JP2007514550A - Method and apparatus for producing durable thin-walled castings - Google Patents

Abstract

Preferably, there is a cooling liquid passage in the insert that bridges the outer water jacket and is preferably shaped to fill the interliner and connected to an outer water jacket core made of the same alloy as the rest of the engine block. A method and apparatus for forming a high quality durable web having a minimum dimension of 3 mm or less between iron liners in an aluminum engine block by utilizing a preformed metal insert.
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Description

Related applications

  The benefit of the filing date prior to provisional application 60 / 531,278 filed on December 18, 2003 in accordance with 37 CFR §1.78 (4) and 35 USC §119 (e) is claimed.

  The present invention is broadly related to techniques for producing cast articles with thin walls and is particularly useful for producing cast aluminum automobile engine blocks having very thin interliner walls.

  This explanation is primarily a constant and urgent need to increase the power-to-weight ratio, resulting in the desire to use minimal amounts of lightweight materials and small dimensions while maintaining strength and integrity and thus effectiveness and reliability. This will be done in terms of availability to existing aluminum engine blocks.

  In recent years, several processes are available for the manufacture of engine blocks, especially for automobiles, among which (1) sand molds containing sand cores (sand cores) defining cavities of a predetermined shape are solidified. Low pressure or gravity filled sand box (sand package) filled with liquid aluminum alloy forming motor block, or (2) Semi-permanent low pressure mold (mold), or (3) Sand core to form internal feature of block A gravity filling mold having (sand core) can be mentioned.

  Engine block designs have changed over time due to the tendency to increase engine power. The size of the motor block tends to be fixed depending on the size of the vehicle body. These blocks need to accommodate larger cylinders, meaning larger diameters, within the same block volume. These designs require the cylinder liners (usually made of iron) to be close to each other so that the aluminum walls formed as webs in the gap between the cylinder liners are constantly becoming thinner (less than about 3 mm). It presents a challenge to the manufacturer.

  Due to the gap between adjacent pairs of cylinder liners that are so thin, the liquid aluminum volume filling such interliner cavities is relatively small and quickly loses heat when in contact with the iron liner, resulting in prematurely. It solidifies and thus clogs the cavity, preventing liquid aluminum from filling the remainder of the cavity.

  It has also been found that increasing the pressure in the aluminum alloy holding furnace does not solve the above problem because the space through which liquid aluminum must flow is too small.

  This uncontrolled solidification occurs even when the iron liner is preheated to a temperature close to that of the liquid aluminum alloy.

  Discussing this same problem, cylinder lumens with computer temperature control fluid pumped through the cylinder lumen mold as well as preheating the liner to delay premature solidification in the thin interliner wall Robert K., June 6, 1995, teaches an elaborate system that also relates to the actual use of a cast plug 14 to form a mold. See US Pat. No. 5,421,397 issued to Hembre et al. However, this proposal, which is unlikely to be cost-effective, also works effectively on internal tensile stresses formed in fragile thin walls for simultaneous cooling of different materials (iron and aluminum) in intimate contact with each other. I can't.

  In other words, even though the aluminum is forced to fill a small interliner cavity, the thin aluminum walls between the cylinder liners have a relatively small amount of aluminum alloy between these liners and the relatively large and cool mass (heavy object) of the liner. Another problem arises that is damaged by thermal stresses generated by rapid heat transfer from and) or generates cracks.

  If these walls are thinned by design considerations so that they are only a few millimeters, this cooling occurs when in contact with liners having different expansion and contraction coefficients. This creates stress in the thin aluminum walls between the adjacent iron liners of the cylinder block, and these thin walls are cracked during cooling, during later machining, or when the finished engine is put into production. Cracks). This can cause oil leaks, compression loss, and other significant engine damage.

  Even if premature cooling does not clog the interliner cavities, control of the cooling rate can be adversely and unpredictably affected, resulting in undesirable differences in the crystal structure of the cooled casting.

  Now that there is less material to dissipate heat from the cylinder, it is becoming more difficult to simply maintain beyond the cooling flow rate as the interliner gap becomes smaller, adding additional or more in the interliner area. There is often a design need for an effective engine cooling passage. Now the current design calls for an aluminum wall interliner thickness of about 2-3 mm. Thus, the creation of cooling passages reduces the aluminum wall thickness of such passages to only about 1 mm.

  Older methods, such as drilling passages in the interliner web, do not work with such small dimensions (such a relatively long length of small diameter bit (cone tip) is expensive and prone to breakage and control without wobbling) Because it is difficult to do). Also, a single round hole to form the passage will only have a diameter of about 1 mm and provide insufficient flow. Several passages are required to obtain sufficient flow and / or the vertical height needs to be several times the horizontal width.

  Some current proposals for providing such cooling passages include special core fabrication techniques that use fragile materials such as sand or other glass. These processes are not ideal and typically may be costly and dangerous.

