US2807847A - Forming an engine water jacket core - Google Patents

Description

Oct. 1, 1957 c. w. LEWIS FORMING AN ENGINE WATER JACKET CORE Filed April 15, 1955 ATTORNEY United States Patent FORMING AN ENGINE WATER JACKET CORE Carl W. Lewis, Detroit, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application April 15, 1955, Serial No. 501,634

3 Claims. (Cl. 22-194) This invention relates to coring for engine cylinder block castings and particularly to a method of forming a water jacket core for an internal combustion engine.

During the past few years the maximum torque and brake horsepower output of internal combustion engines have been continually increased. Although such increases in power may be obtained by a variety of methods, the maximum power output of an engine ultimately is determined by its cylinder displacement. Of course, in modern high-speed internal combustion engines it is preferable to increase displacement by enlarging the diameters of the cylinder bores rather than by lengthening the stroke of the pistons since a short-stroke engine is subject to less piston and cylinder wear and to lower power losses due to friction. At the same time it is highly desirable to retain the overall length of cylinder block castings at a minimum, thereby permitting more effective use of the engine compartment of the automotive vehicle in which it is located. A relatively small engine block also requires less cast iron or other casting metal and reduces the weight of the resultant engine.

Accordingly, there has been a tendency during recent years to increase the displacement of gasoline engines by greatly enlarging cylinder bore diameters without increasing or, in some cases, decreasing the overall size of the cylinder block. This trend has been particularly evident in the manufacture of V-type engines. In turn, the large bore sizes necessitate the use of Water jacket cores having extremely thin walls, especially between the openings or bores in the water jacket cores through which the cylinderdefining portions of the barrel cores extend. In some instances the core walls between these openings are so thin that it is exceedingly difiicult to remove the water jacket cores from the core boxes after the blowing operation without causing breakage of these walls.

A principal object of the present invention, therefore, is to provide a method of forming a water jacket core for an internal combustion engine in a .manner which will permit the diameter of the cylinder bores of the engine to be increased without increasing the length of the cylinder block. A further object of the invention is to provide a process for casting a cylinder block of an internal combustion engine having larger diameter bores than it would be possible to form by conventional methods.

These and other objects are attained in accordance with the present invention by a process which involves molding a water jacket core so as to form flat surfaces on the core walls separating the openings or bores which are provided in the core for receiving barrel cores or barrel-bulkhead cores. The water jacket core, which may be composed of a conventional mixture of core sand and binder, is

subsequently baked in the usual manner, after which the aforementioned flat surfaces are ground to generally cylindrical shape. In this manner the water jacket core may be formed with bores having greater diameters than it would be possible to form by conventional methods.

'In turn, larger diameter barrel cores may be employed, and the resultant cylinder block casting is provided with "ice larger cylinder bores without increasing the outside dimensions of this casting.

Other objects and advantages of this invention will more fully appear from the following detailed description of a preferred embodiment of the invention, reference being made to the accompanying drawing, in which:

Figure l is a perspective view showing a conventional water jacket core for use in casting a cylinder block of an eight-cylinder gasoline engine of the V-type;

Figure 2 is a plan view of a water jacket core formed in accordance with the present invention after removal from the core box or curing oven;

Figure 3 is a plan view of the core shown in Figure 2 after the flat portions of the cylinder-defining walls of the core have been ground to cylindrical shapes;

Figure 4 is an enlarged fragmentary view of the wate jacket core shown in Figures 2 and 3, indicating the method by which excess core material is removed from the flat portions of the inner surfaces of the core walls;

Figure 5 is a fragmentary perspective view, with parts broken away and in section, showing cylinder-defining portions of barrel cores positioned in the openings formed in the completed water jacket core; and

Figure 6 is a fragmentary sectional view of the cylinder block produced by use of the cores shown in Figure 5.

As hereinbefore indicated, it has been found impossible to economically form a satisfactory water jacket core having the aforementioned large diameter bores and rela tively short overall length by merely molding the 'core into its final shape and thereafter baking it, as is conventionally done. When this procedure is attempted, the partition or wall between the cylindrical-openings or bores of the water jacket core in which the barrel portions of barrel cores are inserted prior to pouring the molten casting metal are too thin and weak, thus tending to fail upon removal of the core from the core box.

