DE102010055716B4 - Hydraulic drive - Google Patents

Abstract

Hydraulic drive with a hydraulic motor (4), the inlet (8) of which is connected to a pressure medium source, for example a pump (2) and in the return (10) of which a brake valve (16) is arranged, which is controlled by a control line (22) tapped control pressure or an electrical control signal is applied in the direction of an open position of the brake valve (16) and which is adjustable in the direction of a closed position of the brake valve (16) in the event of a pressure drop in the inlet (8), characterized by a control device (46, 80; 70) , via which the control pressure or the control signal can be set independently of the inlet pressure.

Description

The invention relates to a hydraulic drive according to the preamble of the patent claim 1 .

From the DE 103 20 946 B4 a generic hydraulic drive for a cable winch is known in which a winch drum is driven by a hydraulic motor. The inlet of the hydraulic motor is connected to a pump, preferably a variable displacement pump. The pressure medium flowing off from the hydraulic motor flows off via the return to a tank T. In the event that a pulling load acts on the winch drum, it can accelerate in such a way that the pressure medium volume flow conveyed by the pump is not sufficient to supply the hydraulic motor with enough pressure medium so that the pressure in the inlet drops accordingly and under unfavorable conditions it can even lead to cavitation phenomena in the inlet.

In order to avoid such an undesirable pressure drop in the inlet, the from the DE 103 20 946 B4 known solution, a brake valve, also called a lowering brake valve, is provided, which is biased into a closed position and is acted upon in the opening direction by the pressure in the respective inlet. In the known solution, this brake valve is designed in such a way that it is effective in both directions of rotation of the hydraulic motor, ie when the supply and return flow alternate. When there is sufficient pressure in the inlet, the brake valve is brought into an open position so that the pressure medium volume flow flowing out from the hydraulic motor flows off via the brake valve to the tank. In the event of an undesired pressure drop, the pressure medium volume flow flowing down to the tank is throttled or blocked so that the hydraulic motor is braked accordingly and the pressure in the inlet rises until the brake valve opens again.

With these known solutions, especially with long supply lines and a correspondingly large capacity volume of the supply lines, pressure changes in the supply and thus pressure fluctuations and corresponding fluctuations in the capacity volume of the hose lines can occur, so that the brake valve opens and closes accordingly due to these pressure fluctuations, so that the speed of the hydraulic motor fluctuates accordingly and thus a controlled movement of the load is made more difficult. This vibration behavior of the hydraulic motor can also occur if the pump malfunctions.

In the DE 10 2008 064 064 A1 The applicant describes a hydraulic drive with a lowering brake valve, in which this is acted upon in the opening direction with a control signal that is picked up at a directional valve via which the pressure medium supply to and from the hydraulic motor is controlled. That is to say, in this variant, the pressure medium is not supplied to the hydraulic motor directly as a function of the inlet pressure, so that the vibration behavior is improved in the special cases described above. It was found, however, that the above-described problem can also occur with such an activation of the brake valve.

DE 10 2008 010 270 A1 discloses a hydrostatic drive system with a pump and at least one consumer, which can be alternately brought into connection with the pump and a container by means of a directional control valve that can be confirmed by control signals, in order to control the movement of a positive and a negative load on the consumer.

DE 10 2004 033 891 A1 discloses a hydraulic drive system for controlling a hydraulic consumer, the pressure medium being supplied via a directional control valve arrangement and the process control via separately controllable discharge throttle valves.

In contrast, the invention is based on the object of creating a hydraulic drive in which speed oscillations due to pressure changes in the inlet are prevented or at least reduced.

This object is achieved by a hydraulic drive with the features of claim 1.

Advantageous further developments of the invention are the subject of the subclaims.

