EP0464305A1 - Hydraulic control device - Google Patents

Abstract

In a hydraulic control device for an oscillating load movement system, having a double-acting hydraulic consumer (V) which can alternatively be connected to a pressure source (P) or a return (T) via two separate working lines (9, 10) and a control valve (C), and a load-holding valve (H) which is arranged at least in one working line (10) between the control valve (C) and the hydraulic consumer (V) and can be opened in a controlled manner from the other working line (9) via a control pressure line (16), a dampening device (X) consisting of a bypass channel (23) and an interference restrictor passage (D2) is attached to the control pressure line (16) of the load-holding valve (H). A restrictor passage (D1) which is smaller than the interference restrictor passage (D2) is provided in the control pressure line (16). <IMAGE>

Description

The invention relates to a hydraulic control device of the type specified in the preamble of claim 1.

An oscillating load movement system is, for example, a crane in which oscillating movements occur at the beginning or end of a rapid load movement, also due to large lever ratios, which affect the hydraulic consumer (s) and lead to pressure fluctuations in the hydraulic system. The hydraulic columns of the theoretically incompressible medium show elastic reactions in practice, so that from the interaction of various factors, the oscillating movements and the pressure fluctuations disruptively over a long period of time, i.e. be maintained even during load movement.

It is known (publication D 7100 from Heilmeier & Weinlein, June 1986, p. 2) to suppress the willingness of a hydraulic consumer to vibrate in a hydraulic circuit containing at least one controllable load holding valve by means of an adjustable movement damping throttle in the pilot pressure line of the load holding valve.

The invention has for its object to provide a hydraulic control device of the type mentioned, in which an effective damping of pressure fluctuations is achieved easily and inexpensively.

The object is achieved according to the invention with the features specified in the characterizing part of patent claim 1.

To dampen the pressure fluctuations, only the control pressure circuit of the load holding valve is intervened, nevertheless the damping acts quickly into the working group and the hydraulic consumer. The desired damping is achieved regardless of the type and design of the control valve, which means that the choice of the control valve remains free. A complicated control valve with inlet regulators and load pressure sensing can also be used, which is inherently critical in systems that tend to vibrate because it can excite pressure vibrations. The damping is presumably due to the fact that the hydraulic quantity flowing out of the pilot pressure line cuts the upper and lower crests in the pressure curve in the event of pressure fluctuations and the oscillating pressure curve in the working lines and in the hydraulic consumer is disturbed so that pressure fluctuations quickly subside. The amount flowing away for steaming in the control circuit is small.

It is known to secure the lifting cylinder in a forklift truck by means of a lowering brake which limits the lowering speed to a maximum value regardless of the load. The lowering brake contains an unthrottled bypass channel in the main flow path, which changes the control characteristic with a view to suppressing pressure fluctuations. This principle cannot be used for cranes with double-acting hydraulic consumers.

In the embodiment of claim 2, the block containing the load holding valve remains conventional. It is modified for the additional function with little manufacturing effort. Simply by replacing the block, a hydraulic control device that was already in operation can be retrofitted.

The embodiment according to claim 3 corresponds to the modern modular principle for optionally combinable components. The unit can be easily integrated in the control circuit at the appropriate point. In a previously undamped system, damping is subsequently created by attaching the structural unit. If necessary, the structural unit is integrated into the working group, with the bypass line and the throttle throttle passage being dimensioned larger.

From the interaction between the throttle passage and the interference throttle passage, via which the disturbance volume flows out of the pilot pressure line, results in the rapidly acting damping of pressure fluctuations.

Although it is to be expected that the opening of the load-holding valve will be impaired in the case of a larger disturbance throttle passage compared to the throttle passage, it is surprisingly found that with the unusual design according to claim 5 an unexpected damping is achieved and the load-holding valve works unaffected.

For example, a bore with a 0.8 mm diameter is used as a throttle passage and a bore with 1.0 mm is used as a throttle throttle passage. Basically, the size ratio and the sizes of the passages are individually adapted to the respective requirements.

