EP1558849B1 - Double-circuit hydraulic system - Google Patents

Abstract

The invention relates to a double-circuit hydraulic system for controlling consumers of mobile equipment such as track equipment. Two hydraulic circuits (2, 4) can be interconnected by means of a system provided with interconnection valves (38). According to said invention, a device such as non-return valve makes it possible to ensure that, a high pressure in the circuit supplying reduced quantity of a pressure fluid does not impact another circuit having a low pressure, the circuits (2, 4) being interconnected. In the preferred embodiment, the inventive system provided with interconnection valves comprises two manometers (40, 42) which are exposed to a pumped pressure and the load pressure of the corresponding circuit, the non-return valves being arranged upstream thereof.

Description

The invention relates to a hydraulic two-circuit system for controlling consumers of a mobile device, in particular a tracked device according to the preamble of patent claim 1.

In the US 6,170,261 B1 is a hydraulic dual-circuit system of a mobile device, such as a chain or tracked device disclosed. In such caterpillars, the chassis has two chains, which are each controlled separately via one of the hydraulic circuits. To the two hydraulic circuits of the chain unit are also still a slewing gear and units of equipment, such as the boom, the dipper and the spoon connected. Each of the two hydraulic circuits is fed by a variable displacement pump with pressure medium, which are controlled depending on the highest load pressure of the consumer in each associated circle.

In the event that at least one consumer of the equipment is to be actuated in addition to the two chains, it is possible to interconnect both hydraulic circuits to avoid a low pressure medium supply. When in the US 6,170,261 B1 disclosed solution, this interconnection of the two hydraulic circuits via a connection valve, via which the pressure lines connected to the two pumps and the load pressure signaling lines of the two circuits are interconnected. The control of the interconnection valve takes place in dependence on the pressure medium supply to the additional consumer. In addition, can manually engage the operator and interconnect the two circuits.

The disadvantage of this solution is that, for example, when driving a connected to a hydraulic circuit consumers with high pressure medium demand and low pressure and control of a consumer connected to the other circle with low volume and high pressure both circuits are connected via the interconnection valve, so that the higher load pressure of the latter circle also rests in the former circle. Due to this higher load pressure, the pump of the first circuit is raised, so that both circuits are raised to the higher pressure level. The pressure in the first-mentioned hydraulic circuit must then be adjusted back down to the required pressure level, which results in considerable energy losses. Another disadvantage is that in the solution according to the US 6,170,261 B1 a considerable circuit complexity for tapping the load pressure from the additional consumer and to control the interconnecting valve is required.

The document JP 10061608 refers to a dual-circuit system in which the pump lines of two variable displacement pumps are connectable via a Zusammenschaltventilanordnung. The interconnect valve assembly is supplied pilot pressure from the pump lines and load pressure reporting lines. The above-mentioned disadvantages of US 6,170,261 can not be eliminated by such a two-circuit system.

In contrast, the invention has the object to provide a hydraulic dual-circuit system that allows a simple structure minimizing the energy losses in the case of interconnecting both circles.

This object is achieved by a hydraulic dual-circuit system having the features of patent claim 1.

According to the invention, the two-circuit hydraulic system has a connection valve arrangement with two valve devices, each of which prevents the interconnection of the two circuits in one of the circuits acting higher load pressure is reported at low pressure medium demand in the other circle with lower load pressure and high pressure medium requirement. D. h., In both circles of the actual requirements corresponding load pressure is reported to the respective associated variable, so that in the case in which a high pressure at low pressure medium required in one of the circuits, the variable displacement pump is not raised and thus the energy losses are significantly minimized compared to the solution mentioned above. However, the solution according to the invention makes it possible that, in the case where a high load pressure at high pressure medium requirement is present in one of the two circuits, this high load pressure is reported when switching into the second circuit, if a lower load pressure had previously occurred in this second circuit ,

In a specific embodiment of the invention, the interconnecting valve assembly has two pressure compensators, each associated with one of the circuits. These pressure compensators are each acted upon in the opening direction of the tapped in the respective circuit load pressure and in the closing direction of the respective pump pressure. Furthermore, non-return valves or the like are provided in load pressure lines connected to the pressure compensators which, when the pressure compensator is open, prevent a higher circuit from the one connected from being signaled via the open pressure compensator in the circuit assigned thereto. That is, the message of this higher load pressure in the other circuit is only possible if the pressure compensator associated with the circle with higher load pressure opens.

