GB2030647A

GB2030647A - Internal Combustion Engine Cylinder Block and Crankcase Construction

Info

Publication number: GB2030647A
Application number: GB7931595A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-09-21
Filing date: 1979-09-12
Publication date: 1980-04-10
Also published as: GB2030647B

Abstract

The end wall 24 of a crankcase which is sufficiently strong to support a transmission 34, 35 is bolted to an engine body which comprises a cast block 1 providing the cylinders 2, a robust lower deck 5, upper bearing halves 6 and crankcase side walls which are connected to the bearing halves only through the lower deck. The omission of direct connections between the bearing halves 6 and the crankcase side and end walls contributes together with gaskets between these walls to reduction of noise transmission. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Internal Combustion Engines This invention relates to internal combustion engines, particularly diesel engines, and one aim of the invention is to diminish both the weight of such engines and the noise that they emit in use.

One part of the conventional internal combustion engine (whether diesel or petroldriven) that contributes substantially to both weight and noise is the crankcase. The conventional crankcase is a massive casting, and hence heavy, and as a result of work leading up to the present invention it has now been appreciated that much of the noise emitted by an engine with such a conventional crankcase has been due to the crankcase wails being cast as a single piece together with the upper halves of the main bearings, with several integral stiffening ribs joining the bearing halves to the wall. These connections, it has been appreciated, have readily allowed transmission of transverse vibrations from the bearings to the side walls, causing considerable noise as those walls bow in and out.

Such bowing of the side walls has also led to bowing of the end faces of the engine, leading in turn to distortion of the oil sump.

As another result of the work that led to the present invention, radical re-designs of the conventional engine were proposed in which the engine was provided with a robust lower deck around the level of the pistons at the base of their stroke, but below this level there was no structural strength at all. In one such design there was simply a light-weight, pressed metal trough, similar to a conventional sump but larger so as to enclose the bearings, shaft and cranks, with oil seals, at each end to allow passage for axles of the shaft to protrude. In another such design, escribed for example in UK Patent No.

.1541.421,the crankcase includes a cast unit but is only flexibly attached to the lower deck and is totally unstressed in use. Such designs as these have the disavantage that their iack of structural strength beneath the level of the lower deck imposes the need for much further re-design upon the makers of existing engines in which some good use is made of the structural strength of the crankcase, especially to support an end wall of the engine to which the transmission can be attached.

The present invention is an internal combustion engine comprising a cylinder block including a robust lower deck, main bearings supported from this lower deck, and a crankcase including rigid side walls suspended from the lower deck but without any transverse connection with the driven shaft. At least one of the end walls of the crankcase, when connected to the side walls, is sufficiently rigid for the transmission of the engine to be attached to and suported from it.

Connection between the end and side walls of the crankcase may be by bolting or other rigid means, for instance, and the end wall that supports the transmission may with advantage be formed as a single piece extending upwards across and in register with the end of the cylinder block.

The side walls of the crankcase may be cast of one piece witch the cylinder block, especially with the robust lower deck of that block.

Gaskets to ensure the necessary fluid seal at the joints between the end walls and side walls of the crankcase may with advantage add further damping to minimise transmission of vibrations between end and side walls and vice versa.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a section through part of an engine, taken in the plane including the axes of the cylinders and of the crankshaft, and Figure 2 is a section taken in a plane at right angles which includes the axis of one of the cylinders.

The largest component of the engine shown is a single massive casting 1 including the walls 2 (containing cooling passages 3) of cylinders 4, a robust cylinder block lower deck 5 situated at a level designed to exhibit low mobiiity, the upper halves 6 of main bearings 7, and the cantilevered side walls 8 of crankcase 9. As Figure 2 shows best, walls 8 are stiffened axially by their curved or cranked form, carry an end flange 11 with bosses 10 to which an end wall of the crankcase may be attached by bolts, and are joined to upper main bearing halves 6 by way only of lower deck 5; the traditional cast transverse webs connecting these two parts are absent.

The lower halves 12 of main bearings 7 are secured in place by studs 13, the threaded ends 14 of which screw into threaded sockets formed in the underside of lower deck 5. Studs 13 pass with clearance through bores in upper halves 6.

This method of attachment not only ensures that both halves of the main bearings are supported only from lower deck 5, without any direct transverse connection with the crankcase side walls 8; it also has the useful effect of prestressing the top halves. Main bearings 7 support crankshaft 1 5 which is driven by pistons 1 6 by way of connecting rods 1 7 and cranks 18. At its forward end crankshaft 1 5 carries a stub axle 1 9 which passes through the crankcase front wall 20 by way of an oil seal 21 so that only negligible forces are transmitted from the wall to the axle, and vice versa. Front wall 20 is attached to flange 11 by means of bolts 21 a, and is joined to the front wall 22 of sump 23 by a resilient gasket 22a.As the figures show, sump 23 is connected to the lower edges of side walls 8 and the engine rear wall 24 by similar flexible gaskets 25 and 26 respectively. Axle 1 9 carries a gear 27 by which oil pump 28 (mounted on the lower half of the most forward bearing 7) is driven by an intermediate gear 28a, and also carries driving pulleys 29 and 30.

At the rear end of crankshaft 15, a stub axle 31 projects through a fluid seal 32 in the engine rear wall 24, carries the engine flywheel 33 and is directly attached, by means not shown, to the main input shaft 34 of the transmission. The transmission housing 35 is directly attached to and supported by the rear end wall 24. As Figure 1 shows, wall 24 extends upwards across the rear face of the cylinder block to the level of an upper deck 36 at the top of cylinders 4, where it makes a gasketed joint with the cylinder head structure of which a fragment is shown at 37. Wall 24 is thus a quite substantial structure, including an oil duct 38; it is separate from the main casting 1, being attached to it by bolts such as 39 and in particular the quite customary cast ribs joining the end wall to the upper halves of the main bearings are absent; the only connection between main bearings and wall 24 is by way of lower deck 5.

However, when assembled with casting 1 and with the end faces of cantilevered crankcase side walls 8, and particularly when it extends across the cylinder block also, the end wall 24 is rigid enough to provide support for the transmission and its housing 35.

Claims

1.An internal combustion engine comprising a cylinder block including a robust lower deck, main bearings supported from this lower deck, and a crankcase which is stressed in use and has end wails and side walls, the side walls being suspended from the lower deck but without any transverse connection with the driven shaft between the two end walls, and in which at least one of the end walls is sufficiently rigid for the transmission of the engine to be attached to and supported from it.

2. An internal combustion engine according to Claim 1 in which the end and side walls of the crankcase are separately formed and connected by bolts or the like.

3. An internal combustion engine according to Claim 1 in which the end wall of the crankcase that supports the transmission is formed as a single piece extending upwards over and in register with an end of the cylinder block.

4. An internal combustion engine according to Claim 1 in which the side wails of the crankcase are cast in one piece with the robust lower deck of the cylinder block.

5. Apparatus according to Claim 1, substantially as described with reference to the accompanying drawings.