US3769800A - Hydraulic system - Google Patents

Hydraulic system Download PDF

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Publication number
US3769800A
US3769800A US00252241A US3769800DA US3769800A US 3769800 A US3769800 A US 3769800A US 00252241 A US00252241 A US 00252241A US 3769800D A US3769800D A US 3769800DA US 3769800 A US3769800 A US 3769800A
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United States
Prior art keywords
hydraulic
pressure
conduit
fluid
conduit means
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Expired - Lifetime
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US00252241A
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English (en)
Inventor
S Winter
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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
    • F16H61/47—Automatic regulation in accordance with output requirements for achieving a target output speed

Definitions

  • the present invention relates to hydraulic systems, i
  • Such a hydraulic system can be utilized to regulate the flow of hydraulic fluid from a hydraulic pump to a hydraulic motor to regulate the same at a substantially constant speed or to a hydraulic cylinder to operate the same at a substantially constant thrusting speed.
  • the speed of rotation of the hydromotor or the thrusting speed of the hydraulic cylinder the actual value of the operating parameter is, in the first instance, controlled by the amount .of fluid which the pump conveys.
  • present invention for a hydraulic system comprises, in
  • j 2 amount of hydraulic fluid delivered by said adjustable hydraulic pump including second conduit means connecting said hydraulically actuated adjusting means with said first conduit means sothat said hydraulically actuated adjusting means regulate said pump in dependence upon fluid pressure in said first conduit means.
  • Closure means are provided in said second conduit means and means for opening said! closure means in dependence upon the fluid pressure in said first conduit means after said hydraulic motor are provided.
  • Hydraulic. correcting means are arranged in said conduit means and constructed so that the hydraulic fluid passing through said second conduit means from said first conduit means to said adjusting means will exert, during-a short period after opening said closure means, a higher regulating pressure on said hydraulically actuated adjusting means than thereafter, so that during said period of air pressure the output of said adjustable pump is reduced to a greater extent than thereafter.
  • said hydraulic correcting means comprises a hydraulic proportional-derivative controller which comprises combination, an adjustable hydraulic pump adapted to first and second parallel fluid paths. The paths are com nected in series with said second conduit means.
  • Said first fluid path includes first pressure responsive means arranged to transmit substantially instantaneous pressure changes from one end to the other end of said second conduit means.
  • Said second fluid path includes second pressure responsive means arranged to transmit pressures through one end of said second conduit means which are proportional to the pressures at the other end thereof.
  • said first pressure responsive means comprises a piston having two pressure bearing surfaces slidable in said first fluid path between two end positions in response to pressure differentials on said surfaces of said piston.
  • Biasing means for positioning said piston in a normal predetermined position are provided for restoring said piston to said predetermined position when the pressures have equalized in said second conduitmeans at said'two surfaces.
  • Said second pressure responsive means comprises a'pressure regulating valve which is adjustable.
  • biasing means are provided which cooperate with said closure means to maintain the latterrclosed, said biasing means being adjustable, whereby the opening of said closure means is a function of both the pressure in said first conduit means and the adjustment of said biasing means.
  • FIG. 3 is a side elevational view, in cross-section, of
  • the reference numeral 1 designates an adjustable hydraulic pump having a positioning element 2.
  • the positioning element 2 controls the amount of hydraulic fluid pumped by the hydraulic pump 1 and may be provided with biasing means (not shown) which returns the positioning element 2 to a normal position wherein the adjustable hydraulic pump 1 pumps its rated or maximum amount of fluid needed per unit time.
  • a hydraulically actuated adjusting means 3 Connected to-the positioning element 2 is a hydraulically actuated adjusting means 3 whose output is connected to the positioning element 2 and which is movable to adjust the positions of the latter in response to changes in hydraulic pressure at its input.
  • a primary conduit 4 connects the hydraulic pump 1 with a hydraulic motor 5.
  • the hydraulic motor 5 is operated by'the flow of hydraulic fluid passing through the primary conduit 4 under pressure established by the hydraulic pump 1. After passing through the hydraulic motor 5, the hydraulic fluid passes through a pressure sensitive valve 8,'shown schematically and to be described more fully with respect to FIG. 3, to be discharged through an outlet conduit 6' into a hydraulic fluid reservoir 7.
  • the pressure sensitive valve 8 further includes a channel means 24, to be further described in connection with FIG. 3, which communicates the primary conduit 4 with a secondary conduit 9.
  • the secondary conduit 9 forms part of a feedback path of the hydraulic system and is series-connected with a hydraulic correcting valve 10 which forms one of the important features of the present invention.
  • the hydraulic correcting valve 10 imparts a proportion-derivative characteristic to the operation of the hydraulic system, andparticula'rly the feedback path thereof to thereby stabilize the system in a desirable manner.
  • the hydraulic correcting means 10 generally comprises a housing 10' which is provided with two parallel fluid paths 11 and 12. Connected in series with the fluid path 11 is a pressure regulating valve 11a which is adjustable in a conventional manner.
  • the fluid path 12 is provided with shoulders 12a and 12b at its ends.
  • a piston 13 is slidably mounted within the fluid path 12 and is configurated to seal the two portions of the fluid path 12 whichit forms.
  • the piston 13 has pressure bearing surfaces 13a and 13b which are exposed to the hydraulic fluid present at each side of the piston 13. The hydraulic fluid applies pressures to the bearing surfaces 13a and 13b to thereby produce a differential pressure on the piston 13 which causes it to slide in one direction or another.