In the aforementioned embodiments, the bypass channel branches off from the pilot pressure line. However, it is conceivable to arrange the bypass channel in the cylinder containing the control piston of the load holding valve or in the control piston itself and to connect it to the cylinder part on the rear of the control piston, which is possibly relieved of pressure anyway.

The movement damping throttle is set to operating pressure medium or, for other reasons, set so closely that it would delay the rapid actuation of the load holding valve in the case of cold pressure medium or an abrupt stop pulse. The hydro consumer would then run on under the load. The check valve in the parallel line eliminates this risk according to claim 7, because then for the control of the load holding valve, the pressure medium can quickly flow past the movement damping throttle if the pressure in the one working line and the control line falls below the pressure which opposes the control movement of the load holding valve. When lowering with pressure in one working line, the check valve is kept blocked. In the event of pressure fluctuations during the lowering of the load, the pressure medium is moved by the movement damping throttle; An extreme pressure drop in one working line causes the check valve to open briefly, which contributes to damping. The run-on with cold pressure medium or strictly adjusted motion damping throttle is not carried out.

In the embodiment according to claim 8, the damping device and the movement damping throttle cooperate in the sense of optimal damping.

The closing movement of the control piston is not affected by the check valve according to claim 9, because the pressure medium flows out via the bypass channel.

According to claim 10 through the bypass channel and the interference throttle passage pressure medium flows into the working line containing the load holding valve. A connection of the bypass channel with the return is not necessary. The check valve in the bypass channel ensures that when the other working line is pressurized, no pressure medium reaches a working line via the bypass channel.

According to claim 11, the working lines are not used to derive the pressure medium flowing out for the purpose of damping the pressure vibrations.

The pressure accumulator according to claim 12 helps to allow the pressure fluctuations to subside quickly.

A further expedient embodiment, in which a closing element which is pressed by spring force in the closing direction onto a valve seat located in the working line and a control piston which loads the closing element in the opening direction from the control pressure line, is provided in the load holding valve. In hydraulic control devices for vibrating load movement systems, a geometric area ratio of 1: 3 between the valve seat and the control piston is usually used worldwide. This has proven itself particularly in double-acting differential hydraulic cylinders. By departing from this area ratio, which is enforced as standard, the pressure difference resulting from the pressure medium flowing through the bypass channel is compensated for and the advantage is achieved that a larger quantity of pressure medium moves around the control piston for effective damping and also for control from the working line providing the control pressure move with the same force as before.

Claim 14 gives the person skilled in the art an easy-to-understand instruction on how to achieve optimal damping of the pressure fluctuations while maintaining the regulating or control behavior of the hydraulic control device.

According to claim 15, both working lines of the hydraulic consumer are secured with a load holding valve. Effective damping of pressure fluctuations is achieved regardless of the direction of movement of the load. Linking the bypass channels is a structural simplification.

• Fig. 1 eine schematische Ansicht eines schwingenden Lastbewegungssystems,
• Fig. 2 eine hydraulische Steuervorrichtung als Blockschaltbild,
• Fig. 3 eine Detailvariante,
• Fig. 4 eine weitere Detailvariante,
• Fig. 5 eine weitere Detailvariante,
• Fig. 6 einen schematischen Schnitt durch ein Lasthalteventil,
• Fig. 7 ein Druck/Zeitdiagramm zur Verdeutlichung der Dämpfung in der hydraulischen Steuervorrichtung, und
• Fig. 8 ein Blockschaltbild einer weiteren Ausführungsform.

Embodiments of the subject matter of the invention are explained with the aid of the drawing. Show it:

• 1 is a schematic view of an oscillating load movement system,
• 2 shows a hydraulic control device as a block diagram,
• 3 shows a detailed variant,
• 4 shows a further detailed variant,
• 5 shows a further detailed variant,
• 6 shows a schematic section through a load holding valve,
• 7 shows a pressure / time diagram to illustrate the damping in the hydraulic control device, and
• Fig. 8 is a block diagram of another embodiment.

