US3774641A - Electrohydraulic control arrangement for hydraulic actuators - Google Patents

Electrohydraulic control arrangement for hydraulic actuators Download PDF

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US3774641A
US3774641A US3774641DA US3774641A US 3774641 A US3774641 A US 3774641A US 3774641D A US3774641D A US 3774641DA US 3774641 A US3774641 A US 3774641A
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input
gate
output
arrangement
control
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R Mindner
K Adler
H Flaschar
K Schneider
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
    • F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
    • F15B9/08—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor
    • F15B9/09—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor with electrical control means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C13/00—Control systems or transmitting systems for actuating flying-control surfaces, lift-increasing flaps, air brakes, or spoilers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C13/00—Other constructional features or details
    • B66C13/52—Details of compartments for driving engines or motors or of operator's stands or cabins
    • B66C13/54—Operator's stands or cabins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C2700/00—Cranes
    • B66C2700/08—Electrical assemblies or electrical control devices for cranes, winches, capstans or electrical hoists
    • B66C2700/085—Control actuators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/86493—Multi-way valve unit
    • Y10T137/86574—Supply and exhaust
    • Y10T137/86582—Pilot-actuated
    • Y10T137/86614—Electric

Definitions

  • ABSTRACT A control arrangement for hydraulic actuators in which two hydraulic transmission lines communicating with the actuator are closed when the control slide of a control valve is in neutral position. lnlet and return lines communicate with the hydraulic transmission lines in alternate operative positions of the control slide.
  • the control slide is actuated by a piston moving within a control cylinder.
  • Working fluid is applied to the control cylinder through electromagnetically actu- Foreign Application Priority Data ated valves.
  • a remote control lever provides an adjust- Mar. 26, 1971 Germany P 21 14 639.4 able input parameter through a transducer.
  • the elec- I tromagnetically actuated valves are operated by a reg- [52] U.S. Cl. l3 7/625.64 'ulating amplifier as a function of the input parameter [51] Int. Cl. F16k 11/00 established by the remote control lever.
  • Two flow [58] Field of Search l37/625.64, 625.66, lines communicate with the control cylinder and are 137/625.65, 625.69, 554, 487.5; 251/131, connected to the inlet and return lines by two electro- 251/130, 14, 25, 63, 78 magnetically actuated valves.
  • Threshold switching circuits are connected between the signal amplifiers used [56] References Cited to energize the electromagnetically actuated valves UNITED STATES PATENTS and the regulating amplifier- 3,556,l54 l I971 Kramer 137/625.64 17 Claims, 5 Drawing Figures T M W5 Q 20 1 /7 26 a T 1 4 211 t/i3 5 f I r J Ulla P .52 l y 35 .40 42 [A AA A Q .14 fi r 1 .U U
  • the present invention relates to an electrohydraulic control arrangement for use in conjunction with a hydraulic actuator which is operable in two directions.
  • a control valve is provided with a control slider which closes two lines to the actuator when in neutral position.
  • a regulating amplifier controls the precontrol valves as a function of an input parameter set by a remote control lever.
  • a control arrangement of the preceding known species is already known in the art for actuating the altitude rudder or flaps of an aircraft.
  • the output parameter or value from the deflection angle of the rudder is applied to a second input of the regulating amplifier, so that for every position of the remote control lever, a predetermined deflection angle of the rudder is attained.
  • other hydraulic actuators as for example in automotive cranes, which are driven by double acting hydraulic cylinders or by a hydraulic motor with radial head, it is desired, however, to regulate the velocity rather than the final position.
  • a predetermined velocity of the hydraulic actuator corresponds to every position of the remote control lever.
  • the velocity of the load fork or distributor is to be set or established.
  • Another object of the present invention is to provide an arrangement for controlling a hydraulic actuator, as set forth, which is simple and design and may be readily fabricated.
  • a still further object of the present invention is to provide an arrangement of the foregoing character which may be economically manufactured and economically maintained in service.
  • Another object of the present invention is to provide an arrangement of the foregoing character which is reliable in operation.
  • control cylinder is in the form of a double acting cylinder with two communicating lines.
  • a second and a third precontrol valve connect the two communicating lines with inlet and return lines.
  • Each precontrol valve may be actuated through a magnetic winding which, in turn, is energized by a signal amplifier.
  • the signal amplifiers are connected, through threshold switching circuits, to the output of the regulating amplifier.
  • a first precontrol valve lies between the inlet line and the two other precontrol valves.
  • the first precontrol valve is closed when the remote control lever is in its position.
  • the control slide may be actuated by a close control lever.
  • the velocity of the hydraulic actuator or operating arrangement may be precisely regulated or set, in accordance with a further embodiment of the present invention, by providing that an output parameter or value transducer may be actuated by the control slide.
  • the output transducer and the input transducer are both connected to a summing device in front of the regulating amplifier.
  • FIG. 1 is a schematic diagram of the hydraulic arrangement in conjunction with the electronic control circuitry, in accordance with the present invention
  • FIGS. 2-4 are electrical circuit diagrams of operating circuits shown in block form in FIG. 1;
  • FIG. 5 is a block diagram of a second embodiment of the present invention.
  • a hydaulic operating unit has a double-acting cylinder 11 in which a piston head 12 moves with a piston rod 13.
  • the cylinder 11 is connected to a control valve through lines 14 and 15.
  • a slider bore 17 which guides closely a control slide 23.
  • the slide bore 17 communicates with five chambers 18, 19, 20, 21, 22 and a control cylinder 27.
  • the central chamber 20 is connected with an inlet line 57 through a check valve 33.
  • the two chambers 19, 21 on both sides of a central chamber 20 are connected with the lines 14, 15, while the outer chambers l8, and 22 are connected to the return line 37.
  • the control slide 23 is subdivided into three slider sections by two necked-down portions 24, 25. In the neutral position of the control slide 23, the three slider sections lie closely opposite the chambers 18 to 22, as shown in FIG. 1.
  • a control piston head 26 which is designed in the embodiment in the form of a differential piston, and is movable within the control cylinder 27.
  • an extension 29 which actuates, on the one hand, a double-acting return or resetting arrangement. This extension 29 also is connected, on the other hand, mechanically with a control lever 30 and an output transducer 47.
  • the inlet line 57 is provided with'pressurized fluid from a storage reservoir 31, by means of a pump 32.
  • a hydraulic series-connected circuit between the inlet line 57 and the return line 37 consists of the series combination of a first control valve 34, a first throttle 35, a second control valve 36, a third control valve 38, and a second throttle 39.
  • the control cylinder 27 is, on one hand, connected through a first line 58, to the connecting line between the first control valve 34 and the first throttle 35.
  • the control cylinder 27 is also connected, on the other hand, through a line 59, to the connecting line between the second control valve 36 and the third control valve 38.
  • control valves 34, 36 and 38 become actuated by the electromagnet windings 34a, 36a. and 38a. Each winding becomes controlled from an amplifier 40, 41, 42, respectively.
  • a remote control lever 55 actuates an input transducer 48 which has an output connected to a deadcenter element 50, through an amplifier stage 49. Connected with the output of the dead-center element 50, are the first inputs of three AND-gates 43, 44 and 45. These AND-gates are, in turn, connected to amplifiers 40, 41 and 42, with their outputs. The second input of the first AND-gate 43 is connected, through a fourth AND-gate 46, with the outputs of the second and third AND-gates, 44 and 45, respectively.
  • the AND-gate 46 is constructed in the form of a NAND-gate.
  • the second inputs of the second and third AND-gate 44, 45 are connected each, by way of threshold switches 53, 54, to the output of a regulating amplifier 52.
  • a summing device 51 is connected to the input of this regulating amplifier 52.
  • the input transducer 48 and the output transducer 47 are connected to the inputs of the summing device 51.
  • FIG. 2 shows the circuit diagram of the second threshold switch 54, the third AND-gate 45 and the third amplifier 42.
  • the second threshold switch 54 is designed in the form of a two-stage, feedback-coupled amplifier with two transistors 540, 541 of opposite conductivity type.
  • the first transistor 540 has a base voltage divider 546, 547, an emitter-resistor 544, and a collector resistor 542.
  • the collector of the first transistor 540 is connected to the base of the second transistor 541.
  • the collector of the second transistor 541 is connected, through a feedback resistor 545, to the base of the first transistor 540.
  • This collector of the second transistor 541 is also connected, through a collector resistor 543, to the positive voltage supply line 60.
  • the emitter of the first transistor 540 forms the input of the second threshold switch 54, and is connected, through a diode 548, to the output terminal 52a of the regulating amplifier 52.
  • the third AND-gate 45 is similar to the second threshold switch 54 in the form of a feedback-coupled amplifier with two transistors of opposite conductivity type. Modifications in the circuit design are realized in the respect that the third AND-gate 45, as shown in FIG. 1, is designed in the form of a blocking or inhibiting gate which has a noninverting and one inverting input.
  • the second transistor 451 in the third AND-gate 45 has two collector resistors 453, 453a connected in series. The junction of these two resistors is connected to the second noninverting input of the third AND-gate 45. This junction, furthermore, is connected through a diode 458, to the output of the second threshold switch 54. All remaining components are the same as in the second threshold switch 54, and are thereby not further described.
