Method for controlling the operating state of a hydraulic actuator of a tamping unit of a track construction machine and track construction machine for implementing the method

Abstract

Method for controlling the operating state of a hydraulic actuator (7), which as part of a working unit (4) of a construction machine (14) provides movable mechanical unit components, in particular a tool holder or a tool (6), and whose pressure chambers with their working ports (A, B) are connected to the piping system of a hydraulic circuit by means of at least one control valve (1, 12a, 12b, 12c, 12d, 12e), wherein on the one hand the operating state is maintained when the pressure chambers of the actuator (7) are completely separated from the piping system of the hydraulic circuit by means of the at least one control valve (12a, 12b, 12c, 12d, 12e) and on the other hand a change in the operating state is effected by means of a pulsed control of the at least one control valve (12a, 12b, 12c, 12d, 12e).

Description

[0001] The invention relates to a method for controlling the operating state of a hydraulic actuator, which, as part of a working unit of a construction machine, in particular a tamping unit of a track construction machine, provides movable mechanical unit components, in particular a tool holder or a tamping tool, and whose pressure chambers with their working connections are connected to the piping system of a hydraulic circuit by means of at least one control valve.

[0002] In the prior art, hydraulic actuators are operated using proportional spool valves. Leakage losses are unavoidable with this method. To maintain an operating state of the actuator, such as the piston stroke of a cylinder, in order to clamp a mechanical component, particularly a tamping tool or tamping pick, in a specific position, additional valves, typically unlockable check valves, must be installed in the hydraulic actuator's connecting lines. Controlling these proportional valves requires complex control systems and is usually expensive.

[0003] DE 103 15 460 A1 discloses a valve arrangement with at least two 2 / 2-way valves and a control unit, wherein the 2 / 2-way valves are designed as fast-switching plate armature valves with switching speeds of less than 5 ms, preferably less than 1 ms, and are grouped side by side in a row to form a block and are connected to a channel in such a way that a single supply is provided for the medium that is distributed by the valve unit.

[0004] In a disclosed advantageous application of the valve arrangement, the piston of a pneumatic cylinder can be displaced in its position due to the control of the valves.

[0005] To keep the piston in a position inside the pneumatic cylinder, the valves of the valve assembly are alternately actuated at a high frequency.

[0006] The speed of the moving piston can be changed by altering the pulse width of the signals that control the valves.

[0007] WO 2020 / 052879 A1 discloses a method and a device for tamping under the sleepers of a railway track.

[0008] A tamping unit comprises at least two tamping units, each with opposing tamping tools mounted on a lowerable tool carrier, which are subjected to vibration during the tamping process, lowered into a gravel bed and positioned relative to each other via auxiliary drives.

[0009] To tamp sloping sleepers, such as those used in the area of ​​turnouts, the tamping tool pairs are moved with different adjustment paths in the approach direction to adapt to the slope of the sleeper.

[0010] EP 2 650 549 A2 discloses an electrohydraulic arrangement, a method for controlling the electrohydraulic arrangement and a mobile working machine with the electrohydraulic arrangement.

[0011] The electro-hydraulic arrangement is in particular a steering device which has an actuator, in particular in the form of a steering cylinder.

[0012] To adjust the actuator, a first connection of the actuator can be connected to a pressure medium supply, in particular in the form of a hydraulic pump, via a first supply line and a second connection of the actuator via a second supply line, and the first connection can be connected to a pressure medium sink via a first return line and the second connection via a second return line.

[0013] In the respective supply line and in the respective return line, a valve group with a plurality of fluidically parallel valves is arranged for controlling a pressure medium flow, wherein a sensor determines a position value, in particular an adjustment position, of the actuator and reports it to a control device.

[0014] The actuator is controlled by means of the effective free flow cross-section of the valves, based on a control difference between a given setpoint and the determined actual position.

[0015] The invention is based on the objective of providing an improvement over the prior art for a method of controlling the operating state of a hydraulic actuator of the type mentioned above. A further objective of the invention is to provide an arrangement suitable for carrying out this method.