The solution with two pressure compensators and two check valves is extremely simple, with only the pump pressures and the load pressures must be tapped for control.

In this variant, it is particularly preferred if the pressure compensators are acted upon in addition to the load pressure in the opening direction or by the force of a spring whose spring force is smaller than the pump Δp.

In the case in which the valve assemblies for controlling the consumers and the chassis of the mobile device, for example, the tracked device are assembled in a control block in a plate-like manner, it is preferred that the two pressure compensators and the associated check valves are combined in an intermediate plate, so that the Connection to the two circles is extremely easy.

In the solution described above, the interconnection of the two circuits takes place automatically as a function of the pressures applied to the pressure compensators (pump pressure, load pressure). In the event that intervention is to be arbitrary, it is proposed with an advantageous development of the invention to tap the control pressure acting on the control surface of the pressure compensator effective in the opening direction, for example the load pressure, via a directional control valve. The output port of this directional valve connects, for example, in a basic position, the spring pressure of the associated pressure compensator with the tank, so that this pressure compensator always remains in the closed position and thus an interconnection of the two circuits on this pressure compensator is not possible. In a further switching position of the directional control valve, the higher of the two pump pressures can be applied to this spring chamber. In this switching position, the respective pressure compensator is always open, and both circuits connected via this pressure compensator. In the third switching position is the spring chamber of the load pressure on - the Verschschaltventilanordnung then operates in the above-described automatic mode.

The directional control valve is preferably designed as an electrically operated 4/3-way valve, which is arbitrarily switchable by the operator in one of the three above-described operating positions (automatic operation, locking the circuits and interconnecting the circuits).

The hydraulic dual-circuit system according to the invention can be used particularly advantageously in a caterpillar device in which the hydraulic motors for driving the two chains are actuated via one of the respective circles.

Other advantageous developments of the invention are the subject of further subclaims.

• Figur 1 einen Auszug eines Schaltschemas eines Steuerblockes zur Ansteuerung eines Raupengerätes;
• eine Detaildarstellung des Schaltschemas aus Figur 2 und
• Figur 3 ein Wegeventil zur Ansteuerung von Druckwaagen des Schaltschemas gemäss Figur 2.

In the following, a preferred embodiment of the invention will be explained in more detail with reference to schematic drawings. Show it:

• Figure 1 is an excerpt of a circuit diagram of a control block for controlling a tracked device;
• a detailed representation of the circuit diagram of Figure 2 and
• 3 shows a directional control valve for controlling pressure compensators of the circuit diagram according to FIG. 2.

This excavator control 1 is constructed as a two-circuit system with two hydraulic circuits 2, 4, which are each supplied via a variable displacement pump, not shown, with pressure medium. The excavator provided with the control shown in Figure 1 has a chassis with two chains whose traction drives are supplied via the two circuits 2, 4 independently with pressure medium. In addition to the traction drive, other consumers of the excavator, such as a slewing gear, a stick, a spoon or a boom, are controlled via the two-circuit system.

The control block which implements the excavator control according to FIG. 1 is designed in a disc construction, wherein the two variable displacement pumps, not shown, are connected to pressure ports P ₁ and P ₂ on the control block. This also has a tank connection T and working connections A ₁ , B ₁ and A ₃ , B ₃ , to which the drive of the right or left chain is connected. At other ports A ₂ , B ₂ and A ₄ , B _4, etc., the other consumers of the excavator, such as the drive of the slewing gear, the hydraulic cylinder for actuating the stem, the spoon or the boom are connected. In the illustrated embodiment, it is assumed that are connected to the terminals A2, B _{2 of} the boom and to the terminal A ₄ , B _{4 of} the spoon.

The illustrated control block further has two load pressure connections, hereinafter referred to as LS ₁ and LS ₂ , via which the load in the respective circuit 2, 4 acting load pressure and the flow control valve (not shown) of the variable displacement is performed, thus depending on this highest load pressure is controlled.

