This invention relates to the pre-treatment of iron liners to be cast into aluminium cylinder blocks.
It is common practice in the automotive and engine-manufacturing industry to, wherever possible, keep the weight of the component parts of a vehicle to a minimum. Thus while engine blocks were for long periods cast from cast iron, the cylinder bores were carefully machined to receive the pistons of the engine. However with the introduction of aluminium cylinder blocks, it is necessary to have in the cylinder block an iron cylinder liner in which the piston of the engine operates, due to the fact that aluminium is not a sufficiently wear resistant metal.
It is common practice to position the iron liners in the mould and cast the engine block so that the Iron liners are cast into position. However the liners must be thoroughly cleaned and preheated prior to contact with the molten aluminium metal.
As far as the applicant is aware the cleaning method most commonly employed involves shot blasting the liner with carbon steel shot. This is carried out in a shot blast cabinet, and this process is a difficult process to control based on the orientation of the liners in the shot blast cabinet.
The preheating of the liners is usually by induction heating, using an inductor placed within a void in the centre of the barrel core holding the liner.
The reason for pre-heating the liners prior to casting is to ensure that the lay-up (contact between the parent metal of the cylinder block and the liner) is as high as possible. If a liner is at ambient temperature then the hot liquid metal flowing over it will rapidly cool resulting in defects in the lay-up, these could manifest themselves as cold shuts (two liquid streams coming together but not fusing and leaving a fault line), and gas blows, which are a result of moisture turning to steam and forming a hole in the casting wall.
Because of the potential for heating the liner rapidly, usually within 10 seconds, induction heating is currently the preferred method for preheating the liners in casting operations.
Some of the problems associated with induction heating include:
Fluidised beds are known to be used for heat treatment and also for the cleaning of articles.
It is the object of this invention to provide a solution whereby the problems of cleaning of a liner and the heating of the cylinder liner are overcome.
It is a further object of the invention to provide a means whereby the liner is uniformly preheated to a uniform temperature throughout the liner.
It is a further object of the invention to provide a means whereby the entire liner can be preheated to a selected temperature.
In a preferred form of the invention there is provided a method of providing an iron cylinder liner for incorporation in a cast aluminium block for an internal combustion engine, including the steps of placing tho liner in a heated fluidised bed to simultaneously clean and heat the liner, and positioning the cleaned and heated liner in the sand core of the engine block prior to the casting of the aluminium cylinder block.
Preferably the fluidised bed is heated to the desired temperature.
Preferably the fluidised bed is a fluidised sand bed.
Preferably the sand core receiving the heated liner will be sized to accept the heated and thus expanded liner.
Preferably the subsequent cooling and resultant contraction of the liner will lock the liner onto the sand core in the correct position.
For a better understanding of this invention it will now be described with respect to the preferred embodiment which shall be described herein with the assistance of drawings wherein;
Now referring to the illustrations, and in particular to
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It can be seen then that there are many benefits of using a fluidised sand bed for the heating and cleaning of the liners.
The fluidised bed will result in a scrubbing action on the liners, cleaning them, and by heating the fluidised bed to the required temperature the bed can be heated to +/−1° C. temperature control of the bed media. Anything in the bed will quickly homogenise to the bed temperature. Liners will heat without the differentials seen in induction heating, and the recorded temperature of the bed will be the temperature of the liner, making temperature control easier and more accurate.
The liners will then be taken from the bed preferably by robotic arms and assembled into the sand mould at the required temperature. Because the liner temperature is controlled its expansion will be known, and the sand core receiving the heated liner will be sized to the heated and thus expanded liner. The liner then cools, resulting in its contraction. This contraction will lock the liner onto the sand core in the correct position.
It is thus preferred that the moulds are cast as soon as possible after the liners are assembled into the mould, before the liners have cooled to any degree. Thus resulting in only minimal controlled losses of liner preheat temperature prior to the filling of the moulds. Furthermore, the increased accuracy in temperature control made possible by using fluidised beds makes it possible to compensate for any unwanted cooling in transfer operations by providing additional heating to the liner prior to transfer.
Since the fluidised bed pre-heat cleans all residues from the liner surface without undue wear (as in shot blasting), the liner castings can be reclaimed from un-cast packages and put through the system again.
Thus it can be seen by the invention that there is provided a system whereby articles can be simultaneously cleaned and heated. It is preferred the invention is particularly directed to the cleaning and heating of cylinder liners to be positioned in a sand mould for the casting of aluminium cylinder blocks.
Although one form of the invention has been described in some detail the invention is not to be limited thereto but can include variations and modifications falling within the spirit and scope of the invention
Number | Date | Country | Kind |
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2003900666 | Feb 2003 | AU | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/AU04/00172 | 2/13/2004 | WO | 8/24/2005 |