[0016] According to the invention, these problems are solved by a method according to claim 1 and an arrangement for carrying out this method according to claim 10. Dependent claims specify advantageous embodiments of the invention.

[0017] In its basic embodiment, the invention relates to a method for controlling the operating state of a hydraulic actuator, which, as part of a working unit of a construction machine, in particular a tamping unit of a track laying machine, comprises movable mechanical unit components, especially a tool holder or a tool, and whose pressure chambers with their working ports are connected to the piping system of a hydraulic circuit by means of at least one control valve. On the one hand, the operating state is maintained by means of the at least one control valve when the pressure chambers of the actuator are completely separated from the piping system of the hydraulic circuit, and on the other hand, a change in the operating state is effected by means of a pulsed actuation of the at least one control valve. In this way, proportional valves with their associated disadvantages are not required.Instead, poppet valves are used, which are controlled in a pulsed manner and do not cause any leakage oil losses when disconnected from the hydraulic system.

[0018] An advantageous embodiment of the method according to the invention provides that the pressure fluctuations in the independent pressure controls of the working connections of the pressure chambers of the actuator are dampened by compensating movements through at least one hydraulic accumulator connected to the working connections of the actuator or to the hydraulic piping system.

[0019] It is advantageous for the procedure that the rate of change of the operating state is determined by the clock ratio of the control signal of at least one control valve.

[0020] The clock ratio is the ratio of the duration TA of a signal level of the control signal, which switches a control valve from a passive home position to an active position and keeps it in this position, to the duration TP in which the signal level of the control signal does not result in any change to the passive home position of the control valve.

[0021] Alternatively, the duty cycle is the ratio of the duration TA of a signal level of the control signal, which switches a control valve from a passive home position to an active position and keeps it in this position, to the sum of the total duration TA + TP, which is composed of the above duration TA and the duration TP, in which the signal level of the control signal does not result in any change to the passive home position of the control valve.

[0022] In a particularly advantageous embodiment of the method for controlling the operating state of the hydraulic actuator, the clock rate of the control signal of the control valves is set as a function of the characteristic parameters of the working unit, such that the change in the operating state occurs quasi-continuously over time.

[0023] An example of a characteristic physical quantity of the working unit is the mass of the unit.

[0024] The clock rate f T is the reciprocal of the sum TA + TP, which is composed of the time period TA, during which a control valve is in an active switching position, and the time period TP, during which the control valve is in the passive switching position.

[0025] For the method of controlling the operating state of a hydraulic actuator, it is advantageous if a control valve, which is connected via a connecting line to a first working port of the hydraulic actuator, and another control valve, which is connected via another connecting line to a second working port of the hydraulic actuator, are controlled simultaneously.

[0026] In a further advantageous embodiment of the method, the actuator in the hydraulic piping system can be bypassed by means of a bypass circuit through the control of the control valves.

[0027] In one possible embodiment of the method for controlling the operating state of the actuator, the operating state is characterized by the angle that a movable part of a tamping tool, in particular a tamping pick, of a tamping unit of the track construction machine assumes with respect to a rest position.

[0028] In a further embodiment of the method for controlling the operating state of a hydraulic actuator, the operating state is characterized by the stroke that a piston of the auxiliary cylinder of a tamping unit of a track construction machine assumes with respect to a starting position. In an alternative embodiment of the method for controlling the operating state of the hydraulic actuator, the operating state is characterized by a stroke that a piston of the translationally acting hydraulic cylinder of a lifting unit of a track construction machine assumes with respect to a home position.

[0029] The control valves in the track construction machine for carrying out the above-mentioned procedure are designed as poppet valves to avoid leakage oil losses.

[0030] In one embodiment of the invention, at least one 4 / 3 way seat valve is used.

[0031] A 4 / 3 way seat valve is characterized by four ports, arranged as two inputs and two outputs, and by the three defined switching positions: (1) no connections between both inputs and both outputs, (2) connection between the first input and the first output and the second input and the second output, and (3) connection between the first input and the second output and the second input and the first output.

[0032] It is particularly advantageous if at least two 2 / 2-way seat valves are used per pressure chamber of the hydraulic actuator, as this decouples the control edge of the hydraulic actuator from the control system with at least one 4 / 3-way seat valve.

