Classifications

• • 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
  • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
  • F15B21/08—Servomotor systems incorporating electrically operated control means
  • F15B21/082—Servomotor systems incorporating electrically operated control means with different modes
• • 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
  • F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
  • F15B7/005—With rotary or crank input
  • F15B7/006—Rotary pump input

Definitions

• the invention relates to a hydraulic system for displacement-controlled linear drives, in particular for mobile machines with at least one differential cylinder, at least one high-pressure circuit, which contains at least one pump with an adjustable delivery rate and is connected to a low-pressure system by at least two non-return valves which can be unlocked.
• Hydraulic systems for mobile work machines are based today mainly on valve-controlled principles.
• the various hydraulic consumers such as drives for the working hydraulics, steering, brakes, etc., are controlled by means of hydraulically or electrohydraulically controlled valve arrangements. controlled.
• one or more central pressure supplies often in the form of load-sensing pumps, are used that provide pressure medium flows, which are influenced by single or multi-stage valve arrangements in accordance with the desired behavior of the hydraulic consumers.
• a disadvantage of these valve-controlled hydraulic systems is, in particular, the poor energy efficiency.
• pressure differences are required at the throttle edges of the valves, which in principle leads to high energy losses in hydraulic valve controls. It is not possible to use excess energy at one consumer of the system in the form of potential energy or braking energy for other consumers in the system and thereby to improve the system efficiency, which further worsens the heat development in the system.
• a central pressure medium supply also has the disadvantage that in the event that several consumers have to be operated simultaneously, the volume flows are divided, which complicates the precise regulation and operation of the individual components.
• Safety-relevant circuits in which it must be ensured that individual consumers, such as the steering or brakes, always have sufficient pressure medium available, must always be implemented, for example, using complicated priority valve arrangements.
• a simultaneous movement of several consumers in the system leads to a different system behavior compared to individual movements. All of this leads to very complex and therefore costly and maintenance-intensive valve arrangements, the possibilities of which are also limited with regard to controllability and energy utilization.
• displacement-controlled systems for rotary drives are used, in which a pump with adjustable displacement is used to control or regulate the movement of the hydraulic motor (s). The consumer is thus controlled solely by the volume flow made available by the pump, without a control valve or the like being used in the main circuit.
• the object of the invention is therefore to provide a hydraulic system for linear drives with differential cylinders, in particular for mobile machines, which avoids the various disadvantages of the prior art by using a displacement control of the drives and enables precise, energy-efficient control of linear drives with differential cylinders, inexpensively and is easy to maintain and can be easily integrated into the overall hydraulic system of such machines.
• the invention achieves this in that the check valves are connected to an electronic control device in such a way that switching-free switching is possible between the retraction or extension of the differential cylinder and a floating position function.
• the check valves are located between the two high-pressure lines, which run from the adjustable pump to the differential cylinder, and the common low-pressure system.
• the positive or negative differential volume flow occurring depending on the direction of movement of the piston can flow into the low-pressure system or be sucked out of it. If the volume flow is sucked in from the low pressure system, the corresponding check valve opens automatically. In the event of a flow of volume flow to the low pressure system, the corresponding check valve is unlocked by the system high pressure. To achieve a floating position, the two sides of the Differential cylinders are hydraulically connected to each other, which enables free movement of the piston. For this purpose, the check valves are unlocked so that pressure medium can flow through them in both directions, regardless of the pump volume flow. In this case, the differential volume flow is also compensated for by the low pressure system.
• the control device for regulating the pump delivery rate is designed electronically.
• the delivery rate of adjustable pumps is usually controlled electro-hydraulically. It is therefore particularly advantageous if this control is applied in an integrated manner together with the control device of the check valves, so that safe and precise regulation of the complete circuit behavior is possible. This can prevent, for example, that the pump requests a volume flow when the check valves are unlocked, which would then be briefly closed by the unlocked check valves.
• a further embodiment of the hydraulic system provides that the electronic African control device for controlling the check valves has an electro-hydraulic 4/2-way valve.
• the unblocking connection of the check valves can be alternately connected to one or the other side of the high-pressure circuit, which corresponds to a switchover between the normal differential volume compensation and the floating position of the differential cylinder.
• two electro-hydraulic 3/2-way valves can be used.
• a special embodiment of the hydraulic system provides that a controllable shut-off valve is provided on at least one connection of the differential cylinder.
• a controllable shut-off valve is provided on at least one connection of the differential cylinder.
• Such a shut-off valve allows a connection of the cylinder to be shut off without leakage, which is particularly useful for realizing a holding function.
• the volume flow of the pump brings the cylinder into a certain position and then the high-pressure connection of the differential cylinder is shut off, so that it remains in its position without the pump maintaining the pressure.
