Antipolishing ring

Abstract: An antipolishingring (4) to be used in a cylinder (1) of a large diesel engine, which is supported to a cylinder liner (2) for the purpose of removing possible carbon deposit and carbon residue from the upper portion of a piston (3). The antipolishingring (4) is provided with an arrangement, by means of which the lower edge (4b) of the antipolishingring can be pressed in the radial direction of the cylinder inwards towards the mantle surface of the upper portion of the piston so that the proportion between the diameters of the lower edge (4b) and the upper portion (4a) of the antipolishingring is at its minimum while the engine is running.

Description: The invention relates to an antipolishing ring to be used in a cylinder of a large diesel engine, which is supported to a cylinder liner and the purpose of which is to remove possible carbon deposit and carbon residue from the upper portion of a piston in accordance with the preamble of claim 1. In prior antipolishing ring solutions the inner diameter of the ring is usually slightly smaller than the diameter of the cylinder. If the piston has to be removed out from the cylinder at the maintenance of the engine, also the antipolishing ring has then first to be removed, because otherwise there is not enough space for the piston to be taken out from the cylinder. This fact naturally makes maintenance operations of this kind slower and more difficult to accomplish. An antipolishing ring of this art is known from DE-A-3038235. An object of the invention is to create a new antipolishing ring solution, by means of which i.a. the abovementioned disadvantage in the known solutions can be eliminated. The aim of the invention can be met as is described in claim 1 and in the other claims. In accordance with the invention by providing the antipolishing ring with an arrangement, by means of which the lower portion of the antipolishingring can be pressed in the radial direction of the cylinder inwards towards the mantle surface of the upper portion of the piston so that the proportion between the diameters of the lower edge and the upper portion of the antipolishing ring is at its minimum while the engine is running, the antipolishing ring may be dimensioned so that its diameter is of the same size or almost of the same size as the cylinder liner when it is in the normal temperature, i.e. when the engine is not in use. Then the piston can be pulled past the antipolishing ring out from the cylinder, which makes maintenance of the engine more uncomplicated. According to an embodiment the antipolishing ring is assembled of at least two parts of different material, the thermal expansion of which differ from each other substantially and which are located so that the part, the thermal expansion of which is greater, forms a ring-like element encircling the lower portion of the antipolishing ring and pressing, in the running temperature of the engine, the lower portion of the antipolishing ring towards the piston. In practice the antipolishing ring may then be made of so called invar metal alloy, whereby the said element may advantageously be of aluminium, steel or the like metal having a substantially high thermal expansion coefficient. For example the thermal expansion coefficient of aluminium is of its order of magnitude more than 20 times and of steel clearly more than 10 times higher than that of the invar alloy. The said element may comprise also two or several separate layers arranged radially one inside the other. The element may also comprise several segments or bars, the longitudinal thermal expansion of which causes the desired press effect. Said element may also comprise a hollow space, which may be filled with an expanding pressure medium, for instance by gas, liquid of melted metal. In a further alternative embodiment the said arrangement includes means, for example a set of screws or the like, by means of which the lower portion of the antipolishing ring can be pressed mechanically in the radial direction of the cylinder inwards towards the mantle surface of the piston. In this case the screws can be arranged to effect on the antipolishing ring also through a half-viscose elastomer portion or through a plastic portion. In this embodiment the said supplementary portions are in practice segments, which together form a pressure portion encircling the antipolishing ring. According to a further alternative embodiment the antipolishing ring comprises a set of pressure elements with hollow inner portion to be filled with a pressure medium and the pressure of which is adjustable by means of the said screws or the like. Specially suitable for the purpose are pressure mediums, which are heat-resistant, solidifying and keep well their volume in the operation temperatures of the engine. In practice the pressure medium may with advantage contain for example one or several silicone compounds, for instance silicone rubber and PDMS (polymethylsiloxane), and suitable filling material, for example glass fibre, carbon fibre or the like. In the following, the invention will be described, by way of example, with reference to the enclosed drawing, in which Fig. 1 shows a prior art solution for an antipolishing ring in section, Figures 2-6 show different embodiments of an antipolishing ring according to the invention in section. Fig. 7 is partial section VII-VII of Fig. 5. In the drawing 1 indicates a cylinder of a large diesel engine, inside a cylinder liner 2 of which a piston 3 is arranged to move back and forth. The cylinder liner 2 is provided with an antipolishing ring 4, which in the prior art solution of Fig. 1 forms a small step, the purpose of which is to remove carbon deposit and carbon residue possibly depositing at the upper portion of the piston during the operation of the engine. The upper portion of the piston 3, correspondingly, has a slightly smaller diameter. Therefore, the piston cannot be removed from the cylinder without first removing the antipolishing ring 4. Figures 2-6 show, correspondingly, different solutions according to the invention, in which the diameter of the upper portion 4a of the antipolishing ring 4 nearly corresponds the inner diameter of the cylinder liner 2, but which comprise an arrangement, by means of which a lower portion 4b of the antipolishing ring 4 may be pressed in the radial direction of the cylinder liner towards the mantle surface of the upper portion of the piston so that a desired effect for removal of carbon deposit and carbon coal is achieved. An arrangement according to Fig. 2 is based on a bimetal solution, in which to the lower portion of the antipolishing ring is installed a ring-formed element 5 encircling it and the thermal expansion coefficient of which is substantially higher than of the actual antipolishing ring 4. In this case in the operating temperature of the engine the thermal expansion of the element 5 causes the phenomenon shown in Fig. 2, according to which the lower portion 4b of the antipolishing ring is pressed inwards towards the mantle surface of the upper portion of the piston. The element 5 may with advantage be a divided ring or may comprise a set of segments or bar-like members. In the solution of Fig. 3 the element 5 comprises a uniform ring, the thermal expansion of which, correspondingly, causes the lower portion 4b of the antipolishing ring to be pressed towards the piston when the engine is in use, whereby the temperature at the same time essentially rises. Fig. 3 shows the solution in normal temperature, whereby the engine, thus, is not in use. In this case the element 5 does not prevent pulling the piston out from the cylinder. In the solution of Fig. 4 the element 5 comprises a hollow space 5a, which can be filled with some suitable pressure medium for achieving and further increasing the aforementioned pressing effect. The solution of Fig. 5 for its part comprises a pressing element 7 with a hollow inner space 7a, which can be filled up with a pressure medium and communicating with outer space, whereby the pressure of the inner space 7a and, thus, the pressure effect to be provided can be controlled by means of a screw 6. The elements 7 may advantageously be segments each being provided with an adjusting screw 6 of its own. This is illustrated by Fig. 7, which is a partial section of Fig. 5 and where the pressing element 7 includes four separate segments. The solution of Fig. 6 comprises an element 8 mechanically pressable by means of the screw 6. Also in this case the elements 8 are advantageously segments. The adjusting arrangements of Figures 5 and 6 are shown only as principle solutions, the practical implementations of which can be carried out in many different ways. In order to have the pressing effect under control on different sides of the piston, a sufficient amount of adjusting screws are needed together with some common control system. Also the selections of materials and pressure mediums relating to the different solutions may be carried out, in addition to what has been said above, in different ways within the scope of conventional professional skills in the art. The invention is, thus, not limited to the embodiments shown, but several modifications thereof are feasible within the scope of the attached claims.

