US3823558A - Hydrostatic transmission - Google Patents

Hydrostatic transmission Download PDF

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Publication number
US3823558A
US3823558A US00341609A US34160973A US3823558A US 3823558 A US3823558 A US 3823558A US 00341609 A US00341609 A US 00341609A US 34160973 A US34160973 A US 34160973A US 3823558 A US3823558 A US 3823558A
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United States
Prior art keywords
conduit
pressure
conduit means
control
outlet
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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.)
Expired - Lifetime
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US00341609A
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English (en)
Inventor
E Tittmann
W Romeisch
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/46—Automatic regulation in accordance with output requirements
    • F16H61/472—Automatic regulation in accordance with output requirements for achieving a target output torque
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/4078—Fluid exchange between hydrostatic circuits and external sources or consumers
    • F16H61/4104—Flushing, e.g. by using flushing valves or by connection to exhaust

Definitions

  • ABSTRACT Adriven main pump drives a hydraulic motor through high pressure and low pressure conduits, while a feed pump supplies pressure fluid through a check valve to the low pressure conduit.
  • a control conduit connects the feed pump'with a pressure maintaining valve opening into a low pressure container, and includes a shiftable control valve operated by fluid from the high pressure conduit, but connecting in all positions the feed pump with the pressure maintaining valve.
  • a throttle is provided whose pressure differential is greater than the pressure differential of the check valve between the feed pump and the low pressure conduit.
  • the transmission of the prior art has the disadvantage that for the flushing control valve and also for the feed pump, separate pressure maintaining and feeding pressure safety valves are required, so that the transmission is complicated.
  • the present invention provides a throttle between the feed pump and the control valve, while the control valve is constructed in such a manner that in all positions of the control valve, the
  • feed pump communicates with the pressure maintaining valve, and through the same with a low pressure discharge area.
  • a further advantage of the invention resides in that the throttle obtains a speed-depending increase of the feeding pressure during idling of the hydrostatic transmission, permitting an adjustment of the main pump in this condition even at high rotary speeds.
  • FIG. 1 is a diagram schematically illustrating a hydrostatic transmission according to an embodiment of the invention
  • FIG. 2 is a sectional view illustrating a first control valve construction which may be used in the embodiment of FIG. 1;
  • FIG. 3 is a sectional view illustrating a second control valve construction which may be used in the embodiment of FIG. 1.
  • An adjustable and reversible hydraulic main pump is driven by prime mover 11, which also drives a feed pump 12 in synchronism with the main pump.
  • the main pump 10 is connected by pressure conduits 13 and 14 with a hydraulic motor 15, which may drive the wheels of a vehicle.
  • the feed pump 12 pumps through an outlet conduit 12a, in which a filter 24 is provided, into a control conduit 16 which is connected with a pressure maintaining valve 18 biassed by spring 29 and being subjected to the pressure of the control conduit by a connecting conduit 28 so that the pressure maintaining valve 18 discharges at a certain pressure into the open container 19.
  • Two outlet conduits 20 and 21 branch off the outlet conduit 12a of the feed pump and are connected with inlet and outlet conduits of the main pump 41.
  • Check valves 22 and 23, opening toward the main pump 41, are provided in the outlet conduits 20 and 21.
  • the fluid pumped by the feed pump 12 through an inlet conduit 44 out of an open container 45, is pumped through filter 24 and the one of the outlet conduits 20, 22 which communicates with the low pressure conduit of the two pressure conduits 13, 14.
  • the check valve 23 is held closed, and the check valve 22 opens so that fluid is pumped from the feed pump 12 into the low pressure conduit 13.
  • the outlet conduit 12a communicates with a control conduit 16 in which a flushing control valve 17 is provided.
  • the control valve 17 has three positions, and connects in all three positions, control conduit 16 with the pressure maintaining valve 18 which has a spring 29 and is operated by pressure fluid in the shifting conduit 28.
