DE102021207464A1 - Method of operating a hydraulic winch - Google Patents

Abstract

The invention relates to a hydraulic winch (10) with a parking brake (50), with pressurized fluid being supplied with a second hydraulic machine (40) which has a constantly adjustable second displacement volume. According to the invention, pressure control is carried out shortly before the parking brake (50) is released , With the opening of the parking brake (50) is switched to a volume flow-based adjustment of the second displacement volume.

Description

The invention relates to a method for operating a hydraulic winch.

From the DE 10 2010 055 716 A1 a hydraulic winch controlled by an electronic control device is known. The corresponding winch drum is driven by a first hydraulic machine, and it can be stopped by a switchable parking brake. The first hydraulic machine is supplied with pressurized fluid by a second hydraulic machine, the two hydraulic machines being interconnected in an open hydraulic circuit, the present invention also being applicable to winches with a closed hydraulic circuit.

In the case of the known winch, when the load is lowered, the pressure fluid flowing back from the first hydraulic machine to the tank is routed via a lowering brake valve. The pressure drop at the lowering brake valve holds the load securely, whereby the lowering speed can be sensitively adjusted by continuously adjusting the lowering brake valve.

An advantage of the present invention is that the lowering valve can be eliminated altogether. Furthermore, the energy released when lowering the load is not converted into heat and can be used elsewhere. Nevertheless, when the parking brake is released, there is no fear that the load will move a little, especially lower it. Rather, it is ensured that the load continues to stand still when the parking brake is released, whereby it first moves when this is requested with an operating element.

1. a) Abwarten eines ersten Kommandos zum Öffnen der Haltbremse, wobei zum nächsten Schritt b) übergegangen wird, wenn des erste Kommando erfolgt ist;
2. b) Regeln des Drucks am Hochdruck-Anschluss durch Verstellen des zweiten Verdrängungsvolumens, so dass der mit dem Drucksensor gemessene Druck gleich einem vorgegebenen Soll-Druck ist;
3. c) Öffnen der Haltebremse, wenn der genannte Soll-Druck eingeregelt ist, wobei die genannte Druck-Regelung der zweiten Hydromaschine abgeschaltet wird, wobei stattdessen eine Volumenstrom-basierte Verstellung des zweiten Verdrängungsvolumens durchgeführt wird.

According to claim 1, a method for operating a hydraulic winch is proposed, the winch comprising a rotatable winch drum which is coupled to a traction means, a load being attachable to the traction means, the winch drum being in rotary drive connection with at least one first hydraulic machine, wherein a first displacement volume of the at least one first hydraulic machine is continuously adjustable, wherein all first hydraulic machines have a common high-pressure port and a common low-pressure port, said load being controlled both during the raising and during the lowering by means of the pressure at the high-pressure port is hydraulically supported, wherein the at least one first hydraulic machine can be supplied with pressurized fluid by means of at least one second hydraulic machine, a second displacement volume of the at least one second hydraulic machine being continuously adjustable, with all second hydraulic machines having two common jobs have ts connections, with the higher-pressure of the two working connections being fluidically connected to the high-pressure connection in such a way that the pressure at the higher-pressure working connection is essentially the same as the pressure at the high-pressure connection, with a switchable holding brake being provided with which the winch drum can be stopped, with a pressure sensor is provided with which the pressure at the high-pressure connection can be measured, the method comprising the following steps, which are carried out in the specified order:

1. a) Waiting for a first command to open the parking brake, moving to the next step b) when the first command has been given;
2. b) Regulating the pressure at the high-pressure connection by adjusting the second displacement volume, so that the pressure measured with the pressure sensor is equal to a predetermined target pressure;
3. c) opening the holding brake when said setpoint pressure is adjusted, said pressure regulation of the second hydraulic machine being switched off, with a volume flow-based adjustment of the second displacement volume being carried out instead.

The traction means is preferably a steel cable, although a chain can also be used. The at least one first hydraulic machine is preferably designed as an axial piston machine with a bent-axis design. If a plurality of first hydraulic machines are provided, then they are in rotary drive connection with the winch drum in such a way that their torques add up. The hydraulic parallel connection of the first hydraulic machines according to the claims results in the force caused by the load being distributed evenly to all the first hydraulic machines if, as is preferred, the same first displacement volume is set on them. The first displacement volume can preferably be continuously adjusted in each case between a minimum first displacement volume that is different from zero and a maximum first displacement volume. In particular, the minimum first displacement volume can preferably be set by means of an adjustable end stop, with this setting most preferably being constant while the method is being carried out or while the winch is in operation.