  • the reference numerals are lower by 90, than in the second threshold switch 54.
  • the third amplifier 42 has a transistor 420 and a power transistor 421.
  • the preamplifying transistor 420 is connected with its base, to the output of the third AND-gate 45.
  • the emitter of the preamplifying transistor 420 is connected, through a diode 424, to the negative voltage supply line 62.
  • the collector of this transistor 420 is connected through two resistors 422, 423, to a nonstabilized positive voltage supply line 61.
  • the base of the power transistor 421 is connected to the junction between the resistors 422 and 423.
  • the emitter of the transistor 421 is connected directly with the non-stabilized voltage supply line 61.
  • the collector of the power transistor 421 is connected, furthermore, through a resistor 425 and electromagnetic winding 38a, to the negative voltage supply line 62.
  • a series circuit moreover, leads from the collector of the power transistor 421, to a diode 428 and a resistor 427, and from there to the negative voltage supply line 62, as well as a junction to the feedback resistor 455 within the third AND-gate 45.
  • the remaining AND-gates 42, 44 and 46, as well as the first threshold switch 53 are constructed precisely the same as the second threshold switch 54.
  • the latter is universally insertable, since it is possible to connect as many inputs as desired, to the emitter of the first transistor, through diodes.
  • the threshold level can be set simultaneously with the aid of the base voltage divider of the first transistor.
  • the dead-center circuit 50 shown in FIG. 3, consists of two threshold switches 505, 506 which are also constructed and designed in the form described above.
  • the threshold level of the switch 505 is set at 7 volts, in the embodiments, and the other threshold switch is set to 5 volts.
  • the output of the switch 505 is connected, through a diode 503, to a second output of the other threshold switch 506. With this arrangement, a positive signal is emitted at the output terminal 50a of the deadcenter circuit 50, when the input voltage at the terminal 49a is either below 5 volts or above 7 volts. Within this region, the output terminal 50a is substantially at the potential of the negative voltage supply line 62.
  • FIG. 4 shows the circuit diagram of a pulse stretcher modulator, which can be used in place of the threshold switch 53 or 54.
  • an operational amplifier 530 serves as the active component, and has a noninverting input at the junction of two resistors 533, 534, which form a voltage divider.
  • the inverting input of this operational amplifier 530 is connected, through an input resistor 537, to an input terminal 52a.
  • a resistor 531 is connected between the output of the operational amplifier 530 and the inverting input of the amplifier.
  • a resistor 532 furthermore, is connected between the output of the operational amplifier 530, and the noninverting input.
  • the output of the operational amplifier 530 is, furthermore, connected directly to an output terminal 53a, and to the positive voltage supply line 60, through a resistor 536.
  • a capacitor 535 is connected between the inverting input of the operational amplifier 530, and the negative voltage supply line 62.
  • the second embodiment shown in FIG. 5, is extensively the same as the first embodiment.
  • the components and circuits that are the same in FIG. 5, as they are in FIG. 1, have the same reference numerals, and are also not further described.
  • the first AND-gate 43 has four inputs, of which two are connected the same as in the first embodiment.
  • the other two inputs of the first AND-gate 43 are connected with the outputs of a first OR-gate 73 and a second OR-gate 75.
  • a third threshold switch is connected to the output of the output transducer 47, and a fourth threshold switch 71 is connected to the output of the summing device 51.
  • a first inverter 72 is connected to the output of the third threshold switch 70, and a second inverter 74 is connected to the fourth threshold switch 71.
  • the two inputs of the first OR-gate 73 are connected with the output of the first inverter 72 and the output of the fourth threshold switch 71.
  • the two inputs of the second OR-gate 75 are connected to the output of the third threshold switch 70 and the output of the second inverter 74.
  • Each position of the control slide 23 corresponds to a predetermined fluid flow from the inlet line 57 to one of the lines 14, 15. With this arrangement, a predetermined speed or velocity of the piston head 12 can be established corresponding to a predetermined position of the control slide.
  • the control valves 34, 36, 38 each have two controlled connections and two positions, and are thereby constructed in the form of 2/2-way valves. In the normal inoperative position, the first control valve 34 is closed, and the two other control valves 36, 38 are open. It is possible, thereby, to bring the control slide 23 into any desired position, with the aid of the control lever 30. As a result, any desired velocity of the operating piston head 12 may be attained. Should the control slide 23 be actuated through the electro-hydraulic remote control unit with the aid of the remote control lever 55, then the first control valve 34 becomes opened. When the control piston 26 is to be moved toward the left, then the third control valve 38 must be closed, and the second control valve 36 must be opened.
  • the second control valve 36 must be closed and the third control valve 38 must be opened, in the case that the control piston 26 is to be moved toward the right.
  • the control piston 26 is to be held at a predetermined position outside of its neutral position, then the second control valve 36 and the third control valve 38 must be closed.
  • the summing device 51 is designed so that the output signal of the input transducer 48 is negative, and the output signal of the output transducer 47 is positive. This summing device 51, therefore, computes the difference between the input value and the output value as provided by the transducers.
  • the input transducer 48 and the output transducer 47 are connected to the two inputs of a difference amplifier, which serves simultaneously as the regulating amplifier 52. It is also possible to design the regulating amplifier 52 so that the latter has an input, as shown in FIG. 1. With such an arrangement, an inverting stage must be connected to either the output of the input transducer 48 or the output of the output transducer 47.
  • Such inversion is required in the event that the transducer does not provide already such an inverted signal, relative to the other transducer. Once such inversion has been realized the two signals from the two transducers may be applied, through summing resistors, to the input of the regulating amplifier 52.
  • the input transducer 48 and the output transducer 47 are designed so that their output potentials become shifted in the negative region, when the associated control lever is moved toward the left.
  • the dead-center circuit 50 provides a 0 signal within a-small region about the 0 position of the remote control lever 55 within the so-called dead zone. In all other positions of the remote control lever 55, a 1 signal is emitted.
  • the threshold level of the first threshold switch 53 is set to 5 volts
  • the second threshold switch 54 is set to 7 volts.
  • the output voltage from the regulating amplifier 52 is established at 6 volts, provided the difference between the input value and output value is zero.
  • the first threshold switch 53 provides a 1 signal
  • the second threshold switch 54 provides a 0 signal.
  • the dead-center circuit 50 provides a 1 signal, when the dead zone is exceeded.
  • the output voltage from the regulating amplifier 52 is shifted, thereby, in the positive direction to the extent that the threshold level of the second threshold switch 54 becomes exceeded.
  • the three circuits 50, S3, 54 each provide a 1 signal.
  • At the output of the second AND-gate 44 is a 1 signal and at the output of the third AND-gate 45 is a 0 signal.
  • At the output of the NAND-gate 46 is, thereby, a 1 signal which is applied to the second input of the first AND-gate 43.
  • a 1 signal is, henceforth, also available at the output of the AND- gate 43.
  • the first two control valves become actuated by the amplifiers 40 and 41.
  • the control piston 26 moves, consequently, in the same direction as the remote control lever 55namely toward the right.
  • the output potential of the output transducer 47 is shifted in the positive direction, and the output potential of the regulating amplifier 52 is shiftedin the negative direction, until the threshold level of the second circuit 54 is higher.
  • the third AND-gate 45 also provides a 1 signal which, in turn, actuates the third control valve 38 and, at the same time, the AND-gate 43 by way of the NAND-gate 46.
  • the first amplifier 40 of the first control valve is thereby switched off. As a result, some control valves are now closed, so that the control piston 26 becomes blocked in its position. A predetermined velocity of the operating piston 12 is thereby established, and this piston 12 corresponds precisely to the position of the remote control lever 55, as is required.
  • the threshold level of the first switch 53 becomes the higher value. Both threshold switches provide, thereby, 0 signals. Since the third AND-gate 45 is constructed in the form of a blocking or inhibiting gate and is provided with an inverting input, the output of this AND-gate 45 provides a 1 signal which is applied to the third amplifier 42 and thereby the third control valve 38. As a result, this valve 38 is closed. Since the second control valve 36 becomes simultaneously opened, through the AND-gate 44 and the amplifier 41, and the first control valve 34 also becomes opened through the NAND-gate 46, the AND-gate 43 and the amplifier 40, the control piston 26 is moved toward the left.
  • the functional operation of the first embodiment can be described with the following characteristics: When the remote control lever 55 is deflected past the dead zone, either the second control valve 36 or the third control valve 38 is closed, depending upon the direction of deflection of the lever. Aside from this, the first control valve 34 becomes opened, through the AND-gate 43 and the NAND-gate 46. When the remote control lever 55 is deflected, the first control valve 34 is again closed, through the NAND-gate 46, only until the two other control valves 36 and 38 are simultaneously closed, when the input value is equal to the output value and the control piston 26 is to be held in its position.
  • a particular advantageous of the control arrangement described above resides in the condition that all digital components of the circuitry can be constructed from the same circuit elements, as shown in FIGS. 2 and 3.
  • the base voltage divider 546, 547 of the first transistor 540 is adjusted so that a voltage of 7 volts is available at the tap.
