MXPA06009366A - Casting mold for engine block - Google Patents

Abstract

A casting mold for an engine block and method for manufacturing the casting mold. In one embodiment, the casting mold includes a mold seat with a double-curved surface, and a cast-in cylinder liner. The cylinder liner has an axis and an end surface. The end surface is in tangential contact with the double- curved surface in a seated position prior to any thermal expansion of the cylinder liner. In various embodiments, the cylinder liner becomes slightly unseated upon thermal expansion.

Description

O 2 5 175 For two-letter codes and other abbreviations, refer to the "Guidance Notes on Codes and Abbreviations" appearing at the beginning-ning ofeach regular issue of the PCT Gazette.

FOUNDRY MODEL FOR MOTOR BLOCK FIELD OF THE INVENTION The present invention relates to molds used to produce melts that require cylindrical objects to be embedded in the melt, and in particular to casting molds for engine blocks in cast iron cylinder liners.

BACKGROUND OF THE INVENTION The internal walls of the cylinder bores of internal combustion engines are required to withstand the abrasive action of the piston and its sealing rings. In cast iron motor block models, cast iron provides the required strength. In other models, including some V-engine blocks in which aluminum or other lightweight material is used, the cylinder liners are inserted into the holes to provide adequate wear resistance.

In many engine block casting processes, cylinder liners are an integral part of the melt process and are assembled in the mold before the molten metal is introduced into the mold cavity to form the engine block. After melting, when the mold is removed, then the casting liners are permanently embedded within the molten metal walls of the cylinder bores. To improve the mechanical contact between the cylinder linings and the cylinder bore walls and to avoid imperfections that are caused by the thermal variations between the cylinder linings and the molten metal, the cylinder linings are sometimes preheated using, for example induction heaters.

In the sand casting process, referred to as the Precision Sand Process, a mold package that can be expanded or a package subset 40, shown in Figure 1, is assembled from several mold segments and mold cores 44 which are combined to define, together with the function cylinder liners 46, the internal and external surfaces of the motor block. The mold segments and the mold cores are made of sand bonded with resin. The proper placement of the linings in the mold and the prevention of the migration of the linings during the preheating and melting presents a continuous challenge.

Some attempts to solve this problem provide that the chamfered cylinder liners remain seated on the corresponding chamfered seating surfaces of the mold cores during thermal expansion. The prior art provides chamfered surfaces that are inclined with respect to a plane perpendicular to the axis of the hole and at the specific angles that are calculated to ensure that the liners remain seated and in contact with the seating surfaces during preheating and setting. These angles are calculated using nominal dimensions (theoretical) for the length and radius of the cylinder linings and assume a thermal expansion in the uniform place of the linings. In practice, these ideal conditions are not satisfied and the variation can cause the cylinder liners to exert force against the constraining mold seats. As a result, the mold seats will move in relation to each other and / or the sand bonded with resin will fracture or crush, contaminating the mold. Any of these unintended consequences is undesirable and potentially more catastrophic than a small amount of cylinder liner migration.

Therefore, improved function molds with cast cylinder liners are still necessary.

SYNTHESIS OF THE INVENTION An embodiment of the invention provides a casting mold for a motor block. The casting mold includes a first mold seat with a double arched surface and a casting cylinder liner. The cylinder liner has a shaft and a conical chamfer. The tapered chamfer is in tangential contact with the double arcuate surface in a seated position before any thermal expansion of the cylinder liner. In a related embodiment, the cylinder liner is slightly disengaged from the seated position with thermal expansion.

In another embodiment of the invention, the casting mold includes a second mold seat having a double arcuate surface in contact with the cylinder liner before any thermal expansion.

In yet another embodiment, the first and second mold seats have conical surfaces in contact with the corresponding end surfaces and the cylinder liner so that with thermal expansion, the cylinder becomes slightly disengaged from the seated position. The cylinder liner end surfaces may be double conical or arched surfaces.

Other systems, methods, features and advantages of the invention will be or will be apparent to an expert in the art of examining the following figures and the detailed description. It is intended that all such additional systems, methods, features and advantages are included within the description to be within the scope of the invention and to be protected by the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood from the detailed description and the accompanying drawings. The components in the figures are not necessarily to scale, the emphasis instead is placed on the illustration of the principles of the invention. In addition, in the figures, the reference numbers designate corresponding parts through the different views.

