Fixed Displacement Pump For Use For Conveying A Hydraulic Fluid In A Closed Hydraulic Circuit, Closed Hydraulic Circuit, Construction Machine And Method For Operating A Fixed Displacement Pump In A Closed Hydraulic Circuit

Abstract

The present invention relates to a fixed displacement pump for use for conveying a hydraulic fluid in a closed hydraulic circuit, a closed hydraulic circuit, a construction machine and a method for operating a fixed displacement pump in a closed hydraulic circuit.

What is claimed is: 
     
         1 . A fixed displacement pump for use for conveying a hydraulic fluid in a closed hydraulic circuit, comprising:
 a pump housing;   at least one conveying element arranged inside the pump housing in a conveying chamber and rotatably driven about a rotation axis (R 1 , R 2 ) for conveying purposes, the conveying element having at least one bearing axle extending in axial direction of the rotation axis (R 1 , R 2 ), the conveying element being supported for rotation with the bearing axle about the rotation axis (R 1 , R 2 ) within an axle bearing provided in axial direction next to the conveying element and configured stationary relative to the pump housing;   a fluid pump inlet via which hydraulic fluid to be conveyed can be conveyed from outside the fixed displacement pump into the conveying chamber on a low-pressure side;   a fluid pump outlet via which conveyed hydraulic fluid from the conveying chamber can be discharged from the fixed displacement pump on a high-pressure side; and   a device for discharging a leakage portion of the hydraulic fluid escaping from the conveying chamber via the axle bearing,   wherein the fixed displacement pump has a collection chamber adjacent to the axle bearing for the leakage portion of the hydraulic fluid escaping from the axle bearing,   wherein a sealing device is provided which seals the collection chamber from the low-pressure side and the high-pressure side of the fixed displacement pump, and   wherein the fixed displacement pump has a leakage oil outlet connected to the collection chamber for discharging the leakage oil from the fixed displacement pump.   
     
     
         2 . The fixed displacement pump according to  claim 1 ,
 wherein the collection chamber is configured as a collection chamber that is pressureless with respect to the outside environment during operation of the fixed displacement pump.   
     
     
         3 . The fixed displacement pump according to  claim 1 ,
 wherein the collection chamber has at least one of the following features:   the collection chamber extends through components that are stationary relative to the pump housing and/or stationary relative to the at least one bearing axle;   the collection chamber comprises an annular space surrounding the bearing axle, in particular completely;   the collection chamber comprises a collection head section directly adjoining a face side of the bearing axle in axial direction of the bearing axle;   the collection chamber comprises a collection passage opening passing completely through the bearing axle in axial direction from one face side to the other;   the collection chamber comprises at least one connection channel that connects an annular space surrounding a bearing axle, or a collection head section, or a collection passage opening, with an annular space surrounding a bearing axle, or a collection head section, or a collection passage opening; and   the collection chamber comprises a manifold into which multiple connection channels lead.   
     
     
         4 . The fixed displacement pump according to  claim 1 ,
 wherein the collection chamber is formed partially in and/or on one of the following components of the fixed displacement pump:   in the bearing axle, extending through the latter in axial direction;   in the conveying element, extending through the latter in axial direction;   in a bearing rest in which at least one bearing axle is supported;   in a pump flange, as a surface recess on a side opposite the flanging side;   in a pump cover, as a surface recess on the side opposite an outside of the pump cover; and   in a coupling plate of a tandem pump.   
     
     
         5 . The fixed displacement pump according to  claim 1 ,
 wherein the sealing device has at least one of the following features:   the sealing device is formed in one piece;   the sealing device comprises at least one sealing section completely surrounding the bearing axle radially; and   the sealing device comprises two sealing sections, each of which completely surrounds a bearing axle radially, and a connecting section which connects the two sealing sections.   
     
     
         6 . The fixed displacement pump according to  claim 1 ,
 wherein the fixed displacement pump is an external gearwheel pump, comprising:   two adjacent, meshing gearwheels with a respective external toothing;   two parallel bearing axles arranged at least partially at a same height in axial direction of the rotation axes (R 1 , R 2 ), one bearing axle carrying one gearwheel and the other bearing axle carrying the other gearwheel; and   that the fixed displacement pump has at least one of the following features:   one of the bearing axles is designed as a drive axle protruding from the housing, comprising a positive locking device for engagement of a drive arrangement, in particular a spline gearing; and   only one of the bearing axles, the bearing axle driven by the other bearing axle, comprises a passage opening extending in axial direction completely through the bearing axle and open at both face sides as part of the collection chamber.   
     
     
         7 . The fixed displacement pump according to  claim 1 ,
 wherein the fixed displacement pump is configured as a tandem pump with a first and a second fixed displacement pump unit, the tandem pump having at least one of the following features:   wherein a coupling plate is provided which is arranged directly between two gearwheel pairs of the first and second fixed displacement pump units, and wherein a part of the collection chamber is formed by the coupling plate and/or a respective seal is provided as part of the sealing device on both sides of the coupling plate in the direction of the rotation axis (R 1 , R 2 ) of the gearwheel pairs;   wherein multiple bearing axles have passage openings passing completely through them as part of the collection chamber; and   the tandem pump comprises a single common leakage oil outlet, in a pump cover.   
     