  • the first transistor 540 becomes then turned off, as soon as the potential of the input terminal 52a drops below 7 volts.
  • the voltage drop across the diode 548 and the emitter-base diode of the first transistor 540 become compensated.
  • no continuous collector current of the first transistor is available when the potential of the input terminal 52a is slowly taken off.
  • a rapid switching takes place in the threshold voltage established by the base voltage divider.
  • a NAND-gate can be produced in a simple manner, in that several input terminals can be connected to the emitter of the first transistor 540, by way of several diodes.
  • Such a NAND-gate 506 is shown in FIG. 3 as a component of the dead-center circuit 50.
  • a blocking or inhibiting gate with an inverting and a noninverting input, as required for the third AND-gate 45, is obtained when the emitter of the first transistor 450 is used as the first input and the collector of the second transistor 451 is used as the second input, as shown in FIG. 2 with respect to the blocking gate 45.
  • the emitter potential of the transistor 420 in the second power amplifier 42 is raised by substantially 0.7 volts, through the diode 424, relative to the potential of the negative voltage line 62. In this manner, the transistor 420 is securely turned off when the transistor 451 conducts. Power transistor 421 is also turned off, since the latter is of opposite conductivity type relative to the transistor 420.
  • In front of the electromagnetic winding 38a is the parallel circuit including the resistor 425 and the capacitor 426. Upon turning on the power transistor 421, full operating voltage is applied, through the capacitor 426, to the winding 38, until the capacitor 426 has become charged. As a result, a rapid energizing of the magnet winding 38a is realized.
  • the energy stored within the winding 38a is dissipated in the two resistors 427 and 425, and the resistance within the winding 38a. This results from the condition that the tum-off current of the winding 38a can flow further through the diode 428.
  • the dead zone is the allowable deviation or difference between the input value and output value, or is the region in which the output signal from the switch 53 is a 1 signal and the output from the switch 54 is a 0 signal.
  • the dead zone is provided so that continuous switching or oscillation of the valves is prevented.
  • the dead zone together with the dead time of the control valves, determines the maximum allowable displacement velocity of the control slide 23. This velocity is dependent on the pressure in the inlet line 57, the dimensions of the throttles 35 and 39, and on the surfaces of the control pistons.
  • the displacement velocity and thereby the acceleration of the operating piston 12, is thereby constant.
  • reverse accelerations or delays arise under predetermined conditions, when the remote control lever 55 is deflected, or when the input value is attained by the output value.
  • Such a pulse stretcher modulator is shown in FIG. 4.
  • the input terminal 52a has applied to it the potential of the negative voltage supply line 62, the capacitor 535 is extensively discharged, and the input potential of the inverting input of the operational amplifier is below the potential of the noninverting input, so that the output of the operational amplifier 530 is at positive potential.
  • the output of the operational amplifier provides a 1 signal.
  • the potential of the noninverting input of the operational amplifier 530 is high, and is determined through the resistors 532, 533, 534, whereby the resistor 532 is in parallel, in this case, with the resistor 533.
  • the resistor 536 is substantially small in relation to the resistors 532, 533 and 534.
  • the capacitor 535 becomes charged to the potential of the positive voltage supply line, through the resistors 536, 531 and 537.
  • the potential of the inverting input of the operational amplifier 530 rises.
  • the operational amplifier 530 switches state through the coupling resistor 532, and a 0 signal prevails at the output of this amplifier.
  • the potential at the noninverting input shifts in the direction toward a negative value which is, in turn, determined by the resistors 533, 534 and 532, whereby the resistor 532 is, in this case, in parallel with the resistor 534.
  • the capacitor 535 discharges from the original input potential of the input terminal 52a in direction to the potential of the negative voltage supply line 62, through the resistors 537 and 531.
  • the operational amplifier 530 switches again state, and provides at its output a 1 signal.
  • the pulse stretcher modulator in accordance with FIG. 4 operates similarly to a threshold switch.
  • the output provides a continuous 1 signal.
  • the output voltage exceeds an upper threshold level, then the output provides a continuous signal.
  • the pulse stretcher modulator provides pulses having a repetition frequency dependent upon the magnitude of the input voltage.
  • the potential difference between the lower and upper threshold levels is determined through the relationship between the two resistors 53] and 537.
  • the absolute magnitude of the two threshold levels is, on the other hand, determined by the voltage divider 533, 534, 532.
  • the dead zone is to be as small as possible for attaining a large positional accuracy of the control slide 23.
  • the displacement velocity of the control slide is to be, on the other hand, as large as possible.
  • the dead zone and the dead time of the valves must be matched. The two requirements of maximum possible displacement velocity and smallest possible dead zone are in conflict.
  • the displacement velocity of the control slide 23 is larger than the velocity when the control slide is moved from its 0 position in direction of greater deflection, in the return process. This results from the condition that upon deflection or movement from the 0 position, the spring force is opposed against the hydraulic force in the return arrangement 28, whereas the spring force adds to the hydraulic force during the return process.
  • the displacement velocity in the return process must, therefore, take into account the dead zone.
  • the third threshold switch 70 determines whether the control slide 23 is either to the right or to the left of the 0 position, whereas the fourth threshold switch 71 determines whether the regulating deviation is either positive or negative, i.e., whether the output value has already attained the input value or not.
  • both inverters 72 and 74 provide 1 signals which are transmitted, through the OR-gates 73 and 75, to the two remaining inputs of the first AND-gate 43.
  • the regulating error or deviation becomes 0 or positive, and the fourth threshold switch 71 provides a I signal.
  • a 0 signal lies at the third input of the AND-gate 43, which is connected with the second OR-gate 75, whereas a 1 signal still lies at the fifth input.
  • the first control valve 34 becomes closed. This closing of the valve also remains when the remote control lever 55 is again returned to the 0 position.
  • the control cylinder 27 can thereby have applied fluid from the first control valve 34.
  • the control arrangement described above fulfills, consequently, all of the imposed requirements.
  • the velocity of the operating piston 12 is set to a constant value through the remote control lever 55 as well as through the control lever 30. This constant value depends on the deflection or displacement of the remote control lever or of the lever 30.
  • stretcher modulators it is possible to avoid furthermore accelerations or delays which are too large for small regulating errors or deviations.
  • the remote control lever 55 is at its normal inoperative position, then the control slide 23 can be actuated with the aid of the control lever 30. An output value-return is then made possible to maintain precisely the velocity for the operating piston 12, which is set by the remote control lever.
  • the control arrangement is, thereby, particularly adaptable for automotive cranes, although its area of application is not limited to this field.
  • An electrohydraulic control arrangement for hydraulic operating means operative in two directions comprising, in combination, a control valve with control slides; two hydraulic transmission lines communieating with said operating means and closed by said control slide when in neutral position in said control valve; inlet line means communicating with one of said hydraulic transmission lines when said control slide is in a first operative position; return line means communicating with the other one of said hydraulic transmission lines when said control slide is in a second operative position; control piston means movable within a control cylinder and actuating said control slide; electromagnetically actuated valves for applying working fluid to said control cylinder; remote control lever means for providing an adjustable input parameter; regulating amplifier means actuating said electromagnetic valves as a function of said input parameter; two flow lines communicating with said control cylinder and connected to saidinlet line means and said return line means by two of said electromagnetically actuated valves; signal amplifying means connected to said electromagnetically actuated valves for actuating said electromagnetically actuated valves; and threshold switching means connected between said signal amplifying means and said regulating
  • said dead center circuit comprises two threshold switching circuits having different threshold levels, the input of one threshold switching circuit being connected with a first input of the other threshold switching circuit, the output of said one threshold switching circuit being connected to a second input of the other threshold switching circuit.
  • threshold switching circuits and said AND-gates are two-stage, positive feedback-coupled transistor amplifiers with two transistors of complementary conductivity type.
  • the arrangement as defined in claim 10 including base voltage divider means connected to a first one of said two transistors in said threshold switching circuits for setting the threshold voltage of said threshold switching circuit; and diode means for applying to the emitter of said first transistor the input voltage signal.
  • diode means connected to the emitter of a first transistor of said AND-gates for applying input voltage signals to the emitter of said first transistor of said AND-gates.
  • said pulse stretcher modulator comprises an operational amplifier with a first resistor connected between the output of said amplifier and one input thereof, and a second resistor connected between the output of said operational amplifier and a circuit input thereof; an input resistor connected to the inverting input of said operational amplifier, on terminal of said input resistor being the input signal terminal; and a capacitor connected between said input resistor and ground potential.
  • said fourth AND-gate comprises a NAND-gate.

