Engine block for an internal combustion engine

The present disclosure provides a cylinder block for an internal combustion engine having a first cylinder, a first cylinder sleeve, a second cylinder, and a second cylinder sleeve. The first cylinder defines a first cylindrical wall while the second cylinder defines a second cylindrical wall. The first cylinder sleeve lines the first cylindrical wall while the second cylinder sleeve lines the second cylindrical wall. Each of the first and the second cylinder sleeves define a thrust sleeve region, an anti-thrust sleeve region opposite the thrust sleeve region, and a pair of Siamese regions. The outer wall of each of the first and second cylinder sleeves progressively widens toward the top sleeve surface of each of the first and second cylinder sleeves.

TECHNICAL FIELD

The present disclosure relates to a cylinder block especially for internal combustion engines.

BACKGROUND

In its most general form, an internal combustion engine, or heat engine, includes an engine block in which at least one cylinder is formed, inside which a piston is movably mounted and connected to a crankshaft by a connecting element such as a rod. The engine block comprises three main parts, one of which is called a cylinder block, as it has one or more cylinders.

The cylinder block is covered on one side with a cylinder head (the second main part), in which the means necessary for internal combustion are arranged: in particular, intake means, exhaust means and optional ignition means. On the other side, the cylinder block is covered with an engine crankcase in which a crankshaft (the third main part) is housed.

With reference toFIGS. 2A and 2B, when the combustion engine is the linear-motion piston type, as opposed to a rotary piston engine, the engine block has at least one cylinder112lined by a straight sleeve120, inside which a piston180can move translationally, connected to the crankshaft by a rod. The cylinder bore112is in the shape of a circle and the straight sleeve120also has a Siamese region width154throughout the straight sleeve120. The cylinder head (not shown) for this cylinder block inFIGS. 2A and 2Bcomprises the distribution means for the cylinder or for each of the cylinders: for example, at least one intake valve, at least one exhaust valve, and an optional spark plug, as well as mechanical means for controlling the valves. And the engine crankcase contains the crankshaft and the rod and the oil reservoir needed to lubricate the engine.

Gaskets are used to form a seal between the three main parts of the combustion engine: namely, between the cylinder block and the cylinder head, and between the cylinder block and the engine crankcase. More specifically, the upper seal—i.e., the seal between the cylinder block and the cylinder head—is formed by a cylinder head gasket developed specifically for this purpose.

No matter what mode of operation such an internal combustion engine uses—i.e., two-stroke or four-stroke, compression ignition or spark ignition—this operation will always include the following stages for each of the cylinders: an intake of a fuel and the air needed for combustion, a compression of the fuel/air mixture, an internal combustion of the fuel/air mixture, and an exhausting of the combusted fuel. These four stages are organized into two or four cycles by using an appropriate combustion engine architecture.

It is easy to understand why the design of the internal combustion engine and the choice of material from which it is made are primarily determined by the stresses to which the engine is subjected during the combustion stage, which is a true explosion,

On the other hand, a compromise is sought between an engine that is resistant enough to the static and dynamic stresses to which it is exposed during its operation and an engine that is as light as possible. Taking into account the engine's ability to withstand static stresses and dynamic stresses during its operation, a compromise is sought between 1) an engine that is rigid enough to be able to withstand the pre-stressing forces from the clamp loads of the cylinder head and crankcase, plus the expansion forces resulting from the internal combustion or explosion stages, depending on the thermodynamic cycles and 2) a flexibility or resilience to absorb expansion forces and thereby minimize deformations that could result from the forces and other stresses.

Indeed, deformations are generally related to the dynamic stresses of the thermodynamic cycles. But they are also caused by the pre-stressing forces from the clamp loads of the cylinder head and the head cover covering the cylinder head.

Most of the compromises found for the architecture of an internal combustion engine that incorporate both resistance to stresses and resilience to deformation has to do with the engine design and each of the cylinders is equipped with a cylinder sleeve, made of a hard material, that determines the cylinder bore size.

