Electro-hydraulic linear amplifier

Abstract

Electro-hydraulically proportional controllable linear amplifier with a cylinder (21) and a piston (22) slidably mounted therein with piston rod (23), wherein the piston (22) divides the cylinder interior into a piston chamber (24) and a piston rod chamber (25), wherein the force difference of an actual value force, formed by a measuring spring (30), to a setpoint force, formed by a linear actuator, actuates the control slide of a control valve (35; 71) as a control signal, characterized in that the control loop for controlling the force balance and thus the position of the path, is separated into a mechanical-hydraulic signal circuit (30, 35, 37; 30, 71, 72) and a hydraulic power circuit (40; 73).

Description

[0001] The invention relates to an electro-hydraulically, proportionally controllable linear amplifier with internal force compensation, according to the preamble of patent claim 1.

[0002] DE 10 2004 014 293 A1, 'adjustment unit', is proposed for the first time by means of a tension spring arranged in the hollow piston rod and a proportional magnet arranged directly on the cylinder assembly, wherein on the one hand one end of the tension spring and on the other hand the proportional magnet armature are non-positively coupled directly via the control slide of a hydraulic control valve and form a closed control arrangement via force comparison in such a way that by means of a current setpoint fed to the proportional magnet and the resulting increase in magnetic force, the stroke position of the piston rod is changed and the tensile force of the tension spring force is continuously increased by the piston rod driving the second end of the tension spring along with it, until the force balance: magnetic force = tension spring force is reached and the control valve closes again and thus ends the piston rod movement at the travel position selected in accordance with the current setpoint.This arrangement thus enables a proportional cylinder stroke depending on an electrical current signal, without complex electrical position measuring devices and control electronics.

[0003] A significant further development, based on the same basic principle of mechanical force comparison, but with a fully integrated proportional magnet and direct adjustability of the measuring spring, is the disclosure according to DE 10 2007 048 907 A1. This proposal shows a compact and environmentally insensitive design of an electro-hydraulic proportional actuation unit, commonly referred to as a proportional cylinder, for work machines of all kinds.

[0004] Due to the variety of possible and desired applications, the proposal in DE 10 2008 012 143 A1 is a new arrangement of the functional chain that differs from the previous versions: 'Ranging spring - control valve - linear actuator' in the cylinder axis.

[0005] By expanding the functional chain to include an additional means of transmitting the actual force value, e.g., in the form of a bell crank, the functional chain can penetrate the outer diameter of the working cylinder in such a way that its "control valve - linear actuator" component can be arranged parallel to the axis but outside the projection area of ​​the cylinder's inner diameter, and the measuring spring remains in the cylinder axis. The basic principle: Mechanical force comparison between the actual value spring and the target value specified by the proportional magnet is maintained.

[0006] What all three versions described have in common is the use of the linear actuator as a single-acting proportional magnet, which predetermines two basic positions of the proportional cylinders: retracted when de-energized, extended when fully energized.

[0007] A further proposal according to DE 10 2012 010 726 A1, using a double-acting proportional magnet as a linear actuator, presents a solution for a de-energized intermediate position of the partially extended piston rod while maintaining the same principle of mechanical force comparison in the energized operating state. In the functional chain, which has been expanded by one element compared to the previously known one, an auxiliary spring is connected to the tension measuring spring at a coupling point, the force balance of which determines an intermediate travel position in the de-energized state.

[0008] All four described proposals represent self-contained linear proportional hydraulic actuators, from which the abbreviation "AlphAktor" is derived. This has since become an independent, short designation for this new design, thus expanding the state of the art. The generally known state of the art beyond this is documented in detail in the cited publications and therefore need not be further elaborated upon here.

