WO2004042235A1

WO2004042235A1 - Double-circuit hydraulic system

Info

Publication number: WO2004042235A1
Application number: PCT/DE2003/003126
Authority: WO
Inventors: Thomas Weickert
Original assignee: Bosch Rexroth Ag
Priority date: 2002-11-07
Filing date: 2003-09-19
Publication date: 2004-05-21
Also published as: DE50308813D1; AU2003271543A1; KR101011992B1; JP2006505750A; ATE380942T1; EP1558849A1; EP1558849B1; KR20050059333A

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

description

Hydraulic two-circuit system

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

US Pat. No. 6,170,261 B1 discloses a hydraulic two-circuit system for a mobile device, for example a chain or caterpillar device. In such caterpillar devices, the undercarriage has two chains, each of which can be controlled separately from one another via one of the hydraulic circuits. To the two hydraulic circuits of the chain device, a slewing gear and aggregates of the equipment, such as the boom, the dipper stick and the bucket are also connected. Each of the two hydraulic circuits is supplied with pressure medium by a variable displacement pump, which is controlled as a function of the highest load pressure of the consumers in the respective assigned circuit.

In the event that at least one consumer of the equipment is to be actuated in addition to the two chains, there is the possibility of interconnecting the two hydraulic circuits in order to avoid a supply of pressure medium. In the solution disclosed in US Pat. No. 6,170,261 B1, this interconnection of the two hydraulic circuits takes place via an interconnection 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 valve is controlled depending on the pressure medium supply to the additional consumer. In addition can the operator intervenes manually and interconnect the two circles.

The disadvantage of this solution is that, for example, when controlling a consumer connected to the hydraulic circuit with a high pressure medium requirement and low pressure and when controlling a consumer connected to the other circuit with low volume requirement and high pressure, both circuits are connected via the interconnection valve , so that the higher load pressure of the latter circuit is also present in the first circuit. Due to this higher load pressure, the pump of the first circuit is started up, so that both circuits are raised to the higher pressure level. The pressure in the first-mentioned hydraulic circuit must then be reduced accordingly to the required pressure level, which results in considerable energy losses. Another disadvantage is that the solution according to US Pat. No. 6,170,261 B1 requires a considerable amount of circuitry for tapping the load pressure from the additional consumer and for controlling the interconnection valve.

In contrast, the invention is based on the object of creating a hydraulic two-circuit system which, with a simple structure, enables the energy losses to be minimized when the two circuits are connected together.

This task is performed by a hydraulic two-circuit

System with the features of claim 1 solved.

According to the invention, the hydraulic dual-circuit system has an interconnection valve arrangement with two valve devices, each of which prevents one in one of the circuits from interconnecting the two circuits higher load pressure with a low pressure medium requirement is reported in the other circuit with a lower load pressure and high pressure medium requirement. I.e. , in both circles the load pressure corresponding to the actual requirements is reported to the respectively assigned variable displacement pump, so that in the event that a high pressure is present in one of the circles with a low pressure medium requirement, the variable displacement pump is not started up and thus the energy losses compared to the solution mentioned at the outset are considerably minimized. However, the solution according to the invention allows that in the event that a high pressure is present in one of the circuits with a high pressure medium requirement, this high load pressure is reported to the second circuit if a lower load pressure is present in it.

In a specific embodiment of the invention, the interconnection valve arrangement has two pressure compensators, each of which is assigned to one of the circuits. These pressure compensators are each acted upon in the opening direction by the load pressure tapped in the respective circuit and in the closing direction by 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 which one is connected from being reported to the circuit assigned to it via the open pressure compensator. I.e. , The reporting of this higher load pressure in the other circuit is only possible if the pressure compensator assigned to the circuit with a 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 having to 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, the spring force of which is smaller than the pump Δp.

In the event that the valve arrangements for controlling the consumers and the chassis of the mobile device, for example the caterpillar device, are combined in a control block in plate construction, it is preferred that the two pressure compensators and the associated check valves are combined in an intermediate plate , so that the Ali binding to the two circles is extremely easy.

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

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

The hydraulic two-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 each controlled via one of the circles.

Other advantageous developments of the invention are the subject of further dependent claims.

A preferred embodiment of the invention is explained in more detail below with the aid of schematic drawings. Show it:

Figure 1 shows an extract of a circuit diagram of a control block for controlling a caterpillar device; a detailed representation of the circuit diagram of Figure 2 and

3 shows a directional control valve for actuating pressure compensators of the circuit diagram according to FIG. 2.

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

The control block which realizes the excavator control according to FIG. 1 is of disc construction type, the two variable pumps, not shown, being connected to the control block at pressure connections P_ and P2. This also has a tank connection T and work connections A] _, B] _ and A ₃ , B ₃ , to which the drive of the right or left chain is connected. The other consumers of the excavator, such as the drive of the slewing gear, the hydraulic cylinders for actuating the stick, the bucket or the boom are connected to further connections A ₂ , B2 and A ₄ , B ₄ etc. In the exemplary embodiment shown, it is assumed that the boom is connected to the connections A2, B ₂ and the bucket to the connections A ₄ , B ₄ .

The control block shown also has two load pressure connections, hereinafter referred to as LS ^ and LS ₂ , via which the load pressure acting in the respective circuit 2, 4 is tapped and fed to the flow control valve (not shown) of the variable displacement pump, which is therefore dependent on the latter highest load pressure is controlled.

