Wobble plate engine

A wobble plate engine assembly incorporating as offset mount between the wobble plate and each connecting rod to a piston such that a line of action of the connecting rod at the wobble plate is resolved into a centripetal and tangential component thereby minimizing the component of applied forced directed through the wobble plate and maximizing the force the force applied along the wobble plate. The connections between the wobble plate, connecting rod and pistons incorporate spherical bearings. Also a wobble plate internal combustion engine incorporating the wobble plate engine assembly is presented.

FIELD OF THE INVENTION 
This invention relates to internal combustion engines of the type that 
employ a swash or wobble plate to transfer power from parallel pistons to 
a central shaft. 
BACKGROUND TO THE INVENTION 
Wobble plate engines have been known for many years. Early engines of this 
type comprised a number of parallel pistons disposed about a central 
driven shaft. Lateral displacement of the pistons is transformed to 
rotational motion of the shaft by a wobble or smash plate fixed at an 
angle on the shaft. Reciprocation of the piston causes a tangential 
displacement of the wobble plate thereby rotating the shaft. 
Australian Patent number 14759/23 in the name of Crankless Engines (Aus.) 
Pty Ltd describes a dual swash-plate engine wherein the swash-plates are 
driven by double ended pistons sharing a common combustion chamber. This 
engine, and other engines developed by Crankless Engines (Aus.) Pty Ltd 
where incorporated in motor vehicles. 
Although wobble plate engines have been known for 70 years they have not 
been generally accepted as internal combustion engines. The use has been 
limited to hydraulic pumps and other driven devices as opposed to driving 
devices. Various attempts have been made to improve or modify the basic 
wobble plate design for use in internal combustion engines. 
Australian Patent Application number 41322/85 in the name of S.V. Engine 
Co. Pty Ltd described a number of improvements that could be made to the 
design of a wobble plate engine. These included a damping system for 
stabilization; a balancing arrangement; a linkage arrangement enabling 
variation in the tilt of the wobble plate; and improved overall 
construction features. 
Reference may also be made to United Kingdom Patent number 2101226 in the 
name of Star Motors which describes a high pressure vapour driven engine 
based on a swash plate. The cylinders are arranged around a central power 
shaft in conventional manner. The swash-plate is rotatably mounted on the 
shaft and is connected to the pistons by connecting rods incorporating 
ball joints at each end. The engine is designed to be driven by high 
pressure steam derived from geothermal or solar energy. 
Despite the many years of development the wobble plate engine has failed to 
be accepted for internal combustion engine manufacture. This is because of 
vested interests in cranked engines and because of fundamental design 
problems. One such design problem is the direct load placed on the wobble 
plate by the pistons when they fire. The line of action of the pistons is 
parallel to the axis of rotation of the wobble plate, thus there is a 
large component of force directed through the wobble plate. Only a portion 
of the applied force is directed along the wobble plate to force it to 
rotate. This results in high frictional loads and reduced efficiency of 
the motor. 
OBJECT OF THE INVENTION 
It is an object of the present invention to provide a wobble plate engine 
assembly that overcomes one or more of the above identified problems or at 
least offers the public a useful alternative to existing internal 
combustion engines. 
DISCLOSURE OF THE INVENTION 
In one form, although it need not be the only or indeed the broadest form, 
the invention resides in a wobble plate engine assembly comprising: 
a drive shaft rotatably mounted in a cylinder block; 
one or more pistons mounted for reciprocating movement in a respective 
cylinder in the cylinder block, with the axis of reciprocation of the 
pistons being substantially parallel to a longitudinal axis of the drive 
shaft; 
a wobble hub associated with the drive shaft for rotation therewith; 
a wobble plate rotatably mounted on the wobble hub such that the wobble 
plate remains rotationally stationary while the drive shaft and wobble hub 
rotate; and 
a connecting rod associated with each piston, said connecting rod 
connecting said piston to a respective offset mount on the wobble plate 
such that a line of action of the connecting rod at the wobble plate is 
resolvable into a centripetal and a tangential component. 