[0033] A 2 / 2-way seat valve is characterized by two ports, one arranged as an inlet and one as an outlet, and by two defined switching positions: (1) no connection between inlet and outlet and (2) connection between inlet and outlet.

[0034] Both 4 / 3 way valves and 2 / 2 way valves in seat design are available from various valve manufacturers such as Parker, Rexroth, HAWE, Hydac or Bucher under the designations Parker GS02, Rexroth SEC, HAWE NBVP, Hydac WSM or Bucher WS22.

[0035] An alternative design of the control valve arrangement provides that each control valve consists of at least two parallel-connected valves, either to be able to control larger volume flows of the hydraulic medium or to increase the reliability of the valve arrangement.

[0036] The invention is explained below by way of example with reference to the accompanying figures. These show, in schematic representation: Fig. 1 A proportional slide valve with two unlockable check valves according to the prior art; Fig. 2 A side view of a switch tamping unit with upwardly pivoting tamping tools; Fig. 3 A simplified detail view of Fig. 2 Fig. 4 A schematic representation of Fig. 3 , illustrating the pivoting of the tamping tool; Fig. 5 A tamping unit for the synchronous tamping of up to three sleepers, comprising three individual units with pivotable tamping tools as shown in Fig. 2 includes; Fig. 6a A schematic representation of the control according to the invention of a hydraulic actuator with four fast-switching on / off valves and two hydraulic accumulators; Fig. 6b Alternative 4 / 3 directional seat valve for the arrangement according to Fig. 6a ; Fig. 7 A construction machine on a track with tamping unit and lifting and aligning unit; Fig. 8 The top view of a switch arrangement as part of a track network.

[0037] Fig. 1 represents a state-of-the-art valve arrangement suitable for maintaining the operating state of a hydraulic actuator for a definable period of time.

[0038] A proportional slide valve 1 with three defined switching positions (1) no connections, (2) connection between the first inlet and the first outlet and the second inlet and the second outlet, and (3) connection between the first inlet and the second outlet and the second inlet and the first outlet is connected on the inlet side via a port P and a port T to a hydraulic piping system. Upstream of the working ports A and B of a hydraulic actuator (not shown), a releasable check valve 2a or 2b must be provided between the two outlets of the proportional slide valve to ensure the desired functionality. Without these check valves 2a and 2b, leakage would occur, causing the actuator to change its operating state when the pressure chambers are disconnected from the hydraulic system.

[0039] In Fig. 2 The application of the hydraulic actuator 7 in a tamping unit 4 for tamping a sleeper 9, which together with rails 8 forms a track grid supported on a ballast bed 10, is shown. The tamping unit 4 itself is connected to the machine frame 3 of a track construction machine and comprises a tamping tool with a pair of pivoting arms 5, to which a tamping pick is connected by means of the tamping pick holder 6. Via hydraulic actuators 7, which for this application are designed as translationally acting cylinders, the tamping picks, arranged in two rows with increasing distance from the rail, can be pivoted upwards via their tamping pick holders 6 to enable the use of the tamping tools adapted to the position of the rails 8 at turnouts.

[0040] In Fig. 3 is the stuffing unit of Fig. 2 simplified representation with the essential components for understanding the swiveling process, namely the U-shaped swivel arm 5, the tamping pick holder 6 with tamping pick and the hydraulic actuator 7.

[0041] The process of pivoting is in Fig. 4 illustrated by two schematic diagrams showing the arrangement of Fig. 3 was replaced by a combination of basic geometric-kinematic elements. The tamping pick holder 6 and the tamping pick are connected to the swivel arm 5 of the tamping unit 4 via a rotary bearing. The hydraulic actuator 7 is rotatably connected to the swivel arm 5 of the tamping unit 4 on one side and to the tamping pick holder 6 with the tamping pick on the other. In the initial position of the actuator 7's piston, the tamping pick holder 6 and the tamping pick are aligned parallel to the swivel arm 5 and can thus participate in the tamping process when the tamping unit 4 is lowered.