The second hydraulic machine is preferably designed as an axial piston machine with a swash plate design. The second displacement volumes of a number of second hydraulic machines are preferably set to be the same. The at least one first hydraulic machine and the at least one second hydraulic machine are preferably interconnected in a closed hydraulic circuit. The second displacement volume of the at least one second hydraulic machine can then preferably be adjusted above zero in each case, so that the direction of rotation of the winch drum can be reversed simply by adjusting the second displacement volume. Furthermore, the high-pressure connection is permanently connected to one of the two working connections, in particular the first working connection.

The use of an open hydraulic circuit is also conceivable. In this case, the direction of rotation of the winch drum can be reversed by means of a slide valve. The connection between the two working connections and the high-pressure connection can then be switched over.

In all the interconnections described, there is essentially no pressure drop in the connecting line from the second hydraulic machine to the high-pressure connection of the first hydraulic machine. There, in particular, no load-holding valve or lowering brake valve is provided with which the load can be held during lowering solely by a pressure drop caused by friction. Rather, the second hydraulic machine alone should hold the load hydraulically, so that energy released when the load is lowered is not converted into heat but can be used elsewhere.

Said volume flow-based adjustment can also take place in the manner of a control, for example by setting the first displacement volume proportionally to a desired speed. This is advantageous when the drive motor rotates at a constant speed. The speed of the drive motor measured with the second speed sensor can be taken into account in this control. However, it is also conceivable that regulation will take place. For example, the speed of the winch drum measured with a first speed sensor comes into consideration as the actual variable of this regulation. This speed multiplied by the first displacement volume gives the volume flow between the first and the second hydraulic machine. The assigned setpoint value of the regulation mentioned is, for example, the desired speed of the load or the desired speed of the winch drum. The control variable is the first displacement volume or a control pressure with which this can be influenced. In particular, a regulation can be used to ensure that the load does not move when the operating element 61 is in its neutral position. With pure control, a slow lowering of the load could take place due to leakage.

It is conceivable to combine said regulation with said control by selecting the same type of manipulated variable for both, with the two corresponding individual manipulated variables being added.

The period of time required to regulate the setpoint pressure is largely constant. Accordingly, step c) can be carried out, for example, when a fixed predetermined period of time has elapsed after the beginning of the pressure regulation.

The processes according to step c) are preferably carried out within a short time interval, which is shorter than 0.2 seconds, for example. It is conceivable that all processes are carried out exactly at the same time. However, it is also conceivable that the volumetric flow control starts a little earlier than the opening of the holding brake. The pressure regulation and the volume flow regulation are preferably not active at any time at the same time. The target value of the volume flow control is preferably zero during step c), so that the volume flow control can start when the brake is still closed, without causing undesired increases in pressure as a result.

The pressurized fluid is preferably a liquid and most preferably hydraulic oil.

Advantageous developments and improvements of the invention are specified in the dependent claims.

A load sensor can be provided, by means of which the force on the traction means, which is caused by the load, can be measured, with the target pressure being selected as a function of the force measured with the load sensor. This means that the load moves very little or not at all when the parking brake is opened.

Provision can be made for the traction means to be guided over a deflection roller, with the load sensor comprising a force measuring pin on which the deflection roller is rotatably mounted. Corresponding force measuring bolts are available on the market in many designs, so that an exact force measurement can be implemented in a simple and cost-effective manner.

Provision can be made for a second command to apply the parking brake to be awaited during the volume flow-based adjustment, with the parking brake being applied in response to the second command mentioned, with the volume flow-based adjustment of the second hydraulic machine being terminated, with the the pressure measured by the pressure sensor at the time of the second command is stored, the method according to claim 1 then being carried out again, the target pressure being chosen to be equal to the stored pressure. This means that the load sensor can be dispensed with, although the load only moves slightly when the parking brake is released. This exploits the fact that the load typically does not change when the holding brake is closed, in particular when the winch is used in a crane. When the parking brake is opened for the first time, the setpoint pressure is preferably selected to be large enough to ensure that it is sufficient to lift any load that is to be expected. As a result, the load will increase slightly when the holding brake is released. If the volume flow-based adjustment is implemented as a regulation, as explained above, this effect can be kept small. Preferably, before the parking brake is applied, the setpoint value zero is specified for the volumetric flow control, and it is awaited until this setpoint value has been adjusted. Typically, the operator of the cable winch does this himself. Preferably only when the operator gives the second command while the winch drum is moving is the winch drum brought to a standstill in the manner described, so that the holding brake is not overloaded.

