Abstract:
An improvement in and method of operating a load sensing system in which a variable displacement, pressure compensated pump delivering hydraulic fluid to a fluid operating device through a directional control valve is controlled by a load-sensing system pressure limiter which is set so that the system operates at the maximum continuous system operating pressure. By also setting pump destroke pressure slightly higher than the necessary operating pressure for the load, optimum performance of the pump is realized. The load-sensing system pressure limiter is configured as a poppet which is placed inside of the body of the directional control valve and is biased by an adjustable spring force to the closed position. Preferably, the poppet connects the load sensing core of the directional control valve to an exhaust passage therein so as to require minimal modification of the directional control valve. In a preferred embodiment, the poppet has a bleed-down orifice extending therethrough to unload the load pressure signal when work has been completed or diminished.
Abstract:
A displacement control device of a variable-displacement hydraulic pump which increases the response speed when the pump discharge pressure is low and suppresses increase of the response speed when the pump discharge pressure is high. The displacement control device has a variable-displacement piston 3 which activates a displacement control member 2 of the variable displacement hydraulic pump 1, a circuit 10 which provides a communication between a large-diameter pressure chamber 6 on the variable-displacement piston 3 and an output port 9 of the control valve 7, and a variable restriction valve 11 which is provided in the circuit 10. The restriction valve 11 increases and decreases its opening area when the pump discharge pressure is low and high, respectively. When the pump discharge pressure is low, the pump discharge pressure is smoothly introduced into the large-diameter pressure chamber 6 through the control valve 7, whereas, when the pump discharge pressure is high, the supply of the discharge pressure to the large-diameter pressure chamber is restricted.
Abstract:
A fluid operated pump displacement control system is provided wherein a self pressure is defined as a first control signal, and characterized in that an arbitrary switchable second control signal different from the first control signal is added to the first control signal, and a displacement is adapted to be switched to a displacement corresponding to a value of the second control signal as added to the first control signal. Further, a fluid operated pump displacement control system is provided comprising a control circuit connected to respective displacement control devices of variable displacement pumps and adapted to be operated by discharge pressure fluid from a discrete control pump. A variable torque control valve has a proportional electromagnetic solenoid provided in a circuit connecting the control circuit with the control pump and is adapted to produce a pressure reduction by a discharge fluid pressure of the variable displacement pumps and a propelling force of the proportional electromagnetic solenoid. A detector detects set output conditions of a prime mover for driving the variable displacement pumps, and current is supplied to the proportional electromagnetic solenoid according to the difference between a set reference rotational speed in each of the set output conditions and an actual rotational speed of the prime mover.
Abstract:
Disclosed herein is a device for controlling displacement of a variable displacement hydraulic pump comprising a displacement control system for receiving a discharge pressure of the variable displacement hydraulic pump and a discharge pressure of a fixed displacement hydraulic pump to control the displacement of the variable displacement hydraulic pump. The displacement control system comprises a servopiston including a helical compression spring for maintaining the variable displacement hydraulic pump at a maximum swash angle in a neutral position of associated operating valve, a servovalve including a spool for selectively controlling communication of hydraulic pressure between a control pump and a pair of fluid chambers defined in the servopiston, a control piston connected through a control lever pivotably supported by a pivot pin to the spool and the servopiston, at least two helical compression springs for biasing the control piston and controlling torque and flow so as to approximate same to a constant torque curve, a floating spring seat interposed between the helical compression springs, and a guide rod for guiding the floating spring seat and accommodated in a bore formed in the housing at a base portion thereof to define a pressure chamber pressurized by a biasing spring, the pressure chamber being communicated through a conduit to a discharge passage of the fixed displacement hydraulic pump.
Abstract:
An electro-hydraulic control for a hydrostatic transmission including a variable displacement hydraulic pump, a fixed displacement hydraulic motor, and fluid operable strokers to vary the displacement of the pump. The electro-hydraulic control is in series between the charge pump and the standard manual controller and determines the pressure of the charge fluid ported to the standard controller. The electro-hydraulic control includes a spool biased toward a first position to port fluid from the charge pump to the standard controller, and biased toward a second position to relieve to tank the pressure of fluid ported to the manual controller. The biasing toward the second direction is accomplished, in part, by pressure in a fluid chamber exerting a biasing force on the spool, the fluid chamber being in communication with drain through a variable orifice which is variable in response to a pressure command signal. This signal is generated by control logic including a horsepower command signal generator which is variable to correspond to a maximum desired input horsepower, and circuitry providing a horsepower approximation signal representing the product of motor output speed and the instantaneous pressure command signal. The circuitry compares the horsepower command and horsepower approximation signals and generates a new pressure command signal tending to minimize the difference between the horsepower command and approximation signals. As a result, the commanded maximum system pressure varies, such that the product of maximum system pressure and motor output speed (proportional to pump flow) is constant, for a given input horsepower setting.
