EP3625457B1 - Control device for supplying at least one hydraulic consumer with fluid - Google Patents

Description

The invention relates to a control device for supplying at least one hydraulic consumer with fluid with the features in the preamble of claim 1.

Load sensing systems that make it possible to adapt the pressure and/or volume flow of a hydraulic pump to the conditions required by the consumer are state of the art, see "Wikipedia, The Free Encyclopedia", chapter Load Sensing. As is known, LS systems can be designed as a so-called open center system with constant pumps or as a so-called closed center system with variable pumps, as is the case with the control device mentioned above, which forms the subject of the application. Because of their energy-saving operation, LS systems are advantageously used to control components of the working hydraulics of mobile work equipment. Such equipment, such as agricultural tractors or soil cultivation devices, usually have several hydraulic consumers, such as travel drives, hydraulic steering, lifting drives and the like. When operating such equipment, not all of the existing consumers have to be supplied with full volume flow at the same time during most of the operating phases, so that, for reasons of cost, among other things, it is usually not necessary The variable pump intended as a swivel pump must be designed for a maximum volume flow. If special or extreme work situations occur, for example when using a tractor for field cultivation, an undersupply may possibly occur during maneuvers at the end of the field, in which, in addition to the travel drive, the steering and processing devices with lifting drive simultaneously request the maximum volume flow.

The DE 10 2012 209 142 A1 describes a control device with the features in the preamble of claim 1 for supplying at least one hydraulic consumer with fluid with a variable pump that can be controlled by means of a load sensing pressure, whereby for a case-by-case increase in the volume flow in the inlet of the hydraulic consumer, the load sensing pressure is sent via a control line to a Control device is forwarded, which increases the inlet by switching on a constant pump as soon as an operator initiates the relevant function by actuating the control device, the control device having a first and a second control valve, of which the second control valve can be controlled by the operator.

Further control devices are available from the DE 41 29 508 A1 , the EP 2 672 125 A2 and the DE 10 2014 004 932 B3 out.

Based on this problem, the invention sets itself the task of providing a control device of the type mentioned at the outset, which enables a particularly functionally reliable supply of hydraulic consumers.

According to the invention, this object is achieved by a control device which has the features of patent claim 1 in its entirety.

According to the characterizing part of patent claim 1, an essential special feature of the invention is that the first control valve can be controlled by the load sensing pressure in the control line.

It is also provided that for a case-by-case increase in the volume flow in the inlet of the hydraulic consumer, the load sensing pressure is forwarded via a control line to a control device, which increases the inlet by switching on a fixed pump as soon as an operator activates the relevant amount by actuating the control device Function triggered. This not only provides a type of boost function for extreme work situations, but at the same time provides protection against a possible threat to occupational safety, such as can be caused by an abrupt change in operating behavior when the constant pump is switched on. Because the increase in the incoming volume flow depends on the actuation of the control device by the operator, the risk of performance changes not foreseen by the operator, such as changed steering deflections, accelerated driving or lifting movements, is avoided because the boost function is only activated by the operator can be initiated by the operator.

In preferred embodiments, the first valve is a proportional valve, in particular a 2/2-way proportional valve, which is acted upon on one control side in addition to a spring preload with the load sensing pressure and on its other control side with the inlet pressure in the inlet of the respective hydraulic consumer.

The second valve to be actuated by the operator is advantageously an electromagnetically actuated switching valve, in particular a 2/2-way switching valve, which in its unactuated position releases a fluid path from the constant pump to a storage tank and in its actuated position triggered by the operator the corresponding one Fluid path blocks, so that in this activated state the volume flow of the fixed pump is available to increase the inlet.

The second valve can form a bypass to the first valve in that the inlet and the outlet of the first valve are connected to the inlet and the outlet of the second valve in a fluid-carrying manner.

The output of the constant pump can be connected via a branch point to the input of the first and second valves.

To feed the volume flow of the constant pump to the inlet, the inlet of the constant pump can be connected to the output of the variable pump via a connecting line into which a check valve is connected, in particular in the form of a spring-loaded check valve, which opens in the direction of the variable pump and in the direction of the constant pump closes.

In the connection between the variable pump and the respective hydraulic consumer, the connecting line with the check valve and then a control line can be connected, which applies the inlet pressure to the first valve.

To protect the constant pump, a pressure relief valve is connected in parallel to the second control valve in a bypass line, when the volume flow of the constant pump responds and is forwarded to the storage tank, bypassing the first and second valves.

With particular advantage, the control device can be designed as a control block which contains the first and second valves, the check valve and the pressure relief valve and which has connections for the fluid-carrying connection of the swivel angle pump serving as a variable displacement pump, the constant pump, the respective consumer, the storage tank and the load sensing control line.