Abstract

A control arrangement for hydraulic actuators in which two hydraulic transmission lines communicating with the actuator are closed when the control slide of a control valve is in neutral position. Inlet and return lines communicate with the hydraulic transmission lines in alternate operative positions of the control slide. The control slide is actuated by a piston moving within a control cylinder. Working fluid is applied to the control cylinder through electromagnetically actuated valves. A remote control lever provides an adjustable input parameter through a transducer. The electromagnetically actuated valves are operated by a regulating amplifier as a function of the input parameter established by the remote control lever. Two flow lines communicate with the control cylinder and are connected to the inlet and return lines by two electromagnetically actuated valves. Threshold switching circuits are connected between the signal amplifiers used to energize the electromagnetically actuated valves and the regulating amplifier.

Description

United States Patent 1 Mindner et al.
[ Nov. 27, 1973 ELECTROHYDRAULIC CONTROL ARRANGEMENT FOR HYDRAULIC ACTUATORS Filed: April 11, 1972 Appl. No.: 239,396
Primary ExaminerHenry T. Klinksiek Assistant ExaminerRobert J. Miller Attorney-Striker, Striker, Kontler & Stenby [57 ABSTRACT A control arrangement for hydraulic actuators in which two hydraulic transmission lines communicating with the actuator are closed when the control slide of a control valve is in neutral position. lnlet and return lines communicate with the hydraulic transmission lines in alternate operative positions of the control slide. The control slide is actuated by a piston moving within a control cylinder. Working fluid is applied to the control cylinder through electromagnetically actu- Foreign Application Priority Data ated valves. A remote control lever provides an adjust- Mar. 26, 1971 Germany P 21 14 639.4 able input parameter through a transducer. The elec- I tromagnetically actuated valves are operated by a reg- [52] U.S. Cl. l3 7/625.64 'ulating amplifier as a function of the input parameter [51] Int. Cl. F16k 11/00 established by the remote control lever. Two flow [58] Field of Search l37/625.64, 625.66, lines communicate with the control cylinder and are 137/625.65, 625.69, 554, 487.5; 251/131, connected to the inlet and return lines by two electro- 251/130, 14, 25, 63, 78 magnetically actuated valves. Threshold switching circuits are connected between the signal amplifiers used [56] References Cited to energize the electromagnetically actuated valves UNITED STATES PATENTS and the regulating amplifier- 3,556,l54 l I971 Kramer 137/625.64 17 Claims, 5 Drawing Figures T M W5 Q 20 1 /7 26 a T 1 4 211 t/i3 5 f I r J Ulla P .52 l y 35 .40 42 [A AA A Q .14 fi r 1 .U U
ELECTROHYDRAULIC CONTROL ARRANGEMENT FOR HYDRAULIC ACTUATORS BACKGROUND OF THE INVENTION The present invention relates to an electrohydraulic control arrangement for use in conjunction with a hydraulic actuator which is operable in two directions. A control valve is provided with a control slider which closes two lines to the actuator when in neutral position. A regulating amplifier controls the precontrol valves as a function of an input parameter set by a remote control lever.
A control arrangement of the preceding known species is already known in the art for actuating the altitude rudder or flaps of an aircraft. In such an arrangement known in the art, the output parameter or value from the deflection angle of the rudder is applied to a second input of the regulating amplifier, so that for every position of the remote control lever, a predetermined deflection angle of the rudder is attained. In other hydraulic actuators, as for example in automotive cranes, which are driven by double acting hydraulic cylinders or by a hydraulic motor with radial head, it is desired, however, to regulate the velocity rather than the final position.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a control arrangement in which a predetermined velocity of the hydraulic actuator corresponds to every position of the remote control lever. In the use of an automotive crane, for example, the velocity of the load fork or distributor is to be set or established.
Another object of the present invention is to provide an arrangement for controlling a hydraulic actuator, as set forth, which is simple and design and may be readily fabricated.
A still further object of the present invention is to provide an arrangement of the foregoing character which may be economically manufactured and economically maintained in service.
Another object of the present invention is to provide an arrangement of the foregoing character which is reliable in operation.
The objects of the present invention are achieved by providing that the control cylinder is in the form of a double acting cylinder with two communicating lines. A second and a third precontrol valve connect the two communicating lines with inlet and return lines. Each precontrol valve may be actuated through a magnetic winding which, in turn, is energized by a signal amplifier. The signal amplifiers are connected, through threshold switching circuits, to the output of the regulating amplifier.
In an automotive crane it is advantageous when the operating personnel of the crane, can operate the crane directly when on the vehicle for the crane, as well as from a remote location through a cable. Such possibility is realized with a further embodiment of the present invention, in which a first precontrol valve lies between the inlet line and the two other precontrol valves. The first precontrol valve is closed when the remote control lever is in its position. When the first precontrol valve is closed, furthermore, the control slide may be actuated by a close control lever.
The velocity of the hydraulic actuator or operating arrangement may be precisely regulated or set, in accordance with a further embodiment of the present invention, by providing that an output parameter or value transducer may be actuated by the control slide. The output transducer and the input transducer are both connected to a summing device in front of the regulating amplifier.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram of the hydraulic arrangement in conjunction with the electronic control circuitry, in accordance with the present invention;
FIGS. 2-4 are electrical circuit diagrams of operating circuits shown in block form in FIG. 1;
FIG. 5 is a block diagram of a second embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing and in particular to FIG. 1, a hydaulic operating unit has a double-acting cylinder 11 in which a piston head 12 moves with a piston rod 13. The cylinder 11 is connected to a control valve through lines 14 and 15. Within a housing 16 of the control valve, is a slider bore 17 which guides closely a control slide 23. The slide bore 17 communicates with five chambers 18, 19, 20, 21, 22 and a control cylinder 27. The central chamber 20 is connected with an inlet line 57 through a check valve 33. The two chambers 19, 21 on both sides of a central chamber 20, are connected with the lines 14, 15, while the outer chambers l8, and 22 are connected to the return line 37.
The control slide 23 is subdivided into three slider sections by two necked-down portions 24, 25. In the neutral position of the control slide 23, the three slider sections lie closely opposite the chambers 18 to 22, as shown in FIG. 1. At the right end of the control slide 23, is a control piston head 26 which is designed in the embodiment in the form of a differential piston, and is movable within the control cylinder 27. At the left end of the control slide 23, is an extension 29 which actuates, on the one hand, a double-acting return or resetting arrangement. This extension 29 also is connected, on the other hand, mechanically with a control lever 30 and an output transducer 47.
The inlet line 57 is provided with'pressurized fluid from a storage reservoir 31, by means of a pump 32. A hydraulic series-connected circuit between the inlet line 57 and the return line 37, consists of the series combination of a first control valve 34, a first throttle 35, a second control valve 36, a third control valve 38, and a second throttle 39. The control cylinder 27 is, on one hand, connected through a first line 58, to the connecting line between the first control valve 34 and the first throttle 35. The control cylinder 27 is also connected, on the other hand, through a line 59, to the connecting line between the second control valve 36 and the third control valve 38.
The control valves 34, 36 and 38 become actuated by the electromagnet windings 34a, 36a. and 38a. Each winding becomes controlled from an amplifier 40, 41, 42, respectively.
A remote control lever 55 actuates an input transducer 48 which has an output connected to a deadcenter element 50, through an amplifier stage 49. Connected with the output of the dead-center element 50, are the first inputs of three AND- gates 43, 44 and 45. These AND-gates are, in turn, connected to amplifiers 40, 41 and 42, with their outputs. The second input of the first AND-gate 43 is connected, through a fourth AND-gate 46, with the outputs of the second and third AND-gates, 44 and 45, respectively. The AND-gate 46 is constructed in the form of a NAND-gate.
The second inputs of the second and third AND-gate 44, 45 are connected each, by way of threshold switches 53, 54, to the output of a regulating amplifier 52. A summing device 51 is connected to the input of this regulating amplifier 52. The input transducer 48 and the output transducer 47 are connected to the inputs of the summing device 51.
FIG. 2 shows the circuit diagram of the second threshold switch 54, the third AND-gate 45 and the third amplifier 42. The second threshold switch 54 is designed in the form of a two-stage, feedback-coupled amplifier with two transistors 540, 541 of opposite conductivity type. The first transistor 540 has a base voltage divider 546, 547, an emitter-resistor 544, and a collector resistor 542. The collector of the first transistor 540 is connected to the base of the second transistor 541. The collector of the second transistor 541 is connected, through a feedback resistor 545, to the base of the first transistor 540. This collector of the second transistor 541 is also connected, through a collector resistor 543, to the positive voltage supply line 60. The emitter of the first transistor 540 forms the input of the second threshold switch 54, and is connected, through a diode 548, to the output terminal 52a of the regulating amplifier 52.
The third AND-gate 45 is similar to the second threshold switch 54 in the form of a feedback-coupled amplifier with two transistors of opposite conductivity type. Modifications in the circuit design are realized in the respect that the third AND-gate 45, as shown in FIG. 1, is designed in the form of a blocking or inhibiting gate which has a noninverting and one inverting input. In addition, the second transistor 451 in the third AND-gate 45, has two collector resistors 453, 453a connected in series. The junction of these two resistors is connected to the second noninverting input of the third AND-gate 45. This junction, furthermore, is connected through a diode 458, to the output of the second threshold switch 54. All remaining components are the same as in the second threshold switch 54, and are thereby not further described. The reference numerals are lower by 90, than in the second threshold switch 54.
The third amplifier 42 has a transistor 420 and a power transistor 421. The preamplifying transistor 420 is connected with its base, to the output of the third AND-gate 45. The emitter of the preamplifying transistor 420, is connected, through a diode 424, to the negative voltage supply line 62. The collector of this transistor 420, furthermore, is connected through two resistors 422, 423, to a nonstabilized positive voltage supply line 61. The base of the power transistor 421 is connected to the junction between the resistors 422 and 423. The emitter of the transistor 421 is connected directly with the non-stabilized voltage supply line 61.
The collector of the power transistor 421 is connected, furthermore, through a resistor 425 and electromagnetic winding 38a, to the negative voltage supply line 62. A series circuit, moreover, leads from the collector of the power transistor 421, to a diode 428 and a resistor 427, and from there to the negative voltage supply line 62, as well as a junction to the feedback resistor 455 within the third AND-gate 45. Connected in parallel with the resistor 425, is a storage capacitor 426.
The remaining AND- gates 42, 44 and 46, as well as the first threshold switch 53 are constructed precisely the same as the second threshold switch 54. The latter is universally insertable, since it is possible to connect as many inputs as desired, to the emitter of the first transistor, through diodes. At the same time, the threshold level can be set simultaneously with the aid of the base voltage divider of the first transistor.
The dead-center circuit 50, shown in FIG. 3, consists of two threshold switches 505, 506 which are also constructed and designed in the form described above. The threshold level of the switch 505 is set at 7 volts, in the embodiments, and the other threshold switch is set to 5 volts. The output of the switch 505 is connected, through a diode 503, to a second output of the other threshold switch 506. With this arrangement, a positive signal is emitted at the output terminal 50a of the deadcenter circuit 50, when the input voltage at the terminal 49a is either below 5 volts or above 7 volts. Within this region, the output terminal 50a is substantially at the potential of the negative voltage supply line 62.
FIG. 4 shows the circuit diagram of a pulse stretcher modulator, which can be used in place of the threshold switch 53 or 54. an operational amplifier 530 serves as the active component, and has a noninverting input at the junction of two resistors 533, 534, which form a voltage divider. The inverting input of this operational amplifier 530, is connected, through an input resistor 537, to an input terminal 52a. A resistor 531 is connected between the output of the operational amplifier 530 and the inverting input of the amplifier. A resistor 532, furthermore, is connected between the output of the operational amplifier 530, and the noninverting input. The output of the operational amplifier 530 is, furthermore, connected directly to an output terminal 53a, and to the positive voltage supply line 60, through a resistor 536. A capacitor 535 is connected between the inverting input of the operational amplifier 530, and the negative voltage supply line 62.