The control of the aforementioned consumer takes place in each case via a proportionally adjustable directional control valve 6, which in each case a pressure compensator 8 is connected downstream. The directional control valve 6 has a variable measuring orifice forming a speed part and a directional part, wherein the metering orifice of the pressure compensator 8 is connected upstream and the directional part downstream of the pressure compensator 8 is arranged. Each pressure balance 8 is in the closing direction acted upon by the load pressure and in the opening direction of the pressure downstream of the metering orifice of the directional control valve 6. The pressure compensator piston adjusts itself in dependence on the applied control pressures in a control position in which the pressure drop across the orifice plate of the proportionally adjustable directional control valve 6 is kept contant, so that a load pressure independent flow control is possible. Such LS controls are well known, so that can be dispensed with a detailed description of the structure of the directional control valve 6 and the downstream pressure compensator 8. The control of the directional control valve 6 takes place in each case via pilot valves 10, 12, via which a control pressure is applied to the frontal control surfaces of a slide of the directional control valve 6. These pilot valves are actuated, for example, as a function of the actuating movement of a joystick.

The connections of the directional control valves 6 are connected via a pressure line 14, 16 to the pressure port P ₁ or P ₂ . Furthermore, each directional valve has two working ports, which are each connected via a working line 18 and 20 with the associated load ports A, B. For returning the pressure medium from the consumer, an output connection of the directional control valve 6 is connected via a tank line 22 to the tank connection T of the control block.

In the working lines, pressure limiting valves are provided in each case for limiting the maximum pressure supplied to the consumer, the pressure limiting valves with suction function delimiting the pressure at the working ports A ₂ , B ₂ , B ₁ and B ₃ and A ₄ (not illustrated), so that when the consumer advances pressure medium can be sucked out of the tank in order to avoid cavitation phenomena. A respective connected to the load pressure port LS of the two circuits 2, 4 load pressure signaling line 28, 30 is connected via an LS flow control valve 32 and 34 to the common tank line 22.

The pressure compensators 8 are designed so that they report in their fully open end position at its input pressure (downstream pressure of the orifice plate) in the load pressure line 28 and 30, so that in this is always the highest load pressure in the respective circuit 2 or 4 ,

The above-described directional valves with the associated pressure compensator 8, the pilot valves 10, 12 and the pressure relief valves 24, 25 may each be received in a disk or in a common control block. In order to connect the two hydraulic circuits 2, 4, an interconnecting valve arrangement 38 is provided in an intermediate disc 36, via which the pressure lines 14, 16 of the two hydraulic circuits 2, 4 can be interconnected in certain operating states, so that the actuated consumers of both variable displacement pumps are connected together Pressure medium to be supplied.

The construction of the interconnecting valve arrangement will be explained with reference to the enlarged illustration according to FIG.

The Verschschaltventilanordnung 38 has two pressure compensators 40, 42, which are each biased by a spring 44 in the direction of its open position. The spring force of the spring is designed to be slightly below the pump Δp. If this example, at about 20 bar, the spring force of the spring 44 will be approximately between 10 and 19 bar.

The upper pressure compensator 40 in FIG. 2 is assigned to the circuit 2 and the lower pressure compensator 42 to the circuit 4. The voltage applied to the pressure line 14 (pump pressure) is guided to an effective in the closing direction control surface of the pressure compensator 40 and the voltage applied in the load pressure line 28 of the circuit 2 highest load pressure tapped via a control line 46 and guided to an effective in the opening direction control surface of the pressure compensator 40. In the illustrated embodiment, the control line 46 opens into the spring chamber for the spring 44 a.

Accordingly, the pressure in the pressure line 16 of the second circuit 4 is guided to a closing direction effective control surface of the pressure compensator 42 and the pressure in the load pressure signal line 30 via a further control line 48 in the spring chamber of the pressure compensator 42.

The two input ports P and LS of the pressure compensators 40, 42 are connected to the associated pressure lines 14 and 16 and the load pressure signaling lines 28 and 30, respectively. Upstream of the LS port of the pressure compensators 40, 42 is in each case a check valve 50, 52 is provided, which allows a flow of pressure medium from the load pressure signaling line 14 and 16 to the associated LS connection, but in the opposite direction shuts off.

The two output terminals A, B are connected to the load pressure signaling lines 28, 30 and the pressure lines 14, 16 of the other circle 2, 4.

The function of this interconnecting valve arrangement will be explained with reference to two operating states of the excavator control.