[0009] What all AlphActuators known to date have in common is that, in the described functional chain between the setpoint value (force of the linear actuator) and the actual value (spring force), a 3 / 2 or 4 / 3 control valve compensates for the control deviations by corresponding opening or closing movements on the assigned control edges until force equilibrium between setpoint value force = spring force is reached and thus the selected travel position of the piston rod. The fluid flow rates required for this are determined by the cylinder dimensions of the AlphActuators and the required actuating speeds, whereby the pressure drop across the control edges can vary greatly depending on the operating states of the AlphActuator. The flow forces acting on the control spool are the determining disturbance variables in the control loop of the hydraulic-mechanical control of the AlphActuator and increase with increasing flow rate and increasing pressure drop.The available force of the proportional magnet used as a linear actuator, as a variable control variable, depends on its installation volume and thus limits the maximum possible performance data of the AlphActuator. However, the diverse applications to date have resulted in a demand for expanding the application areas for AlphActuators in terms of larger dimensions, strokes, and increased dynamics.

[0010] An increase in the force of the measuring spring would be possible, but an increase in the magnetic force, while maintaining the installation volume, is limited by natural laws and, if all optimization possibilities regarding magnetic materials and packing densities are exploited, would mean considerable cost increases with a disproportionately small increase in force.

[0011] The present invention is based on the object of designing an electro-hydraulic linear amplifier of the type AlphAktor mentioned at the beginning in such a way that it achieves significantly higher performance data on the hydraulic side with comparable forces of the linear actuator.

[0012] This problem is solved with the features of claim 1.

[0013] The main feature of the invention is that the control circuit for controlling the force balance and thus the travel position is separated into a mechanical-hydraulic signal circuit and a hydraulic power circuit.

[0014] Furthermore, the solution to the problem is that the force balance between the force setpoint and the measuring spring actual value is regulated exclusively via the control valve as a pilot valve and the main fluid flow flows into or out of the cylinder chambers exclusively via the power stage hydraulically connected downstream of the control valve.

[0015] For Alph actuators with two basic positions, a 3 / 2 pilot control valve is preferably provided in the signal circuit.

[0016] For Alph actuators with three basic positions, a 4 / 3 pilot control valve is preferably provided in the signal circuit.

[0017] A particularly advantageous, compact embodiment of the invention is that the signal circuit control valve and the power valve form a functional unit with the same center axis.

[0018] Further advantageous developments of the invention are listed in further subclaims.

[0019] With this invention, the areas of application and possible uses of the previously known AlphActuators are significantly expanded, especially in higher performance ranges, with otherwise the same advantages of the compact design, without electrical displacement measurement and without control electronics, in a robust and environmentally insensitive, closed design

[0020] The protected installation and the compact and closed arrangement of the other components as well as the comparatively small number of parts ensure a high level of operational reliability and prevent corrosion and contamination of the functional parts, even when installed in or on mobile work machines, and thus represent an extremely cost-effective solution, in terms of overall costs, for proportional adjustments of machine functions.

[0021] Further advantages and embodiments of the invention will become apparent from the following description and the drawings. Likewise, the above-mentioned and further listed features can be used individually or in combinations according to the invention. The embodiments shown and described are not to be understood as an exhaustive list, but rather are exemplary in nature for the

[0022] Description of the invention. Proportional solenoids are preferred as linear actuators, but this does not preclude the use of alternative linear actuators with proportional action.

[0023] They show: Fig. 1 Circuit diagram for a first embodiment of the invention. Fig. 2 Simplified partial section of the circuit diagram according to Fig. 1. Fig. 3 Circuit diagram for another embodiment of the invention.

[0024] Fig. Figure 1 shows, in an abstract circuit diagram, the inventive further development of an AlphActuator with two basic positions. The AlphActuator 1 is a self-contained, autonomous functional and structural unit and comprises the actual cylinder unit 20 with the cylinder 21 and the piston 22 slidably mounted therein with the piston rod 23 as a functional unit. The piston 22 divides the cylinder interior into a piston chamber 24 and a piston rod chamber 25. The geometric dimensions of the cylinder unit 20 depend on the planned application in order to be able to transfer the predicted forces and strokes H of the piston rod to the outside. The requirements can vary greatly, and thus also the sizes to be realized for the cylinder unit 20.In the hollow, but outwardly closed, piston rod 23, a tension spring 30 is fastened as an actual force value transmitter with one end 31 thereof inside the piston rod 23 in a manner known for Alpha actuators, such that the tension of the tension spring changes as a function of the stroke H and enables an evaluable 'force information' about the actual stroke value of the piston rod 23 at the opposite, second tension spring end 32, which is independent of the stroke H.