A vibrating load movement system S according to Fig. 1 is, for example, a hydraulic crane 3 mounted on a truck 1 on its vehicle frame 2, the boom components of which are supplied by hydraulic consumers V, e.g. double-acting hydraulic cylinders, are moved when a load F is to be manipulated. At the beginning or at the end of or even during the movement of the load F, forces occur which cause the boom components to vibrate, above all because of the large leverage ratios, which leads to noticeable pressure fluctuations in the hydraulic consumers V, which results in dangerous or unpleasant load movements.

A hydraulic control device L can be seen in the block diagram from FIG. 2, with which the left-hand hydraulic consumer V shown in FIG. 1 is actuated, for example. The hydraulic control device L contains a load holding valve H with a control part A and a damping device X as well as a schematically indicated control valve C, and is from a pressure source P, which is associated with a return tank T, with pressure medium provided.

The hydraulic consumer V is a double-acting differential cylinder 4 with a piston 5, to which the load F acts via a piston rod 8. The chambers 6 and 7 of the cylinder 4 are connected to the control valve C via working lines 9, 10 and can be connected alternately to the pressure source P or the return flow T in order to move the piston 5 in both directions. The control valve has a zero position to stop the load. The load holding valve H is arranged in the other working line 9 and, in order to lower the load F from the one working line 10, is acted upon by pilot pressure which is set by the control valve C.

The load holding valve H contains a valve 11 with a closing element 13, which is loaded in the control direction by a spring 12 and by a control pressure in a control line 15b branching off from the control valve C of the part of the other working line 9. A check valve 14 blocking the flow direction to the control valve C bypasses the valve 11. In the opening direction, the valve element 13 is acted against by the force of the spring 12 by the control pressure of an indicated control line 15a, which branches off from the part of the other working line 9 facing the hydraulic consumer V.

The control part A has a control pressure line 16 which branches off from a branch 17 of the one working line 10 and leads to a connection 18 of the valve 11. A component 19 can be contained in the pilot pressure line 16 to dampen the movements of the closing element 13 or the pilot piston associated therewith (see FIG. 5), which component consists of a motion damping throttle 20, preferably adjustable, and a bypass check valve 21 which is in the direction to a work line 10 blocks. If the bypass check valve 21 is omitted, both closing and opening movements of the closing element 13 are damped.

A bypass line 23 branches off in a branch 22 of the pilot pressure line 16 and contains an interference throttle D2. In this embodiment, the bypass line 23 leads to a node 24 in the part of the other working line 9 facing the control valve C. Between the branches 17 and 22 in the pilot pressure line 16, a throttle passage D1 is provided which is smaller than the interference throttle passage D2 (for example throttle passage D1 0.8mm, choke passage D2 1.0mm). Has. A check valve 25 blocking in the direction of the interference throttle passage D2 can be provided between the interference throttle passage D2 and the node 24.

In the position of Fig. 2, the valve 11 holds the load. The check valve 14 blocks. The part of the working line 9 lying between the load holding valve H and the control valve C is relieved to the return flow T.

To raise the load F, the control valve C is adjusted so that the working line 9 is connected to the pressure source P and the working line 10 to the return line T. The closing element 13 remains in its closed position. The check valve 14 opens. The chamber 7 is pressurized. The piston 5 extends. Pressure medium is discharged from the chamber 6 through the working line 10.

To stop the load F, the control valve C is reset; the state according to FIG. 2 occurs again.

To lower the load F, the chamber 6 and the opening pressure line 16 are pressurized, which opens the closing element 13 against the force of the spring 12. The load F begins to decrease. Pressure medium constantly flows through the bypass duct 23 to the other working line 9, which is connected to the return T. If there are pressure fluctuations in the chambers 6 and 7, the working lines 9, 10 and in the control circuit of the load holding valve H, then these are damped because of the pressure medium flowing out via the bypass duct 23 and the interference throttle passage D2 and because of the movement damping throttle 20.

To stop the load F, the work line 10 is relieved. The check valve 14 is in its blocking position. The closing element 13 is closed, the movement damping throttle 20 damping this movement. Pressure medium flows to a working line 10 and / or through the bypass channel 23 via the check valve 25.