It is first assumed that there is an operating state in which the load connected to the working connections A ₂ , B ₂ , for example the stem, requires a large amount of pressure medium and accordingly a comparatively low pump pressure rests in the hydraulic circuit 2. The connected to the working ports A ₄ , B _{4 of} the second circuit 4 consumers, such as the boom, however, only need a small amount of pressure medium at a relatively high pump pressure. In this operating state, the pressure compensator 42 associated with the second circuit 4 Δpp is held in its closed position by the high pump pressure, while the pressure compensator 40 associated with the first circuit 2 is brought into a control position due to the dropped pump pressure, in which the connections P, LS with the Terminals A, B are connected. This allows the second circuit 4 associated variable pressure fluid to the connected to the first circle 2 stem (ports A ₂ , B ₂ ) promote, so that the higher pressure medium requirement of this consumer is secured. The check valve 50 prevents that the higher, applied in the load pressure signal line 30 load pressure is reported in the load pressure signaling line 28 of the first circuit 2, so that the pressure level in this circle remains low and the energy losses described above do not occur. In its control position, the pressure compensator 50 throttles the pressure medium flow from the higher pressure level prevailing in the second circuit 4 to the pressure level required in the first circuit 2.

It is now assumed that the caterpillar device is in straight travel and both chains are supplied with the full amount of pressure medium. Both variable displacement pumps are fully started and the pressure compensators are acted upon in the closing direction with the maximum pump pressure and are thus closed and both circuits 2, 4 separated from each other. Now becomes another consumer, For example, the boom (ports A ₂ , B ₂ ) switched on, then decreases due to the pressure medium requirement of this consumer, the pressure in the first circuit 2 from. Without Verschschaltventilanordnung 38 then the left chain (port A ₁ , B ₁ ) would not be sufficiently supplied with pressure medium, so that the crawler moves a curve. However, this is prevented by the interconnecting device 30 in the following manner.

Due to the pressure drop in the first circuit 2 and the corresponding reduction of the pump pressure, the pressure compensator 40 is brought into its control position, so that the two circles 2, 4 are connected to each other. As a result of the connection of these two circuits, the pump pressure in the second circuit 4 also decreases, so that the pressure compensator 42 assigned to this circuit accordingly also opens, so that the two circuits 2, 4 are connected to one another via both pressure compensators 40, 42. In other words, a kind of LUDV recirculation system sets in which is operated in subsaturation - the straight ahead of the tracked device is maintained and the connected consumer (boom) is supplied with pressure medium.

In the above-described embodiment, the interposing valve assembly 38 operates automatically and binds the two circuits 2, 4 in the event of undersaturation of one or both circuits. It may now be necessary for both circuits to be arbitrarily interconnected by the operator, for example to ensure optimum supply to one of the consumers. But it may also be necessary to lock the two circles against each other to prevent interconnection.

These variants can be realized in a comparatively simple manner in that the two control lines 46, 48 are not guided directly to the acting in the opening direction control surface of the pressure compensators 40, 42 (spring chamber) but each via a control valve 54, as shown in Figure 3.

The control valve 54 shown in Figure 3 is designed as a 4/3-way valve and has a pressure port P, an LS port LS and a tank port T and a control port S which is connected to the leading to the spring chamber control line 46 and 48 respectively. The LS connection is connected to the load pressure signaling line 28 or 30 of the respective circuit 2, 4. The pressure port P is connected via a shuttle valve 56 with the two pressure lines 14, 16 of the two hydraulic circuits 2, 4 connectable. About the shuttle valve 56 is always the higher of the two pump pressures to the pressure port P out. In the illustrated basic position (0) of the control valve 54, the pressure port P and LS port LS are shut off, and the control line 46 (48) connected to the tank port T. D. h., In the spring chamber of the tank pressure acts, so that the respective pressure compensator 40, 42 is biased by the respective acting pump pressure in the closed position - the two pressure compensators 40, 44 are closed and the two circles 2, 4 locked against each other.

When switching the electrically operated control valve 54 in the switching position (a) of the respective circuit 2, 4 applied load pressure in the control line 46 (48) is switched through - the Verschschaltventilanordnung 38 operates in the same manner as explained with reference to Figures 1 and 2 has been.

When switching the control valve 54 in the position indicated by (b), the pressure port P is connected to the control port S, so that in the spring chamber, the higher of the two pump pressures is effective and the associated Pressure compensator 40 (42) is held by the force of the spring 44 in the open position. That is, the system is then operated as a recirculation system, in which the consumers are supplied by both pumps' with pressure medium.

