A cylinder liner unit for use in an internal combustion engine

Abstract: A cylinder liner unit (10) comprises a plurality of cylinder liners (2) made of a non-aluminum alloy for use in an internal combustion engine and uniformly covered with a layer (3) of an aluminum series alloy around the plurality of cylinder liners so as to be integrally combined by the layer of aluminum series alloy layer in unity. Thereafter, the integrally combined cylinder liner unit is casted in a cylinder block (1) made of an aluminum alloy.

Description: The present invention relates to a method of producing a cylinder block unit for use in an internal combustion engine, and more particularly, to a method of producing a cylinder liner unit which is adapted to be cast in a cylinder block made of an aluminum alloy. Recently, a cylinder block made of an aluminum alloy has been introduced in an engine for use with an automobile in mass production. As a material for cylinder liners, a non-aluminum alloy such as cast iron or ceramics is generally used. Fig.6 is a plan view of a cylinder block of a four-cylinder engine. The cylinder block is manufactured by casting cylinder liners 2 made of a non-aluminum alloy in a cylinder block 1 made of an aluminum alloy. The cylinder block 1 must be provided with a water jacket 5. When manufacturing the cylinder block by casting, it is difficult to precisely position each of cylinder liners 2 in place, so that a metallic mold set for casting liners may be complicated and costly. Japanese Utility Model Laid-Open Application Sho 61-107461 discloses that, as shown in Fig. 6, the thickness of an aluminum alloy base material interposed in interspace D between adjacent cylinder liners 2 is substantially equalized to the wall thickness of the cylinder 2 to prevent deformation of the cylinder liner 2 during thermal expansion. When the interspace D between adjacent cylinder liners 2 is reduced, however, the flow of molten metal becomes worse during the casting operation of large-sized castings such as a cylinder block and defects in casting such as cleavage and cavities in molten metal are liable to occur. This is applicable to an engine having a reduced bore pitch. In order to eliminate the above-mentioned disadvantages of separately casting the cylinder liners 2 one by one, an integrally combined cylinder liner unit 10 made of cast iron as shown in Fig. 5 is employed. The cylinder unit 10 integrally combined by connecting bores 11 with connectiong portions C is casted in a cylinder block 1 made of an aluminum alloy, as shown in Fig. 4. In the case where an integrally combined cylinder liner unit made of cast iron is employed, material of the cylinder block around the liner, which is an aluminum alloy, does not melt and combine with the cast iron of the liner. Consequently, the cylinder block is separated from the cylinder liner at portions A and B shown in Fig. 4 to open outward, resulting in decrease in strength of the cylinder liner and leakage of water and combustion gas. In addition, since a connecting portion C exists in the cylinder liner, the radial wall thickness of the cylinder liner around the bore 11 is not uniform at every circumferential point of the bore. Consequently, when temperature of the cylinder liner rises during running of an engine, a thermal expansion of the cylinder liner is not uniform at every circumferential point thereof and the bore 11 loses its roundness. As a result, there incurs decrease in output due to gas leakage and insufficient compression and increase in consumption due to leakage of lubricant oil. Document GB-A-2194473 discloses a similar cylinder block produced by casting the cylinder block aluminium alloy around the cylinder liners. SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned disadvantages by providing a method of producing a cylinder block unit in which a plurality of cylinder liners made of a non-aluminum alloy are casted in a cylinder block made of an aluminum alloy such that both are firmly combined, so that there are no decrease in output and no increase in consumption of lubricant oil even during running of an engine. The present invention is the method according to the claim. The integrally combined cylinder liner unit, whose liners are pricisely positioned and easily and integrally combined in unity, is capable of being precisely positioned in a cylinder block made of an aluminum alloy when being casted. When the integrally combined cylinder liner unit is cast in the cylinder block made of an aluminum alloy, since