EP1293668A2 - Axialkolbenpumpe mit Druckausgleicheinrichtung - Google Patents

Axialkolbenpumpe mit Druckausgleicheinrichtung Download PDF

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Publication number
EP1293668A2
EP1293668A2 EP02078246A EP02078246A EP1293668A2 EP 1293668 A2 EP1293668 A2 EP 1293668A2 EP 02078246 A EP02078246 A EP 02078246A EP 02078246 A EP02078246 A EP 02078246A EP 1293668 A2 EP1293668 A2 EP 1293668A2
Authority
EP
European Patent Office
Prior art keywords
fluid
rocker cam
housing
rocker
counterbalance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02078246A
Other languages
English (en)
French (fr)
Inventor
Fikreadam A. Damtew
Anthony L. Reilly
Robert E. Stakeley
Robert C. Hodges
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Denison Hydraulics Inc
Original Assignee
Denison Hydraulics Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Denison Hydraulics Inc filed Critical Denison Hydraulics Inc
Publication of EP1293668A2 publication Critical patent/EP1293668A2/de
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
    • F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
    • F04B1/14—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis having stationary cylinders
    • F04B1/141—Details or component parts
    • F04B1/146—Swash plates; Actuating elements
    • F04B1/148—Bearings therefor

Definitions

  • This invention relates to a variable displacement, axial piston pump having a rocker cam pivotally mounted in a rocker cradle formed in the pump housing to thereby permit the displacement of the pump to be changed.
  • a pump includes a rotatably mounted pump barrel having a plurality of longitudinal bores each housing a pump piston.
  • Each piston has a shoe pivotally attached to a head end which projects from the barrel and is retained against a thrust surface formed on the rocker cam.
  • a prime mover rotates the barrel causing the pistons to reciprocate and thereby pump fluid as the piston shoes slide over the thrust surface.
  • the angle of the rocker cam thrust surface determines the displacement of the pump. If the rocker cam is centered, i.e.
  • the thrust surface is perpendicular to the axes of the pistons and they do not reciprocate. If the rocker cam is not centered, i.e. on-stroke, the thrust surface is angled with respect to the ends of the shoes and the piston reciprocates as the barrel is rotated.
  • the rocker cam may be pivoted to change the displacement of the pump by a rotary servo controlled fluid motor as described in U.S. Patent Number 3,967,541.
  • the pump may be put on-stroke by a spring which biases the rocker cam to a full on-stroke position as is common with a pressure compensated pump of the type disclosed in the instant application.
  • One type of pressure compensated pump may be seen in U.S. Patent Number 4,289,452.
  • An axial piston pump for pumping fluid at a set working pressure which comprising a housing, a barrel rotatably mounted in the housing, a plurality of bores in the barrel, a piston mounted for reciprocation in each of said bores, a shoe mounted on the end of each piston, a rocker cam support in the housing, a rocker cam having a pair of spaced arcuate bearing surfaces pivotally mounted in complementary arcuate bearing surfaces formed in said rocker cam support, a thrust surface on said rocker cam, a holddown for clamping said piston shoes against said thrust surface wherein said shoes slide over said thrust surface when said barrel is rotated and the pistons reciprocated in their bores when the rocker cam thrust surface is angled to the axis of said barrel, a counterbalance fluid pocket formed in each of said rocker cam arcuate bearing surfaces, a first fluid passage formed in said housing connected to a source of working pressure fluid for conducting working pressure fluid to one of said counterbalance fluid pockets and a second fluid passage formed in said rocker cam connecting said one and the other
  • a pressure compensated, variable displacement, axial piston pump 10 having a rocker cam pivotally mounted in a cam support or cradle may be seen to include a central housing 12 , having a mounting pilot end 14 and a port cap 16 at the other end.
  • Bolts 17 connect port cap 16 to housing 12 .
  • Housing 12 defines a cavity which houses a rotatable barrel 18 mounted on a drive shaft 20.
  • the inner end of drive shaft 20 is supported in a bearing 22 mounted in the port cap 16 .
  • Drive shaft 20 also is supported in a bearing 24 mounted within housing 12 and has a splined drive end 26 which projects outwardly of housing 12 .
  • Barrel 18 has a plurality of bores 28 equally spaced circumferentially about its rotational axis.
  • Each bore 28 contains a piston 30 having a ball shaped head 32 .
  • a shoe 34 is swedged onto head 32 of piston 30 such that the shoe can pivot about the end of the piston.
  • Each of the shoes is clamped against a flat thrust plate or swash plate surface 36 formed on the face of a pivotal rocker cam 38 utilizing a conventional shoe retainer assembly of the type described in detail in U.S. Patent Number 3,904,318.