  • the control conduit 16 In the illustrated position I], only the control conduit 16 is connected with the pressure maintaining valve 18, while in the control position I the low pressure conduit 32 is also connected with the pressure maintaining valve 18, and in the position III, the high pressure conduit 30 is also connected with the pressure maintaining valve 18.
  • Shifting conduits 42 and 43 respectively connected with pressure conduits 30 and I3, and 32, 14, shift the control valve 17 against the action of springs 26 and 27 which bias control valve 17 toward the normal position II when there is low pressure in the fluid circulated in the transmission.
  • Low pressure conduit 13 is connected with a low pressure conduit 30 which is connected with control valve 17, and a corresponding high pressure conduit 32 is also connected with control valve 17.
  • a portion of low pressure conduit 30 is connected with a shifting valve 31, and a corresponding portion of high pressure conduit 32 is also connected with the shifting valve 31, which has two positions I and II.
  • Shifting conduits 37 and 38 connect low pressure conduit 30 and high pressure conduit 32 with the ends of the shifting valve for operating the same depending upon which of the conduits 30 and 32 is functioning as high pressure conduit, and which is functioning as low pressure conduit.
  • a connecting conduit 33 between conduits 30 and 32 has a pressure limiting, spring-biassed valve 35 operated by fluid pressure in a shifting conduit connected with connecting conduit 34, which also connects conduits 30 and 32 and includes a pressure limiting springbiassed valve 36 controlled by fluid pressure in a conduit connected with connecting conduit 33.
  • Pressure limiting valves 35 and 36 protect the respective highpressure conduit, for example 32, 14 from overloads.
  • pressure limiting valve 36 protects the high pressure conduit 13.
  • the shifting valve 31 always connects the respective high pressure conduit, for example, conduit 14, 32, with a conduit 39 controlling a hydraulic motor 40 operating the adjusting means of the main pump 41 for varying the amount of fluid pumped by the main pump 41.
  • shifting valve 31 is shifted to control position II and control valve 17 is shifted to position III.
  • conduits 14, 32 are the high pressure conduits connected with the outlet of main pump 41
  • conduits 13, 30 are the low pressure conduits connected with the inlet of main pump 41
  • feed pump 12 pumps fluid from container 45 through conduits 12a, 20 and check valve 22 into the low pressure conduits 30, 13.
  • Check valve 23 is closed since the high pressure from the high pressure conduits 14, 32 acts to close check valve 23 against the lower pressure in outlet conduit 41.
  • control valve 17 is shifted against the action of spring 26 to the control position lll.
  • FIG. 2 illustrates a control valve 17 which may be used in the embodiment of FIG. 1, and has a longitudinal bore 47 in which a control slide 46 is slidably mounted.
  • Control slide 46 has piston portions 55, 48 at the ends, each of which closes annular ports 49, 90 in the neutral position of the control slide 46.
  • Chambers 51, 52 are provided at the ends of the bore 47, containing springs 53, 54 which hold the control slide in the neutral position.
  • Pressure conduits 30 and 32 are connected with shifting conduits 42, 43, as described with reference to FIG. 1, which supply pressure fluid to chambers 51 and 52 for shifting the slide 46 to the two outer control positions I and III out of the normal position 1.
  • Filter 24 is omitted in the schematic portion of FIG. 2, for the sake of simplicity.
  • FIG. 3 illustrates the modified control valve 17 in which the slide 56 is guided in a longitudinal bore 57 having three annular grooves 58, 59, 60.
  • Chambers 61, 62 are provided at the ends of the longitudinal bore 57, and contain springs 63, 64 urging the slide 56 to the center normal position.
  • the pressure conduits 30 and 32 directly open into the chambers 61 and 62, respectively, so that shifting conduits 42,- 43- of the embodiment of FIG. 2 are not required.
  • the slide 56 has three piston portions 65, 66, 67.