According to the invention, the hydraulic drive has a hydraulic motor, the inlet of which is connected to a pressure medium source, for example a pump, and in the return of which a brake valve is arranged, which is acted upon by a control pressure tapped via a control line in the direction of an open position and that when the pressure in the inlet drops is adjustable in the direction of a closed position. According to the invention, the control pressure difference effective in the opening direction of the brake valve or the control pressure effective in the opening direction is set via a control valve device which is arranged in a control line and via which the control pressure can be set independently of the inlet pressure. That is, with such an adjustable control valve device, the control pressure difference effective in the opening direction or the control pressure effective in the opening direction can be set via a control valve device which is arranged in a control line and via which the control pressure can be set independently of the inlet pressure. That is, with such an adjustable control valve device, the control pressure effective in the opening direction can be changed as a function of the operating conditions of the hydraulic drive during operation in order to avoid the fluctuations in speed of the hydraulic motor described above. In the most general form of the invention, the control pressure can also be generated electrically by controlling an electrically operated brake valve by means of a microcontroller.

In one embodiment of the invention, the control valve device is designed as an electrically or hydraulically adjustable pressure limiting valve, the opening pressure of which can be adjusted as a function of a pilot signal. In an alternative solution, instead of such a pressure limiting valve, a pressure reducing valve is used, via which a pilot pressure can be reduced to the respectively desired control pressure for the brake valve.

The control valve device can be controlled, for example, as a function of an electrical or hydraulic control signal or a swivel angle of the pressure medium source designed as a variable displacement pump or as a function of an actuating signal of a directional valve by controlling the pressure medium connection of the inlet with a pressure medium source and the return with a low pressure connection of the pump or a tank .

In one embodiment of the invention, an electrically controlled safety valve is provided in a control line of the brake valve, which relieves the pressure of the control line when the drive is switched off.

Another embodiment of the invention provides for a hydraulic safety valve to be provided in a control line of the brake valve, which is acted upon by the pressure in the inlet in the direction of an open position and which is pretensioned by a spring in the direction of a relief position in which the control line in question is connected to a tank is.

The hydraulic drive can be provided with an electrical pressure switch which switches over when an undesired pressure change occurs in the inlet in order to generate an electrical control signal for the brake valve, its control valve device or a safety valve.

The hydraulic drive can be designed with a speed sensor for detecting the hydraulic motor speed and for outputting a speed signal to a microcontroller.

A nozzle can be arranged in a return from the hydraulic motor, via which changes in the return volume flow are converted into a change in the discharge pressure, which acts on the brake valve in the closing direction.

The brake valve can be acted upon in the closing direction by the pressure in the return line from the hydraulic motor.

The hydraulic drive can be designed with a closed or an open circuit.

In one embodiment of the invention, the hydraulic motor is designed as a winch motor.

A preload valve can be provided in the return for hydraulic clamping of the hydraulic motor.

To build up a sufficient return pressure, an auxiliary pump is provided in a variant of the invention.

In a variant of the invention, a microcontroller is provided via which control signals for a directional valve, the brake valve, the control valve device, a safety valve or similar valve devices of the hydraulic drive can be generated.

• 1 ein Schaltschema eines ersten Ausführungsbeispiels eines hydraulischen Antriebs mit Bremsventil;
• 2 ein Ausführungsbeispiel eines hydraulischen Antriebs, bei dem zur Ansteuerung des Bremsventils ein Druckreduzierventil verwendet wird;
• 3 eine Variante des Ausführungsbeispiels gemäß 2 mit einem elektrischen Sicherheitsventil;
• 4 eine Weiterbildung des Ausführungsbeispiels gemäß 3 mit einem zusätzlichen hydraulischen Sicherheitsventil;
• 5 eine Variante des Ausführungsbeispiels gemäß 3 mit einem Druckschalter;
• 6 eine Weiterbildung des Ausführungsbeispiels gemäß 5 mit Druckschalter und einem hydraulischen Sicherheitsventil sowie einem Sensor zur Drehzahlüberwachung und
• 7 einen hydraulischen Antrieb mit rein elektrisch angesteuertem Bremsventil.