• a shut-off valve is also provided on the second connection of the differential cylinder, the cylinder can be completely separated from the hydraulic circuit, while remaining in its position. In this state, the pump and the connected hydraulic circuit can be used to operate a further differential cylinder, which can then also be separated from the circuit via shut-off valves. This allows a further function in the Realize work machine that can alternatively be operated by the other existing cylinders.
• the low-pressure system is designed as an accumulator charging circuit with an accumulator charging valve, a pump with hydraulic accumulator and a pressure limiting valve.
• a design of the low pressure side is characterized by a particularly high energy efficiency.
• the pump only pushes into the low-pressure system when the pressure drops below a set minimum.
• the accumulator charging circuit ensures compliance with a low pressure level between adjustable limit values.
• Such a low-pressure system can be designed centrally for the entire hydraulic system and can supply all displacement-controlled hydraulic circuits according to the invention.
• a further embodiment of the hydraulic system according to the invention is characterized in that the controllable shut-off valve is designed as a seat valve with 3/2-way pilot control. It can also make sense for the controllable shut-off valve to be designed as a continuous valve. With such a valve, the corresponding blocking function of the connection can be easily implemented without the valve opening or closing too suddenly. This prevents unwanted pressure peaks in the system.
• shut-off valves which may be continuously controllable, are provided for alternative and / or simultaneous actuation of further differential cylinders.
• further functions can be implemented on the same high-pressure circuit by means of such valves, whereby these are always operated alternatively to one another.
• the shut-off valves are switched so that the pump with the associated protection and compensation valves is each connected to a differential cylinder or a plurality of the same function connected in parallel and supplies them with pressure medium.
• connections for a passive vibration damping system are provided on the high-pressure circuit.
• damping systems consist of a hydraulic circuit with an accumulator, which reduces the vibrations of the implement, for example when driving with a raised load.
• the vibration damping system is connected directly to at least one connection on one side of the high-pressure circuit and can be switched on and off in order to suppress the undesired vibration states in desired operating situations.
• the electronic control device, the controllable valves and, if appropriate, other hydraulic system components present are designed with the adjustable pump as an integrated component.
• Such an integration of the pump with a number of the valves and the control offers the advantage of an extremely compact design, which can be useful since these components are necessary for every hydraulic function driven by differential cylinder systems.
• the integration reduces the number of individual components, the complexity of the overall system is reduced, the installation effort is reduced and the costs of such a system are reduced in comparison to conventional systems.
• sensors are provided for detecting the system states, in particular the differential cylinder position and the hydraulic pressures. It may also make sense for an electronic control device device for controlling the controllable system components depending on the measured system state and user specifications.
• the drive system according to the invention can also be controlled, i.e. operate in an open chain of effects.
• the invention is also directed to a mobile work machine with at least one hydraulic system, as described in the preceding.
• a plurality of high-pressure circuits with a common low-pressure circuit are provided.
• this has the advantage of additional cost savings, since a single low-pressure circuit with a pump and the further components is sufficient to supply all the hydraulic systems according to the invention.
• FIG. 1 a schematic basic circuit of a hydraulic system according to the invention
• FIG. 2 a circuit of a hydraulic system according to the invention in an expanded version
• FIG. 3 shows a further embodiment
• FIG. 4 shows yet another embodiment
• FIG. 5 shows an overall system for a mobile working machine
• FIG. 6 shows another overall system for a mobile working machine machine.
• a hydraulic system is used to control a hydraulic differential cylinder 2.
• a pump 3 with an adjustable delivery volume and reversal of the delivery direction is connected to the two connections of the differential cylinder 2 via two lines 4 and 5.
• the electronically controllable 4/2-way valve 10 also serves to implement a floating position function. If the valve 10 is switched over (floating position function), the unblocking connections of the check valves 7 and 8 are no longer connected to the opposite side, but to the side lying in their passage direction. As a result, the check valves 7 and 8 open as soon as a pressure is present in one of the two lines 4 or 5 which is slightly higher than the low pressure in the low-pressure system 9. The piston 6 can thus move freely in the differential cylinder 2.
• the pump 3 is expediently set such that it does not require a volume flow, since this would also be compensated for by the quasi-short circuit through the check valves 7 and 8.
• a controllable shut-off valve 11 is provided on a connection of the differential cylinder 2.
• This side of the differential cylinder 2 can thus be shut off without leakage, as a result of which the piston 6 is fixed in this position and a load located thereon is held. As a rule, this is the more heavily loaded piston side of the differential cylinder 2.
• There are pressure sensors 12 in the system which are used to detect the states in serve the high pressure lines.
• a displacement sensor 13 or an angle sensor in the kinematics of the work equipment, which detects the piston position, is located on the hydraulic differential cylinder 2.
• the signals from the sensors 12 and 13 are processed by an electronic control device 14 together with user requests specified by corresponding control elements 15, and the corresponding manipulated variable is determined therefrom, which is transmitted to the electronic control device 16. This then controls the adjustable pump 3 in its displacement volume and thus the volume flow conveyed as well as, if applicable, the switching states of the electronic valves 10 and 11.