The cylinder sleeve can be fixed or mobile, and when it is fixed, it can be durably attached inside the cylinder block or it can be removable.

SUMMARY

The present disclosure provides a cylinder block for an internal combustion engine having a first cylinder, a first cylinder sleeve, a second cylinder, and a second cylinder sleeve. The first cylinder defines a first cylindrical wall while the second cylinder defines a second cylindrical wall. The first cylinder sleeve lines the first cylindrical wall while the second cylinder sleeve lines the second cylindrical wall. Each of the first and the second cylinder sleeves define a thrust sleeve region, an anti-thrust sleeve region opposite the thrust sleeve region, and a pair of Siamese regions. The outer wall of each of the first and second cylinder sleeves progressively widens toward the top sleeve surface of each of the first and second cylinder sleeves. It is understood that the inner and outer walls are substantially co-cylindrical within each corresponding cylinder. The inner and outer walls for each if the first and second cylinder sleeves define a top sleeve surface configured to accommodate at least part of a head gasket.

In the aforementioned example, non-limiting embodiment, the thrust sleeve region and the anti-thrust sleeve region of each of the first and second cylinder sleeves may be aligned with a corresponding thrust region and a corresponding anti-thrust region in each of the first and second cylinders. The pair of Siamese regions in the first and second cylinders may also be disposed opposite to each other. However, it is understood that one of the pair of Siamese regions defined by the first cylinder may be disposed adjacent to a Siamese region of the second cylinder. Similarly, a Siamese sleeve region in the first cylinder sleeve may be disposed proximate to another Siamese sleeve region in the second cylinder sleeve.

The outer wall of each of the first and second cylinder sleeves may define an elliptical cross section while the inner wall of each of the first and second cylinder sleeves defines a circular cross section. The first and the second cylinders each define an elliptical cylinder bore configured to align with the elliptical cross section of the outer wall of the corresponding first and second cylinder sleeves. It is further understood that the Siamese sleeve regions in the first and second cylinder sleeves are configured to undergo thermal expansion when the internal combustion reaches a predetermined temperature. Moreover, the top sleeve surface for each of the first and the second cylinder sleeves may be configured to support a stopper. In the aforementioned example, non-limiting embodiment, a combustion bead may also be spaced apart from each of the first and the second cylinder sleeves yet surrounds each of the first and the second cylinder sleeves.

It is also understood that the thrust sleeve region and the anti-thrust sleeve region each define a thick width at the top sleeve surface of each of the first and second cylinder sleeves while each Siamese region in the pair of Siamese regions in the first and second cylinder sleeves defines a Siamese region width at the top sleeve surface of each of the first and second cylinder sleeves. The thick widths are each greater than each of the Siamese region widths. Moreover, noting that the cylinder sleeve thickness progressively increases in the thrust sleeve region and the anti-thrust sleeve regions of each of the first and second cylinder sleeves, the cylinder sleeve width remains fixed in each Siamese region. Therefore, the Siamese region width at the top sleeve surface of each of the first and the second cylinder sleeves is equal to a sleeve thickness along a longitudinal length of the cylinder sleeve in each Siamese region.

Accordingly, in the aforementioned, non-limiting example embodiment, the top sleeve surface of each of the first and the second cylinder sleeves defines an elliptical shape while the bottom edge of each of the first and the second cylinder sleeves defines a circle shape. Similarly, the top opening of each of the first and the second cylinders defines an elliptical shape while a bottom surface of each of the first and the second cylinders defines a circle shape. Lastly, it is understood that the cylinder block of the present disclosure may optionally include a plurality of sets of cylinder assemblies wherein each set of cylinders assemblies includes the first cylinder, the first cylinder sleeve, the second cylinder, and the second cylinder sleeve.

The present disclosure and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.