     
         8 . The fixed displacement pump according to  claim 1 ,
 wherein the fixed displacement pump comprises a valve device connected to the fluid pump inlet and the fluid pump outlet and/or arranged upstream of the fluid pump inlet and the fluid pump outlet, the valve device having at least one of the following valve functions:   switching between a direct and closed bypass from the fluid pump inlet to the fluid pump outlet and an interruption of the closed bypass;   switching a fluid connection between the fluid pump outlet and a first outlet of the valve device to a fluid connection between the fluid pump outlet and a second outlet of the valve device;   pressure protection of a high-pressure side of the fixed displacement pump and release of a discharge line when a pressure threshold on the high-pressure side is exceeded;   establishing a pressure-protected fluid connection from a feed line to a low-pressure area of the fixed displacement pump; and   dividing the hydraulic fluid flow fed into the functional module block into two partial flows.   
     
     
         9 . The fixed displacement pump according to  claim 1 ,
 wherein the valve device is configured as a modular unit with:   a basic valve block ( 20 ) comprising at least:   a connection opening for connection to the fluid pump inlet;   a connection opening for connection to the fluid pump outlet;   a connection opening for connection to a motor inlet;   a connection opening for connection to a motor outlet;   a connection opening for connection to a feed line;   and a line interruption device with an interruption outlet opening and an interruption inlet opening; and   with a functional module block having a module block inlet opening and a module block outlet opening which is in fluid communication with the module block inlet opening via a valve device and/or a line connection, the functional module block being attached, interchangeably, to the basic valve block such that the interruption outlet opening is in fluid connection with the module block inlet opening and the module block outlet opening is in fluid connection with the interruption inlet opening.   
     
     
         10 . The fixed displacement pump ( 9 ) according to  claim 9 ,
 wherein the functional module block is configured for performing at least one of the following functionalities:   switching between two inlet and two outlet openings;   static pass-through;   switching on/off a feeding function; and   dividing the hydraulic fluid flow fed into the functional module block into two partial flows.   
     
     
         11 . The fixed displacement pump according to  claim 9 ;
 wherein the basic valve block is configured for simultaneous connection of two functional module blocks, for performing at least one of the following functionalities on a closed consumer, a hydraulic motor:   on/off function;   variable drive volume; and/or   reversal of direction.   
     
     
         12 . The fixed displacement pump according to  claim 9 ,
 wherein the valve device, the basic valve block, has a connection for a feed pump, and that the basic valve block has a pressure-protected, switching device for discharging hydraulic fluid from the closed circuit into a discharge line leading to a line connection.   
     
     
         13 . A closed hydraulic circuit, comprising:
 a fixed displacement pump according to  claim 1 ;   a hydraulic consumer, a hydraulic motor, supplied with hydraulic fluid by the fixed displacement pump, with a fluid motor inlet and a fluid motor outlet;   a hydraulic fluid supply line connecting the fluid pump outlet to the fluid motor inlet; and   a hydraulic fluid return line connecting the fluid motor outlet to the fluid pump inlet.   
     
     
         14 . A construction machine, a road paver, with a closed hydraulic circuit according to  claim 13 . 
     
     
         15 . A method for operating a fixed displacement pump operated in a closed hydraulic circuit according to  claim 13 , comprising the steps of:
 a) conveying hydraulic fluid towards a high-pressure side of the closed hydraulic circuit with the aid of the fixed displacement pump;   b) driving a hydraulic consumer, in particular a hydraulic motor, with the aid of the hydraulic fluid conveyed on the high-pressure side;   c) returning the hydraulic fluid from the hydraulic consumer, the hydraulic motor, to the fixed displacement pump on a low-pressure side of the closed hydraulic circuit;   d) collecting leakage oil inside the fixed displacement pump in a separate collection chamber sealed against the low-pressure side and the high-pressure side of the closed hydraulic circuit;   e) draining off the leakage oil from the fixed displacement pump; and   f) feeding hydraulic fluid into the closed hydraulic circuit to compensate for the leakage oil branched off from the closed hydraulic circuit in steps d) and e).   
     
     
         16 . The method according to  claim 15 ,
 wherein the collecting of leakage oil is performed at least partially via a passage opening arranged in a bearing axle.   
     
     
         17 . The method according to  claim 15 ,
 wherein for collecting leakage oil in the collection chamber, the collection chamber is sealed against both the high-pressure side and the low-pressure side of the fixed displacement pump with the aid of a sealing device.   
     
     
         18 . The method according to  claim 15 ,
 wherein the fixed displacement pump is configured as a tandem pump with a first fixed displacement pump unit and a second fixed displacement pump unit, wherein step d) includes combining the leakage oil flows of the first and second fixed displacement pump units and step e) includes draining off the combined leakage oil flows from the tandem pump together.