[0042] If the piston of the hydraulic cylinder is moved by a working stroke h relative to this initial position, the geometric arrangement of the components results in a pivoting of the tamping pick holder 6 and the tamping pick by an angle φ, whereby the tamping pick pivoted in this way is only available for use in the tamping process in this open position and is no longer available at all from a certain opening angle φ n.

[0043] Tamping with one or more tamping picks in the open position is particularly useful in tamping machines whose tamping units 4 cannot be moved horizontally or only to a limited extent, in order to achieve a significantly improved tamping result at turnouts.

[0044] Fig. 5 This represents a variant of the tamping unit 4, in which three identical tamping units 4A, 4B, and 4C, each with individually pivotable tamping pick holders 6 and tamping picks for tamping one sleeper 9 at a time, are arranged to form a combined unit 4 for the synchronous tamping of up to three sleepers 9 of a track grid supported on a ballast bed 10. Hydraulic actuators 7A are used to pivot the tamping picks, the positioning movement is carried out by means of the positioning cylinders 7B, and the lowering of each unit is effected by a hydraulic actuator 7C.

[0045] In Fig. 6a Figure 12 shows a variant of the valve arrangement 12a, 12b, 12c, and 12d, which allows the control of a hydraulic actuator 7, 7A, 7B, 7C according to the method of the invention. The hydraulic actuator 7, 7A, 7B, 7C is a translationally acting actuator with a piston that divides the cylinder pressure chamber into a piston-side pressure chamber and a rod-side pressure chamber. The working port A of the piston-side pressure chamber of the hydraulic actuator 7, 7A, 7B, 7C is connected to port T of the hydraulic piping system by means of valve 12a. Valve 12c, on the other hand, connects A to port P of the hydraulic piping system.

[0046] In contrast, valve 12b enables the establishment of a connection between the working port B of the rod-side pressure chamber of the hydraulic actuator 7 and the port T of the hydraulic piping system, while valve 12d is arranged for the connection of the working port B with the port P.

[0047] Additionally, hydraulic accumulators 13 are located between the pressure chamber connections A, B of the hydraulic actuator 7, 7A, 7B, 7C and the control valves 12a, 12b, 12c and 12d to reduce or prevent pressure fluctuations.

[0048] In Fig. 6a On / off valves, each with two ports and two distinct switching positions (1) and (2), are used as control valves 12a, 12b, 12c, and 12d. The passive default position (1) of such an on / off control valve 12a, 12b, 12c, or 12d disconnects its outlet from its inlet. When the on / off control valve 12a, 12b, 12c, or 12d is activated against a spring force by an electromagnetic actuator, the valve outlet is connected to the valve inlet in the active position (2) such that the hydraulic medium can act either statically or dynamically in the direction of the pressure chamber of the hydraulic actuator 7 as well as in the direction of ports P and T of the hydraulic piping system.

[0049] Fig. 6b shows a 4 / 3 way seat valve 12e as an alternative to the ones in Fig. 6a The 2 / 2 directional seat valves 12a-12d shown are replaced by a 4 / 3 directional seat valve 12e. However, this coupling reduces the flexibility in controlling the actuator 7. Specifically, it is not possible to simultaneously connect both working ports A and B of the pressure chambers to either port P or port T of the hydraulic piping system to perform functions such as positioning the actuator with both pressure chambers under pressure, moving the actuator without resistance in the float position, or purging the pressure chambers. It is also not possible to directly connect port P and port T to bypass the actuator and divert the hydraulic fluid.

[0050] In Fig. 7 A construction machine 14 is depicted on a track, its machine frame connected to a tamping unit 4 and a lifting and aligning unit 15. Analogous to the tamping unit 4, the lifting and aligning unit 15 also contains various hydraulic actuators 7 for performing mostly translational movements.

[0051] Fig. 8 Finally, a track switch arrangement consisting of rails 8 and sleepers 9 is shown as a section of a track network in plan view, with the switch being set by means of the switch setting device 16.

[0052] The subject matter of the invention is not limited to the embodiments shown. In particular, arrangements with at least one 4 / 3-way valve in seat configurations per hydraulic actuator, as well as those with parallel-connected valves per valve position, are also included by the claims.

