Variable displacement gerotor pump

Abstract

A variable displacement pump having an inner rotor (gerotor) and an outer rotor is disclosed. Advantageously, the pump provides a movable outer rotor capable of changing the amount of fluid transferred from an inlet to an outlet. Optionally, a biasing member is connected to the outer rotor for preventing movement of the outer rotor below a predetermined amount of pressure at the outlet.

1 . A variable displacement pump for transferring fluid from an input to an output, the pump comprising: 
 an inner rotor;    an outer rotor in meshing engagement with the inner rotor; and    a body extending from the outer rotor, the body connected to the outer rotor such that movement of the body causes movement of the outer rotor, the body automatically movable in response to changes in fluid pressure at the output.    
   
   
       2 . The variable displacement pump of  claim 1  wherein the body is freely movable in response to pressure at the output.  
   
   
       3 . The variable displacement pump of  claim 1  wherein the body is an eccentric ring.  
   
   
       4 . The variable displacement pump of  claim 3  further comprising: 
 a wing portion extending from the eccentric ring, the wing portion capable of moving the outer rotor.    
   
   
       5 . The variable displacement pump of  claim 4  further comprising: 
 a rack and pinion engaging said eccentric ring, the rack and pinion preventing movement of the eccentric ring below a predetermined pressure.    
   
   
       6 . The variable displacement pump of  claim 1  further comprising: 
 a biasing member preventing movement of the outer rotor if the fluid pressure at the output is below a predetermined fluid pressure.    
   
   
       7 . The variable displacement pump of  claim 6  wherein a portion of the fluid at the output is in fluid communication with the biasing member.  
   
   
       8 . The variable displacement pump of  claim 7  further comprising: 
 a fluid pocket in fluid communication with the output, the fluid pocket receiving a portion of the fluid at the output.    
   
   
       9 . The variable displacement pump of  claim 8  wherein the fluid pocket is a relief channel.  
   
   
       10 . The variable displacement pump of  claim 9  further comprising: 
 a rack in fluid communication with the relief channel, the rack capable of moving the outer rotor if the fluid pressure at the rack is above a predetermined pressure.    
   
   
       11 . The variable displacement pump of  claim 10  further comprising: 
 a biasing member providing a threshold force to the rack to prevent movement of the outer rotor if the fluid pressure is less than the predetermined pressure.    
   
   
       12 . A variable displacement pump for transferring fluid from an input to an output, the pump comprising: 
 an inner rotor having a plurality of teeth;    an outer rotor having a plurality of notches for receiving said teeth, said inner rotor and said outer rotor capable of meshingly engaging to transfer said fluid from said input to said output;    a channel in fluid communication with said output, said channel capable of causing movement of said outer rotor at a predetermined pressure at the output.    
   
   
       13 . The variable displacement pump of  claim 12  further comprising: 
 a wing portion in fluid communication with said channel, the wing portion capable of moving the outer rotor at a predetermined fluid pressure in the channel.    
   
   
       14 . The variable displacement pump of  claim 13  further comprising: 
 an eccentric ring to engages the outer rotor and the wing portion, wherein the wing portion moves the eccentric ring and the outer rotor at the predetermined fluid pressure.    
   
   
       15 . The variable displacement pump of  claim 14  further comprising: 
 a rack and pinion engaging said eccentric ring, the rack and pinion preventing rotation of the eccentric ring below a predetermined fluid pressure.    
   
   
       16 . The variable displacement pump of  claim 14  wherein the eccentric ring has a variable thickness.  
   
   
       17 . A variable displacement pump comprising: 
 a pump body having an inlet and an outlet;    an inner rotor positioned within the pump body, the inner rotor rotating within the pump body;    an outer rotor in meshing engagement with the outer rotor to transfer fluid from the inlet to the outlet;    an eccentric ring engages the outer rotor, the eccentric ring movable with respect to the inner rotor, the eccentric ring capable of causing movement of the outer rotor with respect to the inner rotor; and    a channel in fluid communication with the outlet, the channel causing movement of the eccentric ring at a predetermined pressure at the outlet, the movement of the eccentric ring changing the amount of fluid transferred from the inlet to the outlet per revolution of the inner rotor.    
   
   
       18 . The variable displacement pump of  claim 17  further comprising: 
 a wing portion attached to the eccentric ring, the pressure at the outlet capable of moving the wing portion and the eccentric ring.    
   
   
       19 . The variable displacement pump of  claim 17  wherein the outer rotor moves automatically in response to changes in fluid pressure at the outlet.  
   
   
       20 . The variable displacement pump of  claim 17  further comprising: 
 a biasing member preventing movement of the eccentric ring below the predetermined pressure.