[0025] The second tension spring end 32 is connected via the force-locking connection 33 to the first end of the control slide 34 of a 3 / 2-way control valve 35. The second, opposite end of the control slide 34 of the 3 / 2-way control valve 35 is in turn connected via a force-locking connection 36 to the magnet armature of a

[0026] Proportional pull magnets 37 are connected. These non-positively connected components 30...37 thus form the functional chain 'range spring 30 - control valve 35 - proportional magnet 37' that forms the system for Alph actuators.

[0027] Another 3 / 2-way valve 40 is hydraulically connected downstream of the control valve 35.

[0028] The inlet-side working ports P and T of the 3 / 2-way valve 40 are hydraulically connected to a pressure source 50 via the external pressure port 51 and to a fluid container 60 via the external tank port 61. Internally, the piston rod chamber 25 is continuously connected to the pressure port P via the connecting line 52. The piston chamber 24 is controlled by the 3 / 2-way valve 40 via the connecting line 41 and the working port A. The 3 / 2-way valve 40 is a hydraulically pilot-controlled directional valve, as known to those skilled in the art, which is controlled by the 3 / 2-way control valve 35 via the control line 34.1 and follows the control movements of the 3 / 2-way control valve 35, which is symbolically represented in the circuit diagram by the functional connection 42. The fluid pressure supply of the 3 / 2 control valve 35 is via the control line 34.2 for the pressure and the control line 34.3 to the tank return.

[0029] The circuit diagram of the Fig. 1 is usually shown in the currentless basic position of the AlphAktor according to the invention, the piston bottom chamber 24 is relieved via the 3 / 2-way valve 40 to the tank connection 61, i.e. pressureless, which results from the basic position of the 3 / 2-way control valve 35 since the control line 34.1 is also connected to the tank connection 61 via the 3 / 2-way control valve 35 and thus only the lowest possible pressure (tank pressure) acts on the control side at the 3 / 2-way valve 40.

[0030] If the proportional magnet 37 is energized with a setpoint current, e.g. with half the max. setpoint current, the magnetic force predominates over the force of the tension spring 30, whereby the control slide 34 of the control valve 35 is shifted to the left and control pressure builds up from the supply 34.2 via the control line 34.1 to the control surface of the 3 / 2-way valve 40 until the 3 / 2-way valve 40 finally establishes a fluid connection from the pressure source 50 via the connecting line 41 to the piston chamber 24. Due to the fluid flow into the piston chamber 24, the piston 22 with the piston rod 23 moves to the right, which increases the tension of the tension spring 30 and thus also the force at the tension spring end 32.At half the total stroke H / 2, the tension spring force becomes equal to the current magnetic force, whereby the control slide 34 is again moved far enough to the right into a control closing position so that the control pressure build-up at the downstream 3 / 2-way valve 40 also brings this valve into a control closing position and ends the piston movement at H / 2.

[0031] If the setpoint current at the proportional solenoid 37 is reduced again in the reached stroke position, e.g., H / 2, the functional sequences run in the reverse direction, so that the fluid flows back from the piston chamber 24 via the 3 / 2-way valve 40 into the tank 60. Due to the constant pressure supply to the piston rod chamber via the connecting line 52, the volume compensation on the rod side takes place automatically.

