Cylinder Sleeve System For High Output Engine

Abstract

A cylinder sleeve system for the cylinder block of a high output internal combustion engine includes a circumferential recess in the upper region of each cylinder bore wall that forms with a cylinder sleeve fitted in the bore an annular coolant chamber surrounding the upper region of the sleeve. The chamber has a shallow radial depth, preferably of constant cross section, so as to cause high, generally uniform velocity coolant flow through the chamber, thereby promoting rapid cooling of the upper region. Coolant discharged from the chamber flows to a coolant jacket surrounding the lower region of the cylinder sleeve, where it circulates at reduced velocity to effect slower cooling of the lower region. The coolant in the upper chamber is thus in direct contact with the sleeve while that in the coolant jacket is contained against such direct contact. The recess is sized and located such that the cylinder sleeve is directly supported by the cylinder bore wall over approximately the lower three-fourths of its length. This configuration permits sleeves of reduced wall thickness to be used.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an improved construction for the cylinder block of a high output internal combustion engine, and particularly concerns a cylinder sleeve system for use in such a block which enhances cooling of vital engine parts while allowing cylinder centerline spacing to be reduced without sacrifice in block rigidity.

Due to unfavorable wear conditions in the cylinder bores of heavy duty internal combustion engines, it has been found necessary to abandon a piston running in direct contact with the cylinder block and to adopt an improved construction where the piston runs in a sleeve, or liner, located within the bore. Two types of sleeve constructions have been used; namely, a dry-sleeve construction, in which the coolant does not directly contact the sleeve wall, and a wet-sleeve construction, wherein it does.

The use of such cylinder sleeves, whether of the wet or dry type, affords advantages in respect of increased resistance to wear inasmuch as the sleeves may be centrifugally cast to yield a significantly more dense and harder bearing surface than can be cast in the supporting cylinder block. Since the sleeves are readily removable from the block, there is the added advanatge of enhanced serviceability.

With high output engines, the wet-sleeve construction is especially desired because of its superior cooling capability, particularly with regard to the piston and piston rings. However, the use of such sleeves leads to a detrimental increase in the cylinder centerline spacing and thus of the overall size of the engine. The greater distance between cylinder centerlines is required to achieve satisfactory block strength and rigidity and sleeve resistance to cavitation damage, and results chiefly from increases in both the cylinder sleeve thickness and block wall thickness attendant to the accomplishment of these requirements.

The present invention overcomes these and other objectionable aspects of the prior art.

SUMMARY OF THE INVENTION

In a preferred embodiment, the sleeve system of the invention includes a recess formed in the cylinder bore wall opposite the upper, i.e., the hottest, region of the sleeve which defines with the opposed sleeve wall an annular chamber for directing coolant flow around the upper sleeve region. Preferably the chamber is given a shallow radial depth, so that the coolant flows through the chamber at high velocity in contact with the sleeve. The coolant exiting from the chamber, now heated, is received by a jacket formed around the lower region of the sleeve, where it is circulated more slowly and contained against direct contact with the sleeve wall. Cooling of the lower sleeve region therefore goes forward at a retarded rate relative to that in the upper region. By this arrangement, heat transfer is carried out most efficiently and most rapidly at the hottest, i.e., combustion, region of the cylinder sleeve where maximum cooling is required, but is reduced over the lower region, which receives little of the heat load from combustion. The result is that a more uniform temperature distribution between the upper and lower sleeve regions is obtained.

As another feature of the invention, the upper chamber desirably has a constant cross-section throughout its length, the velocity of the coolant thereby remaining generally uniform as it circulates around the cylinder sleeve. This further improves cooling characteristics by promoting uniform temperature distributions circumferentially of the sleeve. Furthermore, the recess is sized and located such that the sleeve is directly supported by the cylinder bore wall over approximately three-fourths the length of the sleeve. This load-bearing support allows the sleeve to be made thinner in the upper region than comparable wet sleeves of conventional design, which further enhances cooling of the piston and the piston rings, without cavitation damage. Block walls of reduced thickness may also be used, notwithstanding that the advantages of a wet-sleeve construction in respect of cooling is obtained at the upper region of the cylinder, because the combustion loads are borne both by the cylinder bore wall and the outer coolant jacket wall.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be made to the following description of an exemplary embodiment, taken in conjunction with the figures of the accompanying drawings, in which:

FIG. 1 is an end elevational view, in section, of a multiple-cylinder engine block incorporating the improved cylinder sleeve system of the invention; and

FIG. 2 is a partial side elevational view, in section, of the cylinder block of FIG. 1.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

For convenience of description and illustration, the novel cylinder sleeve system of the invention is described and shown herein in connection with a cylinder block having a plurality of in-line cylinder bores, and where the coolant is assumed to be water. It will be understood, however, that like advantages in respect of improved cooling characteristics and savings in engine weight and size are afforded by the invention with other cylinder arrangements, and whether one or a plurality of cylinders are provided. In a similar vein, although the coolant has been referred to herein as water, it will be understood that any suitable coolant may be used.