Figure 1 is a sectional view of a partial mold package shown assembled on a temporary basis; Figure 2a is a partial sectional view of the incorporation of a casting mold according to the present invention; Figure 2b is a partial sectional view of another embodiment of a casting mold according to the present invention; Figure 2c is a partial sectional view of another embodiment of a casting mold according to the present invention; Figure 3 is a partial sectional view of another embodiment of a casting mold according to the present invention; Figure 4 is an enlarged view of detail D of Figure 2a; Figure 5 is an enlarged view of detail E of Figure 2a; Figure 6 is a simplified diagram useful for illustrating an amount of axial desalting with the thermal expansion of a cylinder liner according to the present invention; Y Fig. 7 is a cross-sectional view of the casting mold of the invention showing an amount of lateral disentangling.

DETAILED DESCRIPTION OF VARIOUS INCORPORATIONS OF THE INVENTION The following description of the preferred embodiments is merely exemplary and nature and in no way intended to limit the invention, its application or its uses. Referring to the drawings, it is understood that the components or features that are within the scope of a craftsman of ordinary skill and do not contribute to the understanding of the various embodiments of the invention are omitted from the drawings to improve clarity.

Furthermore, it will be appreciated that the characterizations of the various components and the orientations described herein as being "vertical" or "horizontal" are relative characterizations based only on the particular position or orientation of a given component for a particular application.

Referring to Figure 2a, an embodiment of a casting mold 100 for a motor block is shown in the partial section around an axis of symmetry denoted by "A", which coincides with the longitudinal axis of one of the holes. cylinder cylinder block. It will be understood that the engine block includes one or more cylinder bores, for example 8 holes for a V-8 engine, although for simplicity, the various embodiments of the invention are described in relation to a single cylinder bore; without limiting the invention like this. The casting mold 100 includes several mold parts, such as a block core 102 and a barrel core 104. The mold parts are resin bonded sand cores and can be made using conventional processes such as the core manufacturing process cold phenolic urethane box or a hot box furan. The cores can be made using a variety of sands, such as silica, zirconium, fused silica, etc. It will also be appreciated that the block core 102 and barrel core 104 may each be made as an integral part alternatively as a combination of smaller interconnected mold parts. A cast iron cylinder liner 106 is tightly confined between the block core 102 and the barrel core 104. The cylinder liner 106 has a longitudinal axis "B" which coincides with the axis A when the cylinder liner 106 is aligned in the casting mold and there is no radial or axial displacement or inclination of the axis B with respect to the axis A, as shown in figure 2a. This cylinder liner position 106 is defined here as the "seated position".

The cylinder liner 106 has a first end 108 on one side of the block core 102 and a second end 110 adjacent the barrel core 104. In the embodiment shown in Figure 2a, the first end 108 of the cylinder liner 106 is in contact with a first mold seat 112 on the which will be defined by a part of the block core 102. The first mold seat 112 has a double convex arcuate surface 114, which is symmetrical about the axis A, and has two radii of curvature at each point. Such a surface is generated by revolving an arcuate line around the axis A, which is the axis of revolution or symmetry. The conical or cylindrical surfaces, which can be obtained when a radius goes to infinity, are unique arched surfaces. The double arcuate surface 114 of the first mold seat can be, for example, a part of a sphere or torus.

The cylinder liner 106 makes contact with the surface 114 of the first mold seat 112 along a contact circle 118. The contact circle 118 lies in a plane perpendicular to the axis A and has a radius Rx. In one embodiment, the first end 108 of the cylinder liner includes a first end surface 116, which, in this embodiment, is a tapered chamfer, as best seen in detail D of FIG. 4. The chamfer 116 is tangent to the first mold seat surface 114 along contact circle 118 and defines an angle a2 with the plane of contact circle 118, which is perpendicular to axis A.

