GB2430707A

GB2430707A - Accessory alignment in an internal combustion engine

Info

Publication number: GB2430707A
Application number: GB0519934A
Authority: GB
Inventors: Nathan James Roulson; Ian Robinson; Keith Hall; David George
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2005-10-03
Filing date: 2005-10-03
Publication date: 2007-04-04
Anticipated expiration: 2025-10-03
Also published as: GB0519934D0; GB2430707B

Abstract

An i.c. engine has a cover 16, eg a cam belt cover or an oil pump cover, overlying a face of the cylinder block 10 and having a protruding portion, eg lug 22, which is used as a reference plane for the accurate mounting of a belt-driven accessory 12, eg an air conditioning compressor, water pump, power steering pump or alternator. The accessory 12 may be pivotally supported about an accurately machined upper bolt boss 18 so that it swings clockwise urging a location boss 20 against the lug 22. The remaining bolt lugs 24 thus do not need to be accurately machined. The accurate boss 18 may be replaced by a cast lug 18' having an integral oversize inclined square hole such that a bolt 30 locates accurately against the two upper sides 32 of the hole. In a modification requiring no post-manufacture machining, front location bosses (20'', fig.3) are urged against two protruding timing cover lugs (22'') by an inclined plane (28'') cooperating with the rear location boss (26'').

Description

Accessory Alignment in an Internal Combustion Engine This invention

relates to the locating of accessory devices relative to an engine of a motor vehicle and more specifically to simplifying assembly during vehicle manufacture.

Internal combustion engines require accessories in order to provide features expected in vehicles. These include power steering and air conditioning as well as compulsory accessories also driven by the engine such as the alternator and water pump.

These accessories are primarily belt driven by a pulley mounted on the end of the crankshaft. Correct alignment of the accessory pulleys relative to the crank pulley is important to reduce noise and wear both of the accessory shaft bearings, and of the drive belt. Manufacturers have a varying degree of tolerance as to what is acceptable, but around 0. 4 or 0.5mm misalignment per 100mm bolt span is typical. The accurate tapped holes in the engine structure may be termed datum points.

To achieve correct alignment of the accessory with respect to the plane of the drive belt and crankshaft pulley, the accessory device is usually mounted with a degree of freedom. This is provided by way of a location hole, an elongate hole and a clearance hole in the accessory. Such holes allow the accessory to be satisfactorily positioned in relation to the datum points on the engine and then secured in place by tightening the relevant nuts or bolts. The location hole and elongate hole are normally machined.

The locations of mounting holes drilled in the engine can be accurately machined to within 0.5mm to ensure that the accessory may only able be secured in an exact predetermined the accessory may then be secured located to these three engine datum points by either bolts or by split dowels. This method is preferred for alignment accuracy, but the costs associated with the machining make this technique more expensive.

There is therefore a need to find an inexpensive way to easily and accurately align the accessories to the crank pulley.

With a view to satisfying the foregoing need, a first aspect of the present invention provides an internal combustion engine having a cover overlying a face of the engine and projecting laterally beyond the engine, wherein the part of the mating surface of the cover which projects beyond the engine serves as a reference plane for accurate positioning of an accessory on a face of the engine.

Advantageously, the engine may comprise means for supporting an accessory on the side of the engine block in such a manner that the weight of the accessory acts to urge the accessory in the direction of the reference plane.

The means for supporting may be a pivot or a ramped surface.

According to a second aspect of the present invention, there is provided a method of mounting an accessory on a face of an engine which has a cover overlying a face of the engine and projecting beyond the engine to define a reference plane, the method comprising the steps of supporting the accessory against a face of the engine in such a manner as to permit lateral movement of the accessory towards the reference plane and securing the accessory to the engine while resting under its own weight against the reference plane.

According to a third aspect of the present invention, there is provided an accessory for an internal combustion engine having a mounting aperture for receiving a locating element, characterised in that the aperture is non-circular and has mutually inclined sides for simultaneously contacting circumferentially spaced points on the locating element, in order to position a point on the accessory accurately in relation to the locating element.

The locating element may be a bolt, a pin, a stud or a split dowel.

The accessory may be an air conditioning pump, vacuum pump, water pump, alternator or power steering pump.

The present invention will now be described further by way of example with reference to the accompanying drawings in which: Figure 1 is a side view of an engine accessory located relative to an engine block by means of an embodiment of the present invention, Figure 2 shows a slight variation on the embodiment of figure 1, Figure 3 is a side view of an engine accessory located relative to an engine block by means of a second embodiment of the present invention, and Figure 4 shows an engine accessory bracket located against the engine face.

Figure 1 shows an engine block 10 viewed from the side supporting an accessory 12. The arrangement is equally applicable for mounting an accessory on the top or underneath the engine block.

The accessory 12 refers to any item that is engine driven such as an air conditioning compressor, water pump, power steering pump or alternator. Drive to the accessory is provided by a crankshaft pulley driven belt (not shown) engaging a pulley 14 attached to the shaft of the accessory.

In this first embodiment, the accessory is positioned relative to the drive belt, by being pivotally supported about machined drilled bolt boss 18. The hole is created by accurate machining of the accessory 12. This process allows for the position of the accessory pivot point to be placed to within 0.2mm when bolted to a datum point on the engine block 10.

Attached to the front face of the engine 10 is a cover 16. The cover may be the cam belt or possibly oil pump cover and its rear face represents a datum point on the engine whose position is accurately determined.

Cover 16 is provided with a protruding lug 22, which by virtue of it being integral to the cover's mounting face, also has a well defined position, making it a suitable datum point for relative location of an accessory.

