Variable-volume internal gear pump

Abstract

The invention relates to a variable-volume internal gear pump, in particular for use as an engine lubrication pump for automobiles. The internal gear pump comprises a housing ( 7, 10 ) and a rotor set chamber ( 40 ) formed therein comprising a low pressure chamber ( 17 ) and a high pressure chamber ( 18 ) for a fluid. Inside the rotor set chamber ( 40 ) are an inner rotor ( 2 ) that can be rotatably driven by a shaft ( 1 ) about an axis of rotation (Di) and a rotatable outer rotor ( 3 ) with an outer rotor axis of rotation (Da) that is arranged eccentric with respect to the axis of rotation (Di). When a rotational force is applied, conveyance cells ( 30, 31 ) form between the inner rotor ( 2 ) and the outer rotor ( 3 ) in which the fluid is conveyed from the low pressure chamber ( 17 ) to the high pressure chamber ( 18 ). An adjusting member ( 5 ) upon which axial springs ( 8 ) act and which is guided in the internal gears ( 34 ) of the outer rotor ( 3 ) in axial motion causes a pressure-related axial movement of the inner rotor ( 2 ). The outer rotor ( 3 ) comprises radial channels ( 41 ) in the gaps between the teeth of the internal gears ( 34 ) thereof proximate to the low pressure chamber ( 17 ) and the high pressure chamber ( 18 ). The axial position of the inner rotor ( 2 ) relative to the outer rotor ( 3 ) can be adjusted by the axial motion of the adjusting member ( 5 ), whereupon the volume of the conveyance cells ( 30, 31 ) changes depending on the pressure.

1 . Variable-volume internal gear pump which comprises
 a housing,   a rotor set chamber which is formed in the housing and which has a low pressure chamber with an inlet opening and high pressure chamber with an outlet opening for a fluid,   an inner rotor which is held in the rotor set chamber and is rotatable about an axis of rotation and is drivable by a shaft, and   an outer rotor rotatably held in the rotor set chamber and having an outer rotor axis of rotation arranged eccentrically relative to the axis of rotation, the inner rotor having outer teeth, and the outer rotor having inner teeth, such that the outer rotor rotates with the inner rotor by the outer-inner teeth in a constant rotational ratio and, in the case of a rotary drive, forms delivery cells in which the fluid is transported from the low pressure chamber to the high pressure chamber,   
       wherein
 an adjusting member producing an axial movement of the inner rotor is provided, 
 the adjusting member is guided in an axially moveable manner in the inner teeth of the outer rotor, 
 the outer rotor has radial channels arranged between the tooth spaces of its inner teeth in the region of the low pressure chamber and of the high pressure chamber, 
 the axial position of the inner rotor relative to the outer rotor is variable by the axial movement of the adjusting member and hence the volume of the delivery cells is variable and 
 the outer teeth of the inner rotor have a shape such that axially effective springs are installable between the shaft driving the inner rotor and the tooth contour of the outer teeth. 
 
     
     
         2 . Internal gear pump according to  claim 1 , wherein
 in the inner rotor, the springs which act axially on the adjusting member are arranged between the shaft driving the inner rotor and the tooth contour of the outer teeth and   an adjustment space which is connected to the high pressure chamber and is axially bounded by the adjusting member is formed within the inner teeth of the outer rotor, a pressure within the adjustment space acting axially on the adjusting member against the spring force of the springs with delivery cells located in between, in such a way that, with increasing pressure in the high pressure chamber and the adjustment space, the adjusting member  5  moves against the spring force of the springs and the volume of the delivery cells decreases.   
     
     
         3 . Internal gear pump according to  claim 1 , wherein the springs are supported via a pot-like intermediate member and a securing ring in the axial direction on the shaft. 
     
     
         4 . Internal gear pump according to  claim 1 , wherein the adjusting member has outer teeth which fit with sufficient but little play in the inner teeth of the outer rotor and are therefore axially moveable therein by providing a seal. 
     
     
         5 . Internal gear pump according to  claim 1 , wherein the geometrical shape of the outer-inner teeth is formed as epicycloid or arc-like outer teeth on the inner rotor, which produces the inner teeth of the outer rotor with one tooth more by a self-generating milling movement. 
     
     
         6 . Internal gear pump according to  claim 1 , wherein the geometrical shape of the outer-inner teeth is determined by epi- and hypocycloids. 
     
     
         7 . Internal gear pump according to  claim 1 , wherein the inner rotor is arranged on the shaft driving it, in an axially moveable manner but nonrotatably—in particular secured by a feather key—substantially runout-free. 
     
     
         8 . Internal gear pump according to  claim 1 , wherein the delivery cells are closed in the axial direction and in a position opposite to the adjusting member by a pinion plate whose inner teeth fit with sufficient but little play in the outer teeth of the inner rotor in such a way that the inner rotor is axially moveable within the inner teeth of the pinion plate. 
     
     
         9 . Internal gear pump according to  claim 8 , wherein blading corresponding to a centrifugal pump is arranged or formed on the pinion plate. 
     
     
         10 . Internal gear pump according to  claim 9 , wherein the blading corresponding to the centrifugal pump is axial blading. 
     
     
         11 . Internal gear pump according to  claim 1 , wherein a compensating pressure region subjected to high pressure and acting to compensate the axial forces is provided between the housing and a drive wheel arranged outside the housing on the shaft. 
     
     
         12 . Internal gear pump according to  claim 3 , wherein a compensating pressure region subjected to high pressure and acting to compensate the axial forces is provided between the housing and the pot-like intermediate member. 
     
     
         13 . Internal gear pump according to  claim 1 , wherein the outer teeth of the inner rotor have between 5 and 8 teeth. 
     
     
         14 . Internal gear pump according to  1 , wherein the outer teeth of the inner rotor have six teeth. 
     
     
         15 . Internal gear pump according to  claim 14 , three springs are arranged uniformly distributed over the circumference in the inner rotor. 
     
     
         16 . Internal gear pump according to  claim 1 , wherein the springs are in the form of coil springs.