As illustrated in FIGS. 1 and 2, the cylinder block of 10 of a high output internal combustion engine typically is formed with a plurality of in-line cylinder bores 12 that extend vertically between a cylinder head 14 at their upper ends and a crankcase 16 at their lower ends. A cylinder sleeve 18, i.e., a liner, is located in each bore 12 in snug engagement with the bore wall 20, and is securely held in place by means of a circumferential flange 21 that is received in a cooperating recess 22 in the bore wall. A groove 24 may be provided in the upper surface of the flange 21 for sealing cooperation with the head 14 upon its attachment to the block 10.

In a vertically oriented cylinder block ofthe type portrayed, combustion of course goes forward in the upper regions of the cylinders, and it is these regions which require the greatest degree of cooling. To that end, a recess 26 is formed in the upper region of each bore wall 20. Preferably, the recess is of a relatively shallow but substantially uniform radial depth throughout its circumferential extent. It forms, therefore, an annular chamber 28 with the opposed wall of the sleeve 18 of generally constant cross section and relatively small radial width. The chamber 28 is formed, preferably on opposed sides, with an inlet 30 and an outlet 32 for receiving and discharging, respectively, a flow of cooling water. A seal ring 34 of appropriate design is positioned at the lower end of the recess 26 to prevent leakage of the water along the interface between the lower region of the sleeve and the facing bore wall 20.

A water gallery 36, communicating with the water pump (not shown) through a fitting 38, extends along one side of the cylinder bores 12 in the direction of their alignment, with the inlet 30 to each chamber 28 opening directly into the gallery 36. A flow of cool water is thus delivered from the gallery 36 to the chambers 28, where, by virtue of the shallow radial depth of the chamber, it flows at a controlled high velocity around the sleeves 18 in a direction generally transverse to the direction of alignment of the bores 12. Since the chambers 28 are of constant cross section, the velocity of the water flowing therethrough remains generally uniform, hence promoting uniform temperature distributions circumferentially of the sleeves 18. Moreover, the shallow radial configuration of the chambers 28 utilized to achieve the high velocity flow inherently reduces the block wall thickness required as compared to conventional cast water spaces typically used in wet sleeve systems. As illustrated in FIG. 2, this contributes to closer cylinder centerline spacing.

Upon leaving the outlet 32 from the chambers 28, the water, now heated as a result of heat transferred to it from the upper regions of the sleeves, enters the upper end of a common water jacket 40 formed between adjacent cylinder bore walls 20 (see FIG. 2) and the sidewalls 42 and 44 (see FIG. 1) of the block 10. The water jacket 40 is sized to have a cross section significantly larger than that of the chambers 28, so that the velocity of the water within the jacket 40 is considerably reduced from that in the chambers 28. This feature, together with the use of the already heated water exiting from the chambers 28 as the coolant for the lower regions of the sleeve 18, results in a much slower rate of heat dissipation in those regions. As the lower regions receive very little of the heat load from combustion, not only is a high heat flow rate not required, but slowing or retardation of the heat flow in the lower regions aids in attenuating temperature gradients between the upper and lower sleeve regions, with consequent alleviation of thermal stresses. It will be appreciated also that this dry-sleeve type construction, i.e., a metal-to-metal interface, over the lower sleeve regions contains the cooling water against direct contact with the sleeves 18, and hence further retards heat flow to it from the sleeves.

The water leaves the water jacket 40 through passages 46 to enter the cylinder head 14 for ultimate return to the water pump. If desired, a direct connection 48 may be made between the gallery 36 and the cylinder head 14 for cooling of the hotter regions of the head.

The axial extent of the chambers 28 is sized to afford the desired degree of cooling for a given application. According to a preferred configuration, the lower end of each recess 26 is spaced below the top of the sleeve by a distance approximately one-fourth the length of the sleeve, or, in other words, the lower three-fourths of the sleeve is supported directly by the bore wall 20. The load-bearing support given to the sleeves 18 by this arrangement allows them to be made thinner at the upper region than is practicable, from the standpoint of cavitation damage, with conventional wet-sleeve designs. Thinning of the upper sleeve region in this manner not only allows a further reduction in cylinder centerline spacing, but additionally enhances cooling of the piston and piston rings. For example, with the sleeve 18 supported in the foregoing manner over approximately three-quarters of its length, the thickness of the sleeve 18 may be reduced to approximately two-thirds of that of a comparable wet sleeve without encountering damage due to cavitation.

The foregoing wet-sleeve/dry-sleeve construction affords the still further advantage of allowing the cylinder block wall thicknesses between sleeves to be reduced without loss of rigidity of the cylinder block 10 becuase the combustion loads are taken in large part by both the associated bore wall 20 and the outer walls 42 and 44 of the water jacket. This is to be contrasted with the normal wet-sleeve design, where only an outer water jacket wall is provided to receive loads from the sleeve.

