systèmes pour la conversion de mouvements et d'énergies renouvelables
Motors
& Pumps
Concept MPRBC
Concept POGDC

Special
STIRLING's engines

Back to the main menu

OCTOGONAL PISTON WITH DEFORMABLE CONTROLLED GEOMETRY  (POGDC)

Principles Four times cycle Conversion of the motion System for variable valves' timing (VVT) System to regulate
the compression rate

The conversion of the motion is probably a domain as important as its generation...

If one looks at the history of the volumetric motors, which use pressurized gases rather than kinetic gases, very few are the engines which take care about about this aspect. For example, the engine with pistons, rods and crankshaft , possesses a kinematics, that in addition to be very unbalanced, immediately imposes a frozen law of conversion : even while making vary the radius of the crankshaft or the lentgh of the rods, the kinematics of the TDC/BDC is deplorable (too much long and stationary). One could mention other examples, as the Wankel where the evolution of the volume of the combustion rooms, according to the angle of rotation of the output shaft, is not controllable, because of an epitrochoïdal geometry that imposes all as soon as the triangular geometry of the rotor is chosen.


Most of the engines currently known aren't able to arbitrary impose an evolution of the volume of every room
 according to the angle of rotation of continually rotating shaft of the motor.


And yet, at a time where one tries to pilot the auto-ignition of gases by the rise of temperature during the compression (with new field of research like the controlled auto-ignition (CAI), high charge compression ignition (HCCI), active thermo atmosphere (ATAC), and even piloted detonation...), very few concepts worry about that and bring breaktough about the subject. Only some inventors in Quebec noticed the advantage of a sudden and intense TDC to synchronize the auto-ignition of fresh gases very exactly with the TDC, so that, in a first time, the combustion is the most complete and clean, and in a second time, the relaxation of gases occurs as early as possible to push appropriately the mobile parts of their machine...


However it would be necessary to be capable to generate the volume that one WANTS in EVERY ROOM
 according to the angle of rotation of the rotating shaft of the engine.


In the case of the SYCOMOREEN's rotary pistons engines, it needs to CONTROL the BEATINGS of the pistons... more precisely :
- their angular amplitude
- their minimal and maximal angles of alternative rotation
- but also and especially the law of evolution of the beating during a cycle "mini angle - > maxi angle  - > mini angle"


1. Motion to convert


The POGDC engines are based on an octogonal piston with its heads which periodically move away and come closer.

 

2. Proposed system

It is possible to use a standard system to convert the motion, by order of increasing relevance :

- rod /crank mechanism

- sinus mechanisme

- mechanisms with rotary cam(s) overmultilobed or not.

 

3. Advantages of the mechanism with rotary multilobed cams

 The present mechanism based on a central rotative cam offers very numerous assets :

4. Examples of rotary central cam systems for not rotary POGDC engine

The following pictures show the extreme adaptability of the rotary cams design for all type of not rotary POGDC engines.


POGDC with a 14 lobes central rotary cam
POGDC with a 14 lobes central rotary cam

POGDC with a 6 lobes central rotary cam

POGDC with a 6 lobes central rotary cam


4 MPRBC + 1 POGDC with a 2 lobes rotary central cam

4 MPRBC + 1 POGDC with a 2 lobes rotary central cam


4 MPRBC + 1 POGDC with a 6 lobes rotary central cam

4 MPRBC + 1 POGDC with a 6 lobes rotary central cam


1 POGDC + 4 MPRBC with 4 monolobed cam

1 POGDC + 4 MPRBC with 4 monolobed cams

1 POGDC + 4 MPRBC with 4 hexalobed cams

1 POGDC + 4 MPRBC with 4 hexalobed cams


1 POGDC + 4 MPRBC with 4 heptalobed cams

1 POGDC + 4 MPRBC with 4 heptalobed cams

1 POGDC + 4 MPRBC with 2 counter-rotary bilobed cams

1 POGDC + 4 MPRBC with 2 counter-rotary bilobed cams

5. Examples of mechanism based on cams for rotary POGDC engines

rotary POGDC with fixed carter
examples of parameters for rotary POGDC's variable shapes of the carter, 
rotary POGDC with fixed carter
the lengths of the octogonal deformable piston can be chosen at will too
rotary POGDC with fixed carter

The peripheral cover is parameterized by an analytic formula that finely pilots the volumes of the rooms


Reducing cams with crisscrossed overmultilobed paths for rotary POGDC engines

they allow to divide the initial angular velocity of the octogonal piston by and integer factor.

rotary POGDC with fixed carter and crisscrossed overmultilobed paths  reducing the motion by a factor 2
The blue reducing cam is rotating 2 times lower than the green octogonal piston.
It requires 8 blue lobes

rotary POGDC with fixed carter and crisscrossed overmultilobed paths  reducing the motion by a factor 3
The blue reducing cam is rotating 3 times lower than the green octogonal piston.
It requires 12 blue lobes


rotary POGDC with fixed carter and crisscrossed overmultilobed paths  reducing the motion by a factor 4
The blue reducing cam is rotating 4 times lower than the green octogonal piston.
It requires 16 blue lobes

rotary POGDC with fixed carter and crisscrossed overmultilobed paths  reducing the motion by a factor 5
The blue reducing cam is rotating 5 times lower than the green octogonal piston.
It requires 20 blue lobes

rotary POGDC with fixed carter and crisscrossed overmultilobed paths  reducing the motion by a factor 6
The blue reducing cam is rotating 6 times lower than the green octogonal piston.
It requires 24 blue lobes


6. Over multi-lobed rotary central (2Pi /kpcyclic cam

The rotary central cam can be over multi-lobed, by machining  k . p lobes on the cam where k is positive integer superior or equal to 2.

Why to over multi-lobe the rotary central cam ?

it multiplies by k the numbers 
necessary cycles to 1 have one revolution of the cam...

therefore
it multiplies by k the nominal compactness of the motor !


1. The cam, in addition to convert the motion, plays a complementary role of reducing gearings by a k factor

2. The use of pebbles mounted on ball-bearings converts the power with an output rate of about  95%

(contrary to the successive trains of gearings whose output falls quickly unless 90% by rubbings / barbotages in oil)

3. All this functionalities are achieved by a single part with a thickness of some millimiters
 (laser cuttable or usinable... in a simple plate of steel)


Under the condition to respect transmission angles which lead to acceptable efforts wether the engine works as a motor or a pump, and to give sufficient size to the rotary central cam, k can easily pass 3 or 4, in particular for engines having few pairs of rotary pistons.

The following animation belows show the extreme variety of possible and arbitrary motions with over multi-lobed cams for all type of POGDC engines.



Principles Four times cycle Conversion of the motion System for variable valves' timing (VVT) System to regulate
the compression rate
Performances
& Applications
systèmes pour la conversion de mouvements et d'énergies renouvelables
Motors
& Pumps
Concept MPRBC
Concept POGDC

Special
STIRLING's engines

Back to the main menu