As can be seen from figure 1, the machined bolt boss 18 is located closer to the pulley 14 than the approximate centre of gravity of the accessory. When bolted to the engine through the accurately sized hole in boss 18, the centre of gravity causes the accessory to swing clockwise about the accurate bolt hole in boss 18, urging a location boss 20 against protruding lug 22.

When location boss 20 is forced against the protruding lug 22 a bolt can be inserted into clearance bolt lug 24 and tightened. The clearance bolt lug has a cast hole within it whose diameter is not well defined. The diameter of the hole is larger than that of the bolt it receives thus allowing some clearance for the bolt to locate in the hole drilled in the engine block 10. With this bolt in place, accessory 12 is automatically aligned with the datum points provided by the front face of the engine and the machined hole in the engine block, thus it is automatically aligned within tolerance levels with the drive belt. Crucially, only, the location hole in boss 18 needs to be a location datum for alignment of the accessory to occur.

The alignment accuracy is provided by means of the datum surface that is the front face of location boss 20.

This may be in the form of a flattened circled, or as is shown in the diagram, a standard circular section lug with additional "corners" added to increase the span of the datum surface. The surface is integral with the body of accessory 12 and is produced during casting.

Combining this with the accessory's weight urging it towards correct alignment, time and money is saved during both manufacture and assembly.

In figures 2 and 3, to avoid repetition of their description, like components have been allocated the same reference numerals but with the addition of a or a " to distinguish the different embodiments from one another.

Figure 2 shows a magnified view of an alternative arrangement to the machined bolt boss 18 of figure 1. In figure 2, the machined boss is replaced by a cast lug 18' having a cast integral square hole. The square hole shown has radiused corners to relieve stress in the accessory body. By using an oversize square hole inclined at an angle to the horizontal, the bolt 30 locates against the upper two sides 32 of the hole by virtue of the weight of the accessory. These two sides 32 become datum reference planes for the accessory whilst still allowing it to pivot. This results in the accessory being positioned consistently relative to the accurately placed bolt 30 about which it pivots, without the need for accurate machining of a low tolerance hole in lug 18 on the accessory. This further reduces cost without sacrificing alignment accuracy or ease and speed of assembly.

In figure 3, like the embodiment of figure 2, no post manufacture machining is required. Alignment in this embodiment is provided by cast datum surfaces, provided on three location bosses 20" and 26", two on the front accessory mounting bosses 36" and one on a rear accessory mounting boss 28".

The method of locating the accessory is much the same as that of the embodiment of figure 1 with the exception the accessory 12" does not pivot about a bolt in order that its weight urges it into the correct position. In this embodiment the front location bosses 20" are urged against two protruding timing cover lugs 22" by a horizontal component of the reaction force to the weight of the accessory.

The provision of an inclined plane 28" means that when the weight of the accessory acting downwards forces rear location boss 26" to contact the inclined plane, the resulting reaction force has both vertical and horizontal components, by virtue of its inclination. The angle of inclination will determine the proportion of the weight urging the front location bosses 20" against the two protruding timing cover lugs 22". The inclined plane 28" may be again a cast datum plane for abutting a cast datum plane in the form of rear location boss 26".

Since the location of the accessory 12" relative to the engine block 10" is fixed by the datum planes, the holes 24" cast into the front accessory mounting bosses 36" and the rear accessory mounting boss 38" may be clearance size bolt holes 24".

While the description makes reference to mounting

accessories relative to the engine block, the accessories may be alternatively be located relative to the cylinder head or any other suitable part of the engine.

Dedicated datum faces may be machined on the engine when a protruding interface is not available.

Further, indirect mounting of the accessory to the engine via an intermediate bracket is also possible.

Claims

Claims 1. An internal combustion engine having a cover overlying a face of

the engine block and projecting beyond the face of engine block, wherein the part of the mating surface of the cover which projects beyond the engine block serves as a reference plane for accurate positioning of an accessory on a face of the engine block.
2. An internal combustion engine as claimed in claim 1, comprising means for supporting an accessory on the side of the engine block in such a manner that the weight of the accessory acts to urge the accessory in the direction of the reference plane.
3. An internal combustion engine as claimed in claim 2, wherein the means for supporting comprises a pivot.
4. An internal combustion engine as claimed in claim 2, wherein the means for supporting comprises a ramped surface.
5. A method of mounting an accessory onto a face of an engine block of an internal combustion engine which has a cover overlying a face of the engine and projecting beyond the engine to define a reference plane, the method comprising the steps of supporting the accessory against a face of the engine in such a manner as to permit lateral movement of the accessory towards the reference plane and securing the accessory to the engine while resting under its own weight against the reference plane.
6. An accessory for an internal combustion engine having a mounting aperture for receiving a locating element, characterised in that the aperture is non-circular and has mutually inclined sides for simultaneously contacting -.9- circumferentially spaced points on the locating element, in order to position a point on the accessory accurately in relation to the locating element.
7. An accessory as claimed in claim 6, wherein the locating element is a stud, a bolt or a split dowel.
8. An accessory as claimed in claim 6 or 7 wherein the accessory may be an air conditioning compressor, a power steering pump, a water pump, an alternator or an oil pump.
9. An internal combustion engine substantially as herein described with reference to and as illustrated in the accompanying drawings.
10. A method of mounting an accessory onto a face of an engine block of an internal combustion engine substantially as herein described with reference to and as illustrated in the accompanying drawings.
11. An accessory for an internal combustion engine substantially as herein described with reference to and as illustrated in the accompanying drawings.