Another current embodiment involves casting a solid section between cylinder liners and then opening or machining a very thin gap in the interliner web, the top of which is later closed by welding. And sealing (and thus forming a cooling passage). This procedure requires expensive cutting / machining equipment and tools.
US Pat. No. 5,421,397

  The present invention provides a preformed web insert having the shape required to fit in the narrowest space between adjacent pairs of cylinder liners that are at least 3 mm wide along its location. Introducing the above-mentioned drawbacks of the current technology by introducing. This insert is preferably made from the same alloy aluminum, or optionally from a different alloy, or other suitable material (such as bronze or copper), and a sand core (sand core) defining the water jacket of the block ) Is generated at the same time as it is generated.

  This insert can have an hourglass shape similar to the preformed core discussed in US Pat. No. 6,298,899, and also has the advantage of avoiding the “tilt angle” discussed therein. Although its shape is similar due to its arrangement, the core of the '899 patent serves a very different purpose (including different ideas).

  Applicants' preformed inserts vary considerably with more advantages. The core of the '899 patent is a temporary sand core, but in contrast, Applicants' preformed inserts are effective in place as part of the casting after the water jacket core is removed. This is a permanent solid structure that remains.

  Applicants' preformed inserts are solid and can further incorporate thin-walled pipes, and preferably alternatively have passages integrally formed therein. Thus, a pipe or passage in such an insert can provide an effective and stable cooling fluid passage through a very narrow interliner gap.

  Thus, for automobiles having the need to cast strong thin wall sections in the interliner web between closely aligned pairs of cylinder block liners (otherwise flow, cooling and / or differential stress problems A method of eliminating unfilled space, stress, and / or uncontrolled cooling rate problems (in any casting of the present invention), preferably producing an aluminum alloy engine block that provides sufficient cooling fluid passages It is an object of the present invention to provide a method for achieving this.

  The shape of the web between adjacent cylinder liners filling the gap, and suitable for functioning as part of the casting, including chemical (possibly by some surface melting assisted by agents such as zinc) and / or Or formed from a relatively stress free preformed insert with a mechanically suitable remainder for joining well with a liner which is preferably the same aluminum alloy as the rest of the casting. It is another object of the present invention to provide an automotive engine block made of aluminum alloy.

  Cooling passages that are of the appropriate material and shape to fit into the interliner gap and are already formed therein, and maintain fluid communication with separate areas of the cooling fluid jacket of the engine block Providing a method for manufacturing an aluminum alloy engine block, characterized in that a cooling passage is formed in the narrow interliner gap of the block by providing a cooling passage arranged in a preformed insert Is another object of the present invention.

  In one embodiment of the present invention, the remainder of the product is cast with liquid metal, including a preformed solid element having at least one dimension less than about 3 mm, and then separately with the preformed element already in place, There is thus provided a method for casting a casting, characterized by casting a final casting.

  In another embodiment of the invention, providing a mold for casting an engine block, inserting each of the preformed solid elements between a pair of cylinder liners, and forming a motor block Filling the mold with molten aluminum to provide an aluminum alloy engine block having a cylinder liner (provided).

  In a further embodiment of the invention, a relatively stress-free preformed solid element between the cylinder liners and the remainder of the engine block cast from an aluminum alloy that forms an integral block after solidification of the casting An engine block made of aluminum alloy is provided.

  In a further embodiment of the invention, the solid element can incorporate a cooling passage pipe, or the preformed solid insert is already formed in a cooling passage (optionally removable in place). Have a large core).

  The solution to the problem of filling the mold for an engine block 8 with a thin interliner wall 9 with a liquid aluminum alloy is that a solid insert made of a suitable material forming the rest of the cast block, for example the same aluminum alloy 10 is incorporated. Other suitable materials for this preformed insert include, for example, bronze, copper and alloys and their equivalents. A preformed insert (generally indicated by reference numeral 10) can be forged or extruded.

  The preformed insert 10 is placed between the cylinder liners 12 before introducing the liquid aluminum alloy into the mold. This insert 10 will be fixed in place by liquid aluminum which forms the rest of the block 8 and solidifies. In a preferred embodiment, the preformed insert (see insert 10a or 10b) has a groove 14 for drawing liquid aluminum so that the liquid aluminum cools and hardens between the insert and the aluminum. Give a good bond. Bonding can also occur from surface melting of the insert 10 during casting injection. This can be aided by the addition of a binder such as low molten zinc.

  In a preferred embodiment, thanks to the same or similar expansion and cooling factors between the preformed insert 10 and the liquid aluminum used when pouring into the block mold, one advantage of the present invention is that The forming insert 10 does not leave any residual tension as a result.

  Further, even when the insert 10 is not made of the same alloy, no or little thermal stress is induced in the preformed insert 10 due to aluminum shrinkage or due to the expansion of the iron cylinder liner 12 (insert 10). Is already cooled to a solid, stress-free form). In this way, cracking (cracking) is minimized or eliminated. Furthermore, the present invention advantageously resists tension or cracking caused by subsequent machining procedures such as boring.

