Abstract:
A double internal gear pump has two internal gear pumps having a common pump shaft. A partition is formed between the two internal gear pumps, and the partition has a frustoconical circumferential surface which contacts an opposing in a sealing manner in a pump housing. Pump inlets and pump outlets can be led through the partition. The frustoconical circumferential surface of the partition is advantageous because it removes the necessity of pressing into the pump housing and canting the partition. In addition, a seal on the circumference of the partition is ensured with great realiability.

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2010/064211, filed on Sep. 27, 2010, which claims the benefit of priority to Ser. No. DE 10 2009 045 574.4, filed on Oct. 12, 2009 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The disclosure relates to a double internal gear pump with two internal gear pumps. The double internal gear pump is intended for a slip-controlled (ABS, ASR, ESP, FDR) hydraulic vehicle brake system, each of the two internal gear pumps being intended for a brake circuit. Such pumps in slip-controlled hydraulic vehicle brake systems are also designated as recirculating pumps, although is it customary for piston pumps to be considered, not gear pumps. 
     A double internal gear pump of this type is known from the laid-open publication DE 10 2007 054 808 A1. It has two internal gear pumps with a common pump shaft for joint drive with an electric motor. Pinions of the two internal gear pumps are arranged coaxially next to one another, with an axial clearance, on the pump shaft fixedly in terms of rotation. Ring wheels of the two internal gear pumps are arranged eccentrically to the pinions and the pump shaft and mesh with the pinions at a circumferential point or in a circumferential region. The known double internal gear pump has a pump casing in which the two internal gear pumps are arranged. Located in the pump casing between the two internal gear pumps is a partition which separates the two internal gear pumps spatially by the amount of the thickness of the partition and hydraulically. 
     SUMMARY 
     The partition of the double internal gear pump according to the disclosure possesses a circumferential surface which widens in one direction and which bears against a countersurface in the pump casing. For hydraulic separation of the two internal gear pumps, the circumferential surface of the partition bears sealingly against the countersurface in the pump casing. There is provision per se for the circumferential surface of the partition to bear over a large area against the countersurface of the pump casing over all or part of the circumferential surface of the partition, bearing contact having to be closed in the circumferential direction if hydraulic separation of the two internal gear pumps is to be achieved. However, it is conceivable, for example, also to have, instead of bearing contact over a large area, linear bearing contact along a continuous, preferably closed line. 
     The advantage of the disclosure is that the partition can be inserted into the pump casing more simply than a partition, the circumferential surface of which is axially parallel, for example cylindrical, tilting of the partition in the pump casing being largely ruled out. 
     A further advantage, as compared with a partition having a cylindrical circumferential surface, is more reliable leak tightness of the partition circumferential surface bearing against the countersurface of the pump casing, because there is no risk of the partition being pressed in over an axial travel corresponding to the thickness of the partition unreliably in terms of assembly. Another advantage is more reliable leak tightness of pump connections, that is to say pump inlets and/or outlets, where these are routed through the circumferential surface of the partition and the countersurface of the pump casing. During assembly, any sealing rings at issues of the pump connections in the circumferential surface of the partition or the countersurface of the pump casing come to bear against the respective countersurface only when the circumferential surface of the partition comes to bear against the countersurface of the pump casing. The disclosure prevents such sealing rings from being sheared off when a partition with a cylindrical circumferential surface is pressed into a hollow-cylindrical countersurface of a pump casing. 
     An internal gear pump in the context of the disclosure is also to be understood as meaning what is known as an annular gear pump. 
     The disclosure further discusses subject matter regarding advantageous refinements and developments of the internal gear pump. 
     The partition of the double internal gear pump according to the disclosure has a frustoconical circumferential surface, the cone frustum preferably being a straight circular cone frustum, although this is not mandatory for the disclosure. An oblique cone frustum and/or a cone frustum, the base of which is not a circle, are also possible. Another possibility of a circumferential surface widening in one direction is a pyramid frustum, the base of which can fundamentally be any regular or irregular polygon. The pyramid frustum, too, can be straight or oblique. The countersurface of the pump casing is preferably an exact reciprocal fit with the circumferential surface of the partition. 