• FIG. 2 An extension of this basic principle is shown in more detail in FIG. 2.
• a hydraulic differential cylinder 2 is essentially connected directly to an adjustable pump 3.
• the differential volume flow is compensated for during delivery by the two unblockable check valves 7 and 8, the unblocking connections of which are alternately connected to the opposite or adjacent sides of the high pressure circuit by an electrohydraulic 4/2-way valve 10.
• an electrohydraulic 4/2-way valve 10 To protect the system from overpressures, two high-pressure safeguards 27 are provided.
• the integrated electronic control device 14 controls the control of the individual components, such as the adjustable pump 3, taking into account the measured system states and the user specifications 15.
• the second side of the differential cylinder 2 can also be shut off by an electronically controllable shut-off valve 17.
• an additional differential cylinder 19 is located on two further electronically controllable shut-off valves 18 High pressure circuit connected.
• the first differential cylinder 2 is separated from the hydraulic circuit by the two shut-off valves 11 and 17 and is thereby held in its position. Then the two shut-off valves 18 are opened so that a volume flow required by the pump 3 moves the second differential cylinder 19.
• the differential volumes that occur are compensated again via the two unlockable check valves 7 and 8 in the low-pressure circuit 9.
• the controllable shut-off valves 11, 17 and 18 can, in some applications, also be designed as continuous valves, so that they can be controlled continuously in special situations during operation and thus simultaneous operation of the two differential cylinders 2 and 19 is possible.
• the low pressure in the low pressure system 9 is realized with an accumulator charging circuit.
• a constant pump 20 with an accumulator charging valve 21 and a hydropneumatic accumulator 22 is used.
• a pressure relief valve 23 protects the system against overload.
• the accumulator loading valve 21 ensures that the constant pump 20 only delivers into the low-pressure system 9 when the pressure falls below a set minimum value. Since the accumulator charging valve 21 ensures pure pressure maintenance, the system can be implemented in an energy-efficient manner.
• other combinations for realizing the low pressure system 9 are also possible, for example via a simple combination of a constant pump, accumulator and pressure relief valve or by means of a variable displacement pump.
• This low pressure is also used behind the connection 24 of the adjustable pump 3 to operate the electro-hydraulic adjustment system of this pump.
• the connections 25 and 26 are used to connect a passive vibration damper system. stems on the differential cylinder 2.
• FIG. 3 shows a first modification of the basic principle, in which two 3/2-way valves 28, 29 are used instead of the electrohydraulic 4/2-way valve in order to realize the floating position by switching over the unlocking connections of the unlockable check valves 7, 8 , Furthermore, the low pressure is now applied via a constant pump 20 with a hydropneumatic accumulator 22 and a pressure relief valve 23.
• 4 shows a further modification of the basic principle.
• the floating position is achieved via a bypass by two valves 30, 31, i.e. when the valves are energized, the two cylinder chambers are connected to the low pressure and the differential cylinder 2 can move freely.
• the low pressure is impressed here via a variable displacement pump 20 'with a hydropneumatic accumulator 22 and secured by a pressure relief valve 23.
• this diagram also shows another possibility of supplying the third function with the pump 3.
• Two 3/2-way valves 32, 33 at connections 34, 35 can simply switch the pump 3 to the third function when activated.
• FIG. 5 shows an overall system for a mobile working machine (here wheel loader) with displacement-controlled working hydraulics according to the previously described displacement-controlled linear drive principle (valveless principle) and hydrostatic travel drive.
• the simple coupling of several actuators via the low pressure and with the hydrostatic travel drive further reduces the system effort.
• FIG. 6 shows a further overall system (here wheel loader), a hydrostatic travel drive in the 2-motor concept with a detachable adjustment motor being present and the low pressure for all displacement-controlled ones Main functions are impressed by the return of the hydrostatic fan and a memory.
• An accumulator charging valve connects the return of the fan to the low pressure only when low pressure volume flow is required.
• the electro-hydraulic control of the adjustable pump 3 can be used to implement all other functionalities that are stored in the software, such as fork parallel guidance, automatic feedback control, end of stroke shutdown, variable blade stop, variable cylinder damping (soft dust), shaking or distribution functions on the blade for agricultural engineering Inserts etc.
• the respective variable pump is addressed directly via the control of the device.
• the displacement-controlled actuator can be operated both in position and speed control (example: parallel tool guidance) or in a controlled manner in an open control loop.
• the control processes the operator's request as an input signal (for example via a joystick).

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Fluid-Pressure Circuits (AREA)
• Servomotors (AREA)
• Valve Device For Special Equipments (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=32730591

Family Applications (1)

Country Status (6)

Cited By (2)

Families Citing this family (33)

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• 2003
  • 2003-01-29 DE DE10303360A patent/DE10303360A1/de not_active Withdrawn
• 2004
  • 2004-01-14 DE DE112004000521T patent/DE112004000521D2/de not_active Withdrawn - After Issue
  • 2004-01-14 ES ES04701896T patent/ES2285408T3/es not_active Expired - Lifetime
  • 2004-01-14 AT AT04701896T patent/ATE358777T1/de not_active IP Right Cessation
  • 2004-01-14 EP EP04701896A patent/EP1588057B1/fr not_active Expired - Lifetime
  • 2004-01-14 WO PCT/DE2004/000032 patent/WO2004067969A1/fr active IP Right Grant
  • 2004-01-14 US US10/544,000 patent/US7543449B2/en not_active Expired - Fee Related
  • 2004-01-14 DE DE502004003395T patent/DE502004003395D1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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