In accordance with the present invention, therefore, a water jacket core having exceptionally large diameter bores may be formed by the use of a core box which provides the walls between adjacent bores with flat surfaces. The distance between opposite flat surfaces of the core walls may be approximately the same as the diameter of the bores of the cores heretofore used, while the as-blown diameter of the cylindrical surfaces of the bores in the improved water jacket core may be increased. The core is then baked and the fiat surface portions subsequently ground to provide generally clyindrical bores. This may be accomplished by inserting a cylindrical grinding wheel into each bore to remove the excess core material from the flat core walls. After the core is baked, of course, it is considerably harder and stronger than it was in the as-blown condition. Thus, although the core walls between the bores are exceptionally thin after the grinding operation, they are not readily broken by nor-.

mal handling and casting procedures.

Referring more specifically to the drawing, in Figure l is shown a conventional water jacket core, indicated gen erally by 10, for use in casting a cylinder block of an eight-cylinder gasoline engine of the V-type. This core consists of longitudinally extending side walls 12 and transversely extending connecting walls 14 which define with the longitudinal walls a series of generally cylindrical openings or bores 15 through which cylinderdefining portions of barrel cores or barrel-bulkhead cores are adapted to extend. It will be noted that the transverse walls 14 between adjacent bores in this type of core are relatively thick, thereby permitting the core to 'be formed in its final shape in the core box.

In accordance with this invention, an internal combustion engine may be provided with larger diameter bores without increasing the overall length of the cylinder block by the method indicated in Figures 2 through 4.

Figure 2 shows an elongated water jacket core 16'provided with the usual openings or bores 18 for receiving barrel cores, However, it will be noted that the transversely extending walls 20 between these openings are formed with flat surfaces, as indicated at 22, thereby permitting the thickness of these walls to be approximately the same as the thickness of the transverse walls in the conventional type of water jacket core shown in Figure 1. At the same time the distance between opposite cylindrical surfaces of the longitudinal walls 12 and the transverse walls 20 defining these openings may be appreciably increased.

The mixture of core sand and suitable binder is formed into the shape shown in Figure 2 by being packed, preferably by a blowing operation, into an appropriate core box. This core box is shaped to provide the vertical side surfaces of the laterally extending wall portions 20 with the flat areas 22. The water jacket core thusformed is thereafter removed from the core box and baked in a conventional manner, such as by the use of a core oven, to cure the core binder. Baking times between two hours and eight hours normally may be employed for this type of core, depending on the baking temperature used. Oven temperatures of approximately 300 F. to 450 F. are typical.

The excess core material at the flat areas 22 of the transverse connecting walls 20 is thereafter removed, preferably by a grinding operation, to provide these walls with concave surfaces 24. In this manner, as shown in Figure 3, the barrel core-receiving opeings or bores 18 in the resultant water jacket core are each made generally cylindrical in shape.

Boring bars provided with diamond cutters may be used to grind the flat surfaces 22 of the core. However, for reasons of economy it is preferable to use refractory grinding wheels in production operations. The baked water jacket core can be mounted in a suitable fixture and a bank of four aligned grinding wheels simultaneously inserted intothe four bores 18. It has been found advantageous to use grinding wheels having diameters slightly less than that of the bores in the core. In this manner one flat surface 22 of each transverse wall 20 between the bores canbe ground onthe in-stroke and the opposite flat surface of each wall can be ground on the out-stroke. For the sake of simplicity, of course, it is preferable to grind corresponding sides of the core walls at the same time. After the in-stroke the boring tool 'is movedin a direction which is longitudinal with respect to the water jacket core to its out-stroke position.

Thus in'Figure 4 a grinding wheel, indicated by the broken line 28, is shown in a position where it is removing the excess core material from a surface of a wall 20 after the opposite surface 24 of the adjacent end wall 30 already has been ground to generally cylindrical shape.

With the type of water jacket core shown in the drawing, it is frequently not necessary to form the end walls 30 of the water jacket core 16 with inner fiat surfaces 22 because these walls are usually thicker than the laterally extendingwalls 20 between adjacent bores 18. Moreover, the thickness of the longitudinally extending walls 12 also is not normally critical since the problems with respect to permissible maximum dimensions of a cylinder block primarily pertain to its length rather than its width.

As shown in Figure 5, when the completed water jacket core 16and the other cores which constitute the final cylinder block coring arrangement are assembled, the barrel or cylinder-defining portions 32 of barrel cores or barrel-bulkhead cores extend through the openings 18 in the water jacket core. A pluralityof generally annular spaces or castingcavities 36 is thus provided between the barrel portions and the surrounding water jacket core.