The second end 110 of the cylinder liner 106 is in contact with the second mold seat 120. The second mold seat 120 can make contact with the second end 110, on a conical surface 122, as shown in Figure 2a, or in a double arcuate surface 124, which is similar to the double arcuate surface 114 of the first mold seat 112, as shown in Figure 3. In the embodiment of Figure 2a, the conical surface 122 is inclined at an angle a2 with a plane perpendicular to axis A, as best illustrated in detail # of figure 5. Cylinder liner 106 may also include a second end surface 126 which in this embodiment is a conical chamfer having the same inclination a2 . In the embodiment of Figure 3 the second chamfer 126 makes contact with the double arcuate surface 124 of the second mold seat 120 tangentially at an angle a2, which is defined by the second chamfer 126 and a plane perpendicular to the axis A. When the double arcuate surfaces 114 and 120 of the first and second mold seats 112 and 120 are images identical to each other, a2 = a1 = a. : If all the mold components are properly formed and assembled, in their initial state, before any heating resulting from the heating process (if this is employed) or from the casting process, - • the cylinder liner 106 is seated on the first and second mold seats 112 and 120; this is the axis A of the hole coincides with the axis B of the cylinder liner 106, so that the cylinder liner 106 is not displaced laterally with respect to the axis of the hole A. The cylinder liner 106 is constrained by the mold seats first and second 112 and 120. The angles x and a2 are selected so that the cylinder liner 106 will "disengage" or is no longer tightly confined by the first and second mold seats 112 and 120 when heated. Therefore, the axis B of the cylinder liner 106 will be displaced laterally in relation to the axis A by some amount, as shown in figure 7. A disengaged cylinder liner 106 will be moved out of position by gravity, to the local adhesion of the cylinder. cylinder liner to one or both of seats 112 and 120 or unbalanced metal pressure.

In other embodiments, shown in Figures 2b and 2c, the first mold seat 112 of Figure 2a it can also be configured to have a conical surface which is an identical image of the conical surface 112 inclined at an angle ax = a2 with a plane perpendicular to the axis A such that with expansion the cylinder liner 106 is disengaged from the position seated on the first and second mold seats 112 and 120. The cylinder liner 106 has the first and second end surfaces 116 and 126 that match the conical surfaces 114 and 122 of the mold seats 112 and 120. In the incorporation of figure 2b, the end surfaces 116 and 126 are conical chamfers. In the embodiment of Figure 2c, the end surfaces 116 and 126 of the cylinder liner 106 are double arched surfaces.

A small migration or misalignment of the B axis in relation to A during the preheating and / or melting processes is negligible in comparison to the damage that can be caused if the cylinder liner 106 is constrained to settle during those processes on the mold seats first and second 102 and 120. Therefore, according to the present teachings, the thermal expansion not anticipated and / or does not take into account the cylinder liner 106 that differs from the theory, will be accommodated without pushing apart the seats and / or crushing or fracturing the polluting seat material mold. The thermal expansion not anticipated or not taken into account generally results from normal process variations in the current dimensions and mold seating angles 112 and 120 and cylinder liner 106, as well as non-uniform thermal expansions during preheating and / or mold filling.

The undesirable consequences of an unpredictable thermal expansion of the cylinder liner 106 are avoided in the present invention by designing the mold seats 112 and 120 and the cylinder liner so that the cylinder liner is slightly uneven during thermal expansion. This is achieved by allowing an amount of unconstrained expansion at one or both ends 108 and 110 of the cylinder liner 106. In this aspect, the chamfer angles a? And a2 are selected to exceed the nominal values that are theoretically required to constrict the seat by an amount that will not cause excessive disengagement or misalignment of the cylinder liner 106. The nominal angles required for constant seating for the embodiments of Figs. , 2b and 3 are determined by the following equation: Rx x tan x + R2 x tan a2 = L, Where L is the length of the cylinder liner 106 determined in its contact with the mold seats 112 and 120, and Ri and R2 are the corresponding spokes in contact with the mold seats. If R2 = R2 = R and? = a2 =, then: so a = L / 2R As an example, consider a cast iron liner with R = 47.5 millimeters and L = 140 millimeters. For this cylinder liner, the minal angle a for constricted settlement is equal to 55.84 °, and the coefficient of thermal expansion (k) is equal to 5.9 x 10"e / ° F- For a change in temperature of 1000 ° F, if al and a2 are chosen to be 10 ° greater than the nominal angle value, or 65.84 °, the amount of axial desasentation Ga can be calculated as follows: The change in length is? L: ? L = 1000 X 5.9 X 10"6 X 140 = 0.826 mm The change in radius R is? R: ? R = 1000 x 5.9 x 10"6 x 47.5 = 0.280 millimeters Referring to figure 6, the axial desasentado Ga is measured from the tangents to the mold seats at the initial contact points: Ga = 2? R tan (65.84 °) -? L = 0.424 millimeters Similarly, if only the first angle a2 is increased 10 ° to 65.84 °, while the second angle a2 is maintained at a nominal value of 55.84 °, the axial unsettled Ga is: Ga = 2? R tan (65.84 °) -? R = tan (55.84 °) -? L = 0.212 millimeters Therefore, for the cylinder liner of this example an increase of one of the chamfer angles by 10 ° causes the cylinder liner 106 to be axially disentangled by only 0.212 mm. An increase of both chamfer angles ax and a2 by 10 ° causes the cylinder liner 106 to axially disengage only by 0.424 millimeters.