The hydraulic control device H according to FIG. 3 differs from that of FIG. 2 in that the bypass channel 23 is connected directly to the return T. Furthermore, a check valve 26 blocking in the direction of a working line 10 is provided in the opening pressure line 16. The check valve 26 can also be arranged at the same location in the embodiment according to FIG. 2. The function of the control device is the same as that of FIG. 2. Only no pressure medium can flow back into the one working line 10.

According to FIG. 4, a pressure accumulator 27 is connected to the pilot pressure line 16, expediently between the component 19 and the branch 22. The check valve 26 from FIG. 3 could be provided at the same location. Furthermore, it is indicated that the bypass channel 23 either leads directly to the return T or, as in FIG. 2, to the other working line 9.

In Fig. 5 the hydraulic consumer V (for example the Buckling cylinder in Fig. 1) secured by load holding valves H in both working directions. The bypass channels 23 of both damping devices X are connected to the other pilot pressure line 16.

The valve 11 of the load holding valve is shown schematically in FIG. 6. In its housing 28, the closing element 13 designed as a ball 29 is pressed by the spring 12 onto a valve seat 30 which connects two chambers 31 and 32 to one another. The part of the other working line 9 leading to the chamber 7 is connected to the chamber 31; to the chamber 32, on the other hand, the part of the work line 9 leading to the control valve C. The check valve 14 is located between the chambers 31 and 32. The chamber part 35 lying behind the control piston 34 is relieved of pressure. The valve seat 30 has a cross-sectional area A1, which is in a geometrical area ratio to the application area A2 of the control piston 34, is greater than 1: 4 and preferably greater than 1: 6.5. The pressure in the chamber 32 acts on the closing element 13 parallel to the spring 12 in the closing direction. The pressure in the chamber 31 acts on the closing element 13 parallel to the control piston 34 in the control direction.

The bypass channel 23 could also run through the control piston 34 to the chamber 35 and contain the interference throttle passage D2. It would also be conceivable to lead the bypass channel 23 out on the loading side of the control piston 34.

In Fig. 7, in a diagram, the vertical axis represents pressure and the horizontal axis represents time. The curve P17 represents the pressure curve at the branch 17. The lower curve P18 represents the pressure curve at the connection 18. Both pressures oscillate strongly at the beginning and then calm down until they finally remain constant. A pressure difference dP prevails between the pressures P17 and P18 due to the pressure medium flowing through the bypass duct 23 and the interference throttle passage D2. This pressure difference is compensated for by the size of the pressure surface of the control piston 34 (FIG. 5), so that the load holding valve H operates in the usual way.

In a specific exemplary embodiment, the throttle passage D1 has a diameter of 0.8 mm, the interference throttle passage D2 has a diameter of 1.0 mm, and the control piston 34 has a diameter of 17 mm. The pressure at branch 17 is approximately 90 bar; the pressure P 18 at connection P18, on the other hand, is approximately 40 bar. A pressure difference of approximately 40 bar is reduced via bypass duct 23 and interference throttle passage D2.

In the hydraulic control device L according to FIG. 8, in addition to the embodiment of FIG. 2 or 3, a parallel line 36 is provided, which branches off from the pilot pressure line 16 between the component 19 and the valve 11 and between the throttle passage D1 and the branch 17 into the Control pressure line 16 opens. It bypasses the movement damping throttle 20 and contains a check valve 37 which opens in the direction of a working line 10. The parallel line 36 can also be connected directly to the one working line 10. The check valve 37 allows 11 pressure medium to flow past the throttle 20 when the pressure medium is cold or when the damping throttle 20 is set strictly. In addition, the check valve 37 contributes to the damping because it passes pressure peaks. The bypass channel 23 can be connected to the other working line 9 or directly to the tank T. In the event of pressure fluctuations in the system, the pressure prevailing at the throttle passage D1 keeps the check valve 37 closed, so that the movement damping throttle 20 is properly effective.

The damping device X with or without check valve 37 is particularly useful for control devices in oscillatable load movement systems in which relatively complex control valves are provided with inlet regulators and load pressure sensing, which on the one hand are unaffected by pressure changes on the pump side and work independently of the load, but on the other hand the tendency itself to create or maintain pressure fluctuations in the system. With the design according to the invention, the pressure fluctuations in the system are effectively and quickly dampened regardless of where they originate.