[0032] From the circuit diagram Fig. 1, the main feature of the invention is clearly visible since, in the functional chain 'range spring (30) - control valve (35) - proportional magnet (37)', the control valve 35 only processes control signals (control pressure) of the control deviation between the magnet setpoint and the range spring actual value, and the fluid power flow to or from the cylinder 20 is controlled or regulated exclusively via the downstream 3 / 2-way valve 40 - this can also be seen symbolically in the exclusively dashed line lines (fluid control lines) to or from the 3 / 2-way control valve 35 and the solid line lines (fluid main lines) to or from the working cylinder 20. This separation into signal circuit and power circuit ensures that the actuators or control elements of the controlled system directly involved in the path adjustment are decoupled from the disruptive flow forces of the main fluid flow.

[0033] A circuit diagram Fig. 1 corresponding, but less abstract representation of the invention shows the Fig. 2. The same reference numerals are used for equivalent functional parts. The AlphAktor 1 is shown here in two main assemblies, a cylinder unit 20 and a valve unit 11 with integrated or attached proportional magnet 37. The cylinder unit 20 is fundamentally unchanged from Fig. 1, but with symbolic addition of the piston and piston rod seals. Not shown, but intended, is a seal 7 / 16 outwards between cylinder unit 20 and valve unit 11. The valve unit 11 shows a proposal according to the invention with the integration of the 3 / 2-way control valve 35 into the 3 / 2-way valve 40, marked 40+35, whereby a very compact arrangement is achieved. The control slide 34 of the control valve 35 slides in a control bushing 42.1, which Fig. 1, corresponds to the effective connection 42. Radial openings in the control sleeve 42.1 form the control line 34.2 for supplying the control pressure to the 3 / 2-way control valve 35 and are fed from the annular channel 12, which also simultaneously represents the working connection P of the 3 / 2-way valve 40. The tank connection T is located opposite the spring chamber 43 of the 3 / 2-way valve 40. The connecting line 34.3 in the control sleeve 42.1 to the spring chamber 43 corresponds to the control pressure line 34.3 of the 3 / 2-way control valve 35 to the tank 60. The control spool 34 forms two inner control edge pairs with the control sleeve 42.1, namely the control edge pair 38 on the P side and the control edge pair 39 on the T side. When the control edge pair 38 is open, the control fluid flows from P via the annular channel 34.11 into the control chamber 44; when the control edge 39 is open, the control fluid flows from the control chamber 44 to the tank T via the control line 34.12 running in the slide axis of the control slide 34.The control sleeve 42.1 also forms two control edge pairs on the outer diameter with the annular channel 13 in the housing of the valve unit 11, namely pair 45 on the P side and pair 46 on the T side. The annular channel 13 corresponds to the working port A and has a hydraulic connection to the piston chamber 24 via the fluid line 41. The connection 41.1 serves only to equalize the pressure for the control spool 34. The design of the spring 47 determines the effective control pressure level for the 3 / 2-way valve 40 such that the actuating forces on the control sleeve 42.1 are several times greater than the actuating force of the proportional solenoid 37 in order to control the flow forces in the power section of the control circuit of the AlphaActuator 1 without having a negative effect on the signal circuit.

[0034] If the proportional magnet 37 is energized with a setpoint current, e.g. with half of the max. setpoint current, the magnetic force prevails over the force of the tension spring 30, whereby the control slide 34 of the control valve 35 is displaced to the left, the control edge pair 38 opens, whereby control pressure flows from the P-supply 34.2 via the annular channel 34.11 into the control chamber 44 and

[0035] Pressure builds up on the front control surface 44.1 of the 3 / 2-way valve 40 and the control sleeve 42.1, following the control spool 34, is also displaced to the left, whereby the outer control edge pair 45 opens and establishes a fluid connection from the annular channel 12 to the annular channel 13, and thus the pressurized fluid flows from the pressure source 50 via P and ultimately via the line connection 41 into the piston chamber 24. Due to the fluid flow into the piston chamber 24, the piston 22 moves with the piston rod 23 to the right, which increases the tension of the tension spring 30 and thus also the force at the tension spring end 32. At half the stroke H / 2, the actual tension spring force becomes equal to the current solenoid target force, whereby the control spool 34 moves far enough to the right again into a closed position at the control edge pair 38 opposite the control sleeve 42.1 is shifted so that the control pressure in the control pressure chamber 44 is reduced again, whereby the outer control edge pair 45 also comes into the closed position and the piston movement is thus ended at H / 2.