  • Biasing means in the form of springs 14 and 15 are respectively provided in a somewhat compressed state between the shoulder 12a and the pressure bearing surface 13a, on the one hand, and between the pressure bearing surface 13b and the shoulder 12b, on the other 15 are so selected that with equal pressures against the bearing surfaces 13a and 13b of the piston 13, the same is positioned in a normally median position in the fluid path 12.
  • a differential pressure acts upon the piston 13
  • the piston moves in a direction corresponding to the direction of the differential pressure
  • said springs 14 and 15 restoring the normally median position of the piston 13 as soon as the differential pressure is removed.
  • Channels 16 and 17 connect to the respective ends of the fluid paths -l1 and 12 to thereby bring these fluid paths into fluid communication with each other.
  • the channel 17 is in fluid communication with an inlet opening 18 of the hydraulic correcting valve-10.
  • the secondary conduit 9 discharges into the inlet opening 18.
  • the channel 16 is in fluid communication with the outlet opening 19 of the hydraulic correcting valve 10 and the outlet opening 19 is in fluid communication with the input of the hydraulically actuated adjusting means 3.
  • the connection between the outlet opening 19 and the hydraulically actuated adjusting means 3 is through a conduit 20 which may be considered a part of the secondary conduit 9, and
  • hydraulic correcting valve 10 is connected in series with said secondary conduit.
  • the pressure sensitive valve 8 is provided with a cylindrical bore which hand, respectively.
  • the constants of the springs 14 and has a smooth internal surface.
  • a control plunger 31 is arranged within the bore 30 for sliding movement in directions along the axis of the bore 30.
  • the control plunger 31 forms a closure means, as will presently be described.
  • the control plunger 31 is also provided with an axial bore 32 which has at least an upper smooth surface 31a.
  • the lower portion 31b of the axial bore 32 is threaded as shown. These threads are meshed with a cylindrical damper restriction 23 which itself is provided with a small diameter central bore 23a.
  • a pipe 23 having an upper threaded portion 33a is connected to the upper portion of the pressure sensitive valve 8 as shown to provide a fluid tight seal.
  • the lower portion 33b of the pipe 33 has a smooth external surface and has an outer diameter which is substantially equal to the inner diameter of thesmooth inner surface 31a.
  • the outer diameter of the control plunger 31 ismade substantially equal to the inner diameter of the bore 30 so ,as to provide fluid tight seals between contiguous surfaces so as to prevent passage of hydraulic fluid therebetween.
  • annular sealing ring 310 is provided in an annular slot of the control plunger 31 as shown and the annular sealing ring 31c is made of resilient substance or material whose inner diameter is at least equal to the outer. diameter of the smooth portion 33b but is preferably smaller than the latter.
  • the latter deforms to some extent and its inner diameter becomes lodged to thereby intimately engage the smooth portion 33b of the pipe 33 to thereby ensure that no fluid can pass in whatever clearance which may exist between a smooth portion 33b and the smooth inner surface 31a.
  • the pipe 33 is provided with a central bore which is coaxial with the axis of the control plunger 31.
  • an opening 34 is provided in the pressure sensitive valve 8 which communicates with a cylindrical cavity 34a formed by the pressure sensitive valve housing, the smooth portion 33b as well as the upper surface of the controlplunger 31. Because of the fluid tight relationships described above, the cylindrical cavity 34a can only receive or discharge fluid through the bore 34. A conduit 22, in fluid communication with the conduit 6, discharges into the bore 34.
  • first and second annular slots 35 and 36 are in communication with the exterior of the housing by means of bores 37 and 38, respectively.
  • a conduit'21 in communication with the primary conduit 4, discharges into the bore 37 while the secondary conduit 9 is in fluid communication with the bore 38.
  • the control plunger 31 has a channel 24 parallel to the axis of the bore 30.
  • Two openings 24a and 24b communicate the channel 24 to the exterior of the control plunger 31, said openings being spaced a distance equal to the, distance between bores 37 and 38.
  • a plug 240 closes the channel 24 at the point where it was formed, e.g. by drilling.
  • the pressure sensitive valve housing 8 is provided with a cover 39 at one end thereof which has a bore 39a which is in fluid communication with the axial bore 32.
  • the bore 39a is in fluid communication with the conduit 6' which discharges, as described above, into the reservoir 7.
  • the restriction 23 prevents sudden or abrupt responses in the movement of the control plunger 31 and therefore operates as a damping element on the control plunger 31.
  • the amount of damping which the restriction 23 provides is a function of the diameter of the bore 23a.
  • the restriction 23 therefore has the advantageous effect of reducing oscillatory motion of the control plunger 31 which would be undesirable in many applications.
  • the spring 25 is adjustable tothereby make it possible to select a desired pressure in the primary conduit 4.
  • the spring '25 has not been shown to be adjustable in FiG. 3, the present invention contemplates that the spring can be made so adjustable in any known or conventional manner.
  • a first conduit means is to be defined as a conduit means including theconduits 26, 4, 6 and 6'.
  • a secondfconduit means is to be defined as includingsecondary conduit 9 and conduit 20.
  • conduit 22 The pressure in the conduit 6 is monitored by the conduit 22 and this pressure is provided in the cylindrical cavity 34a.
  • the conduit 22 has been illustrated as being connected to the conduit 6, it is within the scope of the present invention that the conduit 22 be connected directly to the hydraulic motor 5, at a suitable place thereof, wherein the hydraulic fluid has already been utilized to turn the blades of the hydraulic motor.
  • a step increase in pressure at the inlet opening 18 is also transmitted through the fluid path 11 and particularly the pressure regulating valve 110.
  • the pressure regulating valve 11a operates as a proportional controller so that at least for the time when the channel 24 places the conduits 21 and 9 in fluid communication with each other, the higher pressure existing at the right-hand side of the pressure regulating valve 11a is proportionally communicated to the left-hand side thereof until the pressures in channels 16 and 17 have equalized.