Preferred exemplary embodiments of the invention are explained in more detail below with reference to schematic drawings. Show it:

• 1 a circuit diagram of a first embodiment of a hydraulic drive with a brake valve;
• 2 an embodiment of a hydraulic drive in which a pressure reducing valve is used to control the brake valve;
• 3 a variant of the embodiment according to 2 with an electric safety valve;
• 4th a development of the embodiment according to 3 with an additional hydraulic safety valve;
• 5 a variant of the embodiment according to 3 with a push button switch;
• 6th a development of the embodiment according to 5 with pressure switch and a hydraulic safety valve as well as a sensor for speed monitoring and
• 7th a hydraulic drive with a purely electrically controlled brake valve.

The in 1 shown hydraulic drive 1 has a variable displacement pump 2 over which a hydraulic motor 4th is driven with adjustable displacement. This in turn can drive a winch or the like, for example. The variable displacement pump 2 is designed, for example, as an axial piston pump, whereby a swivel angle can be changed in order to adjust the delivery volume. The swivel angle can be measured using a swivel angle sensor 6th are recorded. The variable displacement pump 2 is designed with a conventional pump control, which makes it possible, for example, to keep the pump pressure by a predetermined pressure difference above the individual load pressure in the system. Such pressure and delivery flow control systems are known, so that further explanations are unnecessary.

The drive 1 according to 1 is designed as an open circuit. Accordingly, the pressure medium is from the variable displacement pump 2 via an inlet 8th to an inlet connection of the hydraulic motor 4th promoted and flows from this via a return 10 to a tank T down from which the variable displacement pump 2 Sucks pressure medium. In the case of relatively long supply lines, these can represent a considerable volume of capacity for the pressure medium; this capacity volume is shown in accordance with 1 with the reference number 12th Mistake.

The variable displacement pump 2 is with a brake valve device 14th executed in 1 is indicated by dashed lines. This brake valve assembly 14th has a brake valve 16 that is about a feather 18th and a first brake valve control line 20th is biased into a closed position. In one opening direction, the pressure acts in a control line 22nd , via which a control pressure effective in the opening direction is applied. In the illustrated embodiment, the brake valve 16 designed as a continuously adjustable directional valve with three connections P, Q, U, with an inlet line connected to a connection P in the spring-loaded locking position 24 is shut off, the upstream of a check valve 26th from the inflow 8th branches off. Another connection Q is via an inlet line 28 with the influx 8th connected. Not shown in 1 are positions of the brake valve 16 , in which this opens a pressure medium connection from port Q to port U. In this case the pressure in the now with drain line would be 10 act in the opening direction - this configuration would then be with a reversal of the direction of rotation of the hydraulic motor 4th effective. In the case of a winch drum, however, the in 1 The configuration shown is sufficient, since the load L always acts in one direction and, accordingly, the cavitation and vibration problems only in one direction of rotation of the hydraulic motor 4th occurs when lowering

An output port U of the brake valve 16 is with a branching output line 30th connected via two branch lines 30a , 30b and in each case arranged therein, designed as check valves, feed valves 32 , 34 with the rewind 10 or the inflow 8th are connectable. These feed valves 32 , 34 open towards the return 10 or to the inlet 8th .

The greater of the pressures in the inlet 8th and in return 10 is via a shuttle valve 36 tapped and to a control connection G of the brake valve assembly 14th guided. The area between the two feed valves 32 , 34 is via a flushing line 38 connected to a flushing connection S.

The ones with the influx 8th and the return 10 connected inlet-side connections A, A 'and return-side connections B, B' of the brake valve arrangement 14th are shown in accordance with 1 also shown, but the inlet and outlet side pressure medium flow paths are, for the sake of simplicity, continuously with an inlet 8th or return 10 designated.

As already mentioned, the return ends 10 in the tank T, with a nozzle upstream of the tank 40 is provided. This causes volumetric flow fluctuations in the return 10 converted into corresponding changes in the discharge pressure. As explained above, this discharge pressure acts via the brake control line 20th in the closing direction on the brake valve 16 . The control line 22nd extends through a lid 42 the brake valve assembly 14th through to a connection V, to which a pilot control line 44 is connected to the input of an electrically adjustable pressure relief valve 46 is led. This pressure relief valve 46 is due to the pressure in the pilot line 44 in the opening direction and by the force of a spring and an electromagnet 48 (alternatively also via a control pressure) in the closing direction. As soon as the pressure in the pilot line 44 the force of the spring and the electromagnet 48 exceeds, the pressure relief valve opens 46 a connection to the tank T, so that the pressure in the pilot control line 44 on the pressure relief valve 46 set pressure is limited.