  • the hydrostatic transmission comprises a driven main pump 41, a hydraulic motor 15, high pressure conduit means 14, 32, and low pressure conduit means 13, 30 connecting the main pump 41 with the motor 15; a driven feed pump 12 having outlet conduit means 20, 21 with check valve means 22, 23 connecting the feed pump 12 with the low pressure conduit means 13, 30, and inlet conduit means 44 connected with a low pressure area 45; pressure maintaining valve means 18 opening into a low pressure area 19 for cooling a pressure fluid; a control conduit means 16 connecting the outlet conduit means 20, 21, with the pressure maintaining valve means 18; control valve means 17 in the control conduit means 16 having a plurality of positions, and connecting said outlet conduit means 20, 21, 12a with said pressure maintaining valve means 18, and connecting in one of the positions "I also the low pressure conduit 30, 13 with the pressure maintaining valve means 18 so that heated pressure fluid from the low pressure conduit means 30, 13 is cooled; and throttle means 25 in the control conduit means 16 between the outlet conduit means 20, 21, 12a and the control valve means 17, producing in the control conduit means 16 a pressure differential greater than the pressure
  • Hydrostatic transmission comprising a driven main pump, a hydraulic motor, high pressure conduit means, and low pressure conduit means connecting said main pump with said motor so that said motor is driven by said main pump; a driven feed pump having outlet conduit means with check valve means connecting said feed pump with said low pressure conduit means, and inlet conduit means connected with a low-pressure area; pressure maintaining valve means opening into a low pressure area for cooling a pressure fluid; a control conduit means connecting said outlet conduit means with said pressure maintaining valve means; control valve means in said control conduit means having a plurality of positions, and connecting said outlet conduit means with said pressure maintaining valve means, and connecting in one of said positions also said low pressure conduit means with said pressure maintaining valve means so that heated pressure fluid from said low pressure conduit means is cooled; and throttle means in said control conduit means between said outlet conduit means and said control valve means, producing in I said control conduit means a pressure differential greater than the pressure differential of said check valve means.
  • said main pump includes means for reversing the flow therethrough so that said high pressure conduit means becomes a low pressure conduit means, and said low pressure conduit means becomes a high pressure conduit means; wherein said check valve means connect said outlet conduit means of said feed pump with the respective low pressure conduit; and wherein said control valve means has a normal position connecting only said outlet conduit means with said pressure maintaining valve means, and two control positions for connecting also the respective high pressure conduit with said pressure maintaining valve means; and comprising shifting conduits connected with said low pressure and high pressure conduit means for shifting said control valve means between said normal position and the control position associated with respective high pressure conduit means.
  • control valve means includes a valve slide movable between said normal position and two outer control positions; springs at the ends of said valve slide urging said valve slide to said normal position; and wherein said valve slide closes one of said shifting conduits before opening the other.
  • Hydrostatic transmission as claimed in claim 1 comprising a filter in said outlet conduit means of said feed pump upstream of said throttle means.
  • outlet conduit means of said feed pump include a first outlet conduit connecting said feed pump with said control conduit, and second and third outlet conduits connecting a point of said first'outlet conduit upstream of said throttle means with said high pressure conduit means and said low pressure conduit means, respectively, and wherein said second and third outlet conduits contain check valves, respectively, opening toward said main pump.
  • said main pump includes hydraulic adjusting means; comprising a shifting valve means operated by the pressure fluid in said low pressure and high pressure conduit means to connect said high pressure conduit means with said hydraulic adjusting means for varying the amount of fluid pumped by said main pump.
  • said outlet conduit means of said feed pump include a first outlet conduit connecting said feed pump with said control conduit, and second and third outlet conduits connecting a point of said first outlet conduit upstream of said throttle means with said high pressure conduit means and said low pressure conduit means, respectively, and wherein said second and third outlet conduits contain check valves, respectively, opening toward said main pump; and comprising a filter in said first outlet conduit.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Fluid Gearings (AREA)
  • Fluid-Pressure Circuits (AREA)
US00341609A 1972-04-17 1973-03-15 Hydrostatic transmission Expired - Lifetime US3823558A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2218472A DE2218472A1 (de) 1972-04-17 1972-04-17 Hydrostatisches getriebe