  • rocker cam 38 has a pair of arcuate bearing surfaces 40 which are received in complementary arcuate bearing surfaces 42 which comprise a rocker cam support or cradle 44 formed in mounting pilot end 14 in housing 12 .
  • Rocker cam 38 pivots about a fixed axis perpendicular to the axis of rotation of barrel 18 to change the displacement of pump 10.
  • the prime mover not shown, affixed to spline drive end 26 rotates drive shaft 20 and barrel 18 within housing 12.
  • rocker cam 38 and thrust surface 36 are shown in a position of maximum fluid displacement.
  • Rocker cam 38 may be pivoted clockwise to reduce the displacement of pump 10 .
  • pump 10 of the instant embodiment is depicted as a pressure compensated pump which does not cross center, the instant invention described hereinbelow applies equally to a rocker cam type variable displacement axial piston where rocker cam 38 may be pivoted clockwise across center such that the intake and exhaust ports are reversed and the device is providing maximum fluid displacement in the opposite direction.
  • Such a pump may be seen in U.S. Patent Number 5,076,145 .
  • the instant invention also applies equally to a rocker cam type, variable displacement pump having a rotary servo or linear servo type control.
  • a piston 52 is slidably mounted in a bore 54 formed in a cylinder 56 rigidly mounted within port cap 16 .
  • a spring 58 around cylinder 56 biases piston 52 against a button 60 mounted on one side of rocker cam 38 to force the rocker cam to pivot to a position of maximum fluid displacement.
  • a stroking piston 62 is slidably mounted in a bore 64 of a cylinder 66 rigidly secured in port cap 16 at a position within pump housing 12 diametrically opposite that of biasing piston 52. Stroking piston 62 engages a button 68 mounted in rocker cam 38 at a position diametrically opposite that of button 60.
  • rocker cam 38 when rocker cam 38 is pivoted counterclockwise sufficiently to cause working pressure fluid to be expelled from pump 10 at a relatively high pressure, large pumping forces are exerted through pistons 30 to rocker cam 38 . These forces are transmitted through the complementary arcuate bearing surfaces 40 and 42 into rocker cam support 44. The large pumping forces cause large friction forces to occur at the interface of rocker cam bearing surfaces 40 and rocker support bearing surfaces 42 to make movement of rocker cam 38 within rocker support 44 very difficult.
  • plane bushings 70 are inserted between rocker cam arcuate bearing surfaces 40 and rocker support arcuate bearing surfaces 42 as depicted in Fig. 2. While plain bushings 70 reduce the aforementioned frictional forces to some extent, they are inadequate by themselves to reduce the frictional forces to a satisfactory level.
  • working pressure fluid is supplied to counterbalance pockets 72 and 74 formed in the rear faces 76 of rocker cam 38 as depicted in Figures in 2, 5 and 6.
  • the areas of the counterbalance pockets 72 and 74 are designed such that when they receive working pressure fluid they reduce the force required to pivot rocker cam 38 within cam support 44 to within desirable levels.
  • working pressure fluid has been supplied to counterbalance pockets in rocker cam where the working pressure fluid source is a pumping piston and fluid is supplied to the piston shoe and thereafter to bores in the thrust plate which bores connect to the counterbalance pockets.
  • Applicant has discovered a unique means for supplying working pressure fluid to the counterbalanced pockets 72 and 74 formed in the rear face 76 of rocker cam 38 where the fluid source is in the housing 12 .
  • Fluid passage 78 connected to a source, not shown, of working pressure fluid is formed in housing 12 .
  • Fluid passage 78 opens into a fluid passage 80 formed in housing 12 one end of which is closed by a plug 82 which may be replaced with a sensor or other device utilizing working pressure fluid for control purposes.
  • a hollow roll pin 84 is mounted in a central bore of plain bushing 70 , in cam support arcuate bearing surface 42 and in a corresponding bore in housing 12 .
  • Roll pin 84 serves two purposes. It anchors plain bushing 70 on cam support or cradle 44 and it intersects fluid passage 80 to thereby connect that passage to a fluid passage 86 formed in rocker cam 38 and in arcuate cam surface 40 .
  • Fluid passage 86 intersects an angled fluid passage 88 formed in rocker cam 38 and closed by a plug 90 .
  • Fluid passage 88 intersects an oppositedly angled passage 92 closed at one end by a plug 94.
  • the fluid passage 96 which parallels fluid passage 86 has one end which intersects fluid passage 92 at a right angle and another end which opens into fluid pocket 74 formed in rear face 76 of rocker cam 38.
  • a roll pin 98 anchors plain bushing 70 to cam support surface 44.
  • the instant invention provides a means of taking source of working pressure fluid in the pump housing and supplying the fluid to the counterbalance pockets 72 and 74 formed in the rear face 76 of rocker cam 38 which pockets are connected through passages formed in rocker cam 38 .