The second embodiment shown in FIG. 5, is extensively the same as the first embodiment. The components and circuits that are the same in FIG. 5, as they are in FIG. 1, have the same reference numerals, and are also not further described. In the second embodiment, the first AND-gate 43 has four inputs, of which two are connected the same as in the first embodiment. The other two inputs of the first AND-gate 43 are connected with the outputs of a first OR-gate 73 and a second OR-gate 75. A third threshold switch is connected to the output of the output transducer 47, and a fourth threshold switch 71 is connected to the output of the summing device 51. A first inverter 72 is connected to the output of the third threshold switch 70, and a second inverter 74 is connected to the fourth threshold switch 71. The two inputs of the first OR-gate 73, are connected with the output of the first inverter 72 and the output of the fourth threshold switch 71. In a similar manner, the two inputs of the second OR-gate 75 are connected to the output of the third threshold switch 70 and the output of the second inverter 74.
For the purpose of describing the functional operation of the electro-hydraulic control arrangement, the arrangement of the hydraulic valves is described first. Each position of the control slide 23 corresponds to a predetermined fluid flow from the inlet line 57 to one of the lines 14, 15. With this arrangement, a predetermined speed or velocity of the piston head 12 can be established corresponding to a predetermined position of the control slide.
The control valves 34, 36, 38, each have two controlled connections and two positions, and are thereby constructed in the form of 2/2-way valves. In the normal inoperative position, the first control valve 34 is closed, and the two other control valves 36, 38 are open. It is possible, thereby, to bring the control slide 23 into any desired position, with the aid of the control lever 30. As a result, any desired velocity of the operating piston head 12 may be attained. Should the control slide 23 be actuated through the electro-hydraulic remote control unit with the aid of the remote control lever 55, then the first control valve 34 becomes opened. When the control piston 26 is to be moved toward the left, then the third control valve 38 must be closed, and the second control valve 36 must be opened. In the reverse situation, the second control valve 36 must be closed and the third control valve 38 must be opened, in the case that the control piston 26 is to be moved toward the right. When, finally, the control piston 26 is to be held at a predetermined position outside of its neutral position, then the second control valve 36 and the third control valve 38 must be closed.
These four different valve positions are set or established by the electronic circuit in dependency on the position of the remote control lever lever 55 and the output signal of the output transducer 47. In the following description of the functional operation, the digital circuitry is described in conjunction with the designations of a 1 signal and 0 signal as in common usage. When an AND-gate provides a 1 signal, it is implied that its output is substantially at the potential of the positive supply line 60. Conversely, when the output of the AND-gate emits a 0 signal, then the potential of the output of the AND-gate is substantially at the negative voltage supply line 62. The output transducer 47, the input transducer 48, the amplifying stage 49 and the regulating amplifier 52, all provide analog signals. These analog signals are converted to digital signals in the dead center circuit 50, as well as in the two threshold switches 53, 54. The remaining circuitry operates, then, on the basis of only digital signals.
The summing device 51 is designed so that the output signal of the input transducer 48 is negative, and the output signal of the output transducer 47 is positive. This summing device 51, therefore, computes the difference between the input value and the output value as provided by the transducers. In a practical design, the input transducer 48 and the output transducer 47 are connected to the two inputs of a difference amplifier, which serves simultaneously as the regulating amplifier 52. It is also possible to design the regulating amplifier 52 so that the latter has an input, as shown in FIG. 1. With such an arrangement, an inverting stage must be connected to either the output of the input transducer 48 or the output of the output transducer 47. Such inversion is required in the event that the transducer does not provide already such an inverted signal, relative to the other transducer. Once such inversion has been realized the two signals from the two transducers may be applied, through summing resistors, to the input of the regulating amplifier 52.
The input transducer 48 and the output transducer 47 are designed so that their output potentials become shifted in the negative region, when the associated control lever is moved toward the left. The dead-center circuit 50 provides a 0 signal within a-small region about the 0 position of the remote control lever 55 within the so-called dead zone. In all other positions of the remote control lever 55, a 1 signal is emitted. In the embodiment, the threshold level of the first threshold switch 53 is set to 5 volts, and the second threshold switch 54 is set to 7 volts. At the same time, the output voltage from the regulating amplifier 52 is established at 6 volts, provided the difference between the input value and output value is zero. When the input value is equal to the output value, the first threshold switch 53 provides a 1 signal, and the second threshold switch 54 provides a 0 signal.
When the remote control lever 55 is moved toward the right, then the dead-center circuit 50 provides a 1 signal, when the dead zone is exceeded. The output voltage from the regulating amplifier 52 is shifted, thereby, in the positive direction to the extent that the threshold level of the second threshold switch 54 becomes exceeded. At this point, the three circuits 50, S3, 54 each provide a 1 signal. At the output of the second AND-gate 44 is a 1 signal and at the output of the third AND-gate 45 is a 0 signal. At the output of the NAND-gate 46, is, thereby, a 1 signal which is applied to the second input of the first AND-gate 43. A 1 signal is, henceforth, also available at the output of the AND- gate 43. As a result, the first two control valves become actuated by the amplifiers 40 and 41. The control piston 26 moves, consequently, in the same direction as the remote control lever 55namely toward the right.
In view of this arrangement, the output potential of the output transducer 47 is shifted in the positive direction, and the output potential of the regulating amplifier 52 is shiftedin the negative direction, until the threshold level of the second circuit 54 is higher. Then the third AND-gate 45 also provides a 1 signal which, in turn, actuates the third control valve 38 and, at the same time, the AND-gate 43 by way of the NAND-gate 46. The first amplifier 40 of the first control valve is thereby switched off. As a result, some control valves are now closed, so that the control piston 26 becomes blocked in its position. A predetermined velocity of the operating piston 12 is thereby established, and this piston 12 corresponds precisely to the position of the remote control lever 55, as is required.
If, now, the remote control lever 55 is moved toward the left, then, after passage through the 0 region and the dead zone, the threshold level of the first switch 53 becomes the higher value. Both threshold switches provide, thereby, 0 signals. Since the third AND-gate 45 is constructed in the form of a blocking or inhibiting gate and is provided with an inverting input, the output of this AND-gate 45 provides a 1 signal which is applied to the third amplifier 42 and thereby the third control valve 38. As a result, this valve 38 is closed. Since the second control valve 36 becomes simultaneously opened, through the AND-gate 44 and the amplifier 41, and the first control valve 34 also becomes opened through the NAND-gate 46, the AND-gate 43 and the amplifier 40, the control piston 26 is moved toward the left.
In summary, the functional operation of the first embodiment can be described with the following characteristics: When the remote control lever 55 is deflected past the dead zone, either the second control valve 36 or the third control valve 38 is closed, depending upon the direction of deflection of the lever. Aside from this, the first control valve 34 becomes opened, through the AND-gate 43 and the NAND-gate 46. When the remote control lever 55 is deflected, the first control valve 34 is again closed, through the NAND-gate 46, only until the two other control valves 36 and 38 are simultaneously closed, when the input value is equal to the output value and the control piston 26 is to be held in its position.
A particular advantageous of the control arrangement described above resides in the condition that all digital components of the circuitry can be constructed from the same circuit elements, as shown in FIGS. 2 and 3. In the second threshold switch 54, according to FIG. 2, the base voltage divider 546, 547 of the first transistor 540, is adjusted so that a voltage of 7 volts is available at the tap. The first transistor 540 becomes then turned off, as soon as the potential of the input terminal 52a drops below 7 volts. The voltage drop across the diode 548 and the emitter-base diode of the first transistor 540 become compensated. As a result of the positive feedback coupling of the resistor 545, no continuous collector current of the first transistor is available when the potential of the input terminal 52a is slowly taken off. Instead, a rapid switching takes place in the threshold voltage established by the base voltage divider. From the circuit of the threshold switch 54, a NAND-gate can be produced in a simple manner, in that several input terminals can be connected to the emitter of the first transistor 540, by way of several diodes. Such a NAND-gate 506 is shown in FIG. 3 as a component of the dead-center circuit 50. A blocking or inhibiting gate with an inverting and a noninverting input, as required for the third AND-gate 45, is obtained when the emitter of the first transistor 450 is used as the first input and the collector of the second transistor 451 is used as the second input, as shown in FIG. 2 with respect to the blocking gate 45.
The emitter potential of the transistor 420 in the second power amplifier 42 is raised by substantially 0.7 volts, through the diode 424, relative to the potential of the negative voltage line 62. In this manner, the transistor 420 is securely turned off when the transistor 451 conducts. Power transistor 421 is also turned off, since the latter is of opposite conductivity type relative to the transistor 420. In front of the electromagnetic winding 38a, is the parallel circuit including the resistor 425 and the capacitor 426. Upon turning on the power transistor 421, full operating voltage is applied, through the capacitor 426, to the winding 38, until the capacitor 426 has become charged. As a result, a rapid energizing of the magnet winding 38a is realized. After switching off the power transistor 421, the energy stored within the winding 38a is dissipated in the two resistors 427 and 425, and the resistance within the winding 38a. This results from the condition that the tum-off current of the winding 38a can flow further through the diode 428.
The dead zone is the allowable deviation or difference between the input value and output value, or is the region in which the output signal from the switch 53 is a 1 signal and the output from the switch 54 is a 0 signal. The dead zone is provided so that continuous switching or oscillation of the valves is prevented. The dead zone together with the dead time of the control valves, determines the maximum allowable displacement velocity of the control slide 23. This velocity is dependent on the pressure in the inlet line 57, the dimensions of the throttles 35 and 39, and on the surfaces of the control pistons. The displacement velocity and thereby the acceleration of the operating piston 12, is thereby constant. As a result, reverse accelerations or delays arise under predetermined conditions, when the remote control lever 55 is deflected, or when the input value is attained by the output value. These displacement transitions become softer when the two threshold circuits 53, 54 become replaced by pulse stretcher modulators.
Such a pulse stretcher modulator is shown in FIG. 4. When the input terminal 52a has applied to it the potential of the negative voltage supply line 62, the capacitor 535 is extensively discharged, and the input potential of the inverting input of the operational amplifier is below the potential of the noninverting input, so that the output of the operational amplifier 530 is at positive potential. Thus, the output of the operational amplifier provides a 1 signal. The potential of the noninverting input of the operational amplifier 530 is high, and is determined through the resistors 532, 533, 534, whereby the resistor 532 is in parallel, in this case, with the resistor 533. The resistor 536 is substantially small in relation to the resistors 532, 533 and 534. When a predetermined potential prevails at the input terminal 52a, the capacitor 535 becomes charged to the potential of the positive voltage supply line, through the resistors 536, 531 and 537. As a result, the potential of the inverting input of the operational amplifier 530 rises. When this potential exceeds the potential prevailing at the non-inverting input, the operational amplifier 530 switches state through the coupling resistor 532, and a 0 signal prevails at the output of this amplifier. At the same time, the potential at the noninverting input shifts in the direction toward a negative value which is, in turn, determined by the resistors 533, 534 and 532, whereby the resistor 532 is, in this case, in parallel with the resistor 534. The capacitor 535 discharges from the original input potential of the input terminal 52a in direction to the potential of the negative voltage supply line 62, through the resistors 537 and 531. When the potential at the inverting input is below the potential of the noninverting input, then the operational amplifier 530 switches again state, and provides at its output a 1 signal.