Provision can be made for a maximum first displacement volume to be set on the at least one first hydraulic machine while the holding brake is being opened. This reduces unwanted movement of the load to a minimum when the parking brake is released from the outset.

It can be provided that while the parking brake is open, the second displacement volume is selected to be essentially proportional to the deflection of a control element of the winch. Within the framework of the control explained above, this proportionality can be precisely achieved. In the context of the control explained above, it is only approximately achieved due to the influence of disturbance variables.

The operating element is preferably an operating lever which, starting from a neutral position, can be moved in two opposite directions in order to set two opposite directions of movement of the load or the winch drum. The deflection is to be understood as an amount of the movement of the control element measured from the neutral position.

It can be provided that while the deflection of the operating element falls below a predetermined limit value, a maximum first displacement volume is set on the at least one first hydraulic machine, with a first displacement volume that is reduced compared to the maximum first displacement volume being set. As a result, the cable drum can be moved particularly quickly when the operating element is deflected far. The limit value mentioned can be selected differently depending on the direction of deflection of the operating element, ie depending on the desired direction of movement of the load.

Provision can be made for the pressure measured with the pressure sensor and/or the load measured with the load sensor to be taken into account in the named reduction in the first displacement volume. The first displacement volume is preferably only reduced to such an extent that the pressure measured with the pressure sensor does not exceed a predetermined limit value. It should be noted that the measured load can be calculated from the measured pressure from the known dimensions of the winch and the set first displacement volume and vice versa. However, this only applies if the parking brake is open. When the parking brake is closed, the load can be held by the parking brake alone, so that the pressure at the high-pressure connection can become arbitrarily small and, due to leaks, it also becomes as long as the pressure control according to the invention is not active.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

• 1 einen hydraulischen Schaltplan der der Erfindung zugrunde liegenden hydraulischen Winde.

The invention is explained in more detail below with reference to the accompanying drawings. It shows:

• 1 a hydraulic circuit diagram of the hydraulic winch on which the invention is based.

1 shows a hydraulic circuit diagram of the hydraulic winch 10 on which the invention is based. The winch 10 comprises a rotatable cable drum 20 on which a traction means 21 in the form of a steel cable is wound. The winch 10 is part of a crane, for example. The traction mechanism 21 is accordingly guided over a rotatable deflection roller 23 so that it can lift the load 22 counter to the direction 11 of gravity or lower it in the direction 11 of gravity. The direction of the corresponding force on the traction means 21 is directed away from the winch drum 21 in both cases.

In the present case, the winch drum 20 is in rotation with a single first hydraulic machine 30 riebsverbindung, preferably a direct coupling, ie a coupling without a gear, is given. In the case of very large cranes, it happens that the winch drum is driven by a plurality of first hydraulic machines, which are coupled to the winch drum in such a way that their torques add up. For this purpose, the winch drum can be provided with a ring gear, with the associated pinions of the first hydraulic machines engaging in the ring gear at different points. Several first hydraulic machines are hydraulically connected in parallel, so that they have a common high-pressure and a common low-pressure connection 31; have 32 The corresponding first displacement volumes are preferably set the same, so that all first hydraulic machines contribute the same torque.

The high-pressure connection 31 is the connection of the first hydraulic machine 31, to which the pressure that hydraulically supports the weight of the load is applied. This connection does not change sides on the first hydraulic machine 30 during raising or lowering, regardless of whether the winch 10 (as shown) is operated in the closed hydraulic circuit or in the open hydraulic circuit.

The first hydraulic machine 30 is preferably designed as an axial piston machine with a bent-axis design. Its first displacement volume is preferably constantly adjustable between a minimum first displacement volume that is different from zero and a maximum first displacement volume. The two end values are preferably set by means of a mechanical end stop, and they remain unchanged during operation of the winch 10. The first displacement volume cannot be set to zero, since the load would then fall when the holding brake 50 is released.