[0036] If, in the stroke position reached, e.g. H / 2, the setpoint current at the proportional magnet 37 is reduced again, the functional sequences run in the opposite direction, so that the fluid flows back from the piston chamber 24 via the 3 / 2-way valve 40 into the tank 60. The inner control edge pair 39 opens and relieves the control pressure chamber 44 to the tank pressure T, so that the control sleeve 42.1, which follows the control slide 34, also opens the outer control edge pair 46 to the return flow T, whereby the pressure fluid can flow out of the piston chamber 24 and the piston moves to the left until the again reduced tension spring force is equal to the reduced magnetic force and the movement comes to a standstill.

[0037] According to the invention, the fluid inflow or outflow to or from the cylinder 20 takes place exclusively via the power section 42.1 of the control valve combination 40+35 and thereby decouples the signal section 30 - 34 - 37 from the flow forces in the power circuit.

[0038] The inventive concept is also applicable to the AlphAktor version with currentless intermediate position, a design proposal shows the Fig. 3.

[0039] The cylinder unit 20 of the AlphAktor 2 is unchanged with the tension measuring spring 30, the force measuring side 32 of which is however coupled to the free end of another compression spring 70, whereby the resulting force from the addition or subtraction of both spring forces is transmitted as an actual value force via the mechanical tension / compression connection 32.1 and the slide of the 4 / 3 control valve 71 to the double-acting proportional magnet 72 and in the functional chain 'Ranging spring (30) - control valve (71) - proportional solenoid (72)' is evaluated for control purposes. Since this arrangement allows three basic positions of the AlphaActuator 2, the control valve 71 must also be a 4 / 3 valve and, consequently, the proportional solenoid 72 must also be double-acting with two solenoid windings a and b.

[0040] According to the invention, a 4 / 3-way valve 73 is hydraulically connected or coupled to the 4 / 3-way control valve 71 via the operative connection 74, so that the 4 / 3-way valve 73 directly follows the control movements of the 4 / 3-way control valve 71. The working port A of the 4 / 3-way valve 73 is connected to the piston crown chamber 24 via the fluid line 73.1 and the working port B is connected to the piston rod chamber 25 via the fluid line 73.2. On the input side, the 4 / 3-way valve 73 is hydraulically connected to the pressure source 50 and to the tank 60 in a known manner, as is the 4 / 3-way control valve 71 via the control lines 71.3 to P and 71.4 to T. The working port a of the 4 / 3-way control valve 71 is connected to the control pressure chamber 73.6 of the 4 / 3-way valve 73 via the control line 71.1 and the working port b is connected to the opposite control pressure chamber 73.5 via the control line 71.2.

[0041] In the shown, currentless basic position of the AlphActuator 2, the actual stroke position results from the ratio of the spring forces of springs 30 and 70. If the compression spring 70 is designed with half the spring force of the max. force of the measuring spring 30, then at H / 2 the resulting measuring force at the coupling point 32 = 0 N and the piston rod 23 has its basic operational position at H / 2 in this case.

[0042] When the magnetic winding a of the proportional magnet 72 is energized with a setpoint current, the 4 / 3-way control valve 71 is pulled in the direction of the switching position I, whereby the control pressure chamber 73.5 is pressurized with control pressure via the control line 71.2, whereby in turn the 4 / 3-way valve 73 is also moved to its switching position I and thereby the fluid flow from P via the