DETAILED DESCRIPTION

Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present disclosure, which constitute the best modes of practicing the present disclosure presently known to the inventors. The figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the present disclosure that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the present disclosure and/or as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

It is also to be understood that this present disclosure is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present disclosure and is not intended to be limiting in any way.

The phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. The phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.

The terms “comprising”, “consisting of”, and “consisting essentially of” can be alternatively used. Where one of these three terms is used, the presently disclosed and claimed subject matter can include the use of either of the other two terms.

The advantage of an internal combustion engine design having a cylinder block with sleeved cylinders is to have both a light, resilient engine and rigid cylinders, especially cylinders that are hard enough to withstand the friction of the piston.

However, it has been observed that, when the cylindrical wall of a traditional cylinder is lined with a straight cylinder sleeve (SeeFIGS. 2A-2B), this produces a major problem that arises primarily at the time of the combustion stage, when the stresses from the explosion and attendant thermal changes are added to the stresses on the cylinder block from the compression forces. Thus, the cylinder block design, as mentioned above, must address the necessity of forming a seal between the cylinder block and the cylinder head, among other requirements. This seal is formed by means of a cylinder head gasket made of a plurality of superimposed foil sheets, for example. In this way, the cylinder head gasket is capable of forming a seal between the cylinder block and the cylinder head with a predetermined flexibility in an axial direction of the cylinder.

However, this seal can only be completely effective when the cylinder block surface facing the surface of the cylinder head behaves more or less uniformly the whole time the engine is running. It is easy to see that making the cylinder block out of two materials—i.e., the cylinder block itself from a light, relatively soft alloy and the cylinder sleeve(s) from a heavy, hard material—also results in different thermal behaviors for the two components of the cylinder block. In addition, thermal behavior requires careful consideration in the design of the cylinder block, since it is more or less difficult to design the air or liquid cooling system for the cylinder block, depending on the dimensions of the cylinder block and the number of cylinders and their arrangement.

Furthermore, in many engines the top sleeve surfaces of the cylinder sleeves are lower than a plane determined by the contact surface between the cylinder block and the cylinder head. Consequently, in such a situation the cylinder head gasket rests primarily or even exclusively on the light metal body of the cylinder block. Moreover, at the moment of combustion—that is, the moment the fuel explodes—the expansion of each of the cylinder sleeves produces extraordinary pressure on the bridge142(FIG. 2A) formed by the part of the cylinder block located between two neighboring cylinders. The compression exerted on this part of the cylinder block plays its own part in increasing the fragility of the cylinder block.

Another major drawback is the expansion of this very part that forms the bridge between two neighboring cylinders. This expansion exerts strong pressure, first of all, on the cylinder head gasket, because the metal becomes plastic in this part of the cylinder block. This expansion exerts strong pressure on the two neighboring sleeves as well, to “create” the space needed for its expansion. The resulting deformation of the cylinder sleeves is very detrimental to the contact between the inner walls of the sleeves and the corresponding pistons. Lastly, as the engine cools, the plasticity of the metal—particularly when it is aluminum—can cause cracks to form between the sleeves and the cylinder block, which impairs the head gasket seal. One location that is particularly subject to these stresses and is particularly critical in determining whether the cylinder block can withstand thermal stresses is the space between two neighboring cylinders.

In the traditional design of a cylinder block with at least two sleeved cylinders112,114the cylinder sleeves120have the general shape of a straight cylindrical tube with a Siamese region width154wherein an inner wall guides a piston180translationally and an outer wall to be supported by the cylindrical wall of the recess that forms the cylinder. (SeeFIGS. 2A-2B). The inner and outer walls of the sleeve are substantially co-cylindrical, but not necessarily rotationally cylindrical, and they delineate between them a top sleeve surface of the sleeve intended to accommodate at least part of a head gasket.