The line of action of the connecting rod at the offset mount is offset 
tangentially from a diameter through the wobble plate. 
In preference the engine assembly comprises at least four pistons with at 
least some of the pistons having a line of action of opposite direction to 
the other pistons thereby maintaining balance. 
The wobble hub is preferably formed separate from the drive shaft but keyed 
to the drive shaft so as to rotate with the drive shaft. 
The wobble plate may suitably be rotatably mounted on the wobble hub by a 
wobble bearing. The wobble bearing may be a thrust or roller bearing. 
In preference the offset mount comprises a pair of upstanding lugs. One lug 
is preferably an extension of a diameter of the wobble plate and the other 
lug is preferably offset from the first lug along a line parallel to a 
tangent to the wobble plate diameter. 
The connection between the connecting rods and offset mounts preferably 
incorporate spherical bearings permitting twist and rotation of the 
connecting rods. The connection between the connecting rods and pistons 
preferably incorporate similar bearings. 
In an alternate form the offset mount comprises a single lug with a 
spherical bearing attached on opposite sides thereof in cantilever 
fashion. In this form there is suitably a connecting rod connected to each 
spherical bearing which connect to oppositely acting pistons. 
In a further form the invention resides in an internal combustion engine 
incorporating a wobble plate engine assembly as herein described with the 
addition of one or more cylinder heads incorporating a valve assembly. 
The internal combustion engine may be four stroke or two stroke, depending 
primarily on the design of the valve assembly. The engine is preferably 
four or six cylinder and double ended.

DETAILED DESCRIPTION OF THE DRAWINGS 
In the drawings, like reference numerals refer to like parts. 
Referring to FIG. 1, there is shown a partial exploded view of a six 
cylinder wobble plate engine 1. The engine 1 comprises a wobble hub 2 
fixed to a central drive shaft 3. A wobble plate 4 is rotationally mounted 
to wobble hub 2 by wobble bearing 5. The wobble bearing 5 allows for 
rotational motion of the wobble hub 2 and drive shaft 3 relative to the 
wobble plate 4. 
In the embodiment shown the wobble hub 2 is integrally formed with the 
drive shaft 3 as a single casting. Alternatively, the wobble hub 2 can be 
keyed to the drive shaft 3 or fixed by other conventional means. 
The wobble plate 4 has a plurality of offset mounts, such as 6, located on 
the outer perimeter. There is one offset mount per piston 7. Each piston 7 
is connected to the offset mount 6 by conrod 8. At one end the piston and 
conrod are connected by gudgeon pin 9. At the other end, the conrod is 
connected to offset mount 6 by big end pin 10. 
The offset mount 6 consists of spaced apart upright lugs. In the embodiment 
shown two adjacent offset mounts share a common central lug 11. The 
central lug 11 is an extension of a diameter of the wobble hub. The 
adjacent offset mounts are formed with the offset lugs 12 and 13 which are 
displaced along a tangent to the wobble plate. This can be seen more 
clearly in FIG. 2. The big end pin 10 extends through the lugs 11, 12 and 
13. In the particular embodiment shown the pin 10 has a head 14 at one end 
and a thread 15 at the other end to screw into lug 12. Spherical bearings 
16 and 17 are mounted on the big end pin 10. Conrods 8 and 18 are mounted 
on the spherical bearings 16 and 17 respectively. The spherical bearings 
permit twist and rotation of the conrods. 
The gudgeon pins 9 connecting the pistons 7 to the other end of the 
conrods, such as 8, have similar spherical bearing assemblies. The pistons 
7 reciprocate in cylinders 19 housed in cylinder block 20. For clarity 
only one half of the cylinder block is shown. The drive shaft 3 is 
supported in the cylinder block 20 on roller bearing 21. 