The winch drum 20 can be stopped with the holding brake 50 if the load 22 is not to move. The holding brake 50 is preferably only switched over when the winch drum 20 is stationary. Only in an emergency is the holding brake 50 intended to brake the winch drum 20 in order to reduce its speed. For this reason, the parking brake 50 is actuated by means of a single-acting brake cylinder 51, the spring of which biases the parking brake 50 into the closed position. The holding brake can be opened by means of the hydraulic brake valve 51, which is designed, for example, as an electrically actuated 2/2-way valve. The brake valve 51 is connected to a control device 13 .

The first hydraulic machine 30 is preferably adjusted by means of a single-acting adjusting cylinder (not shown), it being preferably designed in such a way that it is adjusted toward the maximum first displacement volume without adjusting pressure in the adjusting cylinder. Accordingly, the actuating pressure causes a reduction in the first displacement volume. The control pressure mentioned is provided, for example, by an electrically adjustable pressure reducing valve which is connected to the control device. When the load 22 is raised, the first hydraulic machine 30 is operated as a motor, and when the load 22 is lowered it is operated as a pump. In both cases, the higher pressure is present at the high-pressure connection 31 .

The second hydraulic machine 40 is designed, for example, as an axial piston machine with a swash plate design. The corresponding second displacement volume can preferably be adjusted beyond zero, so that the direction of movement of the load 22 can be reversed simply by adjusting the second displacement volume. When the load 22 is raised, the second hydraulic machine 40 works as a pump, and when the load 22 is lowered, it works as a motor. The second displacement volume is preferably adjusted by means of a double-acting adjusting cylinder, with the two adjusting chambers each being connected to an assigned, electrically adjustable pressure-reducing valve, which in turn is connected to the control device 13 .

The second hydraulic machine 40 is in rotary drive connection with a drive motor 12 which is designed, for example, as an internal combustion engine, in particular as a diesel engine. The drive motor 12 preferably drives further assemblies (not shown), so that the energy released when the load 22 is lowered can be used in a simple manner to relieve the load on the drive motor 12 . In the simplest case, the speed of the drive motor 12 is adjusted to a fixed, predetermined constant speed. If the control device 13 reports the current power requirement required for driving the winch drum 20 to the controller of the drive motor 12, the energy consumption of the overall system can be minimized, for example.

If a plurality of second hydraulic machines 40 are provided, then these are connected hydraulically in parallel, and they are preferably in rotary drive connection with the drive motor via a common drive shaft.

The first and the second hydraulic machine 30; 40 are presently interconnected in your closed hydraulic circuit. The first working connection of the second hydraulic machine 40 is permanently connected to the high-pressure connection 31 the second hydraulic machine 30 connected. No valves or the like that could cause a pressure drop are arranged in the corresponding line. In particular, no lowering brake valve is provided there, on which there is a pressure drop when the load is lowered, which holds the weight of the load and which converts the energy released when the load is lowered into heat.

The pressure sensor 60 measures the pressure at the high-pressure connection 31, being connected to the control device 13. An operating element 61 is also provided, which is also connected to the control device 13 . The operating element 61 is designed, for example, as an operating lever which, starting from a neutral position, can be pivoted in two opposite directions. In the spring-loaded neutral position, the winch drum 20 does not move. When the operating lever is pivoted forward as seen by the operator, the load 22 is lowered, with the lowering speed being approximately proportional to the deflection of the lever. When the operating lever is pivoted backwards, the load 22 is lifted, with the lifting speed being approximately proportional to the lever deflection. The position of operating element 61 is preferably transmitted to control device 13 in the form of an electrical or digital signal. The second command for closing parking brake 50 can be given, for example, when operating element 61 is in its neutral position for a predetermined period of time with holding brake 50 open. The first command to open the parking brake 50 can be given, for example, when the operating element 61 is deflected out of the neutral position when the parking brake is closed.

The first speed sensor 62 on the winch drum 20 can be used to set a speed of the winch drum that is in a fixed ratio to the deflection of the operating element 61 . In particular, it can be used as an actual variable in the regulation explained above as part of the volume flow-based adjustment. A speed of the drive motor 12 that changes over time can be taken into account with the second speed sensor 63, for example by the second displacement volume being adjusted accordingly.