Claims (15)

1. Hydraulic control device for a vibrating load movement system, with a double loadable hydraulic consumer (V), which can be connected to a pressure source (P) or a return (T) via two separate working lines (9, 10) and a control valve (C) , with a load holding valve (H) arranged in at least one working line (10) between the control valve (C) and the hydraulic consumer (V) and controllable from the other working line (9) via a pilot pressure line (16), characterized in that in the pilot pressure line (16) of the load holding valve (H) has a bypass duct (23) branching from the pilot pressure line (16) with an interference throttle Passage (D2) existing hydraulic damping device (X) is arranged for pressure fluctuations. 2. Hydraulic control device according to claim 1, characterized in that the damping device (X) is incorporated into a block (B) containing the load holding valve (H). 3. Hydraulic control device according to claim 1, characterized in that the damping device (X) is an independent unit connected to the pilot pressure line (16) of the load holding valve (H). 4. Hydraulic control device according to claims 1 to 3, characterized in that a throttle passage (D1) is provided in the pilot pressure line (16) between the branch (22) of the bypass channel (23) and the one working line (10). 5. Hydraulic control device according to claim 4, characterized in that the interference throttle passage (D2) is larger than the throttle passage (D1). 6. Hydraulic control device according to claim 5, characterized in that the diameter ratio of the throttle passages (D1, D2) is approximately 1: 1.25. 7. Hydraulic control device according to claims 1 to 6, wherein in the opening pressure line (16) a movement damping throttle and a in the opening direction of the load holding valve (H) opening bypass check valve (21) for the movement damping throttle (20) are provided, characterized in that in one Movement damping throttle bypassing parallel line (36) is arranged in the direction of a working line (10) opening check valve (37), and that the parallel line (36) between the throttle passage (D1) and one working line (10) to the pilot pressure line (16) or directly to which a working line (10) is connected. 8. Hydraulic control device according to one of claims 1 to 7, characterized in that the bypass channel (23) branches off between the movement damping throttle (20) and the throttle passage (D1) from the pilot pressure line (16). 9. Hydraulic control device according to claim 8, characterized in that in the opening pressure line (16) between the throttle passage (D1) and the one working line (10) in the direction of the working line (10) blocking check valve (26) is arranged. 10. Hydraulic control device according to one of claims 4 to 9, characterized in that the bypass channel (23) is connected on the downstream side to the load holding valve (H) containing other working line (9), and that in the bypass channel (23) between the interference throttle passage (D2 ) and the other working line (9) a check valve (25) blocking in the direction of the pilot pressure line (16) is arranged. 11. Hydraulic control device according to one of claims 4 to 9, characterized in that the bypass channel (23) is connected directly to the return (T). 12. Hydraulic control device according to one of claims 1 to 11, characterized in that between the throttle passage (D1) and the interference throttle passage (D2), a pressure accumulator (27) is connected. 13. Hydraulic control device according to one of claims 1 to 12, wherein in the load holding valve (H) a closing element (13) pressed by spring force in the closing direction onto a valve seat (30) lying in the working line (9) and a control piston (34) are provided, which is acted upon from the pilot pressure line (16) and loads the closing element in the pilot direction, characterized in that the geometric area ratio (A1: A2) between the valve seat (30) and the contact surface of the pilot piston (34) is greater than 1: 4, preferably greater than 1: 6.5. 14. Hydraulic control device according to one of claims 1 to 13, characterized in that the geometric area ratio (A1: A2) of the control piston (34) and valve seat (30) and the diameter ratio of the throttle passages (D1, D2) are coordinated so that For a selectable ratio between the pilot pressure (P18) on the pilot piston (34) and the pressure in the working line (10) providing the pilot pressure (P17), rapid damping of pressure fluctuations in the hydraulic consumer (V) is achieved. 15. Hydraulic control device after one of claims 1 to 14, characterized in that both working lines (9, 10) of the hydraulic consumer (V) contain a load-holding valve (H), each with a damping device (X), and in that the bypass channels (23) are linked to one another.

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