GB2152186A

GB2152186A - Engine coupler

Info

Publication number: GB2152186A
Application number: GB08423168A
Authority: GB
Inventors: Herbert A Bankstahl; Alvin A Zemlicka
Original assignee: Brunswick Corp
Current assignee: Brunswick Corp
Priority date: 1983-12-27
Filing date: 1984-09-13
Publication date: 1985-07-31
Also published as: JPS60107425U; GB8423168D0; DE3436599A1; SE8406525L; SE8406525D0

Abstract

In a flexible coupling for coupling the flywheel (18) of an engine to a hub (19) attached to a driven shaft by a shock absorbing elastomeric annulus (29) compressed between the driven shaft (17) and the hub (19), the hub (19) is coupled to the flywheel (18) by spring members (20) attached to the hub (19) and the flywheel (18) by bolts. The spring members (20) can accommodate significant angular misalignments between the flywheel (18) and the driven shaft (17). <IMAGE>

Description

SPECIFICATION Engine coupler This invention relates to shaft couplings and particularly to a flexible coupling suitable for coupling an engine to a driven device.

It is desirable to provide a flexible coupling between an engine and a driven device particularly when there is a possibility of misalignment between the engine drive shaft and the driven shaft. In some installations, such as a stern driven unit which uses an inboard engine to drive an outboard propulsion unit mounted on the stern of the boat, it is desirable to use a flexible coupling which requires a minimum amount of axial space. Rubber couplings have frequently been used to couple the engine of a stern drive unit to the outboard drive unit, and while they have been generally acceptable, under some conditions such as a substantial angular misalignment under high power loadings the rubber connections have failed.

According to the present invention, there is provided a flexible coupling assembly for coupling the drive shaft of an engine to a generally coaxial driven shaft, said coupling assembly comprising: a flywheel which, in use, is fixed to said drive shaft, said flywheel including a planar surface perpendicular to the axis of said drive shaft; a hub which, in use, is attached to said driven shaft, said hub including a planar surface perpendicular to the axis of said driven shaft and facing said flywheel; a first set of spring members each formed of spring strip and lying in plane generally perpendicular to the axes of said drive shaft and said driven shaft; a first flywheel attachment means for attaching said set of spring members to said planar surface to said flywheel at a flywheel attachment point radially spaced from the axis of said drive shaft; and a first hub attachment means for attaching said set of spring members to said planar surface of said hub at a hub attachment point radially spaced from the axis of said driven shaft.

Preferably, the flexible coupling assembly includes a spacer between the flywheel and the set of springs and between the hub and the set of springs. It is also desirable to locate the flywheel attachment point on a line extending perpendicular to a radius from the axis of the driven shaft to the hub attachment point.

In the preferred embodiment the flexible coupling assembly includes second and third sets of spring members identical to the first set and equally spaced around the axes of the drive shaft and driven shaft.

The invention will be further described by way of non-limitative example with reference to the accompanying drawings, in which: Figure 1 is a side view of a stern drive, broken away to show an embodiment of the coupling of the invention; Figure 2 is an end view of the coupling of Fig. 1; Figure 3 is a sectional view through the coupling.

Referring now to the drawings a stern drive 10 incorporating the present invention is illustrated. The stern drive 10 includes a fourcycle engine 11 mounted on stringers, not illustrated, forming part of a boat hull 1 2. An outboard propulsion unit 1 3 is mounted on the transom 14 of the boat.A coupling 1 5 is provided to connect the crankshaft 1 6 of the engine 11 to the input shaft 1 7 of the outboard propulsion unit 1 3. Because the engine and outboard propulsion unit 3 are mounted on separate elements of the boat hull 1 2 which typically will flex in response to loads on the hull, the coupling 1 5 must accommodate the resulting misalignment and axial displacement between the engine crankshaft 1 6 and the input shaft 1 7 of the outboard unit 13.

The coupling 1 5 includes a flywheel 1 8 fixed to the drive or crankshaft 16, a hub 1 9 attached to the driven input shaft 1 7 of the outboard propulsion unit 13, and three sets of spring members 20 connected between the flywheel 18 and the hub 19. The spring members 20 are oriented to be loaded in tension under the normal engine rotation, and flex to accommodate misalignment between the crankshaft 16 and the driven shaft 1 7.

The flywheel 1 8 is formed as a generally circular disc and has gear teeth 21 around its periphery for engaging an engine starter, not illustrated. The flywheel 1 8 includes a planar annular surface 22 facing the hub 1 9 and a central circular recess 23 also facing the hub 19. The flywheel 18 is attached to the flange 24 at the end of the crankshaft 1 6 by six bolts 25 essentially equally spaced around the central recess 23. Three threaded holes 26 are provided equally spaced about the circumference near the outer edge of the planar surface 22 for attaching the spring members 20.

The hub 1 9 includes a main body 27 within which is fitted a mounting sleeve 28 and an elastomeric annulus 29. The hub body 27 includes an outer flange 30 having diameter slightly less than the diameter of the recess 23 in the flywheel 18. Three holes 31 are provided equally spaced about the circumference of the flange 30 for attaching the spring members 20. A small ridge 32 is formed on the hub flange adjacent the end of each of the spring members 20 to prevent the inadvertent assembly of the spring members 20 in the wrong orientation.