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Reciprocating Pumps (AREA)
  • Details Of Reciprocating Pumps (AREA)
EP02078246A 2001-09-12 2002-08-07 Axialkolbenpumpe mit Druckausgleicheinrichtung Withdrawn EP1293668A2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US951796 1997-10-16
US09/951,796 US20030047066A1 (en) 2001-09-12 2001-09-12 Axial piston pump with rocker cam counterbalance feed

Publications (1)

Publication Number Publication Date
EP1293668A2 true EP1293668A2 (de) 2003-03-19

Family

ID=25492160

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02078246A Withdrawn EP1293668A2 (de) 2001-09-12 2002-08-07 Axialkolbenpumpe mit Druckausgleicheinrichtung

Country Status (4)

Country Link
US (1) US20030047066A1 (de)
EP (1) EP1293668A2 (de)
JP (1) JP2003139046A (de)
CA (1) CA2391544A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014187546A1 (de) * 2013-05-22 2014-11-27 Hydac Drive Center Gmbh Axialkolbenpumpe

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7086225B2 (en) * 2004-02-11 2006-08-08 Haldex Hydraulics Corporation Control valve supply for rotary hydraulic machine
US7124677B2 (en) * 2004-02-11 2006-10-24 Haldex Hydraulics Corporation Swashplate assembly
DE102009021717A1 (de) * 2009-05-18 2010-11-25 Robert Bosch Gmbh Hydraulisches Gerät
DE102012214830B4 (de) 2012-08-21 2022-06-30 Robert Bosch Gmbh Hydrostatische Axialkolbenmaschine mit verstellbarer Schrägscheibe oder Schenkwiege und zugehörigem Gleitlager mit hydrostatischem Druckfeld, dessen Randkonturausbildung den Leckagestrom ins Gehäuse minimiert
CN103075317B (zh) * 2013-02-04 2016-08-10 陕西航天动力高科技股份有限公司 一种双泵式轴向变量柱塞泵

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014187546A1 (de) * 2013-05-22 2014-11-27 Hydac Drive Center Gmbh Axialkolbenpumpe
US10527029B2 (en) 2013-05-22 2020-01-07 Hydac Drive Center Gmbh Axial piston pump

Also Published As

Publication number Publication date
CA2391544A1 (en) 2003-03-12
JP2003139046A (ja) 2003-05-14
US20030047066A1 (en) 2003-03-13

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