Fig. 1

in Symboldarstellung die Schaltung des Ausführungsbeispiels der erfindungsgemäßen Steuervorrichtung, wobei der Betriebszustand ohne bedarfsmeldendes LS-Signal und bei nicht betätigter Steuereinrichtung dargestellt ist;

Fig. 2

eine der Fig. 1 entsprechende Darstellung, wobei der Betriebszustand bei bedarfsmeldendem LS-Signal und bei nicht betätigter Steuereinrichtung dargestellt ist;

Fig. 3

eine den Fig. 1 und 2 entsprechende Darstellung, wobei der Betriebszustand ohne bedarfsmeldendes LS-Signal und bei betätigter Steuereinrichtung dargestellt ist; und

Fig. 4

eine den Fig. 1 bis 3 entsprechende Darstellung, wobei der Betriebszustand bei bedarfsmeldendem LS-Signal und bei betätigter Steuereinrichtung dargestellt ist.

The invention is explained in detail below using an exemplary embodiment shown in the drawing. Show it:

Fig. 1

a symbolic representation of the circuit of the exemplary embodiment of the control device according to the invention, the operating state being shown without a demand-reporting LS signal and with the control device not actuated;

Fig. 2

one of the Fig. 1 corresponding representation, whereby the operating state is shown when the LS signal indicates a need and when the control device is not actuated;

Fig. 3

one the Fig. 1 and 2 corresponding representation, whereby the operating state is shown without a demand-reporting LS signal and with the control device actuated; and

Fig. 4

one the Fig. 1 to 3 Corresponding representation, whereby the operating state is shown with the LS signal reporting demand and with the control device actuated.

The control device according to the invention has a control device designated 2 in the figures, the components of which are combined to form a control block 4. The control block 4 has a first input connection 6, which is connected to the output 8 of a variable displacement pump in the form of a swivel pump 10, which is connected to a storage tank 12 on the input side. A second input connection 13 of the control block 4 is connected to the output 14 of a fixed displacement pump 16, which, like the swivel pump 10, can be driven by a motor and is connected to the storage tank 12 on the input side. The constant pump 16 is present Example formed by a gear pump. A demand-reporting LS signal can be fed to a third input connection 18 of the control block 4; more precisely, if there are several consumers to be supplied, the highest LS signal that occurs is fed via shuttle valves. A first output connection 20 on the control block 4 leads to the consumer inlet 22, and a second output connection 24 leads to the storage tank 12.

The swivel pump 10 is part of a closed center system, which is otherwise not shown, so that the swivel angle is set via a pressure regulator DR in accordance with the LS signal. To clarify the course of the oil flows that occur in the Fig. 1 to 4 As a result of the different operating states shown, the lines carrying the oil flow are marked with a larger line width. In the control block 4, a supply line is designated 26, which leads from the first input connection 6 to the first output connection 20 and thus to the inlet 22. A control line that supplies the LS pressure from the third input port 18 to the control device 2 is designated 28. As further components, the control block 4 contains a first control valve 30 and a second control valve 32, of which the first valve 30 is a 2/2-way proportional valve and the second valve 32 is a 2/2-way switching valve. The latter can be actuated electromagnetically when triggered by an operator, and can be brought against the force of a return spring 34 from an unactuated switching position, which corresponds to the flow position, into an actuated switching position in which the valve 32 is blocked. The first valve 30 is acted upon on the one hand by a compression spring 36 and with the respective LS pressure supplied via the control line 28 and on the other hand is acted upon by the inlet pressure prevailing in the supply line 26 via a further control line 38. The output 14 of the fixed pump 16 is connected to the input 42 of the first valve 30 and to the input 44 of the second valve 32 via the second input connection 13 and via a branch point 40. This means that the switch position is not actuated of the second valve 32 from the output 14 of the fixed pump 16, a fluid path to the second output port 24 of the control block 4 and thus to the storage tank 12 is open. When the second valve 32 is in the non-actuated switching position, the volume flow of the constant pump 16 is therefore diverted to the tank without being throttled.

The output 14 of the constant pump 16 is also connected via a connecting line 46 to the supply line 26 leading from the swivel pump 10 to the inlet 22, a check valve 48 being inserted into the connecting line 46, which opens in the direction of the supply line 26. This connecting line 46 is connected to the supply line 26 in front of the control line 38, viewed in the direction of flow. The first valve 30, like the second valve 32, is connected on the output side to the second output connection 24 of the control block 4 and thus to the storage tank 12. The control block 4 is completed by a pressure relief valve 50, which secures the constant pump 16 to the storage tank 12 and is inserted as a bypass to the second valve 32 between its inlet 44 and its outlet 52 connected to the tank.

The Fig. 1 shows an operating state in which the second valve 32 is in the unactuated switching position, i.e. the open position. Regardless of the valve position of the first valve 30, as mentioned, the volume flow of the fixed pump 16 is diverted from the branch point 40 towards the tank. At the state of Fig. 1 the first valve 30 is not pressurized via line 38 with a demand-reporting LS pressure. The first valve 30, which together with the constant pump 16 forms the pressure compensator of an open center system, is therefore controlled from the blocking position by the supply pressure of the pivot pump 10 prevailing in the control line 38 against the action of the compression spring 36, so that in this state A fluid path to the tank is also formed via the outlet 54 of the first valve 30. In Fig. 1 This oil flow is illustrated with lines drawn with greater thickness.