[0043] Fluid line 73.1 introduces into the piston chamber 24 of the cylinder 20, at the same time the piston rod chamber 25 is connected to the tank 60 via the fluid line 73.2 and the 4 / 3-way valve 73, so that the fluid in the piston rod chamber 25 can flow away. The inflowing fluid quantity moves the piston 22 with the piston rod 23 to the right, so that the stroke H increases and thus also the force of the measuring spring 30 due to the increasing tension. The piston rod 23 extends until force equilibrium is reached between the currently specified magnet target force and the resulting actual force increased by the stroke at the coupling measuring point 32, whereby the 4 / 3 control valve 71 is returned to its control center, corresponding to switching symbol 0, and as a result the 4 / 3-way valve 73, which inevitably follows the 4 / 3 control valve 71, also ends the inflow or outflow into or from the cylinder 20 in its switching position 0.As long as the setpoint current remains unchanged, the corresponding piston rod position H-IST also remains, regardless of external force acting on the piston rod 23, since the slightest change in the length of the tension measuring spring 30 disturbs the equilibrium and the mechanical-hydraulic control chain restores force equilibrium. If the setpoint current at the proportional solenoid 37, winding a, is reduced, the functional sequences run in the opposite direction, so that the 4 / 3-way valve 73 in switching position II reverses the fluid flows and fluid flows from P into the piston rod chamber 25 and on the opposite side flows back from the piston chamber 24 to the tank 60 until force equilibrium is reached again.

[0044] As can be seen from the description and illustration in Fig.As can be seen from Figure 3, the control arrangement is composed of the two corresponding functional units according to the invention in order to free the actual control chain from the flow forces acting as a disruptive force. This can be seen in the circuit diagram from the fact that the actual control valve 71, in the functional chain 'range spring (30) - control valve (71) - proportional solenoid (72)', is hydraulically connected only to control lines 71.1...71.4 (dashed lines), and that the hydraulically pilot-controlled 4 / 3-way valve 73, through which the larger fluid quantities flow to / from the cylinder, is hydraulically connected to the main lines 73.1, 73.2 (solid lines). The hydraulic pilot control enables higher actuation forces to be realized on the 4 / 3-way valve 73, which are not possible purely electromagnetically with a comparable installation space.

Claims

[1] Electro-hydraulically proportionally controllable linear amplifier with a cylinder (21) and a piston (22) with a piston rod (23) mounted therein so as to be displaceable, the piston (22) dividing the cylinder interior into a piston chamber (24) and a piston rod chamber (25), the force difference between an actual value force, formed by a measuring spring (30), and a setpoint force, formed by a linear actuator, actuating the control slide of a control valve (35; 71) as a control signal, characterized by that the control circuit for controlling the force balance and thus the travel position is separated into a mechanical-hydraulic signal circuit (30, 35, 37; 30, 71, 72) and a hydraulic power circuit (40; 73). [2] Electrohydraulically proportionally controllable linear amplifier according to claim 1, characterized bythat the force balance between the force setpoint (37, 72) and the measuring spring actual value (30) is regulated exclusively via the control valve (35, 71) as a pilot valve and the main fluid flow flows into or out of the cylinder chambers (24, 25) exclusively via the power circuit (40, 73) hydraulically connected downstream of the control valve (35, 71). [3] Electrohydraulically proportionally controllable linear amplifier according to claim 1 or 2, characterized by that the control valve in the mechanical-hydraulic signal circuit is a 3 / 2 control valve (35) and the hydraulically downstream power valve is a 3 / 2 directional control valve (40). [4] Electrohydraulically proportionally controllable linear amplifier according to claim 1 or 2, characterized by that the control valve in the mechanical-hydraulic signal circuit is a 4 / 3 control valve (71) and the hydraulically downstream power valve is a 4 / 3 directional control valve (73). [5] Electrohydraulically proportionally controllable linear amplifier according to one of claims 3 or 4, characterized by that the signal circuit control valve (35, 71) and the power valve (40, 73) form a functional unit (40, 35; 71,73) with the same center axis. [6] Electrohydraulically proportionally controllable linear amplifier according to one of claims 1 to 5, characterized by that the actual value measuring spring (30) can be adjusted from the outside.

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