Abstract:
The invention relates to a hydraulic assembly comprising a variable electric motor and a hydrostatic variable displacement pump which can be coupled thereto and the pivoting angle of which can be adjusted by means of a hydromechanical adjustment device, the pivoting angle being detectible by means of a pivoting angle sensor and a working pressure of the variable displacement pump being detectible by means of a pressure sensor. A speed of the electric motor can be varied depending on the pivoting angle sensor and the pressure sensor.
Abstract:
Engin de travaux publics du type chargeur-excavateur, comportant un circuit hydraulique (1) alimentant un ou plusieurs actionneurs hydrauliques, ledit circuit hydraulique étant équipé d'une pompe (4) à débit variable, apte à fonctionner selon deux modes distincts, à savoir un mode dit de "pleine puissance" dédié au fonctionnement en excavateur, et un mode dit de "puissance réduite" dédié au fonctionnement en chargeur, caractérisé , en ce qu'il comporte également un capteur de température (20) permettant de déterminer la température de l'huile circulant dans le circuit hydraulique (1), et des moyens pour faire basculer automatiquement le fonctionnement de la pompe (4) du mode de "pleine puissance" vers le mode de "puissance réduite", lorsque la température de l'huile dépasse un seuil prédéterminé.
Abstract:
Die Erfindung bezieht sich auf eine Dickstoffpumpe mit Fördermengensteuerung. Die Dickstoffpumpe weist einen vorzugsweise als Verbrennungsmotor ausgebildeten Antriebsmotor (50), eine mit dem Antriebsmotor kuppelbare, vorzugsweise als Reversierpumpe ausgebildete Hydropumpe (6) mit variablem Verdrängungsvolumen (V), und zwei an die Hydropumpe (6) angeschlossene, über diese im Gegentakt ansteuerbare und mit je einem Förderzylinder (7, 7') für die Dickstoffe gekoppelte Hydrozylinder (5, 5') auf. Dem Antriebsmotor (50) ist ein Regler zur Einstellung der Drehzahl (N) zugeordnet, während der Hydropumpe (6) ein Stellglied (18, 20) zur Einstellung des Verdrängungsvolumens (V) zugeordnet ist. Weiter ist eine Steuereinheit (54) zur Einstellung der Motordrehzahl (N) und des Verdrängungsvolumens (V) vorgesehen. Erfindungsgemäß weist die Steuereinheit (54) ein Einstellorgan (56) zur Einstellung der Dickstoff-Fördermenge (F) der Förderzylinder (7, 7') sowie eine auf die Stellung des Einstellorgans (56) ansprechende Steuerelektronik (108) zur softwaregestützten Sollwertvorgabe für den Drehzahlregler und für das Verdrängungsvolumen-Stellglied (20) auf. Mit diesen Maßnahmen wird erreicht, dass der Bedienungskomfort der Dickstoffpumpe verbessert und der Kraftstoffbedarf sowie die Schall- und Abgasemission im praktischen Einsatz reduziert werden.
Abstract:
Offenbart ist ein Hydroaggregat mit einem regelbaren Elektromotor und mit einer daran koppelbaren hydrostatischen Verstellpumpe, deren Schwenkwinkel über eine hydromechanische Verstelleinrichtung einstellbar ist. Dabei sind der Schwenkwinkel über einen Schwenkwinkelsensor und ein Arbeitsdruck der Verstellpumpe über einen Drucksensor erfassbar. Eine Drehzahl des Elektromotors ist in Abhängigkeit des Schwenkwinkelsensors und des Drucksensors regelbar.
Abstract:
Eine elektrohydraulische Steueranordnung ist mit einer verstellbaren Fluidpumpe und mit einem drehzahlvariablen elektrischen Antrieb ausgestattet. Eine Druckerfassungseinrichtung erlaubt die Erfassung des Fluiddrucks. Der Hauptregelkreis dieser elektrohydraulischen Steueranordnung besitzt ein Drehzahlstellglied des elektrischen Antriebs als Stellglied. Mittels des Hauptregelkreises lässt sich der Fluiddruck und damit z.B. eine durch eine Zylinder ausgeübte Kraft oder eine nachgeordnete Stellgröße wie z.B. eine Position oder eine Geschwindigkeit regeln. Ein Verdrängungsvolumenstellglied der Fluidpumpe wird mittels einer Nebenstellkette in Abhängigkeit von dem erfassten Fluiddruck angesteuert.