The control device 13 preferably comprises a programmable digital computer. The corresponding program carries out, for example, a sequence of calculation rounds which are continuously executed at a constant time interval of, for example, 1 ms. At the start of a round of calculations, the position of operating element 62, the measured value of pressure sensor 60 and the measured values of first and second speed sensors 62; 63 read. The control signals for the first and the second hydraulic machine 30; 40 and the holding brake 50 are determined, these being output at the end of the calculation round. A completely feedback-free calculation preferably takes place within a calculation round. Feedback is preferably implemented solely by using intermediate results from earlier calculation rounds. With this basic structure of the program, the method according to the invention can be implemented without further ado. In particular, the pressure regulation according to the invention can be carried out, for example, by means of a PID controller, which is implemented by the program mentioned.

Reference List

10

winch

11

direction of gravity

12

drive motor

13

control device

20

winch drum

21

traction means

22

load

23

pulley

24

load sensor

25

force measuring pin

30

first hydraulic machine

31

high pressure connection

32

low pressure connection

40

second hydraulic machine

41

first working port

42

second working port

50

holding brake

51

brake cylinder

52

brake valve

60

pressure sensor

61

control element

62

first speed sensor

63

second speed sensor

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102010055716 A1 [0002]

Claims (8)

Method for operating a hydraulic winch (10), the winch (20) comprising a rotatable winch drum (20) which is coupled to a traction means (21), a load (22) being able to be attached to the traction means (21), wherein the winch drum (20) is in rotary drive connection with at least one first hydraulic machine (30), wherein a first displacement volume of the at least one first hydraulic machine (30) is continuously adjustable, wherein all first hydraulic machines (30) have a common high pressure and a common low pressure - have a connection (31; 32), whereby by means of the pressure at the high-pressure connection (31), said load is supported hydraulically both during lifting and during lowering, wherein the at least one first hydraulic machine (30) can be supplied with pressure fluid by means of at least one second hydraulic machine (40), wherein a second displacement volume of the at least one second hydraulic machine (40) can be continuously adjusted, with all second hydraulic machines (40) having two common working connections ( 41; 42), the higher-pressure of the two working ports (41; 42) being fluidically connected to the high-pressure port (31) in such a way that the pressure at the higher-pressure working port (41; 42) is essentially equal to the pressure at the high-pressure port ( 31) is, wherein a switchable holding brake (50) is provided, with which the winch drum (20) can be stopped, wherein a pressure sensor (60) is provided, with which the pressure at the high-pressure connection (31) can be measured, the method comprising the following steps, which are executed in the given order: a) Waiting for a first command to open the parking brake (50), with the next step b) being passed when the first command has been given; b) controlling the pressure at the high-pressure connection (32) by adjusting the second displacement volume, so that the pressure measured by the pressure sensor (60) is equal to a predetermined target pressure; c) opening the holding brake (50) when said setpoint pressure has been adjusted, said pressure control of the second hydraulic machine (40) being switched off, with a volume flow-based adjustment of the second displacement volume being carried out instead. procedure after claim 1 , wherein a load sensor (24) is provided, by means of which the force on the traction means (21) can be measured, which is caused by the load (22), the target pressure being selected depending on the force measured with the load sensor (24). will. procedure after claim 2 , wherein the traction means (21) is guided over a deflection roller (23), wherein the load sensor (24) comprises a force measuring pin (25) on which the deflection roller (23) is rotatably mounted. procedure after claim 1 , wherein a second command to close the parking brake (50) is awaited during the volume flow-based adjustment, the holding brake (50) being closed in response to the second command mentioned, the volume flow-based adjustment of the second hydraulic machine (40) being terminated is, wherein the pressure measured by the pressure sensor (60) at the time of the second command is stored, the method then being followed claim 1 is carried out again, with the desired pressure being selected to be equal to the stored pressure. Method according to one of the preceding claims, a maximum first displacement volume being set on the at least one first hydraulic machine (30) while the holding brake (50) is being opened. Method according to any preceding claim, wherein while the parking brake (50) is open, the second displacement volume is selected substantially proportional to the deflection of a control element (61) of the winch (10). procedure after claim 6 , wherein while the deflection of the operating element (61) falls below a predetermined limit value, a maximum first displacement volume is set on the at least one first hydraulic machine (30), a first displacement volume that is reduced compared to the maximum first displacement volume being set. procedure after claim 7 , the pressure measured by the pressure sensor (60) and/or the load measured by the load sensor (24) being taken into account in said reduction of the first displacement volume.

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