This process is repeated periodically, whereby the pulse repetition frequency of the output pulses of the operational amplifier 530 is dependent upon the magnitude of the input potential prevailing at the terminal 52a. When this input potential is sufficiently high, then the capacitor 535 can no longer discharge sufficiently through the resistor 531, so that the output of the operational amplifier 530 remains continuously at negative potential.
The pulse stretcher modulator in accordance with FIG. 4 operates similarly to a threshold switch. Thus, when the input voltage drops below a predetermined threshold level, then the output provides a continuous 1 signal. When, on the other hand, the output voltage exceeds an upper threshold level, then the output provides a continuous signal. When the input voltage lies between the lower and upper threshold levels, the pulse stretcher modulator provides pulses having a repetition frequency dependent upon the magnitude of the input voltage. The potential difference between the lower and upper threshold levels is determined through the relationship between the two resistors 53] and 537. The absolute magnitude of the two threshold levels is, on the other hand, determined by the voltage divider 533, 534, 532.
When two pulse stretcher modulators in accordance with FIG. 4, are used in place of the two threshold switches 53, 54, then the three control valves 34, 36 and 38 are controlled in a pulse-wise manner when the output value differs by small amounts from the input value. As a result, the displacement velocity of the control slide 23 and thereby the acceleration of the operating piston 12 become essentially smaller. With this arrangement, softer transitions in the motion are realized. For a smaller dead zone and corresponding larger positional accuracy, larger final velocities of the control slides are possible. The rest of the functional operation is precisely the same as when using the threshold switches.
The dead zone is to be as small as possible for attaining a large positional accuracy of the control slide 23. At the same time, the displacement velocity of the control slide is to be, on the other hand, as large as possible. In order that a stable operation of the arrangement may be obtained, the dead zone and the dead time of the valves must be matched. The two requirements of maximum possible displacement velocity and smallest possible dead zone are in conflict.
In the first embodiment of FIG. 1, the displacement velocity of the control slide 23 is larger than the velocity when the control slide is moved from its 0 position in direction of greater deflection, in the return process. This results from the condition that upon deflection or movement from the 0 position, the spring force is opposed against the hydraulic force in the return arrangement 28, whereas the spring force adds to the hydraulic force during the return process. The displacement velocity in the return process must, therefore, take into account the dead zone.
In order to make possible a smaller dead zone, other force relationships are selected in the circuit embodiment of FIG. 5. Thus, the hydraulic force acts on the differential piston 26 only upon deflection or movement from the 0 position,- but not during the return process. This may be attained because in the return process the first control valve 34 is basically closed.
To determine whether a deflection process or a return process prevails, the components 70 to 75 are used. The third threshold switch 70 determines whether the control slide 23 is either to the right or to the left of the 0 position, whereas the fourth threshold switch 71 determines whether the regulating deviation is either positive or negative, i.e., whether the output value has already attained the input value or not.
In order that the first control valve 34 becomes opened, all four inputs of the first AND-gate 43 must have I signals. The manner in which the I signals at the first two inputs are derived, is already described above. These first two inputs are connected with the outputs of the dead center circuit 50 and the third AND-gate 56. Assume, now, as an example, that the control slide 23 becomes moved towards the left, and has not as yet attained the input value. Then the third threshold switch provides a 0 signal and the fourth threshold switch 71 also provides a 0 signal, since the output voltage of the output transducer 47 as well as from the summing device, are negative. In this case, both inverters 72 and 74 provide 1 signals which are transmitted, through the OR-gates 73 and 75, to the two remaining inputs of the first AND-gate 43. As soon as the input value is attained, the regulating error or deviation becomes 0 or positive, and the fourth threshold switch 71 provides a I signal. At this point, a 0 signal lies at the third input of the AND-gate 43, which is connected with the second OR-gate 75, whereas a 1 signal still lies at the fifth input. As a result, the first control valve 34 becomes closed. This closing of the valve also remains when the remote control lever 55 is again returned to the 0 position. Upon return of the control slide 23, the control cylinder 27 can thereby have applied fluid from the first control valve 34.
In the second embodiment of FIG. 5, it is also possible to use pulse stretcher modulators in accordance with FIG. 4, instead of the first two threshold switches 53 and 54.
The control arrangement described above, fulfills, consequently, all of the imposed requirements. The velocity of the operating piston 12 is set to a constant value through the remote control lever 55 as well as through the control lever 30. This constant value depends on the deflection or displacement of the remote control lever or of the lever 30. When using both stretcher modulators, it is possible to avoid furthermore accelerations or delays which are too large for small regulating errors or deviations. When the remote control lever 55 is at its normal inoperative position, then the control slide 23 can be actuated with the aid of the control lever 30. An output value-return is then made possible to maintain precisely the velocity for the operating piston 12, which is set by the remote control lever. The control arrangement is, thereby, particularly adaptable for automotive cranes, although its area of application is not limited to this field.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of electro-hydraulic control arrangements differing from the types described above.
While the invention has been illustrated and described as embodied in an electro-hydraulic control arrangement, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:
1. An electrohydraulic control arrangement for hydraulic operating means operative in two directions comprising, in combination, a control valve with control slides; two hydraulic transmission lines communieating with said operating means and closed by said control slide when in neutral position in said control valve; inlet line means communicating with one of said hydraulic transmission lines when said control slide is in a first operative position; return line means communicating with the other one of said hydraulic transmission lines when said control slide is in a second operative position; control piston means movable within a control cylinder and actuating said control slide; electromagnetically actuated valves for applying working fluid to said control cylinder; remote control lever means for providing an adjustable input parameter; regulating amplifier means actuating said electromagnetic valves as a function of said input parameter; two flow lines communicating with said control cylinder and connected to saidinlet line means and said return line means by two of said electromagnetically actuated valves; signal amplifying means connected to said electromagnetically actuated valves for actuating said electromagnetically actuated valves; and threshold switching means connected between said signal amplifying means and said regulating amplifying means.
2. The arrangement as defined in claim 1 wherein a first one of said electromagnetically actuated valves is connected between said inlet line means and said two electromagnetically actuated valves, said first one of said electromagnetically actuated valves being closed when said remote control lever means is in position.
3. The arrangement as defined in claim 2 including a close control lever for actuating said control slide when said first one of said electromagnetically actuated valves is closed and said two electromagnetically actuated valves are open.
4. The arrangement as define in claim 2 including a dead center circuit; an input parameter transducer actuated by said remote control lever means; and a first amplifier in said signal amplifying means connected to said first one of said electromagnetically actuated valves, the input of said first amplifier being connected through said dead center circuit to said input parameter transducer.
5. The arrangement as defined in claim 4 wherein said dead center circuit comprises two threshold switching circuits having different threshold levels, the input of one threshold switching circuit being connected with a first input of the other threshold switching circuit, the output of said one threshold switching circuit being connected to a second input of the other threshold switching circuit.
6. The arrangement as defined in claim 4 including AND-gates connected to a second amplifier and a third amplifier in said signal amplifying means; a threshold switching circuit connected to a first input of each AND-gate, the second inputs of said AND-gates being connected to said dead center circuit.
7. The arrangement as defined in claim 6 including an AND-gate connected to the input of said first amplifier, a first input of said AND-gate connected to said first amplifier being connected to said dead center circuit, said AND-gate connected in front of said first amplifier being a first AND-gate and said AND-gates connected to said second and third amplifiers being respectively second and third AND-gates; a fourth AND-gate connected between the second input of said first AND- gate and the outputs of said second and third AND- gates.
8. The arrangement as defined in claim 4 including an amplifying stage connected in series with the input of said dead center circuit.
9. The arrangement as defined in claim 1 including output parameter transducer means actuated by said control slide; input parameter transducer means actuated by said remote control lever means; and summing means with inputs connected to said input and output parameter transducer means, the output of said summing means being connected to said regulating amplifying means.
10. The arrangement as defined in claim 7 wherein said threshold switching circuits and said AND-gates are two-stage, positive feedback-coupled transistor amplifiers with two transistors of complementary conductivity type.
1 l. The arrangement as defined in claim 10 including base voltage divider means connected to a first one of said two transistors in said threshold switching circuits for setting the threshold voltage of said threshold switching circuit; and diode means for applying to the emitter of said first transistor the input voltage signal.
12. The arrangement as defined in claim 10 including diode means connected to the emitter of a first transistor of said AND-gates for applying input voltage signals to the emitter of said first transistor of said AND-gates.
13. The arrangement as defined in claim 4 including second and third AND-gates connected to second and third amplifiers in said amplifying means; and pulse stretcher modulator means connected to first inputs of said second and third AND-gates, the second inputs of said AND-gates being connected to said dead center circuit, said pulse stretcher'modulator means controlling intermittently said electromagnetically actuated valves when the output signals of said regulating amplifier means are substantially small, said electromagnetically actuated valves being continuously unactuated when the output signals of said regulating amplifier means are substantially large.
14. The arrangement as defined in claim 13 wherein said pulse stretcher modulator comprises an operational amplifier with a first resistor connected between the output of said amplifier and one input thereof, and a second resistor connected between the output of said operational amplifier and a circuit input thereof; an input resistor connected to the inverting input of said operational amplifier, on terminal of said input resistor being the input signal terminal; and a capacitor connected between said input resistor and ground potential.
15. The arrangement as defined in claim 9 including a third threshold switch connected to the output of said output parameter transducer means; and a forth threshold switching circuit connected to the output of said summing means.
16. The arrangement as defined in claim 15 including a first OR-gate and a second OR-gate, the output of said third threshold switching circuit being connected to said second OR-gate and to said first OR-gate; a first inverter circuit connected between said output of said third threshold switching circuit and said first OR-gate; a second inverter circuit connected between the output of said fourth threshold switching circuit and said second OR-gate, the output of said fourth threshold switching circuit being also connected to said first OR- gate, the outputs of said OR-gates being connected to the inputs of said first AND-gate.
17. The arrangement as defined in claim 7 wherein said fourth AND-gate comprises a NAND-gate.
t t l