     Preferably, the double internal gear pump is arranged in a hydraulic block of a hydraulic slip-controlled vehicle brake system, said hydraulic block forming the pump casing (claim  3 ). The hydraulic block connects the double internal gear pump hydraulically to further hydraulic components of the slip control of the vehicle brake system, such as solenoid valves, nonreturn valves, hydraulic accumulators and hydraulic dampers. The hydraulic block is connected to a brake master cylinder and wheel brakes of the vehicle brake system are connected to the hydraulic block. The two internal gear pumps of the double internal gear pump are separated hydraulically from one another, and each of the two internal gear pumps is assigned to a brake circuit of the vehicle brake system. The internal gear pumps form so-called recirculating pumps of the slip-controlled vehicle brake system. 
     A further advantage of the disclosure is the possibility of premounting the two internal gear pumps or at least their pinions and the partition arranged between them as a subassembly on the pump shaft and of inserting the subassembly into the pump casing (claim  4 ). This is possible because the partition does not have to be pressed into the pump casing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be explained in more detail below by means of an embodiment illustrated in the following figures. 
         FIG. 1  shows an axial section through a double internal gear pump according to the disclosure; 
         FIG. 2  shows a radial section through a partition of the double internal gear pump from  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The double internal gear pump  1  according to the disclosure, illustrated in  FIG. 1 , has two internal gear pumps  2 ,  2 ′ which are separated hydraulically from one another and have a common pump shaft  3  for driving them. The internal gear pumps  2 ,  2 ′ are provided as hydraulic pumps for the two brake circuits of a hydraulic vehicle brake system, not illustrated, having slip control (ABS, ASR, ESP, FDR). Such hydraulic pumps are also designated as recirculating pumps. The two internal gear pumps  2 ,  2 ′ are arranged in mutually parallel planes radial to the pump shaft  3  and at an axial distance from one another. Pinions  4 ,  4 ′ of the internal gear pumps  2 ,  2 ′ are fastened fixedly in terms of rotation on the pump shaft  3  and on account of the common pump shaft  3  are coaxial to one another. The pinions  4 ,  4 ′ are surrounded by ring wheels  5 ,  5 ′ which are arranged eccentrically to the pump shaft  3  and to the pinions  4 ,  4 ′ and which mesh with the pinions  4 ,  4 ′ at a point or in a region on the circumference. In the exemplary embodiment, the ring wheels  5 ,  5 ′ are arranged with opposite eccentricity, that is to say are arranged with an offset in circumferential direction of 180 degrees. However, this is not mandatory for the embodiment, and the ring wheels  5 ,  5 ′ may also be arranged eccentrically in the same direction, that is to say without offset in the circumferential direction or with any desired offset in the circumferential direction. The ring wheels  5 ,  5 ′ are arranged at a fixed location and rotatably in a pump casing  6  or a cover  7  of the pump casing  6 . 
     Sickle-shaped blades  8 ,  8 ′ are fastened pivotably in a pump space between the ring wheels  5 , 5 ′ and the pinions  4 ,  4 ′ by means of pins  9 ,  9 ′. Tooth tips of teeth of the pinions  4 ,  4 ′ and of the ring wheels  5 ,  5 ′ brush along the sickle-shaped blades  8 ,  8 ′ which seal off tooth interspaces on the circumference of the toothings. The internal gear pumps  2 ,  2 ′ are therefore what are known as sickle pumps, the disclosure not being restricted to this form of construction, but instead also possibly having, for example, annular gear pumps (not illustrated). The pump spaces are sickle-shaped spaces which are located between the pinions  4 ,  4 ′ and the ring wheels  5 ,  5 ′ of the internal gear pumps  2 ,  2 ′ and which extend over a limited circumferential region from a pump inlet to a pump outlet. 
     Between the internal gear pumps  2 ,  2 ′ is located a partition  10  which, in the exemplary embodiment, is in the form of a circular disk with a middle hole  11  for the passage of the pump shaft  3 . A circumferential surface  12  of the partition  10  is frustoconical, that is to say the circumferential surface  12  of the partition  10  widens in one axial direction or tapers in the opposite axial direction. The circumferential surface  12  bears sealingly against a countersurface  13  in the pump casing  6 . The countersurface  13  is in the form of an inner cone frustum having an exact fit with the circumferential surface  12 . The partition  10  separates the two internal gear pumps  2 ,  2 ′ spatially by the amount of the thickness of the partition  10 , and the partition  10  separates the two internal gear pumps  2 ,  2 ′ hydraulically from one another. The partition  10  seals off the internal gear pumps  2 ,  2 ′ on the end faces, facing it and bearing against it, of the internal gear pumps  2 ,  2 ′ or the pinions  4 ,  4 ′, the ring wheels  5 ,  5 ′ and the sickle-shaped blades  8 ,  8 ′. The partition  10  is sealed off at the pump shaft  3  by means of sealing rings  14 . Pump connections, to be precise pump inlets and pump outlets, are routed through the partition  10 , although this is not illustrated in  FIG. 1  for the sake of simplicity. They are described further below with reference to  FIG. 2 . 
