Geometric profiles of a gerotor or troichodal pump.

[Tophinater]

Hello All,
Im a first time poster that is having a lot of trouble with some mathematical modeling. Im currently working on a school project where I am optimizing a gerotor MOTOR for the greatest amount of displacement per rotation of the shaft. I have found many volumetric equations in many papers however when it comes to actually constructing the profile itself I cant seem to figure it out. Heres some of the code I have in Matlab:

%equations for gerotor profiles

N = 5; %the tooth number
m = 1; %tooth number difference between inner and outer rotor
c = .1; %eccentricity between inner and outer gear

R = 7; %radius of hypotroid circle
r = 30; %radius of hypotroid circle to center of gear
a = 1:.1:500;
p1 = 5:.1:504;
p2 = N/(N+m)*p1;

t1 = 1:.1:500;
t2 = (N+m)/N*t1;

%equations for profile of outer gear
xo = -r*sin(p1-p2) - R*sin(a+p1-p2) - c*sin(p2);
yo = r*cos(p1-p2) + R*cos(a+p1-p2) - c*cos(p2);

%equations for profile of inner gear
xi = -r*sin(t1-t2+p1-p2) + R*sin(a+t1-t2+p1-p2) - c*(sin(t2)-sin(t1-t2-p2));
yi = r*cos(t1-t2+p1-p2) - R*cos(a+t1-t2+p1-p2) - c*(cos(t2)+cos(t1-t2-p2));


hold on
plot(xo,yo)
%plot(xi,yi)
axis square
grid on

If you actually go and run this code you see that the profiles produced create curves that dont look much like a gerotor at all. Theres a lot of loops and under cutting. Anyone have any experience with troichodal profiles that can help me out?

 

[israelkk]

Promoting, selling, recruiting and "student posting"
are not allowed in the forums.

 

[Tophinater]

OK, Im also solving this problem for work as well. I work for a supplier that uses these to power cooling fans in cars. Can you help me now?

 

[hydtools]

Before trying to manufacture gerotor elements, get data sheets from Parker Hannifin Corp., Nichols Portland

2400 Congress St
Portland, ME 04102-1949

Tel: (207) 774-6121

They have a selection of types and displacements from which I created custom motors and pumps by selecting appropriate lengths of the elements that fit my needs. No sense trying to model the gerotor when elements already exist. Unless you like the exercise and want to spend money for the precision manufacturing processes and tooling.

Ted

 

[hydtools]

Or see this link

http://fluid.power.net/techbriefs/papers/proc_gamez_montero.pdf

A paper on maximizing the trochoidal pump.

Ted

 

[Tophinater]

Thanks for the link hydtools but I already have that paper.