Axial piston pumps

An axial piston pump, comprising a pump housing assembly, a base plate, and an inlet and outlet flange, wherein the base plate is located at a bottom of the pump housing assembly, the inlet and outlet flange is located at a top of the pump housing assembly, the pump housing assembly, the base plate, and the inlet and outlet flange enclose an inner chamber configured to accommodate other structures of the axial piston pump including a piston cylinder assembly, a piston and piston forced return assembly, and a swash plate assembly, and a transmission shaft passes through the inlet and outlet flange and is connected to the piston cylinder assembly, wherein

• the piston and piston forced return assembly includes a piston assembly and a forced return mechanism, the piston assembly includes a ceramic piston and a ceramic slipper combined together, and the forced return mechanism includes a return plate, a spherical hinge, a return guide column, and preload springs;
• the ceramic slipper is connected to the return plate and is supported on a swash surface of the swash plate assembly;
• a plane of the spherical hinge and the return plate form a plane friction pair, and a spherical surface of the spherical hinge is hinged to a spherical socket of the return guide column;
• the return guide column is installed in a return guide sleeve of the piston cylinder assembly, a side of the return guide column opposite to the spherical socket is provided with a plurality of spring holes for installing the preload springs, and ends of the preload springs protrude from the spring holes and abut against the piston cylinder assembly;
• the piston cylinder assembly includes a piston cylinder and a hydrostatic inner ring disposed on an outer side of the piston cylinder, the ceramic piston of the piston assembly is movably disposed in a piston sleeve of the piston cylinder, one end of the piston cylinder is drivingly connected to the transmission shaft, and a center hole at another end of the piston cylinder is provided with the return guide sleeve, and the return guide sleeve cooperates with the return guide column in the forced return mechanism to provide cooperative guiding;
• the pump housing assembly includes a pump housing on an outer side and a hydrostatic outer ring on an inner side, and the hydrostatic outer ring and the hydrostatic inner ring are both made of a ceramic material and form a hydrostatic main bearing;
• the hydrostatic outer ring is supported on a support surface at an end of the hydrostatic inner ring, an outer cylindrical surface of the hydrostatic inner ring is provided with a hydrostatic pad, an outer cylindrical surface of the hydrostatic outer ring is provided with a high-pressure water annular groove, and the high-pressure water annular groove communicates with the hydrostatic pad through a hydrostatic main bearing pressure supply hole provided in the high-pressure water annular groove;
• and one end of the hydrostatic outer ring is provided with a hydrodynamic support friction surface, which frictionally contacts the support surface, and the hydrodynamic support friction surface is provided with a plurality of first Archimedean spiral convection grooves along a circumferential direction of the hydrodynamic support friction surface;
• the hydrostatic pad of the hydrostatic inner ring has a wedge-shaped stepped structure, including a first hydrostatic water pad and two second hydrostatic water pads, one second hydrostatic water pad is disposed at each axial end of the first hydrostatic water pad, and the first hydrostatic water pad is lower than the two second hydrostatic water pads, forming a stepped structure;
• and the two second hydrostatic water pads each have a wedge-shaped structure, and a small diameter end of each of the two second hydrostatic water pads is connected to the first hydrostatic water pad;
• the spherical socket of the return guide column is provided with a central through hole and an Archimedean spiral damping groove is arranged surrounding the central through hole;
• a bottom surface of the spherical hinge is provided with a convection damping hole penetrating through the spherical surface of the spherical hinge, the convection damping hole communicates with the central through hole, and a labyrinth hydrostatic support water pad is disposed surrounding the convection damping hole;
• the piston assembly includes the ceramic piston and the ceramic slipper, a ball head of the ceramic piston is provided with a center hole and a ball head damping groove surrounding the center hole, and the ball head damping groove is an Archimedean spiral groove;
• and a center of an end surface of the ceramic slipper is provided with a slipper damping hole capable of communicating with the center hole, and a third hydrostatic water pad having a sealing band is disposed surrounding the slipper damping hole;
• two ends of the hydrostatic main bearing are respectively provided with a flow distribution and distribution sealing axial thrust bearing and an end axial bearing, wherein the flow distribution and distribution sealing axial thrust bearing is adjacent to the inlet and outlet flange, and the end axial bearing is located at a bottom of the axial piston pump and is disposed surrounding the swash plate assembly;
• the flow distribution and distribution sealing axial thrust bearing includes a thrust plate guiding assembly, a thrust plate assembly, and a port plate assembly coaxially arranged in sequence;
• the thrust plate guiding assembly, the thrust plate assembly, and the port plate assembly all have annular disk-shaped structures, an outer side of a center hole of the thrust plate guiding assembly is coaxially provided with a pre-sealing thrust mechanism, the pre-sealing thrust mechanism is connected to an end surface of the piston cylinder of the piston cylinder assembly, and a guide member on the thrust plate guiding assembly is sealingly connected to the piston sleeve of the piston cylinder;
• and the flow distribution and distribution sealing axial thrust bearing is provided with a medium channel communicating with the piston sleeve;
• the end axial bearing is cylindrical, including a poly-ether-ether-ketone (PEEK) collar and an alloy core embedded in the PEEK collar, an end surface of the PEEK collar facing the hydrostatic main bearing is provided with a composite surface, the composite surface contacts an inner ring friction surface of the hydrostatic inner ring, the composite surface includes a wedge-shaped surface, a bearing support surface, and a second Archimedean spiral convection groove connected in sequence, an angle of the wedge-shaped surface ranges from 1° to 2°, and a plurality of the composite surfaces are sequentially arranged along a circumferential direction on an end surface of the end axial bearing;
• the pre-sealing thrust mechanism includes a thrust retaining ring and a plurality of thrust springs installed on a same side of the thrust retaining ring, the plurality of thrust springs are arranged at intervals along a circumferential direction of the thrust retaining ring, the thrust retaining ring is installed in an annular groove on an end surface of the piston cylinder assembly, and the annular groove is provided with thrust spring guide holes for accommodating the thrust springs;
• the thrust plate assembly includes a thrust plate support ring and a thrust plate ceramic wear ring connected coaxially, an outer cylindrical surface of the thrust plate ceramic wear ring is assembled on an inner cylindrical surface of the thrust plate support ring, and the thrust plate support ring is a metal ring;
• and the thrust plate ceramic wear ring is provided with a plurality of valve holes at intervals along a circumferential direction;
• the port plate assembly includes a port plate support ring and a port plate ceramic wear ring connected coaxially, the port plate support ring is a metal ring, an outer cylindrical surface of the port plate ceramic wear ring is assembled on an inner cylindrical surface of the port plate support ring, and the port plate ceramic wear ring is provided with a plurality of port plate orifices at intervals along a circumferential direction;
• and
• through holes on the thrust plate guiding assembly, the port plate orifices on the port plate assembly, and the valve holes on the thrust plate assembly communicate to form the medium channel.