  • the piston 13 has again moved to its median position shown .in FIG. 1.
  • the hydraulic correcting valve may be defined as a proportional-derivative hydraulic controller.
  • the abrupt movement of the piston 13 causes the hydraulically actuated adjusting means to at least initially cause the adjustable hydraulic pump 1 to pump less fluid than would normally be desired.
  • the positioning element 2 comes to rest in a position corresponding to the small or no load operation which is manifested in the'pressure in conduit 4.
  • biasing means (not shown) which cooperate with said positioning element 2 to restore the same towards a normal, full load position.
  • the hydraulic correcting valve 10 has been described as providing a proportional-derivative control action in the feedback conduit of the hydraulic system, the present invention also contemplates the utilization of proportional-integral or proportional- ,integral-derivative hydraulic controllers where such alternate forms of controllers are more suitable to properly stabilize a system.
  • a three action controller it may be necessary to add a third parallel path similar to paths l1 and 12 including pressure responsive means which provides an output which is a function of the integral of the input pressure.
  • FIG. 2 shows a schematic block diagram of the hydraulic system, showing the characteristics of the respective elements of the system abovedescribed.
  • the hydraulic pump 1 and the hydraulically actuated adjusting means 3' have been combined and are shown to have a linear response.
  • the output of the hydraulic pump 1 is directly a function of the pressure applied to the input Q of the hydraulically actuated adjusting means 3.
  • the hydraulic correcting means 10' is represented by a characteristic curve which illustrates that during a short time period after the opening of the closure means, which comprises the control plunger 31, a higher regulating pressure is applied to said hydraulically actuated adjusting means than thereafter, so that during said period of high pressure, the output of said adjustable pump 1 is reduced to a greater extent than thereafter.
  • the characteristic curve of the pressure sensitive valve 8 is shown to be a step function since, ideally, the pressure Q in the secondary conduits 9 is substantially equal to zero when there is no fluid communication between the conduit 21 and 9 to the channel 24, the pressure O in the conduit 9 rising steeply in the critical position of the control plunger 31 when such fluid communication is achieved to a value which is substantially equal to the pressure existing in the primary conduit 4.
  • the pressure sensitive valve 8' illustrated schematically in FIG. 2, is shown to have two inputs A and B.
  • the input A is in actuality theoutput from the hydraulic motor 5', the input of the latter being connected to the hydraulic pump, hydraulically actuated adjusting means combination 1', 3 respectively.
  • the input B represents a desired value at the output of the hydraulic motor 5'.
  • the actual value A represents the pressure which exists in cylindrical cavity 34a and which is derived from the conduit 6 which represents the pressure at the output of the hydraulic motor 5.
  • the pressure which represents the actual value of the output pressure of the hydraulic motor operates on the plunger 31 to move the same in a downward direction.
  • the actual value A has been designated by a plus sign and the desired value B has been designated by a negative sign, these two signs illustrating that the desired and the actual values operate in different directions or are out of phase insofar as the pressure sensitive valve 8' is concerned.
  • a hydraulic system comprising, in combination, an adjustable hydraulic pump adapted to deliver hydraulic fluid; first conduit means connected to said adjustable hydraulic pump; a hydraulic motor arranged in said first conduit means and driven by said hydraulic fluid delivered by said adjustable hydraulic pump; hydraulically actuated adjusting means for reducing the amount of hydraulic fluid delivered by said adjustable hydraulic pump including second conduit means connecting said hydraulically actuated adjusting means with saidfirst conduit means so that said hydraulically actuated adjusting means regulates said pump in dependence upon the fluid pressure in said first conduit means; closure means in said second conduit means; means for opening said closure means in dependance upon the fluid pressure in said first conduit means after said hydraulic motor; and hydraulic correcting means arranged in said second conduit means and constructed so that the hydraulic fluid passing through said second conduit means from said first conduit means to said adjusting means will exert, during a short time period after opening of said closure means, a higher regulating pressure on said hydraulically actuated adjusting means than thereafter, so that during said period of higher pressure
  • said hydraulic correcting means comprises a hydraulic proportional-derivative controller.
  • said hydraulic connecting means comprises first and second parallel fluid paths connected in series with said second conduit means, said first fluid path including pressure responsive means arranged to transmit substantially instantaneous pressure changes from one end to the other end of said second conduit means, and said second fluid path includ-ing pressure regulating means arranged to transmit pressures to one end of said second conduit means which are proportional to the pressures at the other end thereof.
  • said pressure responsive means comprises a piston having two pressure bearing surfaces slidable in said first fluid path between two end positions in response to pressure differentials on said surfaces of said piston; and biasing means for positioning said piston in a normal predetermined position and for restoring said piston to said predetermined position when the pressures have equalized in said second conduit means at said two surfaces.
  • said first fluid path includes two shoulder portions in the regions of its ends, and wherein said biasing means comprises a pair of helical springs, each spring being compressively positioned between a respective shoulder portion and a pressure bearing surface of said piston.
  • a system as defined in claim 3, wherein said pressure regulating means comprises :a pressure regulating valve.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Control Of Fluid Pressure (AREA)
  • Control Of Fluid Gearings (AREA)
US00252241A 1971-05-12 1972-05-11 Hydraulic system Expired - Lifetime US3769800A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19712123404 DE2123404A1 (de) 1971-05-12 1971-05-12 Hydraulikanlage mit einer verstellbaren Pumpe