The control of the electromagnet 48 takes place via a signal line 50 which, for example, to a microcontroller, which will be explained later 70 connected. Instead of this electrically adjustable pressure relief valve 46 Of course, a hydraulically adjustable pressure limiting valve can also be used, in which this is acted upon by a control pressure which is effective in the closing direction and which can be set, for example, via a pressure reducing valve or the like.

The pressure in the control line 22nd and the pilot line 44 is via an auxiliary pump 52 constructed, the pressure connection to a connection M of the cover 42 is connected, which in turn is in a charging line 54 opens out inside the lid 42 with the control line 22nd connected is. In the area between the connection M and the confluence, a damping valve arrangement is provided, which is designed as a throttle check valve 56d that is effective in both directions. From the control line 22nd branches in the lid 42 furthermore a flushing channel 58 with a filter and a choke 59 away. The irrigation channel 58 branches outside the lid 42 and is on the one hand with the supply or flushing line 38 and on the other hand connected to a leakage connection L.

As 1 can be inferred by a suitable choice of the control pressure in the control line 22nd and accordingly by setting the pressure relief valve appropriately 46 the control pressure effective in the opening direction, ie in the sense of an opening of the pressure medium connection between the ports P and U, can be set to prevent undesired opening of the brake valve 16 to avoid. Ie the control of the brake valve 16 does not necessarily take place via the pressure on the inlet side but can be controlled as a function of other operating parameters. It is possible, for example, to adjust the pressure relief valve 46 depending on the swivel angle of the variable displacement pump 2 , from the speed of the hydraulic motor 4th to choose from the setting of a directional control valve (not shown here) for controlling the pressure medium flow within the hydraulic drive or from other parameters. The response behavior of the brake valve 16 can thus be adapted to the respective conditions so that the vibrations and cavitation phenomena mentioned at the beginning can be avoided or at least reduced to a minimum.

2 shows a variant of the embodiment according to 1 . The in 2 shown hydraulic drive 1 basically has the same structure as the one based on 1 explained drive and also serves to drive a winch drum 60 . The drive shaft of the winch drum 60 is about a clutch 62 with an output shaft 64 the hydromachine 4th connected, the winch drum 60 via a holding brake 67 can be set. The pressure medium supply of the hydraulic motor 4th takes place again via the variable displacement pump 2 , via the pressure medium in the inlet 8th is promoted, which is with the inlet connection of the hydraulic motor 4th connected is. Its return connection is via the return 10 connected to the tank T, in which case the pressure in the return line 10 via a preload valve 66 is increased compared to the tank pressure.

The direction of rotation of the hydraulic motor 4th is in accordance with the exemplary embodiment 2 via an electrically operated directional control valve 68 set, for example via a microcontroller 70 is adjusted based on a control signal from the user. The continuously adjustable directional valve 68 has a pressure port P, a tank port T and two working ports A, B. The working port A is on the return 10 and the working connection B to the inlet 8th connected and is thus connected to the corresponding connections A, B of the brake valve assembly 14th in pressure fluid connection. Port P of the directional control valve 68 is via a pump line 72 with the pressure connection of the variable displacement pump 2 and the tank connection T of the directional control valve 68 via a tank line 74 connected to the tank T. The preload valve explained above is accordingly 66 in the tank line 74 intended.