On a traditional cylinder block having two or more cylinders, each equipped with a straight cylinder sleeve, there is an alternation between less thermally conductive hard areas, formed by the cylinder sleeves, and thermally conductive softer areas formed by different parts of the body of the cylinder block. Due to the limited space available between two neighboring cylinders, it is generally impossible to insert coolant channels so as to avoid overheating the space between two neighboring cylinders during the combustion stage. This results in a high risk of cracking, which can impair the resistance of the cylinder block to operating stresses.

Another disadvantage (often a major one) is thermal expansion of the light metal—aluminum, for example—in the space bridge142(FIG. 2A) between two cylinders. This exerts very strong pressure on the cylinder head gasket (the interbore area becomes plastic) and bends the sleeves in the interbore area toward the inside of the cylinder barrels, which is very detrimental to the proper piston/sleeve interaction. Accordingly, the present disclosure provides a cylinder block10(FIG. 1) which resolves the aforementioned issues.

Therefore, the present disclosure provides a cylinder block10for an internal combustion engine wherein the cylinder sleeves20,22maintain position—rotationally within the cylinder (about axis25inFIG. 3A) and axially within the cylinder (along axis25inFIG. 3A). As described herein, the cylinder sleeves20,22include a tapered cross-section along the longitudinal axis25of each cylinder which prevents undesirable axial movement of the cylinder sleeves20,22due to thermal expansion. The cylinder sleeves20,22also include an elliptical cross-section in plan view (FIG. 1) to prevent rotational axis within the cylinder (about axis25inFIG. 3A). Accordingly, a cylinder block according to the present disclosure includes a first cylinder12, a first cylinder sleeve20, a second cylinder14, and a second cylinder sleeve22. The first cylinder12defines a first cylindrical wall16while the second cylinder14defines a second cylindrical wall18. The first cylinder sleeve20lines the first cylindrical wall16while the second cylinder sleeve22lines the second cylindrical wall18. Each of the first and the second cylinder sleeves14,22define a thrust sleeve region28, an anti-thrust sleeve region30opposite the thrust sleeve region28, and a pair of Siamese sleeve regions32. The outer wall26of each of the first and second cylinder sleeves20,22progressively widens along longitudinal axis25(toward the top sleeve surface34) of each of the first and second cylinder sleeves20,22. However, the thick widths52at the thrust and anti-thrust sleeve regions28,30are each greater than the Siamese region widths52at the Siamese sleeve regions.

The aforementioned configuration accommodates the thermal expansion which may occur in the first and second cylinder sleeves20,22which occurs in the regions (Siamese regions) disposed between each cylinder. It is understood that water jacket disposed proximate to the thrust and anti-thrust regions prevents the thrust sleeve region28and the anti-thrust sleeve regions30from overheating and undergoing excessive thermal expansion. Moreover, the elliptical configuration of each of the first and second cylinder sleeves20,22at and proximate to each top sleeve surface34also prevents each of the first and second cylinder sleeves20,22from rotating within each cylinder or cylinder bore. As shown inFIGS. 3A-3C, the inner and outer walls24,26are substantially co-cylindrical within each corresponding cylinder. The inner and outer walls24,26for each if the first and second cylinder sleeves20,22define a top sleeve surface34configured to accommodate at least part of a head gasket36.

In the aforementioned example, non-limiting embodiment, the thrust sleeve region28and the anti-thrust sleeve region30of each of the first and second cylinder sleeves20,22may be aligned with a corresponding thrust region29(FIG. 1) and a corresponding anti-thrust region31(FIG. 1) in each of the first and second cylinders12,14. The pair of Siamese regions42,42′ in the first and second cylinders12,14may also be disposed opposite to each other. However, it is understood that one Siamese region42of the pair of Siamese regions42defined by the first cylinder12may be disposed adjacent to a Siamese region42′ in the pair of Siamese regions42′ for the second cylinder14. Similarly, a Siamese sleeve region32in the first cylinder sleeve20may be disposed proximate to another Siamese sleeve region32in the second cylinder sleeve22. The cylinder block10experiences very high temperatures in the Siamese regions42(and Siamese sleeve regions32) between each cylinder12,14while the thrust and anti-thrust regions29,31(FIG. 1) of the cylinder block10experience relatively lower temperatures due to the proximate water jackets82. Moreover, in light of the combustion occurring closer to the top portion21of each of the cylinders12,14, the top portion21of each of the first and second cylinders12,14(and each of the first and second cylinder sleeves20,22) experience a higher temperature gradient relative to the bottom portion23of each of the first and second cylinders12,14and each of the first and second cylinder sleeves20,22. SeeFIG. 3A.

