Engine block of a diesel engine with integrated cylinder head, and casting method

Abstract

An engine block of a diesel engine cast integrally with the cylinder head, with a number of cylinders in line, including an outer wall (21) and a cylinder wall (13) for each cylinder with a first cooling space (22) for a liquid cooling medium and with a second cooling space (25) on top of a cylinder ceiling (14) with openings (15,16) for gas exchange valves, the first cooling space (22) enclosing all the cylinder walls (13) entirely. In order to strengthen and cooling the vulnerable zone at the transition from cylinder wall (13) to cylinder ceiling (14) the first cooling space of adjacent cylinders forms a gap (23) with a width (35) constant or increasing from top to bottom.

Claims

1. Engine block of a diesel engine cast integrally with a cylinder head, comprising a plurality of cylinders in line, including an outer wall (21) and a cylinder wall (13) for each cylinder with a first cooling space (22) for a liquid cooling medium between them and with a second cooling space (25) on top of a cylinder ceiling (14) with openings (15,16) for gas exchange valves, the first cooling space (22) enclosing all the cylinder walls (13) entirely and extending all around upwards beyond the cylinder ceiling (14), wherein the first cooling space (22) between the cylinder walls (13) of adjacent cylinders forms a gap (23) with a width (35) which is one of (a) constant and (b) increasing from top to bottom, wherein the gap (23) extends upward beyond the cylinder ceiling (14) and ends in an extension (24) overlapping and partly embracing the cylinder ceiling (14).

2. Engine block according to claim 1, wherein the first cooling space (22) overlaps (30) the cylinder ceiling (14) at least in the region of the openings (16) for the exhaust valves.

3. Engine block according to claim 1, wherein a first horizontal transverse bore (27) is provided by means of which the two cooling spaces (22,25) are connected, the first transverse bore (27) penetrating an outer wall (21) and hitting the first cooling space (22), which cooling space (22) reaches beyond the cylinder ceiling (14), wherein a second horizontal transverse bore (33) is provided for connecting the two cooling spaces (22,25), the bore (33) penetrating the outer wall (21) on the opposite side and ending near the injector, in this way the cooling liquid flowing upwards from the first cooling space (22) is directed to the injector (17).

4. Engine block according to claim 1, wherein the outer wall (21) and the cylinder wall (13) for each cylinder are integral portions of the engine block cast integrally with the cylinder head.

5. Process for casting an engine block according to claim 1, wherein parts of a core are formed separately in core moulds and a core part (22*) corresponding to the first cooling space (22) is made in the region of the gap (23) between adjacent cylinders by means of separate inserts (43,53) having a shape which corresponds to the constant width of the gap or the width of the gap increasing from top to bottom, wherein the inserts (53) are slid into the core mould for shaping the core in vertical direction (57), and the core part made in the core mould (50) including the insert (53) is lifted out vertically and the insert is removed sideways.

6. Process according to claim 5, wherein the insert (53) has a dove-tail shaped guideway (54) at its backside which is opposite the side facing the core part (22*).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention will be described and commented along with the following drawings:

(2) FIG. 1: A longitudinal section of a generic engine according to the state of the art,

(3) FIG. 2: A longitudinal section of a part of an engine according to the invention,

(4) FIG. 3: A cross section of the engine of FIG. 2 along III-III in FIG. 5,

(5) FIG. 4: A cross section of the engine of FIG. 2 along IV-IV in FIG. 5,

(6) FIG. 5: A horizontal section of the engine of FIG. 2 along V-V in FIGS. 3,

(7) FIG. 6: A cross section through the mould for casting the engine block of FIG. 2,

(8) FIG. 7: A core mould for making a core part for the casting mould according to the inventive method.

DETAILED DESCRIPTION

(9) Referring to FIG. 1, the problem the invention sets out to solve will be explained with regard to the state of the art. The engine block 1 with a number of cylinders in line is cast integrally with the cylinder head part 2. The cylinder walls 3 enclose the combustion space 5 and are enclosed by cooling spaces and circulated around by a cooling liquid (normally water). In the casting mould, the cooling spaces are materialized by sand core parts. These are formed in special core moulds. In order to withdraw the core parts from the core mould without damage, a draft angle of some degrees must be implemented; all the more the thinner and more fragile the core parts are. The core is particularly thin in the gap 6 between the cylinder walls 3 of adjacent cylinders. Due to the draft angle, the width of the gap 6 increases from below up to the cylinder ceiling 4 and the wall thickness of the cylinder walls therefore decreases. By this, the cylinder walls 3 are thinnest in the transition to the cylinder ceiling 4, the region of highest mechanical and thermic strain. This weakness limits the specific power of the engine, lest cracks would occur in this region.