The Fig. 2 shows an operating state in which the constant pump 16 also makes no contribution to increasing the inflow quantity because the second valve 32 is again inactive, so that the volume flow of the constant pump 16 is diverted to the tank. Unlike Fig. 1 However, an LS pressure is effective at the first valve 30, which signals the need for additional supply to the inlet 22. Together with the effect of the compression spring 36, the first valve 30 is therefore controlled into the blocking state. Although no volume of the pivot pump 16 flows out via the valve 30, since the second valve 32 is not actuated, a diversion takes place via this valve, so that the fixed pump 16 in turn makes no contribution to the supply.

In the operating state of Fig. 3 the second valve 32 is switched to the blocking state by the operator, so that no outflow of volume from the constant pump 16 occurs via this valve 32. At the same time, however, no LS pressure acts on the first valve 30 via the control line 28, which is sufficient to control the first valve 30 into the blocking position against the supply pressure acting via the control line 38, so that the proportional valve 30 enables a flow to the tank. Despite the second valve 32 being actuated, no boost function is triggered.

At the in Fig. 4 In the state shown, an LS pressure is effective on the first valve 30 via the control line 28, which signals an additional supply, so that the first valve 30 is controlled into the blocking position. At the same time, the boost function is triggered by the operator by pressing the second valve 32 into the blocking position. In these valve positions, the entire volume flow of the constant pump 16 is fed into the supply line 26 via the branch point 40, the first check valve 48 and the connecting line 46 and increases the volume flow in the inlet 22. Since the boost function also increases when the LS pressure and the additional supply are requested thereby blocked first valve 30, as shown in Fig. 2 is shown, can only be triggered if the operator, as in Fig. 4 shown, the second Valve 32 is actuated, the invention provides a safety-enhancing hydraulic locking of the boost function.

Claims (9)

1. Control device for supplying at least one hydraulic load with fluid having a variable displacement pump (10) that can be controlled by means of a load-sensing pressure (LS), wherein, in the event of an increased volume flow in the feed (22) of the hydraulic load, the load-sensing pressure (LS) is transferred to a control apparatus (2) by means of a control line (28), said control apparatus carrying out the increase in the feed (22) by switching on a fixed displacement pump (16) as soon as an operator initiates the corresponding function by actuating the control apparatus (2), wherein the control apparatus (2) comprises a first (30) and a second control valve (32), the second control valve (32) of which can be controlled by the operator, characterised in that the first control valve (30) can be controlled by the load-sensing pressure (LS) in the control line (28).
2. Control device according to claim 1, characterised in that the first valve is a proportional valve, in particular a 2/2-way proportional valve (30), which, on one of its control sides, in addition to a spring preload (36), is loaded with the load-sensing pressure (LS) and, on its other control side, with the feed pressure in the feed (22) of the respective hydraulic load.
3. Control device according to either claim 1 or claim 2, characterised in that the second valve is an electromagnetically actuatable switching valve, in particular a 2/2-way switching valve (32), which, in its unactuated position, releases a fluid path from the fixed displacement pump (16) to a storage tank (12, T) and, in its actuated position, as initiated by the operator 25, blocks the corresponding fluid path.
4. Control device according to any of the preceding claims, characterised in that the second valve (32) is arranged in the bypass to the first valve (30), the inlet (42) and the outlet (54) of the first valve (30) being connected in a fluid-conveying manner to the inlet (44) or the outlet (52) respectively of the second valve (32).
5. Control device according to any of the preceding claims, characterised in that the outlet (14) of the fixed displacement pump (16) is connected via a branch point (40) to the inlet (42 or 44 respectively) of the first (30) and the second valve (32).
6. Control device according to any of the preceding claims, characterised in that the outlet (14) of the fixed displacement pump (16) is connected to the outlet (8) of the variable displacement pump (10) via a connecting line (46), in which a stop valve (48) is connected, in particular in the form of a spring-loaded non-return valve, which opens in the direction of the variable displacement pump (10) and closes in the direction of the fixed displacement pump (16).
7. Control device according to claim 6, characterised in that, in the connection (26) between the variable displacement pump (10) and the respective hydraulic load, first the connecting line (46) is connected to the stop valve (48) and then a control line (38) is connected which loads the first valve (30) with the feed pressure.
8. Control device according to any of the preceding claims, characterised in that a pressure-limiting valve (50) is connected in parallel with the second control valve (32) in a bypass line, and, when said pressure-limiting valve responds, the volume flow of the fixed displacement pump (16) is transferred to the storage tank (12, T), bypassing the first (30) and second valve (32).
9. Control device according to any of the preceding claims, characterised in that it is designed as a control block (4), which includes

   - the first (30) and second valve (32),

   - the stop valve (48) and

   - the pressure-limiting valve (50)

   and ports (6, 13, 20, 24, 18) for the fluid-conveying connection to the swivel angle pump (10) provided as the variable displacement pump, the fixed displacement pump (16), the respective load, the storage tank (12, T) and the load-sensing control line (28).

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