The outer wall26of each of the first and second cylinder sleeves20,22may define an elliptical cross section44while the inner wall24of each of the first and second cylinder sleeves20,22defines a circular cross section46. The first and the second cylinders12,14each define a tapered cylinder bore47configured to align with the elliptical cross section44of the outer wall26of the corresponding first and second cylinder sleeves20,22. The tapered cylinders (or cylinder bores)12,14are tapered along longitudinal axis24(FIG. 3A). It is further understood that the Siamese sleeve regions32in each of the first and second cylinder sleeves20,22are configured to undergo thermal expansion when the internal combustion reaches a predetermined temperature. However, due to the tapered nature of each of the first and the second cylinder sleeves20,22along the longitudinal axis25, each cylinder sleeve20,22will not thermally expand to the point at which the sleeves20,22expand and disrupt the gasket seal36which interfaces with the cylinder head (not shown). As shown, the top sleeve surface34for each of the first and the second cylinder sleeves14,22may be configured to support a head gasket36. In the aforementioned example, non-limiting embodiment, a combustion bead48may also be spaced apart from each of the first and the second cylinder sleeves14,22yet surrounds each of the first and the second cylinder sleeves14,22.

It is also understood that the thrust sleeve region28and the anti-thrust sleeve region30each define a thick width52at the top sleeve surface34of each of the first and second cylinder sleeves20,22while each Siamese region in the pair of Siamese regions42,42′ in the first and second cylinder sleeves20,22defines a Siamese region width54at the top sleeve surface34of each of the first and second cylinder sleeves20,22. The thick widths52in the anti-thrust sleeve regions30and thrust sleeve regions28are each greater than each of the corresponding Siamese region widths54. Accordingly, the elliptical configuration56at each top sleeve surface34prevents each cylinder sleeve20,22from rotating within each cylinder bore12,14. As shown inFIGS. 3A-3C, the cylinder sleeve thickness52(thick width52) progressively increases along the longitudinal axis25in the thrust sleeve region28and the anti-thrust sleeve regions30of each of the first and second cylinder sleeves20,22while the cylinder sleeve width (Siamese region width54) also progressively increases along the longitudinal axis25in each Siamese sleeve region32. However, it is understood that thick width52at any point along axis25is greater than any corresponding Siamese region width54along axis25. Therefore, as shown inFIG. 3C, the Siamese region width54at the top sleeve surface34of each of the first and the second cylinder sleeves14,22similarly progressively increases (like that in the anti-thrust region and thrust region) along the longitudinal length/axis25of the cylinder sleeve20,22.

Accordingly, referring now toFIG. 5, in the aforementioned, non-limiting example embodiment, the top sleeve surface34of each of the first and the second cylinder sleeves14,22defines an elliptical shape56while the bottom edge58of each of the first and the second cylinder sleeves14,22defines a circle shape60. Similarly, the top opening62of each of the first and the second cylinders12,14defines an elliptical configuration66while a bottom surface64of each of the first and the second cylinders12,14defines a circle configuration68. Lastly, it is understood that the cylinder block10of the present disclosure may optionally include a plurality of sets50of cylinder assemblies (as shown inFIG. 1) wherein each set50of cylinders assemblies includes the first cylinder12, the first cylinder sleeve20, the second cylinder14, and the second cylinder sleeve22.