Afterthe cores are assembled and positioned in a suitablegreen sand mold, the molten cast iron or other casting metalis poured around the cores and into the cavities, such as spaces 36, in conventional manner.

between adjacent cylinder walls is exceedingly small, as

indicated at 44, but yet is suflicient to provide proper circulation of cooling water through the water jacket 46. In the cylinder block shown in Figure 6 the outer walls 48 of the water jacket are curved laterally outwardly at 50 to improve circulation of the coolant through the portions 52 of the water jacket passage adjacent the sides of the cylinder bores.

Of course, the water jacket core 16 may be of a shape other than that shown in the drawing. For example,

this core may contain different types of core locators,

venting holes and other appropriate recesses necessary to form a casting of the desired configuration. deuce, while a specific embodiment 'of'theprcsent invention has been shown and described in detail, it will be understood that the scope of the invention-is not to be limited thereby except as defined in the following claims.

I claim:

1. A process'for forming a water jacket core for use in casting acylinder block of an internal combustion engine, said process comprising blowing a mixture of core sand and binder'into a core box shaped to form an elongated water jacket core having a plurality of open ings extending therethrough for receiving cylinder-delining portions of barrel cores, the walls of said water jacket core defining each of said openings being formed with a generally cylindrical inner surface having an as-blown contour and dimensions which are identical to the tinished contourand dimensions thereof, said walls having transversely extending portions provided with substantially flat surface areas, the radius of curvature of the generally cylindrical surface defining each openingbeing greater than the distance from the center of said opening to an adjacent flat surface area of saidtransversely extending wall portions, removing said core from said core box and subsequently curing it by baking at an elevated temperature, and thereafter grinding each of said flat surfacesinto generally cylindrical shape.

2. A method of forming a coring assembly for use in casting a cylinderblock of an internal combustion engine, said method comprising blowing a mixture of core sand and suitable binder into a core box to thereby form an elongated water jacket core having longitudinally extending side walls and a plurality of laterally extending walls connecting said side walls, said side walls being pr0vided with generally cylindrical inner surfaces having final contours and dimensions in the as-blown condition, said laterally extending walls being provided with oppositely disposed flatsurface areas which extend generally perpendicular to said side walls and define therewith a 55 plurality ofopenings extending through said cores, the

radius of curvature of each generally cylindrical surface being greater than'onehalf the distance between oppo- 'sitely disposed flat surface areas, thereafter removing said water jacket core from said core box and baking it at an elevated temperature,subsequently grinding the flat surface areas of said laterally extending walls until said openings are of generally cylindrical shape, and thereafter positioning the water jacket core around barrel cores so that cylinder-defining portions of said barrel cores protrude through said openings andare spatially separated from said walls.

3. A method'of forming a cylinder block of an internal combustion engine which comprises blowing a mixture of core'sand and binder intoa core box shaped to form'an' elongated water' jacket core having a plurality of openings formed by longitudinally extending side walls-and a' plurality of laterally extending walls' connectingsaid side Walls, said side walls being provided with generally cylindrical inner surfaces having final contours and dimensions in the as-blown condition, said laterally extending walls being provided with flat surface areas which extend generally perpendicular to said side walls, the radius of curvature of the generally cylindrical surface defining each opening being greater than the distance from the center of said opening to an adjacent flat surface area of said transversely extending wall portions, thereafter removing said core from said core box and baking it in an oven at an elevated temperature, removing said cured core from said oven and grinding the flat surface areas of said laterally extending Walls so as to cause said surface areas to form a generally cylindrical continuation of the inner surfaces of said side walls, subsequently inserting cylinder-defining portions of baked sand barrel cores into said openings to thereby provide a plurality of annu'lar spaces between said cylinder-defining portions and the walls of said water jacket core, positioning said water jacket core and said barrel cores in a green sand mold, and thereafter pouring molten metal around said cores and into said spaces.

References Cited in the file of this patent UNITED STATES PATENTS 1,954,460 Steeb Apr. 10, 1934 2,238,785 Walton Apr. 15, 1941 FOREIGN PATENTS 704,359 Great Britain Feb. 17, 1954 OTHER REFERENCES Dietert: Modern Core Practices & Theories, published by Am. Foundrymens Assoc., Chicago, Ill., 1942, pages 310-312.

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