A cup 33 formed on the aft side of the flange 30 holds the elastomeric annulus 29 and the sleeve member 28. At the rear, the sleeve member 28 is held in axial alignment with the hub 1 9 by a washer 34a engaging the outer surface of the sleeve member 28 and the inner surface of the hub cup 33. At the forward end alignment is provided by piloting the sleeve member 28 directly on the hub 19. The inner wall of the sreeve member 28 is provided with splines to engage the splines on the input shaft 1 7 of the outboard propulsion unit 1 3. The elastomeric annulus 29 is preferably formed of live rubber bonded to the sleeve member 28.The sleeve member 28 and the elastomeric annulus 29 are pressed into the cup 33 and retained there by a spring retaining ring 34 which engages a groove 35 around the inner circumference of the cup 33. The elastomeric annulus 29 is sufficiently compressed to enable it to carry substantial torsional loads and still absorb torsional shock loading between the hub member and the driven shaft. Such shock loading can occur when the engine starts.

should the propeller of the propulsion unit impact an underwater structure, or the loading can occur from the normal engine loading.

The hub 1 9 and flywheel 1 8 are coupled by the spring members 20. The spring members 20 are sufficiently long to give the desired flexibility to the assembly thereby allowing the coupling to accommodate angular misalignment and axial displacement. The width of the spring members is determined by flexibility and fatigue life considerations, since an excessive width would limit the flexibility of the spring member while an excessively narrow width would reduce the fatigue life.

The thickness of the spring members 20 is determined primarily by the effect of thickness on the fatigue life of the spring members 20.

If the spring member 20 is too thick the bending stresses in the member will rise rapidly thus limiting the usefulness of the device. Providing sets of two, three, or four spring members 20 attached between the same point allows the load carrying ability of the coupling to be substantially increased within the limitations imposed by the forego ing considerations.

The spring members 20 are provided with hole near their ends for attachment to the flywheel 1 8 and the hub 1 9. The spring members 20 are attached to the flange 30 of the hub 1 9 by bolts extending through the holes 31 in the flange 30 and engaging nuts 37. Washers 38 are provided between the spring members 20 and the bolt heads to protect the spring members 20. The spring members 20 are attached to the flywheel 1 8 by bolts 39 engaging the threaded holes in the flywheel 1 8. Washers are provided between the spring members 20 and the flywheel 1 8 to serve as spacers to protect the srping 20 from rubbing on the edge of the central recess 23 and washers 41 are provided between the bolt head and the spring members 20.The ridges 32 on the hub flange 30 assure that the spring members 20 are installed in the correct orientation so that they will be loaded in tension during normal engine operation.

In the preferred embodiment the spring members 20 are formed of SAE 1095 Spring Steel to provide the desired spring characteristics. The spring members are water quenched from 1450'F and tempered at 800to. The spring members are approximately six inches long. 7/8 inch wide. and 0.033 inches thick.

In operation it is apparent that the coupling will transmit torque and that the spring members will bend to accommodate angular misalignment.

A coupling constructed as described herein with three sets of spring members was satisfactory to carry 330 horespower at 4800 rpm's. A similar coupling contructed with three sets of four spring members was satisfactory to carry 370 horsepower at 5200 rpm's. The couplings are capable of accommodating misalignments of up to at least three degrees.

Claims

1. A flexible coupling assembly for coupling the drive shaft of an engine to a generally coaxial driven shaft, said coupling assembly comprising: a flywheel which, in use. is fixed to said drive shaft, said flywheel including a planar surface perpendicular to the axis of said drive shaft; a hub which, in use, is attached to said driven shaft, said hub including a planar surface perpendicular to the axis of said driven shaft and facing said flywheel; a first set of spring members each formed of spring strip and lying in plane generally perpendicular to the axes of said drive shaft and said driven shaft; a first flywheel attachment means for attaching said set of spring members to said planar surface to said flywheel at a flywheel attachment point radially spaced from the axis of said drive shaft; and a first hub attachment means for attaching said set of spring members to said planar surface of said hub at a hub attachment point radially spaced from the axis of said driven shaft.

2. The flexible coupling assembly defined in claim 1 wherein said flywheel attachment means includes a spacer between said flywheel and said set of spring means.

3. The flexible coupling assembly defined in claim 2 wherein said flywheel attachment point is located on a line extending perpendicular to a radius from the axis of said driven shaft through said hub attachment point.

4. The flexible coupling assembly defined in claim 1, 2 of 3 further comprising second and third sets of spring members identical to said first set, said sets of spring members equally spaced around the axes of said drive shaft and said driven shaft, second and third flywheel attachment means for attaching said second and third sets to said flywheel, and second and third hub attachment means for attaching said second and third sets to said hub.

5. The flexible coupling assembly defined in claim 4 wherein said first, second and third flywheel attachment means lie radially outside the outer circumference of said hub.

6. The flexible coupling assembly defined in claim 5 wherein said flywheel includes a central circular recess facing said hub and said first, second and third hub attachment means lie radially inside the outer circumference of said recess.

7. The flexible coupling assembly defined in any one of the preceding claims and further comprising a shock absorbing mounting means for mounting said hub on said driven shaft.

8. The flexible coupling assembly defined in claim 7 wherein said hub includes an annular portion and said shock absorbing mounting means includes an elastomeric annulus between said annular portion and said driven shaft.

9. The flexible coupling assembly defined in claim 8 wherein said shock absorbing means includes a sleeve member between said elastomeric annulus and said driven shaft.

10. The flexible coupling assembly defined in claim 9 wherein said hub includes an alignment means for holding said sleeve member coaxial with said hub.

11. The coupling assembly defined in any one of the preceding claims wherein each spring member is in the form of a flat plate.

1 2. A flexible coupling constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

1 3. A drive comprising an internal combustion engine having a drive shaft, a propulsion unit having a driven shaft and a drive coupling according to any one of the preceding claims interconnecting the drive shaft of the engine and the driven shaft of the propulsion unit.