffness whilst at the same time being economical of metal utilisation. In accordance with the invention there is provided a light metal cylinder liner for an internal combustion engine produced by squeeze forming characterised in that one or more woven glass fibre elements are incorporated in the metal matrix of the liner during the squeeze forming operation to provide enhanced strength to the liner at pre-determined positions therein. The or each said woven glass fibre strengthening element may be incorporated in the metal matrix to extend axially along at least part of the cylindrical wall portion of the liner and, if desired, the or each said element may extend radially of said cylinder wall portion to the radially inner surface of the liner. Preferably the or each woven glass fibre strengthening element is incorporated in the metal matrix at one or more radially outwardly extending flanges of the liner; the preferred arrangement being that the or each said strengthening element is incorporated in the metal matrix to extend axially along a cylindrical wall portion of the liner and radially outwardly of said wall portion into a said flange extending radially outwardly thereof. Also in accordance with the invention there is provided a method of manufacturing a light metal cylinder liner for an internal combustion engine by squeeze forming characterised in that one or more woven glass fibre strengthening elements are located within the mould of a squeeze forming press at one or* ore pre-determined positions corresponding to the or each position at which it is desired to provide enhanced strengthening to the liner; molten light metal is introduced into the mould; the mould is closed under pressure so that molten metal is displaced by the mould closure to cause the metal to penetrate the interstices of the or each said woven glass fibre element; the metal is maintained under pressure whilst solidi ication thereof takes place and the or each said woven glass fibre element becomes embedded in the metal and that the mould is then opened and the squeeze formed liner extracted therefrom. In such method the or each woven glass fibre strengthening element is preferably located in the mould of the squeeze forming press at one or more positions corresponding to the or each position at which a radially outwardly extending flange of the liner is to be formed during the squeeze forming operation; a said woven glass fibre strengthening element thereby subsequently being incorporated in the metal matrix at a said radially outwardly extending flange of the squeeze formed liner. The or each woven glass fibre strengthening element is preferably shaped to extend axially along a cylindrical wall portion of the squeeze formed liner and to extend radially outwardly of said wall portion into a said flange extending radially outwardly thereof. The term "squeeze forming" as used throughout this specification and claims will be understood to refer to a method which comprises introducing liquid metal into a first part of a mould, closing the mould under pressure so that the liquid metal is displaced by the mould closure to fill a cavity within the mould without entrapping air, maintaining "the metal under pressure whilst solidification takes place so as to ensure that any shrinkage cavities which may form are closed and filled, and then opening the mould and removing the formed article. Other features of the invention will become apparent from the following description given herein solely by way of example with reference to the accompanying drawings wherein:- Figure 1 is a diagrammatic side cross-sectional view through a squeeze formed light metal cylinder liner in accordance with the invention having a woven glass fibre strengthening element extending into the radially outwardly extending flanges of the liner, Figure 2 is a stress graph showing stress concentrations at a flange area due to principal stresses, and Figure 3 is a diagrammatic view of the flange area of Figure 2 showing the incorporation of a woven glass reinforcement. In Figure 1 of the drawings there is shown a cylinder liner 10 in the form of a substantially cylindrical element produced by squeeze forming of an aluminium alloy. The formed article is provided with a pair of axially spaced radially outwardly extending annular flanges 12 and 14 whereby the cylinder may be "compression mounted" in an engine block. Referring to Figure 2 of the drawings, it will be seen that stress concentrations due to principal stresses are exhibited principally at and adjacent the .transition area between a mounting flange and the liner body. These stress concentrations could cause failure at the transition area and it is therefore desirable to strengthen such area in accordance with the invention. In accordance with the invention and as shown in Figure 3 of the drawings a strengthening element in the form of a woven glass fibre preform 18 is located adjacent to and extending along the outer surfaces of the flange and liner body. The strengthening element 18 is carefully positioned in the mould cavity of the squeeze forming press prior to the introduction into the cavity of the liquid metal and, during the squeeze forming operation, the said element