material of the outer surroundings of the integrally combined cylinder liner unit is the same series one as the material of the cylinder block, both the cylinder liner unit and cylinder block are firmly combined by melting. The outer surroundings of the cylinder liner unit are thus strengthened and no leakage of water and gas occurs. In addition, the radial wall thickness of the cylinder liner is uniform in all circumferential points thereof and the cylinder liner deforms by thermal expansion in a true circle, incurring no decrease in output and no increase in consumption of lubricant oil. Thus, the present invention avoids any likelihood that defects in casting may be caused and has effects to improve performance of an engine manufactured by using the cylinder block casting. BRIEF DESCRIPTION OF THE DRAWINGS Figs.1 to 3 show an embodiment of a cylinder liner unit according the present invention, Fig.1 being a plan view of a cylinder block, Fig.2 being a plan view of an integrally combined cylinder liner unit and Fig.3 being a section view taken on line X-X in Fig.2; Figs.4 to 6 show a conventional art, Fig.4 being a plan view of a cylinder block in which an integrally combined cylinder liner unit shown in Fig.5 is casted, Fig.5 being a perspective view of an integrally combined cylinder liner unit and Fig.6 being a plan view of another conventional cylinder block. DESCRIPTION OF PREFERRED EMBODIMENT An embodiment of a cylinder liner unit produced according to the method of the present invention is described hereinafter with reference to the accompanying drawings. An integrally combined cylinder liner unit shown in Fig.2 is manufactured by covering four cylinder liners 2 made of a non-aluminum alloy such as cast iron or ceramics with an aluminum alloy by casting so as to be integrally combined therewith in unity. Namely, aluminum alloy layers 3 around the cylinder liners 2 are integrally combined by connecting portions 4 to form a monolithic unit as a whole. The aluminum alloy layer 3 may be an aluminum series alloy material which melts and combines with an aluminum alloy of the cylinder block 1. The state in which the integrally combined cylinder liner unit is casted in the cylinder block 1 made of an aluminum alloy in an ordinary manner is shown in Fig.1. When casting the cylinder block 1, the integrally combined cylinder liner unit is casted in the cylinder block while forming water jackets 5. At this time, all cylinder liners 2 have been integrated by the aluminum layers 3 in a monolithic unit, so that the accuracy of positioning the cylinder liners 2 may be improved. Even when a bore pitch between the cylinder liners is reduced, there is no portion to impede the flow of molten metal in the outer configuration of the integrally combined cylinder liner unit shown in Fig.2. As a result, no defect in casting occurs and it is possible to manufacture a cylinder block of good quality. The cylinder block 1 includes the aluminum layer 3 around four cylinder liners 2. The outer edge of the aluminum alloy layer 3 melts and combines with the cylinder block 1 made of the same series material as that of the aluminum alloy layer, so that both can be firmly combined. As a result, there is no separation even at a portion C which is liable to separate in a conventional cylinder block and the surroundings of the cylinder liner 2 are strengthened, so that there may be no leakage of water and gas. The radial wall thickness of the cylinder liner 2 is uniform at every point of the circumference thereof. Consequently, an engine manufactured by employing the casting according to the present invention, during running, deforms in a true circle by thermal expansion, so that no decrease in output and no increase in consumption of lubricant oil may occur.

Claims: A method of manufacturing a cylinder block (1) of an internal combustion engine, said cylinder block (1) comprising a plurality of non-aluminium cylinder liners (2), characterized by the following steps: arranging the plurality of cylinder liners (2) in predetermined positions and forming an integral cylinder liner unit (2, 3, 4) by uniformly casting a layer (3) of an aluminium-series alloy around the liners (2) and subsequently forming the cylinder block (1) by casting an aluminium-series alloy around said integral cylinder liner unit (2, 3, 4).

Inventors: OHTA MASANORI, OHTA, MASANORI
Applicants: ISUZU MOTORS LTD, ISUZU JIDOSHA KABUSHIKI KAISHA
Application year: 1989
Main classification: F02F1
IPC codes: F02B75, F02F7, B22D19, F02F1