(10) FIG. 2 shows the engine block according to the invention in longitudinal section, the section being only through part of an engine of, for example, 6 cylinders. The engine block 10 comprises a cylinder part 11 and an integral head part 12. Each cylinder comprises a cylinder wall 13 and a cylinder ceiling 14 with an opening 15 for a suction valve, an opening 16 for an exhaust valve and an opening for an injector 17 (FIG. 3). An inlet channel 31 leads to opening 15 and an exhaust channel 32 (FIG. 4) starts from opening 16.

(11) FIG. 3 is a first cross section of the engine block. Cylinder wall 13 and cylinder ceiling 14 enclose a combustion space 18 each. Each cylinder wall is enclosed by a first cooling space 22. It is common to all cylinders and its outer enclosure is an outer wall of the engine block 10. The first cooling space extends from the lower region of the engine block 10 upwards and ends higher than the outer surface of the cylinder ceiling 14 at 29. The first cooling space 22 forms a gap 23 (see FIG. 2) between adjacent cylinders. The width 35 of this gap 23 according to the invention is constant or decreases from bottom to top or even has a special contour. There could be a bridge between adjacent cylinders, for example. This gap 23 extends upwards beyond the cylinder ceiling 14 and ends in an extension 24 overlapping and partly embracing the cylinder ceiling 14. By this, the thickness of the cylinder wall 13 in the vulnerable region (8 in FIG. 1) is not reduced or even increased and the transition to the cylinder ceiling 14 is circumflown.

(12) The cylinder head part 12 includes a second cooling space 25 separated from the first cooling space 22 by a partition wall 26. The partition wall 26 is of crumbled shape and, taking part in the in the formation of inlet channel 31, exhaust channel 32 and the opening for the injector 17, has also vertical regions. Between these, the partition wall 26 extends downwards until the outer surface of the cylinder ceiling 14 with which it merges. The second cooling space 25 thus ends lower than the top region 29 of the first cooling space 22. In order to connect the second cooling space 25 with the first cooling space 22, merely a first horizontal transverse bore needs to be drilled in the readily cast engine block and closed by a plug 28 at its outer end.

(13) FIG. 4 shows a second section across the engine block 10 in a different parallel plane. This section runs across the opening 16 for the exhaust valve. Here, it is clearly visible that the first cooling space 22 very substantially overlaps the cylinder ceiling 14 in the region of the exhaust valve, at 30. A second transverse bore 33 can be seen here on the other longitudinal side 21 of the engine block, also connecting the first cooling space 22 with the second cooling space 25. Its outer end is closed by a ball 34. The second transverse bore 33 is directed towards the injector 17, cooling this sensitive organ as well.

(14) Horizontal section of FIG. 5 is in a plane through the center lines of the transverse bores 27, 33. It intersects the partition wall 26 separating the two cooling spaces (22,25), and also the outer walls 21, see the hatched patches. It shows the first cooling space 22 between the outer walls 21 and the cylinder walls 13 of the individual cylinders and the gap 23 between adjacent cylinders. The core, mentioned below, corresponds to the first cooling space 22. The core includes core parts in and around this gap 23, of particular concern. The situation would be similar with an engine with four valves per cylinder.

(15) FIG. 6 shows the casting mould for casting an engine block according to the invention, summarily indicated with 40, as an introduction to the description of the casting method according to the invention. In a two-part core box (OK and UK), indicated only by the separation line 41, core partsnot shown in detailare inserted. The core parts correspond to the hollows of the cast piece (for example core part 22* to the first cooling space 22, and so on). Essential for the invention is core part 22* for the first cooling space 22. Further core parts are core part 25* for the second cooling space 25 and the core parts corresponding to the channels 31, 32.

(16) FIG. 7 depicts the forming tool essential for the casting process according to the invention. Its purpose is the making of the core part 22* and it is summarily indicated with 50. The inner contour of the outer walls 56 of the forming tool corresponds to the inner contour of the outer wall 21 of the engine block and the towers 51 correspond to the outer contour of cylinder wall 13 and cylinder ceiling 14. Each of the towers 51 has a vertical (thus not inclined by the draft angle) dovetail groove 52 for an insert 53 which is shifted (arrow 57) into the grooves in vertical direction as part of the forming tool for making the core part

(17) The insert 53 has a front surface 55 with a generatrix that is also vertical or even of arbitrary shape. In the latter case, the shape of the front surface can have particular features (for example also crevasses corresponding to a bridge between adjacent cylinders, not shown). The front surface 55 corresponds to the shape of core part 42 in the gap 23 between adjacent cylinders. As next step, the core part is built by insufflating core sand into the core mould 50. The so shaped core part 42 is extracted along the dovetail grooves 54 from the core mould together with the insert 53. This is enabled by the vertical guidance provided by the grooves 54. As next step, the inserts 53 are separated from the core part 42 in horizontal direction and core part 22* is ready for fitting in the mold, with the contour of the gap 23 according to the invention.