Claims

1. A method for controlling the operating state of a hydraulic actuator (7) which, as part of a tamping unit (4) of a track construction and maintenance machine (14), sets movable mechanical unit components, in particular a tool holder or a tool (6), and whose pressure chambers are connected with their working connectors (A, B) to the line system of a hydraulic circuit via at least one control valve (1, 12a, 12b, 12c, 12d, 12e), characterized in that on the one hand, the operating state is maintained when the pressure chambers of the actuator (7) are completely separated from the line system of the hydraulic circuit by means of the at least one control valve 12a, 12b, 12c, 12d, 12e) and, on the other hand, a change in the operating state is effected by means of a clocked actuation of the at least one control valve (12a, 12b, 12c, 12d, 12e).

2. A method according to claim 1, characterized in that the pressure fluctuations in the pressure controls, independent of one another, of the working connectors (A, B) of the pressure chambers of the actuator (7) are damped by at least one hydraulic accumulator (13) connected to the working connectors of the actuator (7) or to the hydraulic line system through equalizing movements.

3. A method according to claim 1 or 2, characterized in that the time rate of the operating state change is determined by a clock ratio of an actuation signal of at least one control valve (12a, 12b, 12c, 12d, 12e).

4. A method according to claim 3, characterized in that a clock rate of the actuation signal of the control valves (12a, 12b, 12c, 12d, 12e) is set as a function of characteristic variables of the tamping unit (4), such as its mass, in such a way that the change in the operating state is quasi-continuous in time.

5. A method according to one of the claims 1 to 4, characterized in that the control valve (12a, 12c, 12e), connected to a first working connector (A) of the hydraulic actuator (7) via a connector line, and the other control valve (12b, 12d, 12e), connected to a second working connector (B) of the hydraulic actuator (7) via a further connector line, are actuated simultaneously.

6. A method according to one of the claims 1 to 4, characterized in that by actuating the control valves (12a, 12b, 12c, 12d), the actuator (7) in the hydraulic line system is bridged by a bypass circuit.

7. A method according to one of the claims 1 to 6, characterized in that the operating state is characterized by an angle (φ) that a movable part of a tamping tool (6) of the tamping unit (4) of the track construction and maintenance machine (14) assumes with respect to a rest position.

8. A method according to one of the claims 1 to 6, characterized in that the operating state is characterized by a stroke (h) that a piston of a squeezing cylinder (7B) of the tamping unit (4) of the track construction and maintenance machine (14) assumes with respect to a home position.

9. A method according to one of the claims 1 to 6, characterized in that the operating state is characterized by a stroke (h) that a piston of the translatorily acting hydraulic actuator (7C) of the lifting unit (15) of the track construction and maintenance machine (14) assumes with respect to a home position.

10. A track construction and maintenance machine (14) with a tamping unit (4) with movable mechanical unit components, in particular a tool holder or a tool (6), and at least one hydraulic actuator (7) including pressure chambers with attached control valves (1, 12a, 12b, 12c, 12d, 12e) and a line system of a hydraulic circuit for carrying out a method according to one of the claims 1 to 9, characterized in that each of the control valves (12a, 12b, 12c, 12d, 12e) is designed as a seat valve.

11. A track construction and maintenance machine (14) according to claim 10, characterized in that each pressure chamber is actuated by at least two control valves (12a, 12b, 12c, 12d) each, which are characterized by two connections each, which are arranged as an inlet and as an outlet, and by two defined switching positions: - no connection between inlet and outlet and - connection between inlet and outlet.

12. A track construction and maintenance machine (14) according to claim 10, characterized in that the pressure chambers are actuated by at least one control valve (12e), which is characterized by four connections each, which are arranged as two inlets and as two outlets, and by the three defined switching positions: - no connections between both inlets and both outlets, - connection between the first inlet and the first outlet and the second inlet and the second outlet, and - connection between the first inlet and the second outlet and the second inlet and the first outlet.

13. A track construction and maintenance machine (14) according to one of the claims 10 to 12, characterized in that each control valve (12a, 12b, 12c, 12d, 12e) consists of at least two valves connected in parallel.

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