Disclosed is a hydraulic dual-circuit brake system for controlling consumers of a mobile device, such as a tracked device. The two hydraulic circuits can be interconnected via a Zusammenschaltventilanordnung, with a device, such as check valves, ensures that when interconnecting the circuits a higher load pressure at low pressure medium requirement in one of the circuits is not reported in the other circle with lower load pressure. In a preferred variant, the interconnecting valve arrangement has two pressure compensators, which are each acted upon by the pump pressure and the load pressure in the associated circuit and which check valves are connected upstream.

LIST OF REFERENCE NUMBERS

1

excavator control

2

first circle

4

second circle

6

way valve

8th

pressure compensator

10

pilot valve

12

pilot valve

14

pressure line

16

pressure line

18

performance

20

performance

22

tank line

24

Pressure relief valves

26

Pressure relief valves

28

Load pressure signaling line

30

Load pressure signaling line

32

LS flow control valve

34

LS flow control valve

36

washer

38

Interconnecting valve arrangement

40

pressure compensator

42

pressure compensator

44

feather

46

control line

48

control line

50

check valve

52

check valve

54

control valve

56

shuttle valve

Claims (8)

1. Hydraulic double-circuit system for activating consumers of a mobile appliance, in particular of a tracked appliance, wherein a variable displacement pump is associated with each hydraulic circuit (2, 4), via which pump the associated consumers can be supplied with pressure medium, and wherein the two circuits (2, 4) can be connected together via an interconnection valve arrangement (38) such that the variable displacement pump of one circuit (2, 4) delivers pressure medium into the other circuit (4, 2), so that this other circuit (4, 2) can be supplied with pressure medium via both variable displacement pumps, and wherein the variable displacement pumps are in each case activated in accordance with the load pressure in the respective associated circuit (2, 4), wherein the interconnection valve arrangement (38) has two valve devices (40, 42; 50, 52), each of which is associated with one of the circuits (2, 4) and via which, in accordance with the load pressure and with the pump pressure in the one, associated circuit (2, 4), the connection to the other circuit (4, 2) can be controlled in the opening sense, characterised in that the line sections (28, 30) of the two circuits which carry the load pressure can be connected via the interconnection valve arrangement (38), and the connection of the line sections which carry the load pressure is formed such that the load pressure of the other circuit (4, 2) cannot be signalled to the one, associated circuit (2, 4).
2. Double-circuit system according to Claim 1, wherein the interconnection valve arrangement (38) has two pressure-maintaining valves (40, 42), of which one pressure-maintaining valve (40) is acted upon in the closing direction by the pump pressure acting in one of the circuits (2) and in the opening direction by the load pressure, and the other pressure-maintaining valve (42) is accordingly acted upon by the pump pressure and by the load pressure in the other circuit (4), and which can be connected via the pressure and LS lines (14, 16; 28, 30) of the two circuits (2, 4), wherein non-return valves (50, 52) are provided in the LS lines (28, 30), which valves prevent a control oil flow from the circuit (2, 4) with the higher load pressure into the circuit (4, 2) with the lower load pressure.
3. Double-circuit system according to Claim 1 or 2, wherein the pressure-maintaining valves (40, 42) in each case have a spring (44) which is active in the opening direction and the spring force of which is lower than the pressure drop at the pump.
4. Double-circuit system according to any one of the preceding Claims, wherein the interconnection valve arrangement (38) is accommodated in an intermediate plate (36) of a valve block.
5. Double-circuit system according to any one of the preceding Claims, with a locking device (54) for locking the interconnection valve arrangement, so that either a double- or a single-circuit system can be set.
6. Double-circuit system according to Claims 2 and 6, wherein the locking device has a respective control valve (54) which is associated with one pressure-maintaining valve (40, 42) and via which a spring chamber of the pressure-maintaining valve (40, 42) can be acted upon either by the load pressure in the associated circuit (2, 4), by the tank pressure or by the higher of the pump pressures.
7. Double-circuit system according to Claim 6, wherein the control valve (54) is an electrically actuated 4/3-way valve.
8. Double-circuit system according to any one of the preceding Claims, wherein the consumers are running gear drives for two chains of a tracked appliance and further units of the equipment of the tracked appliance, such as, for example, a shovel, a handle, a boom and a slewing mechanism.

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