Although the invention has been described with reference to a specific embodiment thereof, many modifications and variations may be made by one skilled in the art without departing from the inventive concepts disclosed. Accordingly, all such modifications and variations are intended to be included within the spirit and scope of the appended claims.

Claims

We claim:

1. A cylinder block for an internal combustion engine, comprising:

means defining a plurality of vertically extending in-line cylinder bores adapted for the combustion of a fuel-air mixture in the upper regions thereof,

a cylinder sleeve located in each bore in snug engagement with the bore wall, the bore wall extending over substantially the full length and around the full circumference of the sleeve,

means forming a circumferential recess in the wall of each cylinder bore opposite the upper region of the sleeve, the recess extending fully around the sleeve and defining with the opposed wall of the sleeve an annular chamber surrounding the upper sleeve region,

a coolant inlet to each chamber,

a coolant outlet from each chamber, and

means defining a coolant jacket surrounding the lower regions of the cylinder sleeves, whereby coolant delivered to the upper chambers flows therethrough in direct contact with the sleeve walls, thereby promoting rapid cooling over the upper region of the sleeves, and coolant delivered to the jacket is contained against direct contact with the sleeve walls, thereby promoting slower cooling over the lower regions of the sleeves.

2. A cylinder block according to claim 1 wherein the radial depth of each upper chamber is smaller than that of the coolant jacket so as to provide a higher velocity coolant flow in the upper chamber than in the jacket.

3. A cylinder block according to claim 2 wherein the outlet from each upper chamber communicates with the coolant jacket, whereby the coolant delivered to the jacket is preheated by passage through the upper chamber prior to entering the jacket.

4. A cylinder block according to claim 3 wherein each upper chamber has a substantially constant cross section over its full circumferential extent whereby the coolant flows therethrough at a generally uniform velocity.

5. A cylinder block according to claim 1 wherein the lower end of each recess is spaced from the upper end of the sleeve by a distance approximately one-quarter the length of the sleeve, whereby each sleeve is directly supported by the cylinder bore wall over approximately three-quarters of its length.

6. A cylinder block according to claim 1 further comprising means in each cylinder bore defining a seal for preventing leakage of coolant from the upper chamber along the interface between the lower region of the sleeve and the cylinder bore wall.

7. A cylinder block according to claim 1 further comprising:

a coolant gallery extending along one side of the cylinder bores in the direction of alignment thereof, and wherein the inlet to each annular upper chamber is located on the gallery side of the chamber in communication with the gallery for receiving a coolant flow therefrom.

8. A cylinder block according to claim 7 wherein the outlet from each annular chamber is located on the opposite side of the chamber from the inlet, whereby the coolant flows through the chamber in a direction generally transverse to the direction of alignment of the cylinder bores.

9. A cylinder sleeve assembly comprising:

a block having at least one cylinder bore formed therein adapted for the combustion of a fuel-air mixture in the upper region thereof,

a cylinder sleeve located in the bore in snug engagement with each bore wall, the bore wall extending over substantially the full length and around the full circumference of the sleeve,

means forming a circumferential recess in each bore wall opposite the upper region of the sleeve, the recess extending fully around the sleeve and defining with the opposed wall of the sleeve an annular chamber surrounding the upper sleeve region,

a coolant inlet to each chamber,

a coolant outlet from each chamber, and

means, including an outer wall spaced from each cylinder bore wall, defining a coolant jacket surrounding the lower region of each sleeve, whereby coolant delivered to each upper chamber flows therethrough in direct contact with the sleeve wall, thereby promoting rapid cooling of the upper region of the sleeve, and coolant delivered to the jacket is contained against direct contact with the sleeve wall, thereby promoting slower cooling of the lower region of the sleeve.

10. A cylinder sleeve assembly according to claim 9 wherein the radial depth of each upper chamber is smaller than that of the coolant jacket so as to provide a higher velocity coolant flow in the upper chamber than in the jacket.

11. A cylinder sleeve assembly according to claim 10 wherein the outlet from each upper chamber communicates with the coolant jacket, whereby the coolant delivered to the jacket is preheated by passage through the upper chamber prior to entering the jacket.

12. A cylinder sleeve assembly according to claim 11 wherein each upper chamber has a substantially constant cross section over its full circumferential extent, whereby the coolant flows therethrough at a generally uniform velocity.

13. A cylinder sleeve assembly according to claim 9 wherein the lower end of each recess is spaced from the upper end of the sleeve by a distance approximately one-quarter the length of the sleeve, whereby the sleeve is directly supported by the cyinder bore wall over approximately three-quarters of its length.

14. A cylinder sleeve assembly according to claim 9 further comprising means defining a seal for preventing leakage of coolant from the upper chamber along the interface between the lower region of the sleeve and the cylinder bore wall.

15. A cylinder block according to claim 8 wherein each upper chamber has a substantially constant cross section over its full circumferential extent, whereby the coolant flows therethrough at generally a uniform velocity.