  In a further embodiment of the invention, the cooling liquid passage 15 is preferably arranged with an insert 10b or 10c together with a cooling fluid conduit having the shape required to fit into the gap between the cylinder liners, for example. Is formed in or as part of the preformed insert 10. This passage 15 can take the form of an embedded thin-walled pipe 17 (made of steel or the like) as shown in FIG. 1, or a bridging core (bridging core) 16 as shown in FIG. Can be formed integrally with the insert. In order to facilitate the joining of the insert cooling passage in the insert 10b and the outer water jacket cooling passage (formed by the water jacket core 6), a removable bridging core (bridging core) 16 is pre-formed. When used to form the passage 15 in the insert 10b, it will remain in place until after the casting of the engine block is complete (and then removed with the removal of the jacket core 6). Known examples of such bridging cores (bridging cores) include salt, carbon, or glass (see US Pat. No. 6,205,959).

  The invention is for example injected into the holding furnace for pushing up the liquid aluminum alloy through a suitable connecting conduit into a holding furnace for the liquid aluminum alloy and a mold located at the top of the holding furnace. Can be implemented with current processes and equipment that can include a source of pressurized gas, typically nitrogen. The liquid alloy is forced into all mold cavities, and after the mold is full, the liquid flow is stopped by a suitable device, such as a slide valve or gate, and then the mold is disconnected from the holding furnace, This process is repeated with the next mold to be filled. A mass of heat-absorbing material, also known as chill (or heat sink device) (cooling metal (or heat sink)), is currently liquid aluminum to direct solidification in the desired direction for producing high quality castings. It can be placed under the proprietary process of the assignee of the present application in contact with the alloy. Such controlled cooling can now be interrupted by the small interliner gap encountered in modern aluminum automobile engine blocks, but is overcome by use of the present invention.

  The preferred conditions for using the present invention are less than 3 mm, but the method needs to apply a reduced residual stress to the interliner cross section thanks to this solidification process or for some other reason mentioned above. In some cases, the same applies to thicker interliner dimensions.

  Those skilled in the art will recognize or be able to ascertain without undue experimentation any of the numerous equivalent means equivalent to the embodiments of the invention described herein. All such equivalents are considered to be within the scope of the present invention and are covered by the appended claims.

  Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein. All publications, patent applications, patents and other references cited herein are incorporated by reference in their entirety. In case of collision, the present specification, including explanations of terms, will adjust. In addition, these materials, methods, and examples are illustrative only and not intended to be limiting.

  Although preferred embodiments of the invention and modifications thereof are described in detail herein, the invention is not limited to these precise embodiments and modifications and the invention described in the appended claims. It should be understood that other modifications and variations can be envisaged by those skilled in the art without departing from the spirit and scope of the present invention.

Three preformed solid aluminum inserts (each suitable for the present invention) with each such insert having a bridging cooling passage core and incorporated by a bridging core with a jacket core at each interliner gap position. 1 is an isometric view (perspective view) of a core of a mold for forming a water jacket (ie, cooling passage) of an aluminum engine block incorporating an embodiment); FIG. Engine cylinder block having a cylindrical iron liner that fits closely into each of the cylinder lumens and a solid aluminum insert (no passage) disposed within the interliner gap of each pair of liners of the finished block FIG. 2 is a top view of the stylization of the engine (thus showing the relationship of engine parts in which the present invention can be effectively implemented). FIG. 3 is a stylized vertical section taken along section line AA of FIG. FIG. 3 is a stylized top view according to a different preferred embodiment of the present invention similar to FIG. 2, but with each preformed insert incorporating a bridged cooling fluid flow passage (shown in dotted lines). FIG. 5 is a stylized vertical cross section taken along section line AA of FIG. An isometric view of a solid preformed insert showing two bridging cores extending through either end of the upper portion of the preformed insert to form an interliner gap bridged cooling fluid flow passage (perspective view) Figure). 2 is an isometric view (perspective view) showing two iron liners attached to the core of a mold having a solid preformed insert (according to the preferred embodiment of FIGS. 2 and 3) that fits into the interliner gap. is there.

Claims (5)

  Casting a casting comprising a preformed (preformed) solid element having a dimension of less than about 3 mm and casting the remainder of the product with liquid metal to form a final cast product A method characterized by that.   A method of manufacturing an aluminum alloy engine block including a cylinder liner, comprising: preparing a mold for casting the engine block; and inserting a preformed solid element between the cylinder liners. And filling the mold with molten aluminum alloy to form the motor block.   Including a preformed, relatively stress free solid element between the cylinder liners and a remainder of the engine block cast from the aluminum alloy that forms an integral block after solidification of the casting. An engine block made of aluminum alloy.   3. A method according to claim 1 or 2, characterized in that the preforming element has at least one bridging passage (bridging passage) therein. The bridging passages extend through the interliner gaps between each pair of cast iron liners and extend between opposing halves of a water jacket core (water jacket core) that forms part of the engine mold. Method according to claim 4, characterized in that it is formed by a bridging core).

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