Engine Block for an Internal Combustion Engine of a Motor Vehicle and Method of Manufacturing an Engine Block for an Internal Combustion Engine of a Motor Vehicle

Abstract

An engine block for an internal combustion engine of a motor vehicle has a cylinder within which a piston can be movably accommodated between a top dead center and a bottom dead center and has a cylinder bore, the internal cylinder diameter of which expands in the direction of the bottom dead center. The internal cylinder diameter expands only below the region in which a piston system change takes place during operation of the internal combustion engine. The internal cylinder diameter tapers from the top dead center to the region.

Claims

1.-5. (canceled)

6. An engine block for an internal combustion engine of a motor vehicle, comprising: a cylinder within which a piston is movably accommodated between a top dead center and a bottom dead center; wherein the cylinder has bore and wherein an inner diameter of the bore widens in a direction of the bottom dead center; wherein the inner diameter only widens below a region in which a piston system change takes place during operation of the internal combustion engine and wherein the inner diameter tapers from the top dead center to the region.

7. The engine block according to claim 6, wherein the inner diameter widens to the bottom dead center.

8. The engine block according to claim 6, wherein the inner diameter widens conically.

9. A method for producing an engine block for an internal combustion engine of a motor vehicle having a cylinder within which a piston is movably accommodated between a top dead center and a bottom dead center, comprising the step of: machining a bore of the cylinder such that an inner diameter of the bore widens in a direction of the bottom dead center, such that the inner diameter only widens below a region in which a piston system change takes place during operation of the internal combustion engine, and such that the inner diameter tapers from the top dead center to the region.

10. The method according to claim 9, wherein the widened inner diameter is produced by honing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a side cross section of two different cylinders of an engine block, wherein a respective piston is at top dead center; and

[0015] FIG. 2 is a further side cross section of the two cylinders, wherein the respective pistons are at bottom dead center.

DETAILED DESCRIPTION OF THE DRAWINGS

[0016] In the figures, identical or functionally identical elements are provided with identical reference signs.

[0017] Two different cylinders 10, 12, which are each part of respective combustion engines not shown in detail, are shown in a cut side view in FIG. 1. The respective pistons 14 are arranged in FIG. 1 in their top dead center OT. The cylinders 10, 12 are both shown in the heated state, which they reach after a certain duration in the fired operation of the respective combustion engines. The shape of the cylinders 10, 12 shown here corresponds to that of the cylinders 10, 12 when they reach their usual operating temperature during operation of the respective combustion engines.

[0018] The two cylinders 10, 12 differ with respect to the geometry of the respective cylinder bores 16, 18. In the heated state shown here, the diameter D of the cylinder bore 16 of the left cylinder 10 decreases in the direction of a bottom dead center UT of the piston 14. The cylinder bore 16 therefore tapers downwards in accordance with the present diagram. In the cold state, however, the diameter D of the cylinder bore 16 of the left cylinder 10 is constant, i.e., it does not change in the axial direction of the cylinder bore 16.

[0019] In the heated state shown here, the diameter D of the cylinder bore 18 of the right of the two cylinders 12 also changes in the axial direction of the cylinder 12. However, the diameter D of the cylinder bore 18 widens below an area X in which a piston system change of the piston 14 takes place during operation of the combustion engine. Starting from area X, the diameter D of the cylinder bore 18 widens conically in the direction of the bottom dead center UT of the piston 14, with the diameter D of the cylinder bore tapered from top dead center OT to area X. The diameter D of the cylinder bore 18 widens in the direction of the bottom dead center UT of the piston 14.

[0020] This form of the cylinder bore 18, which widens in an area B, is achieved by not producing the cylinder bore 18 with a constant diameter D. The cylinder bore 18 is not produced with a constant diameter D. Instead, the cylinder bore 18 is produced in such a way that it expands in the cold state in area B, i.e., the diameter D increases from area X of the piston system change to the bottom dead center UT. The degree of diameter enlargement in the cold state of cylinder 12 is selected so that cylinder 12 has a trumpet-like widening shape in the direction of the bottom dead center UT even at operating temperature. In contrast to the left cylinder 10, the cylinder bore 18 of the right cylinder 12 does not taper in the direction of the bottom dead center UT when heated, but instead widens in the direction of the bottom dead center UT when heated.

[0021] FIG. 2 shows the two pistons 14 guided in the respective cylinders 10, 12 in their respective bottom dead centers UT. Again, the two cylinders 10, 12 are shown in the heated state, which they reach after a certain operating time of the respective combustion engines. As already explained, the left of the two cylinders 10 has a cylindrical shape in the cold state with a constant diameter D of the cylinder bore 16, whereas the right of the two cylinders 12 in the cold state expands the cylinder bore 18 in the area B in the direction of the bottom dead center UT.

[0022] Due to the completely cylindrical shape of the cylinder bore 16 in the cold state and other factors, such as the required tightening of cylinder head bolts, different thermal expansions of the cylinder 10 in fired operation and pressures occurring inside the cylinder 10 during combustion, there are, as can be seen in FIGS. 1 and 2, significant deviations from the ideal cylinder shape which the cylinder bore 16 has in the cold state.

[0023] In the case of the left of the two cylinders 10, the problem arises in the heated state shown here that the piston 14 in the fired state has an overlap 20 with the cylinder bore 16 due to the diameter D decreasing in the direction of the bottom dead center UT. In the vicinity of the bottom dead center UT, the piston diameter is larger than the diameter D of the cylinder bore 16. The piston 14 therefore touches the cylinder bore 16 during the up and down movement between the top dead center OT and the bottom dead center UT. As a result, friction losses occur and unwanted noises develop.

[0024] In the case of the right cylinder 12, on the other hand, wherein the diameter D of the cylinder bore 18both in the cold and in the heated stateexpands successively in region B in the direction of the bottom dead center UT in region B, there is a certain piston clearance of piston 14 in the radial direction in the entire region B. In the case of the right cylinder 12, on the other hand, the diameter D of the cylinder bore 18 expands in the direction of the bottom dead center UT in the same direction as in the cold state. This has a positive effect on noise development and friction losses, which can therefore be minimized.

[0025] Due to the trumpet-shaped diameter expansion of the cylinder bore 18 in area B, a certain distance 22 is always maintained between the cylinder bore 18 and the piston 14 in the radial direction. Due to the expansion of the cylinder bore 18 in the direction of the bottom dead center UT, a radial increase in play is achieved between the piston 14 and the cylinder bore 18. This means that overlapping conditions between the piston 14 and the cylinder bore 18 can be ruled out. As a result, considerable consumption and acoustic advantages can be achieved.