Claims: An antipolishing ring (4) to be used in a cylinder (1) of a large diesel engine, which is supported to a cylinder liner (2) for the purpose of removing possible carbon deposit and carbon residue from the upper portion of a piston (3), characterized in that the antipolishing ring (4) is provided with an arrangement, by means of which the lower portion (4b) of the antipolishing ring can be pressed in the radial direction of the cylinder inwards towards the mantle surface of the upper portion of the piston so that the proportion between the diameters of the lower edge (4b) and the upper portion (4a) of the antipolishing ring is at its minimum while the engine is running. An antipolishing ring according to claim 1, characterized in that it is assembled of at least two parts (4;5) of different material, the thermal expansion of which differ from each other substantially and which are located so that the part, the thermal expansion of which is greater, forms a ring-like element (5) encircling the lower portion (4b) of the anti-polishingring and pressing, in the running temperature of the engine, the lower portion (4b) of the antipolishing ring towards the piston. An antipolishing ring according to claim 2, characterized in that it is made of so called invar metal alloy and the said element (5) is of aluminium, steel or the like metal having a substantially high thermal expansion coefficient. An antipolishing ring according to claim 2 or 3, characterized in that the said element comprises several segments or bars, the longitudinal thermal expansion of which causes the desired press effect. An antipolishing ring according to claim 2 or 3, characterized in that the said element (5) comprises two or several separate layers arranged radially one inside the other. An antipolishing ring according to claim 2, characterized in that the said element (5) comprises a hollow space (5a), which can be filled with an expanding pressure medium, for instance gas, liquid or melted metal. An antipolishing ring according to claim 1, characterized in that the said arrangement includes means, for example a set of screws (6) or the like, by means of which the lower portion (4b) of the antipolishing ring can be pressed mechanically in the radial direction of the cylinder inwards towards the mantle surface of the piston. An antipolishing ring according to claim 7, characterized in that the screws (6) are arranged to effect on the antipolishing ring (4) through a half-viscose elastomer portion or through a plastic portion (8). An antipolishing ring according to claim 7, characterized in that it includes a set of pressure elements (7) with hollow inner portion (7a) to be filled with a pressure medium and the pressure of which being adjustable by means of the said screws (6) or the like.

Inventors: PARO DANIEL, PARO, DANIEL
Applicants: WAERTSILAE NSD OY AB
Application year: 1995
Main classification: F16J10
IPC codes: F16J10, F02B3