Claims (17)

1. An electrohydraulic control arrangement for hydraulic operating means operative in two directions comprising, in combination, a control valve with control slides; two hydraulic transmission lines communicating with said operating means and closed by said control slide when in neutral position in said control valve; inlet line means communicating with one of said hydraulic transmission lines when said control slide is in a first operative position; return line means communicating with the other one of said hydraulic transmission lines when said control slide is in a second operative position; control piston means movable within a control cylinder and actuating said control slide; electromagnetically actuated valves for applying working fluid to said control cylinder; remote control lever means for providing an adjustable input parameter; regulating amplifier means actuating said electromagnetic valves as a function of said input parameter; two flow lines communicating with said control cylinder and connected to said inlet line means and said return line means by two of said electromagnetically actuated valves; signal amplifying means connected to said electromagnetically actuated valves for actuating said electromagnetically actuated valves; and threshold switching means connected between said signal amplifying means and said regulating amplifying means.
2. The arrangement as defined in claim 1 wherein a first one of said electromagnetically actuated valves is connected between said inlet line means and said two electromagnetically actuated valves, said first one of said electromagnetically actuated valves being closed when said remote control lever means is in 0 position.
3. The arrangement as defined in claim 2 including a close control lever for actuating said control slide when said first one of said electromagnetically actuated valves is closed and said two electromagnetically actuated valves are open.
4. The arrangement as define in claim 2 including a dead center circuit; an input parameter transducer actuated by said remote control lever means; and a first amplifier in said signal amplifying means connected to said first one of said electromagnetically actuated valves, the input of said first amplifier being connected through said dead center circuit to said input parameter transducer.
5. The arrangement as defined in claim 4 wherein said dead center circuit comprises two threshold switching circuits having different threshold levels, the input of one threshold switching circuit being connected with a first input of the other threshold switching circuit, the output of said one threshold switching circuit being connected to a second input of the other threshold switching circuit.
6. The arrangement as defined in claim 4 inCluding AND-gates connected to a second amplifier and a third amplifier in said signal amplifying means; a threshold switching circuit connected to a first input of each AND-gate, the second inputs of said AND-gates being connected to said dead center circuit.
7. The arrangement as defined in claim 6 including an AND-gate connected to the input of said first amplifier, a first input of said AND-gate connected to said first amplifier being connected to said dead center circuit, said AND-gate connected in front of said first amplifier being a first AND-gate and said AND-gates connected to said second and third amplifiers being respectively second and third AND-gates; a fourth AND-gate connected between the second input of said first AND-gate and the outputs of said second and third AND-gates.
8. The arrangement as defined in claim 4 including an amplifying stage connected in series with the input of said dead center circuit.
9. The arrangement as defined in claim 1 including output parameter transducer means actuated by said control slide; input parameter transducer means actuated by said remote control lever means; and summing means with inputs connected to said input and output parameter transducer means, the output of said summing means being connected to said regulating amplifying means.
10. The arrangement as defined in claim 7 wherein said threshold switching circuits and said AND-gates are two-stage, positive feedback-coupled transistor amplifiers with two transistors of complementary conductivity type.
11. The arrangement as defined in claim 10 including base voltage divider means connected to a first one of said two transistors in said threshold switching circuits for setting the threshold voltage of said threshold switching circuit; and diode means for applying to the emitter of said first transistor the input voltage signal.
12. The arrangement as defined in claim 10 including diode means connected to the emitter of a first transistor of said AND-gates for applying input voltage signals to the emitter of said first transistor of said AND-gates.
13. The arrangement as defined in claim 4 including second and third AND-gates connected to second and third amplifiers in said amplifying means; and pulse stretcher modulator means connected to first inputs of said second and third AND-gates, the second inputs of said AND-gates being connected to said dead center circuit, said pulse stretcher modulator means controlling intermittently said electromagnetically actuated valves when the output signals of said regulating amplifier means are substantially small, said electromagnetically actuated valves being continuously unactuated when the output signals of said regulating amplifier means are substantially large.
14. The arrangement as defined in claim 13 wherein said pulse stretcher modulator comprises an operational amplifier with a first resistor connected between the output of said amplifier and one input thereof, and a second resistor connected between the output of said operational amplifier and a circuit input thereof; an input resistor connected to the inverting input of said operational amplifier, on terminal of said input resistor being the input signal terminal; and a capacitor connected between said input resistor and ground potential.
15. The arrangement as defined in claim 9 including a third threshold switch connected to the output of said output parameter transducer means; and a forth threshold switching circuit connected to the output of said summing means.
16. The arrangement as defined in claim 15 including a first OR-gate and a second OR-gate, the output of said third threshold switching circuit being connected to said second OR-gate and to said first OR-gate; a first inverter circuit connected between said output of said third threshold switching circuit and said first OR-gate; a second inverter circuit connected between the output of said fourth threshold switching cirCuit and said second OR-gate, the output of said fourth threshold switching circuit being also connected to said first OR-gate, the outputs of said OR-gates being connected to the inputs of said first AND-gate.
17. The arrangement as defined in claim 7 wherein said fourth AND-gate comprises a NAND-gate.
US3774641D 1971-03-26 1972-04-11 Electrohydraulic control arrangement for hydraulic actuators Expired - Lifetime US3774641A (en)