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US3769800A true US3769800A (en) 1973-11-06

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US00252241A Expired - Lifetime US3769800A (en) 1971-05-12 1972-05-11 Hydraulic system

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US (1) US3769800A (de)
CH (1) CH531744A (de)
DE (1) DE2123404A1 (de)
FR (1) FR2139377A5 (de)
GB (1) GB1348852A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5454223A (en) * 1993-05-28 1995-10-03 Dana Corporation Hydraulic load sensing system with poppet valve having an orifice therein
US20160062367A1 (en) * 2013-04-11 2016-03-03 Primetals Technologies Germany Gmbh Hydraulic arrangement having decoupled operation of two valve devices

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2851705C2 (de) * 1978-11-30 1983-08-11 Mannesmann Rexroth GmbH, 8770 Lohr Förderstrom-Druckregelungsvorrichtung für ein hydrostatisches Getriebe

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2238061A (en) * 1938-05-12 1941-04-15 Manly Corp Fluid pressure system and control therefor
US2255783A (en) * 1940-02-17 1941-09-16 Manly Corp Fluid pressure device and system
US3444689A (en) * 1967-02-02 1969-05-20 Weatherhead Co Differential pressure compensator control

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2238061A (en) * 1938-05-12 1941-04-15 Manly Corp Fluid pressure system and control therefor
US2255783A (en) * 1940-02-17 1941-09-16 Manly Corp Fluid pressure device and system
US3444689A (en) * 1967-02-02 1969-05-20 Weatherhead Co Differential pressure compensator control

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5454223A (en) * 1993-05-28 1995-10-03 Dana Corporation Hydraulic load sensing system with poppet valve having an orifice therein
US20160062367A1 (en) * 2013-04-11 2016-03-03 Primetals Technologies Germany Gmbh Hydraulic arrangement having decoupled operation of two valve devices
US9836067B2 (en) * 2013-04-11 2017-12-05 Primetals Technologies Germany Gmbh Hydraulic arrangement having decoupled operation of two valve devices

Also Published As

Publication number Publication date
CH531744A (de) 1972-12-15
FR2139377A5 (de) 1973-01-05
DE2123404A1 (de) 1972-11-23
GB1348852A (en) 1974-03-27

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