The one between the two feed valves 32 , 34 flushing line opening into it 38 the brake valve assembly 14th is - as explained above - led to the flushing connection S and there to a feed pressure line 76 connected, which in turn with a pressure connection of a feed pump 78 is connected, for example with the same pump shaft as the variable displacement pump 2 is driven. To avoid backflow to the feed pump 78 is in the feed pressure line 76 a check valve 80 arranged. The structure of the brake valve 16 with the corresponding supply lines is the same as in the exemplary embodiment described above, so that reference can be made to the corresponding explanations. This brake valve too 16 is just the return 10 assigned. When the direction of rotation of the hydraulic motor is reversed 4th and appropriate protection via a brake valve, this can also be carried out with a corresponding function so that the pressure in the then effective return (in 2 Intake 8th ) is throttled. In the case of the present, only one branch protecting construction of the brake valve 16 is this via the control line 22nd applied in the opening direction with a pressure which is not via a pressure relief valve as in the previously described embodiment, but via a pressure reducing valve 80 is set. Acts in the closing direction in the variant according to 2 just the spring 18th . The brake control line 20th is according to the variant 2 not provided. In principle, of course, in the embodiment according to 1 the brake control line 20th omitted.

The pressure reducing valve 80 is designed to be electrically adjustable in the present case, with the control signal via the microcontroller 70 depending on the aforementioned parameters, for example the speed of the hydraulic motor 4th , the swivel angle of the variable displacement pump 2 , the control signal of the directional valve 68 , the speed of the variable displacement pump 2 , Etc. can be controlled. In the case where the variable displacement pump 2 If the speed is variable, the speed signal should be correlated with the swivel angle in order to then determine the delivery volume flow of the variable displacement pump 2 to obtain and depending on this delivery volume flow the pressure reducing valve 80 to adjust. The inlet pressure of the pressure reducing valve 80 is a pilot pressure that is applied to the inlet of the pressure reducing valve 80 connected pilot pressure line 82 is applied. This can for example be connected to an auxiliary pump or the like in order to increase the input pressure (pilot pressure) of the pressure reducing valve 80 to adjust. This also has a tank connection connected to the tank T and a working connection A, which is connected via the pilot control line 44 with the control line 22nd connected is.

The speed of the hydraulic motor 4th is via a speed sensor 84 recorded. The brake valve assembly 14th according to 2 also has two secondary pressure relief valves to protect the respective inlet and outlet branches 85 , 86 that the pressure in the inlet 8th or in return 10 limit to a maximum value and, in their closed position, shut off the pressure medium connection to the respective low-pressure branch without leaks and, when this limit pressure is exceeded, open a pressure medium connection of the respective branch to the low-pressure branch. The structure of such secondary pressure relief valves 85 , 86 with a leak-free shut-off position is known, so that further explanations are unnecessary. In terms of function, the exemplary embodiment corresponds to FIG 2 the one out 1 , d .H. by controlling the brake valve 16 More or less independent of the inlet pressure, the initially problematic vibrations and undesired operating states due to a faulty response of the brake valve can occur 16 be avoided.

3 shows a variant of the embodiment according to 2 , the only essential difference being that in the embodiment according to 3 in the pilot line 44 an electrically operated safety valve 88 is provided which is spring-biased into a position in which the control line 22nd is relieved towards the tank T. When energizing an electromagnet via the microcontroller 70 becomes the safety valve 88 brought into the illustrated passage position, in which the opening direction on the brake valve 16 Acting control pressure via the pressure reducing valve 80 is set. In the event of a power failure, the safety valve switches 88 automatically to the basic position in which the control line 22nd is connected to the tank T and thus the brake valve 16 is held in its locked position.

4th shows a development of the embodiment according to 3 , downstream of the electrically adjustable safety valve 88 a hydraulically adjustable safety valve 90 is provided, which in principle has the same switching function as the embodiment described above. In other words, a connection to the control line is established in a spring-loaded basic position 22nd steered open towards tank T. The hydraulically adjustable safety valve is in the opening direction 90 due to the pressure in the inlet 8th acted upon by a safety line 92 from the inflow 8th is tapped. Via this hydraulically adjustable safety valve 90 thus becomes the brake valve 16 when the pressure in the inlet drops 8th held below a limit in the closed position.

Both safety valves 88 , 90 are designed as 3/2-way switching valves.

5 shows a variant of the embodiment according to 3 , with an additional pressure switch 94 is provided, which is about the pressure in the inlet 8th is actuated and then a corresponding signal to the microcontroller 70 releases, so that it controls the pressure reducing valve in a manner suitable for the respective operating state as a function of this pressure.