Publications (1)

Publication Number Publication Date
US3823558A true US3823558A (en) 1974-07-16

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Family Applications (1)

Application Number Title Priority Date Filing Date
US00341609A Expired - Lifetime US3823558A (en) 1972-04-17 1973-03-15 Hydrostatic transmission

Country Status (6)

Country Link
US (1) US3823558A (de)
JP (1) JPS4915866A (de)
CH (1) CH550347A (de)
DE (1) DE2218472A1 (de)
FR (1) FR2181344A5 (de)
GB (1) GB1420148A (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3971215A (en) * 1974-06-06 1976-07-27 Marion Power Shovel Company, Inc. Power shovel and crowd system therefor
US3999387A (en) * 1975-09-25 1976-12-28 Knopf Frank A Closed loop control system for hydrostatic transmission
US5095698A (en) * 1989-07-31 1992-03-17 Linde Aktiengesellschaft Hydrostatic transmission
US20070028610A1 (en) * 2005-08-05 2007-02-08 Toshifumi Yasuda Working vehicle
CN104930022A (zh) * 2015-06-24 2015-09-23 海特克液压有限公司 一种带冲洗阀的液压传动装置
CN109469665A (zh) * 2017-09-07 2019-03-15 罗伯特·博世有限公司 静液的阀装置、具有所述阀装置的静液的传动机构和具有所述传动机构的静液的驱动装置
CN111417803A (zh) * 2017-10-09 2020-07-14 波克兰液压工业设备公司 疏通入口过滤器

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2781532B1 (fr) * 1998-07-22 2000-10-13 Poclain Hydraulics Ind Dispositif de valve pour un moteur hydraulique apte a entrainer une masse d'inertie importante

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2255783A (en) * 1940-02-17 1941-09-16 Manly Corp Fluid pressure device and system
US3175354A (en) * 1962-03-08 1965-03-30 Council Scient Ind Res Hydraulic transmission systems
US3230699A (en) * 1964-01-21 1966-01-25 Sundstrand Corp Hydrostatic transmission
US3360934A (en) * 1966-05-06 1968-01-02 Int Harvester Co Hydrostatic transmission dual pressure charge-servo system
US3429123A (en) * 1967-08-29 1969-02-25 Leblond Mach Tool Co R K Speed control system
US3650108A (en) * 1968-09-20 1972-03-21 Sigma Hydrostatic transmission control

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2255783A (en) * 1940-02-17 1941-09-16 Manly Corp Fluid pressure device and system
US3175354A (en) * 1962-03-08 1965-03-30 Council Scient Ind Res Hydraulic transmission systems
US3230699A (en) * 1964-01-21 1966-01-25 Sundstrand Corp Hydrostatic transmission
US3360934A (en) * 1966-05-06 1968-01-02 Int Harvester Co Hydrostatic transmission dual pressure charge-servo system
US3429123A (en) * 1967-08-29 1969-02-25 Leblond Mach Tool Co R K Speed control system
US3650108A (en) * 1968-09-20 1972-03-21 Sigma Hydrostatic transmission control

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3971215A (en) * 1974-06-06 1976-07-27 Marion Power Shovel Company, Inc. Power shovel and crowd system therefor
US3999387A (en) * 1975-09-25 1976-12-28 Knopf Frank A Closed loop control system for hydrostatic transmission
US5095698A (en) * 1989-07-31 1992-03-17 Linde Aktiengesellschaft Hydrostatic transmission
US20070028610A1 (en) * 2005-08-05 2007-02-08 Toshifumi Yasuda Working vehicle
US7409827B2 (en) * 2005-08-05 2008-08-12 Kanzaki Kokyukoki Mfg. Co., Ltd. Working vehicle
CN104930022A (zh) * 2015-06-24 2015-09-23 海特克液压有限公司 一种带冲洗阀的液压传动装置
CN109469665A (zh) * 2017-09-07 2019-03-15 罗伯特·博世有限公司 静液的阀装置、具有所述阀装置的静液的传动机构和具有所述传动机构的静液的驱动装置
CN109469665B (zh) * 2017-09-07 2022-11-04 罗伯特·博世有限公司 静液的阀装置、具有所述阀装置的静液的传动机构和具有所述传动机构的静液的驱动装置
CN111417803A (zh) * 2017-10-09 2020-07-14 波克兰液压工业设备公司 疏通入口过滤器

Also Published As

Publication number Publication date
JPS4915866A (de) 1974-02-12
FR2181344A5 (de) 1973-11-30
GB1420148A (en) 1976-01-07
DE2218472A1 (de) 1973-10-31
CH550347A (de) 1974-06-14

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