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DE (1) DE2114639A1 (en)
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US4215723A (en) * 1976-06-11 1980-08-05 Hitachi, Ltd. Fluid pressure servo valve assembly
US4422474A (en) * 1981-09-14 1983-12-27 Ford Motor Company Electro-hydraulic remote valve
US4540018A (en) * 1981-08-28 1985-09-10 Mannesmann Rexroth Gmbh Pressure control valve
US4657041A (en) * 1984-08-31 1987-04-14 Aisin Seiki Kabushiki Kaisha Oil pressure control apparatus
US4804009A (en) * 1982-06-08 1989-02-14 Johnson Service Company Pneumatic interface apparatus for control of process systems
US4934143A (en) * 1987-04-29 1990-06-19 Vickers, Incorporated Electrohydraulic fluid control system for variable displacement pump
US20070181196A1 (en) * 2006-02-07 2007-08-09 Sturman Digital Systems, Llc Spool valve
US20120255617A1 (en) * 2011-04-07 2012-10-11 SMC Coporation Pilot-operated three-position switching valve
US20170002937A1 (en) * 2014-07-24 2017-01-05 Kyb Corporation Directional control valve
US9970557B2 (en) * 2016-06-27 2018-05-15 Travis Victor Dean Loewen Multi-pilot variable pressure relay valve
WO2021231276A1 (en) * 2020-05-09 2021-11-18 Emerson Process Management Valve Automation, Inc. Universal logic circuit for electro-hydraulic actuator

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US4282711A (en) * 1979-07-26 1981-08-11 Deere & Company Hydrostatic transmission control system
CA1151979A (en) * 1978-06-01 1983-08-16 Reiner C. Onken Electro-hydraulic regulating drive and a fast-switching magnetic valve for use therein
MX152961A (en) * 1979-07-26 1986-07-09 Deere & Co IMPROVEMENTS TO HYDROSTATIC TRANSMISSION CONTROL DEVICE
JPS5689491A (en) * 1979-12-14 1981-07-20 Kobe Steel Ltd Master slave device
JPS57197334A (en) * 1981-05-26 1982-12-03 Komatsu Ltd Electric oil pressure controller for construction vehicle
DE3140301A1 (en) * 1981-10-10 1983-04-28 Bosch und Pierburg System oHG, 4040 Neuss CONTROL DEVICE FOR A PRESSURE CONTROLLED ACTUATOR
FI117717B (en) * 1999-07-09 2007-01-31 Ciba Sc Holding Ag Surface Adhesive Composition

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US22728A (en) * 1859-01-25 Washing-machine
GB735502A (en) * 1948-10-30 1955-08-24 Northrop Aircraft Inc Improvements in combined aileron and landing flap

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4215723A (en) * 1976-06-11 1980-08-05 Hitachi, Ltd. Fluid pressure servo valve assembly
US4540018A (en) * 1981-08-28 1985-09-10 Mannesmann Rexroth Gmbh Pressure control valve
US4422474A (en) * 1981-09-14 1983-12-27 Ford Motor Company Electro-hydraulic remote valve
US4804009A (en) * 1982-06-08 1989-02-14 Johnson Service Company Pneumatic interface apparatus for control of process systems
US4657041A (en) * 1984-08-31 1987-04-14 Aisin Seiki Kabushiki Kaisha Oil pressure control apparatus
US4934143A (en) * 1987-04-29 1990-06-19 Vickers, Incorporated Electrohydraulic fluid control system for variable displacement pump
US7775240B2 (en) * 2006-02-07 2010-08-17 Sturman Digital Systems, Llc Spool valve
US20100200090A1 (en) * 2006-02-07 2010-08-12 Sturman Digital Systems, Llc Spool Valve
US20070181196A1 (en) * 2006-02-07 2007-08-09 Sturman Digital Systems, Llc Spool valve
US7958909B2 (en) 2006-02-07 2011-06-14 Sturman Digital Systems, Llc Spool valve
US20120255617A1 (en) * 2011-04-07 2012-10-11 SMC Coporation Pilot-operated three-position switching valve
US8925587B2 (en) * 2011-04-07 2015-01-06 Smc Corporation Pilot-operated three-position switching valve
US20170002937A1 (en) * 2014-07-24 2017-01-05 Kyb Corporation Directional control valve
US9970556B2 (en) * 2014-07-24 2018-05-15 Kyb Corporation Directional control valve
US9970557B2 (en) * 2016-06-27 2018-05-15 Travis Victor Dean Loewen Multi-pilot variable pressure relay valve
WO2021231276A1 (en) * 2020-05-09 2021-11-18 Emerson Process Management Valve Automation, Inc. Universal logic circuit for electro-hydraulic actuator

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PL75123B1 (en) 1974-12-31
GB1383823A (en) 1974-02-12
FR2130067B1 (en) 1975-08-29
DE2114639A1 (en) 1972-10-05
IT950735B (en) 1973-06-20
FR2130067A1 (en) 1972-11-03
SE372600B (en) 1974-12-23

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