During operation of the engine the explosive energy in the cylinder 19 
causes the piston 7 to push the conrod 8 against the offset mount 6. In 
prior known wobble plate engines the mount is not offset so the conrod is 
pushing on an axis parallel to the drive shaft. This is shown clearly in 
FIG. 3a and FIG. 3b which show a plan and side view of the operative 
elements of a wobble plate engine assembly incorporating an in-line mount. 
A vector diagram of forces would show that the engine can not start if the 
firing piston is at top dead centre because the firing piston is pushing 
directly against the wobble plate as depicted by arrow 22 in FIGS. 3a and 
3b. If the engine is already running the "dead" spot is momentary and the 
piston pushes against the "down hill run" of the rotating wobble plate. 
Nonetheless, the prior art engines suffer reduced efficiency due to this 
problem. 
The operative elements of a wobble plate engine assembly according to the 
present invention are depicted in FIGS. 4a and 4b. The spherical bearing 
23 connecting the piston (not shown) to the conrod 24 and the spherical 
bearing 25 connecting the conrod 24 to the wobble plate 4 allow twist and 
rotation of the conrod. Because the conrod 24 is pushing at an offset 
position and is able to twist and rotate, energy applied in direction of 
arrow 22 is resolved into centripetal and tangential components. These 
forces cause the wobble plate to nod as shown by arrows 26a and 26b in 
FIG. 4a. This motion is translated by the wobble plate into rotation of 
the wobble hub and drive shaft in direction of arrow 27. 
The twist and rotation of the conrod minimises sheer and compressive forces 
and maximises energy transfer to the wobble plate 4. The effect is that 
the engine 1 is able to start without a starter motor. Furthermore, a 
flywheel is not required for operation of the engine. It will be 
appreciated that the present invention substantially overcomes the 
problems of the assembly depicted in FIG. 3a and FIG. 3b. 
A cross-sectional view of a four cylinder embodiment of the invention is 
shown in FIG. 5. As with the six cylinder embodiment the four cylinder 
engine 28 comprises a wobble hub 29 formed as part of a drive shaft 30. A 
wobble plate 31 is rotationally mounted to wobble hub 29 by bearing 32. 
Conrods, such as 33, link the wobble plate 31 with each of a plurality of 
pistons 34. The connection between the conrod 33 and the piston 34 is with 
a gudgeon pin 35 incorporating a spherical bearing as previously 
described. The pistons 34 reciprocate in cylinders, such as 36, formed in 
cylinder block 37. The drive shaft 30 is supported in the cylinder block 
37 by thrust bearings, such as 38. 
An offset mount as previously described may be used to connect the conrod 
33 to the wobble plate 31. Alternatively, the cantilever arrangement of 
FIG. 6 may be used. In the alternative arrangement the offset mount is 
replaced by a single lug 39 extending from the wobble plate 40. Spherical 
bearings, such as 41 are connected to the lug 39 by suitable means. In the 
embodiment shown the connection is by double ended bolt 42. As with the 
previously described embodiment the conrods, such as 43, are able to twist 
and rotate on the spherical bearing 41 thereby minimising sheer and 
compressive forces. 
The range of oscillation of the wobble plate 4 is seen most clearly in FIG. 
3. The inventors have found that this oscillation is most suitably 
approximately 15 degrees, that is, 7.5 degrees either side of centre. 
Rotation of the wobble plate is prevented by a ball and track stabiliser 
shown in FIG. 7. A ball 44 is fixed to the wobble plate 4. A stabiliser 
plug 45, including a track 46, mounts in the cylinder block (not shown). 
As the wobble plate 4 moves, the ball 44 runs in track 46 thereby 
stabilising the motion of the wobble plate 4. 
It will be appreciated that the double ended engines described herein have 
the advantage of being in balance since opposite acting pistons are fired 
simultaneously. Single ended engines can be built that incorporate the 
offset mounts and therefore have the operating advantages of the 
embodiments detailed but will not have the balance advantage. 
The engines described herein can be built as two stroke or four stroke 
engines. 
Throughout the specification the aim has been to describe the preferred 
embodiments of the invention without limiting the invention to any one 
embodiment or specific collection of features.