The cylinder liner 106 is free to migrate laterally to the inlet center line as a result of Ga. Referring to Figure 7, it can be shown that the lateral displacement GL is equal to (Ga / 2) / tan a. In the present example if both angles are increased by 10 °, this results in 0.095 millimeters of lateral migration.

It will be appreciated from these calculations that by increasing one or both of the chamfer angles ax and a2 by as much as 10 ° of the nominal values that keep the cylinder liner 106 seated with thermal expansion, only the small radial or axial disengagement of the cylinder liner 106 will occur while many other advantages are realized in addition to preventing fracture or crushing of the mold seat. For example, the double arcuate surface 114 reduces or eliminates the wear of the mold seat 112 against the corner of the chamfer 116 of the cylinder liner 106. The increased chamfer angles ax and a2 facilitate the insertion of a mold seat 102 inside. of the cylinder liner 106 during the assembly of the mold 100 so that the cylinder liner 106 can be assembled correctly, especially in the case of the V-type engines where the cylinder liners 106 are typically non-vertical at the moment when the mold is assembled, as illustrated in Figure 1, in which the mold pack 40 is supported on a temporary base 50.

The chamfer angles greater than a2 and a2 result in a smaller amount of lateral displacement GL for a given amount of unsettled axail Ga. The smaller lateral displacement GL helps to provide better control of any cylinder liner 106 which are unfastened following the mold assembly due to dimensional imperfections in the block core 102, the barrel core 104 and the cylinder liners 106. when the casting mold 100 is assembled.

Although several embodiments of the invention have been described, it will be apparent to those with ordinary skill in the art that other embodiments and implementations are possible which are within the scope of this invention. Therefore, the invention is not restricted except in light of the attached clauses and their equivalents.

Claims (26)

R E I V I N D I C A C I O N S

1. A casting mold for an engine block, the casting mold comprises: a mold seat comprising a double arched surface; Y a casting cylinder liner comprising an axis and a conical chamfer, wherein the conical chamfer is in tangential contact with the double arcuate surface in a seated position absent from the thermal expansion of the cylinder liner.

2. The casting mold as claimed in clause 1, characterized in that the conical chamfer forms an angle a with a plane perpendicular to the axis, so that the cylinder liner is detached from the seated position with thermal expansion.

3. The casting mold as claimed in clause 1, characterized in that the double arched surface is a spherical segment.

. The casting mold as claimed in clause 1, characterized in that the double arched surface is a toroidal segment.

5. A casting mold for an engine block, the casting mold comprises: a first mold seat comprising a first double arched surface; a second mold seat comprising a second conical surface; Y a casting cylinder liner comprising an axis and the first and second conical chamfers, wherein the first and second chamfers respectively are in contact with the first and second surfaces in the first and second contact circles in a seated position, so that with thermal expansion the cylinder liner is disengaged from the seated position.

6. The casting mold as claimed in clause 5, characterized in that the first and second chamfers form an angle and a2 respectively in relation to a plane perpendicular to the axis, and where ax is greater than the angle defined by tan_1 (L / 2R) and a2 is equal to tan "1 (L / 2R), where L is the length of the cylinder liner between the circles of contact and R is the inner radius of the cylinder liner in the contact circles.

7. The casting mold as claimed in clause 5, characterized in that the chamfers first and second they form the angles x and a2 respectively in relation to a plane perpendicular to the axis, where ax is greater than angle defined by tan "1 (L / 2R) and a2 equals tan" 1 (L / 2R), where L is the length of the cylinder liner between the circles of contact and R is the inner radius of the cylinder liner in contact circles.