6th shows an embodiment that the two safety valves 88 , 90 according to the embodiment in 4th and the pressure switch 94 from the embodiment according to 5 combined so that the functionality of the brake valve assembly 14th is largely optimized.

7th finally shows a fully electronic variant in which the brake valve 16 not - as in the embodiments described above - is designed to be hydraulically but electrically adjustable. This electrical adjustment of the brake valve 16 takes place via the microcontroller 70 depending on the operating parameters of the hydraulic drive 1 , for example the swivel angle of the variable displacement pump 2 , the set delivery volume flow, the set displacement of the hydraulic motor 4th , the adjustable or - as in the embodiments according to the 2 until 7th - Can be designed as a constant motor. The speed of the hydraulic motor 4th is also in this embodiment via a speed sensor 84 and the pressure in the inlet 8th via a corresponding pressure transducer 96 detected and via the microcontroller 70 into a control signal for the brake valve 16 converted.

Of course, such sensors 84 , 96 can also be used in all of the other exemplary embodiments described above to control the brake valve 16 or the pressure reducing valve 80 or the pressure relief valve 46 to be controlled in a suitable manner.

The applicant reserves the right to use the embodiment according to 7th with a purely electrical actuation of the brake valve 16 to make your own independent claim.

Disclosed is a hydraulic drive with a hydraulic motor, to which a brake valve is assigned, which is acted upon by a control pressure in the opening direction. This control pressure can be adjusted essentially independently of the pressure in the inlet or outlet of the drive.

Claims (14)

Hydraulic drive with a hydraulic motor (4), the inlet (8) of which is connected to a pressure medium source, for example a pump (2) and in the return (10) of which a brake valve (16) is arranged, which is controlled by a control line (22) tapped control pressure or an electrical control signal is applied in the direction of an open position of the brake valve (16) and which is adjustable in the direction of a closed position of the brake valve (16) in the event of a pressure drop in the inlet (8), characterized by a control device (46, 80; 70) , via which the control pressure or the control signal can be set independently of the inlet pressure. Drive after Claim 1 wherein the control device is a control valve device which has an electrically or hydraulically adjustable pressure relief valve (46), the opening pressure of which can be adjusted as a function of a pilot signal. Drive after Claim 1 wherein the control device is a control valve device which has an electrically or hydraulically adjustable pressure reducing valve (80) via which a pilot pressure can be reduced to the control pressure. Drive according to one of the preceding claims, wherein a control valve device as a function of an electrical or hydraulic control signal or a swivel angle of the pressure medium source designed as a variable displacement pump or as a function of a control signal of a directional valve (68) for controlling the pressure medium connection of the inlet (8) with the pressure medium source and the Return (10) with a low pressure connection of the pump (2) or a tank (T) is adjustable. Drive according to one of the preceding claims, wherein an electrically controlled safety valve (88) is provided in the control line (22, 44) which relieves the control line (22) when the power is switched off. Drive according to one of the preceding claims, with a hydraulic safety valve (90) which is biased by the pressure in the inlet (8) in the opening direction and via a spring (18) in the direction of a relief position in which the control line (22) is relieved of pressure. Drive according to one of the preceding claims, with a pressure switch (94) which switches over at a predetermined pressure in the inlet (8) to generate an electrical control signal for the brake valve (16), its control valve device (46, 80) or a safety valve (88) to generate. Drive according to one of the preceding claims, with a speed sensor (84) for detecting the speed of the hydraulic motor (4). Drive according to one of the preceding claims, with a nozzle (40) in the return (10). Drive according to one of the preceding claims, wherein this is designed as an open or closed circuit. Drive according to one of the preceding claims, wherein the hydraulic motor (4) is a winch motor. Drive according to one of the preceding claims, with a preload valve (66) in the return (10). Drive according to one of the preceding claims, with an auxiliary pump (52) for building up a pilot pressure. Drive according to one of the preceding claims, with a microcontroller (70) for generating control signals for the brake valve (16), a directional control valve (68), a control valve device (46, 80), a safety valve (88, 90) or the like.

Images