GB2187817A

GB2187817A - Crankshafts

Info

Publication number: GB2187817A
Application number: GB08606448A
Authority: GB
Inventors: Graham Ernest Atkin
Original assignee: Rover Co Ltd
Current assignee: Rover Co Ltd
Priority date: 1986-03-15
Filing date: 1986-03-15
Publication date: 1987-09-16
Also published as: GB8606448D0; GB2187817B

Abstract

In a crankshaft having a crankpin 1 with a hollow bore 8, a sleeve 9 is provided to provide an annular region 12 for oil communicating between drillings 10, 11 from the centre of the main bearing and the drillings 13, 14 leading to the big end bearing surface. The sleeve 9 is made of two parts which are inserted from opposite ends of the bore 8 and engage together for securement within the bore. <IMAGE>

Description

SPECIFICATION Crankshafts This invention relates to crankshafts.

In order to reduce the rotational inertia of a crankshaft it is known to provide a hollow cylindrical bore through the crankpin (big end bearing), the bore running parallel to the axis of the crankpin, which is formed for example by coring or drilling.

If the crankpin bearing is lubricated by a drilling extending from an oilway in the crankshaft to the big end bearing via the hollow region, the ends of the hollow region must of course be closed off. The region thus fills with oil but this nevertheless reduces the rotational inertia of the crankshaft compared to the situation where the crankpin is solid. In the interests of reducing the inertia still further it has been proposed (German Patent Publication No. 1008527) to provide a sleeve in the hollow bore. This provides an annular volume of oil to connect the drilling from the main oilway of the crankshaft to the drilling opening at the big end bearing, and reduces the rotational inertia compared to the situation where the entire volume of the bore is filled with oil.

The sleeve seals around its circumference at each end to the wall of the bore.

However, such an arrangement poses manufacturing difficulties because the sleeve which seals against the wall of the bore must be inserted through one end of the bore, with the result that one end of the sleeve is dragged through the bore, impairing its surface finish and hence its ability to seal against the wall of the bore.

The invention provides a crankshaft having a bore through at least one crankpin, a sleeve positioned within the bore to define an annular region, a passage for lubricating fluid extending from the interior of a main bearing region.

to the annular region and a passage for lubricating fluid extending from the annular region to the bearing surface of the crankpin, the sleeve being formed by two inserts which are adapted to be inserted from opposite ends of the bore and be secured together within the bore.

This solves the manufacturing difficulties encountered with the previous design since neither of the regions that seal against the bore have to be dragged through the bore.

Advantageously, one insert has an aperture, and the other has an open-ended tubular extension, which is mechanically deformed around the aperture. Preferably, each insert has a shoulder which can engage against each other. Each insert preferably has longitudinallyextending flutes which assist in location of the inserts within the bore and increase the stiffness of the inserts.

A crankshaft constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial section of a part of the crankshaft showing two main bearings and one crankpin, the crankpin having a sleeve positioned within a bore; and Figure 2 is a perspective view of an insert which forms part of the sleeve shown in Fig.

1.

Referring to the drawings, the crankshaft is for a six cylinder engine, and may be a steel forging. In the drawings, however, only one crankpin (big end bearing) 1 is shown together with the two adjacent main bearings 2, 3. The big end bearing 1 accommodates two big ends (not shown) of connecting rods. Webs 4, 5 connect the big end and main bearings in the usual way while counterweights 6, 7 are provided to balance the revolving masses.

The crankpin 1 is bored out (if necessary the adjacent counterweights are also bored out to obtain axial access to the crankpin) at 8 to reduce the rotational inertia, and a twopart sleeve 9 is positioned in the bore. Drillings 10, 11 extend from the centre of the main bearing to the annular clearance 12 between the sleeve 9 and the bore 8. Further drillings 13, 14 extend from the other side of the annular clearance 12 to oil holes 15, 16 at the surface of the big end bearing. The centre of the main bearing is supplied with oil under pressure by means (not shown).

The left-hand insert is shown in detail in Fig.

2 it is generally tubular and has a stepped sealing portion 17, raised flutes 18, and a projecting shoulder 19 with a tubular connecting part 20 projecting from the shoulder. The right-hand insert is the same as the left-hand one, except that it does not have the tubular connecting part but instead has a circular aperture to receive the connecting part of the other insert.

The assembly of the two parts is as follows. The left-hand insert is pressed in through the left-hand side of the bore 8 and the right-hand insert is pressed in through the right-hand side of the bore. Two tools which engage the inner periphery of the shoulders of the inserts are inserted into each end of the bore (through apertures drilled in adjacent counterweights if necessary to gain access to the bore) and are pressed together until the shoulders are firmiy in contact. This has the result that the sealing portions are in interference sealing fit with the wall of the bore. A third tool is then inserted through the centre of the hollow right-hand tool and the tubular connecting part 20 is stretched outwardly in a clinching operation until it engages the underside of the shoulder of the right-hand insert.

The two parts of the insert are now mechanically connected together.

The use of a two-part sleeve avoids the need to drag one of the ends of the sleeve right through the bore. The flutes 18, while adding to the stiffness of the insert, also reduce still further the volume of oil in the annular space and also serve to locate the inserts.

The inserts may be pressings. The bore in the crankpin may be drilled out or, if the crankshaft is cast, they may be formed by cores during the casting operation.

Claims

1. A crankshaft having a bore through at least one crankpin, a sleeve positioned within the bore to define an annular region, a passage for lubricating fluid extending from the interior of a main bearing region to the annular region and a passage for lubricating fluid extending from the annular region to the bearing surface of the crankpin, the sleeve being formed by two inserts which are adapted to be inserted from opposite ends of the bore and be secured together within the bore.

2. A crankshaft as claimed in claim 1, wherein one insert has an aperture, and the other has a tubular extension passing through the aperture and opened out to mechanically engage the inserts together.

3. A crankshaft as claimed in claim 1 or claim 2, wherein each insert has a shoulder and a stepped sealing portion, the sealing portions being in intereference fit with the wall of the bore when the shoulders abut each other.

4. A crankshaft as claimed in claim 3, wherein each insert has raised flutes extending parallel to the axis of the bore which engage the wall of the bore.

5. A crankshaft substantially as hereinbefore described with reference to the accompanying drawings.

6. An internal combustion engine having a crankshaft as claimed in any one of claims 1 to 5.