8. A casting mode for an engine block, the casting mold comprises: a mold seat comprising a conical surface; a casting cylinder liner comprising an axis and contacting the conical surface in a seated position in the absence of thermal expansion, wherein the conical surface is inclined at an angle a perpendicular to the axis, so that with thermal expansion the lining cylinder is disengaged from the seated position.

9. A casting mold for an engine block, the casting mold comprises: a first mold seat comprising a first conical surface; a second mold seat comprising a second conical surface; a casting cylinder liner comprising an axis and the first and second end surfaces contacting the first and second surfaces in a seated position in the absence of thermal expansion, wherein the first and second surfaces are inclined at an angle ax and a2 respectively with a plane perpendicular to the axis so that with thermal expansion the cylinder liner is disengaged from the seated position.

10. The casting mold as claimed in clause 9, characterized in that at least one of the first and second end surfaces is a conical surface.

11. The casting mold as claimed in clause 9, characterized in that at least one of the first and second end surfaces is a double arched surface.

12. A casting mold for an engine block, the casting mold comprises: a first mold seat comprising a first double arched surface; a second mold seat comprising a second double arcuate surface; Y a molten cylinder liner comprising an axis and the first and second chamfers wherein the first and second chamfers respectively are in tangential contact with the first and second surfaces in the first and second contact circles in a seated position, so that with thermal expansion the cylinder liner is disengaged from the seated position.

13. The casting mold as claimed in clause 12, characterized in that the first and second chamfers are inclined at angles aa and a2 respectively in relation to a plane perpendicular to the axis, where a2 is greater than the angle defined by tan_1 (L / 2R) and a2 is equal to tan_1 (L / 2R), where L is the length of the cylinder shell between the contact circles and R is the inner radius of the cylinder liner in contact circles.

14. The casting mold as claimed in clause 12, characterized in that the first and second chamfers form the angles ax and a2 respectively in relation to a plane perpendicular to the axis, where a is greater than the angle defined by tan "1 (L / 2R) and a2 is greater than tan "1 (L / 2R), where L is the length of the cylinder shell between the contact circles and R is the inner radius of the cylinder shell in the contact circles.

15. The casting mold as claimed in clause 14, characterized in that a1 = a2.

16. The casting mold as claimed in clause 12, characterized in that each double arched surface comprises a spherical part.

17. The casting mold as claimed in clause 12, characterized in that each double arched surface comprises a toroidal part.

18. A casting mold for a motor block, the casting mold comprises: a first mold seat comprising a first surface; a second mold seat comprising a second surface; Y a casting cylinder liner comprising an axis and the first and second end surfaces, wherein the first and second end surfaces are relatively in tangential contact with the first and second surfaces of the seated position so that with thermal expansion in the cylinder liner, it is removed from the seated position.

19. The casting mold as claimed in clause 18, characterized in that the first surface is double arched.

20. The casting mold as claimed in clause 18, characterized in that the first surface is conical.

21. A method for manufacturing a casting mold for an engine block, the method comprises: providing a first mold seat comprising a first surface; providing a second mold seat comprising a second surface; Y placing a casting cylinder liner in a seated position in contact with the first and second surfaces respectively on the first and second end surfaces of the cylinder liner in the absence of thermal expansion, wherein the first surface is shaped so that the thermal expansion the cylinder liner is dislodged.

22. The method as claimed in clause 21, characterized in that the first surface comprises a double arcuate part in contact with the first end surface of the cylinder.

23. The method as claimed in clause 21, characterized in that the first surface comprises a conical part in contact with the first end surface of the cylinder liner.

24. The method as claimed in clause 21, characterized in that the second surface is shaped so that with the thermal expansion the cylinder liner is detached from the seated position.

25. The method as claimed in clause 24, characterized in that the second surface comprises a double arched part in contact with the second end surface of the cylinder liner.

26. The method as claimed in clause 24, characterized in that the second surface comprises a conical part in contact with the second end surface of the cylinder liner. SUMMARY A casting mold for an engine block and a method for manufacturing the casting mold. In one embodiment, the casting mold includes a mold seat with a double arched surface and a casting cylinder liner. The cylinder liner has a shaft and an end surface. The end surface is in tangential contact with the double arcuate surface in a seated position before any thermal expansion of the cylinder liner. In several embodiments, the cylinder liner is slightly set back with thermal expansion.