     Arranged on those end faces of the internal gear pumps  2 ,  2 ′ which face away from the partition  10  are pressure disks  15 ,  15 ′ which seal off the internal gear pumps  2 ,  2 ′ on these end faces and, in the illustrated exemplary embodiment, at the same time form shaft bearings for the pump shaft  3 . In the casing cover  7 , the pump shaft  3  is sealed off by means of a sealing ring  16 , and a pump drive with an electric motor, not illustrated, is provided on this side. The pump casing  6  is closed on the other end face. 
     The internal gear pumps  2 ,  2 ′ and the partition  10  arranged between them can be premounted as a subassembly on the pump shaft  3  and be inserted as a finished subassembly into the pump casing  6 . The pump casing  6  may be a specific component; in the exemplary embodiment the pump casing  6  is a hydraulic block of the slip control device of the hydraulic vehicle brake system, the hydraulic pumps of which form the two internal gear pumps  2 ,  2 ′ (not illustrated). Such hydraulic blocks for slip-controlled hydraulic vehicle brake systems are known per se, and, in addition to the hydraulic pumps, that is to say, here, the internal gear pumps  2 ,  2 ′, further hydraulic components, such as solenoid valves, nonreturn valves and hydraulic accumulators, are inserted into them and are connected to one another by means of bores so as to form hydraulic circuits. 
       FIG. 2  depicts a section through a mid-plane of the partition  10  radially to the pump shaft  3 , and the frustoconical circumferential surface  12  can be seen, and also angled and partly stepped bores which form the pump inlets  17 ,  17 ′ and pump outlets  18 ,  18 ′. The pump inlets  17 ,  17 ′ and pump outlets  18 ,  18 ′ form pump connections of the two internal gear pumps  2 ,  2 ′ of the double internal gear pump  1  according to the disclosure. The pump inlets  17 ,  17 ′ and pump outlets  18 ,  18 ′ issue axially parallel through end faces of the partition  10  into the pump spaces of the internal gear pumps  2 ,  2 ′ upstream or downstream of the sickle-shaped blades  8 ,  8 ′ in the circumferential direction. The pump inlets  17 ,  17 ′ and pump outlets  18 ,  18 ′ have in the circumferential surface  12  of the partition  10  issues through which they communicate with corresponding pump connections in the pump casing  6  (hydraulic block). At the issues of the pump inlets  17 ,  17 ′ and pump outlets  18 ,  18 ′, sealing rings  19  are inserted in annular steps in the circumferential surface  12  of the partition  10  and, in the non-deformed state, project somewhat beyond the circumferential surface  12  of the partition  10 . When the partition  10  is inserted into the pump casing  12 , the sealing rings  19  come to bear against the frustoconical countersurface  13  which compresses the sealing rings  19  such that they are flush with the circumferential surface  12 . The sealing rings  19  thereby bear with prestress against the frustoconical countersurface  13  and seal off the pump inlets  17 ,  17 ′ and pump outlets  18 ,  18 ′ at the transition from the pump casing  6  into the partition  10 . 
     Valves of the two internal gear pumps  2 ,  2 ′ are inserted into the pump inlets  17 ,  17 ′ and into the pump outlets  18 ,  18 ′. In the exemplary embodiment illustrated, pressure reducing valves  20 ,  20 ′ are inserted into the pump inlets  17 ,  17 ′. The pressure reducing valves  20 ,  20 ′ are designed as linear slide valves, the pistons  21 ,  21 ′ of which can be displaced counter to spring elements  22 ,  22 ′ by being acted upon hydraulically with pressure. During displacement, the pistons  21 ,  21 ′ reduce passage areas of the pump inlets  17 ,  17 ′ and thus limit the hydraulic pressure. The valves in the pump outlets  18 ,  18 ′ are non-return valves  23 ,  23 ′. They have valve balls  24 ,  24 ′ which are loaded by spring elements  25 ,  25 ′ against valve seats. Non-return valves without spring elements may also be used. 
     A bore  26  which is continuous in the diameter direction leaves from the middle hole  11  to the pump inlets  17 ,  17 ′, so that liquid which may possibly overcome the sealing rings  14  is discharged to the pump inlets  17 ,  17 ′.