becomes embedded within the metal alloy matrix with the metal having penetrated the interstices of the woven element 18 during the squeeze forming operation. The alloy may conveniently comprise that known as LM13 which is- a piston alloy. Alternatively the alloy may be that known as LM30 which is a hypereutectic silicon alloy which gives primary silicon crystals in the metal matrix which crystals can be used, after special treatment, as the actual wear surface at the bore 16 of the liner. Such primary silicon crystals can be left proud of the liner bore to increase the wear properties of the metal matrix. It will be appreciated that a squeeze formed light metal cylinder liner having woven glass fibre inserts in accordance with the invention can provide both enhanced strength and stiffness to the liner at pre-determined positions therein. The annular form of woven glass fibre strengthening element provides added hoop strength at those positions of the liner at which the woven elements are provided i.e. at the liner flanges whilst, if desired, the overall strength and stiffness of the liner may be enhanced by providing an annular cylindrical woven glass fibre element to extend axially over substantially the whole length of the cylindrical wall portion of the liner. The actual weave pattern of the glass fibre elements can be selected to suit the particular requirements of strength and stiffening enhancement and the or each said woven element can be provided to a pre-form shape locatable either directly in the mould prior to the introduction o molten light metal thereto or as a "sock" located on the punch of the squeeze forming press. If desired ' , the or each woven glass fibre strengthening element may be incorporated into the metal matrix of the liner to extend radially of the cylinder wall portion thereof to the radially inner surface of the liner.

Claims: CLAIMS 1. A light metal cylinder liner (10) for an internal combustion engine produced by squeeze forming characterised in that one or more woven glass fibre elements (18) are incorporated in the metal matrix of the liner during the squeeze forming operation to provide enhanced strength to the liner at pre-determined positions therein. 2. A cylinder liner as claimed in Claim 1 further characterised in that the or each woven glass fibre strengthening element (18) is incorporated in the metal matrix to extend axially along at least part of a cylindrical wall portion of the liner. 3« A cylinder liner as claimed in Claim 2 further characterised in that the or each woven glass fibre element (18) extends radially of said cylinder wall portion to the radially inner surface (16) of the liner. 4« A cylinder liner as claimed in Claim 1 further characterised in that the or each woven glass fibre strengthening element (18) is incorporated in the metal matrix at one or more radially outwardly extending flanges (12, 14) of the liner. 5. A cylinder liner as claimed in Claim 4 further characterised in that the or each woven glass fibre strengthening element (18) is incorporated in the metal matrix to extend axially along a cylindrical wall portion of the liner and radially outwardly of said wall portion into a said flange (12, 14) extending radially outwardly thereof. 6. A method of manu acturing a light metal cylinder liner (10) for an internal combustion engine by squeeze forming characterised in that one or more woven glass fibre strengthening elements (18) are located within the mould of a squeeze forming press at one or more pre-determined positions corresponding to the or each position at which it is desired to provide enhanced strength to the liner; molten light metal is introduced into the mould; the mould is closed under pressure so that molten metal is displaced by the mould closure to cause the metal to penetrate the interstices of the or each said woven glass fibre element (18); the metal is maintained under pressure whilst solidification thereof takes place and the or each said woven glass fibre element becomes embedded in the metal and that the mould is then opened and the squeeze formed liner (10) extracted therefrom. • * 7. A method according to Claim 6 further characterised in that the or each woven glass fibre strengthening element (18) is located in the mould of the squeeze forming press at one or more positions corresponding to the or each position at which a radially outwardly extending flange (12, 14) of the liner is to be formed during the squeeze forming operation; a said woven glass fibre element thereby subsequently being incorporated in the metal matrix at a said radially outwardly extending flange (12, 14) of the squeeze formed liner (10). 8. A method according to Claim 7 further characterised in that the or each woven glass fibre strengthening element (18) is shaped to extend axially along a cylindrical wall portion of the squeeze formed liner (10) and to extend radially outwardly of said wall portion into a said flange (12, 14) extending radially outwardly thereof.

Inventors: ADDIS PHILIP ROBERT JAMES, BARLOW JOHN, ADDIS, PHILIP, ROBERT, JAMES, BARLOW, JOHN
Applicants: GKN TECHNOLOGY LTD, GKN TECHNOLOGY LIMITED
Application year: 1986
Main classification: F02F1
IPC codes: C22C47, F02B1, F02F1, F16J10