The control of the aforementioned consumers takes place in each case via a proportionally adjustable directional valve 6, which is connected downstream of a pressure compensator 8. The directional control valve 6 has a speed part which forms a variable measuring orifice and a directional part, the measuring orifice being connected upstream of the pressure compensator 8 and the directional part being arranged downstream of the pressure compensator 8. Each pressure compensator 8 is in the closing direction acted upon by the load pressure and in the opening direction by the pressure downstream of the metering orifice of the directional valve 6. The pressure compensator piston adjusts itself to a control position depending on the control pressures present, in which the pressure drop across the measuring orifice of the proportionally adjustable directional control valve 6 is kept constant, so that volume flow control independent of the load pressure is made possible. Such LS controls are well known, so that a detailed description of the structure of the directional control valve 6 and the downstream pressure compensator 8 can be dispensed with. 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 front control surfaces of a slide of the directional control valve 6. These pilot valves are actuated, for example, depending on 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 connection P] _ or P2. Furthermore, each directional control valve has two working connections, each of which is connected to the associated consumer connections A, B via a working line 18 or 20. To return the pressure medium from the consumer, an outlet connection of the directional control valve 6 is connected to the tank connection T of the control block via a tank line 22.

To limit the maximum pressure supplied to the consumer, pressure relief valves are also provided in the working lines, the pressure limiting valves limiting the pressure at the working connections 2, B ₂ , B] _ and B ₃ and A ₄ (not shown) being designed with a suction function so that when the consumer runs ahead, pressure medium can be sucked in from the tank in order to avoid the. A load pressure signaling line 28, 30 connected to the load pressure connection LS of the two circuits 2, 4 is connected to the common tank line 22 via an LS flow control valve 32 or 34.

The pressure compensators 8 are designed in such a way that, in their fully opened end position, they report the pressure present at their inlet (pressure downstream of the measuring orifice) into the load pressure line 28 or 30, so that the highest load pressure in the respective circuit 2 or 4 is always in this ,

The directional valves described above with the associated pressure compensator 8, the pilot valves 10, 12 and the pressure limiting valves 24, 25 can each be accommodated in a disk or in a common control block. To connect the two hydraulic circuits 2, 4, an interconnection valve arrangement 38 is provided in an intermediate disk 36, via which, under certain operating conditions, the pressure lines 14, 16 of the two hydraulic circuits 2, 4 can be connected together, so that the controlled consumers of both variable pumps be supplied together with pressure medium.

The structure of the interconnection valve arrangement is explained on the basis of the enlarged illustration according to FIG. 2.

The interconnection valve arrangement 38 has two pressure scales 40, 42, which are each biased in the direction of their open position by a spring 44. The spring force of the spring is designed so that it is slightly below the pump Δp. If this is, for example, approximately 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 circuit 2 and the lower pressure compensator 42 to circuit 4. The pressure (pump pressure) applied to the pressure line 14 is led to a control surface of the pressure compensator 40 which is effective in the closing direction and the highest load pressure which is present in the load pressure line 28 of the circuit 2 is tapped via a control line 46 and is guided to a control surface of the pressure compensator 40 which is effective in the opening direction. In the illustrated embodiment, the control line 46 opens into the spring space for the spring 44.

Accordingly, the pressure in the pressure line 16 of the second circuit 4 becomes a control surface of the pressure compensator 42 which is effective in the closing direction and the pressure in the

Load pressure reporting line 30 via a further control line

48 guided into the spring chamber of the pressure compensator 42.

The two input connections P and LS of the pressure compensators 40, 42 are connected to the assigned pressure lines 14 and 16 and the load pressure signaling lines 28 and 30, respectively. A check valve 50, 52 is provided upstream of the LS connection of the pressure compensators 40, 42, which enables a pressure medium flow from the load pressure signal line 14 or 16 to the assigned LS connection, but blocks in the opposite direction.

The two output connections A, B are connected to the load pressure measuring lines 28, 30 and the pressure lines 14, 16 of the respective other circuit 2, 4.

The function of this interconnection valve arrangement is explained on the basis of two operating states of the excavator control. It is initially assumed that there is an operating state in which the consumer connected to the working connections A ₂ , B ₂ , for example the handle, requires a large amount of pressure medium and accordingly there is a comparatively low pump pressure in the hydraulic circuit 2. The consumer connected to the working connections A ₄ , B _{4 of} the second circuit 4, for example the boom, on the other hand, should only require a small amount of pressure medium at a comparatively high pump pressure. In this operating state, the pressure compensator 42 assigned to the second circuit 4 Δpp is held in its closed position by the high pump pressure, while the pressure compensator 40 assigned to the first circuit 2 is brought into a control position due to the drop in pump pressure, in which the connections P, LS are included the connections A, B are connected. As a result, the variable displacement pump assigned to the second circuit 4 can deliver pressure medium to the stem (connections A ₂ , B2) connected to the first circuit 2, so that the higher pressure medium requirement of this consumer is ensured. The check valve 50 prevents the higher load pressure present in the load pressure reporting line 30 from being reported into the load pressure reporting line 28 of the first circuit 2, so that the pressure level in this circuit 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 ahead and both chains are supplied with the full amount of pressure medium. Both variable pumps are fully started up and the pressure compensators are pressurized with the maximum pump pressure in the closing direction and are therefore closed and both circuits 2, 4 are separated from each other. If another consumer rather, for example the boom (connections A ₂ , B2) is switched on, the pressure in the first circuit 2 drops due to the pressure medium requirement of this consumer. Without the interconnection valve arrangement 38, the left chain (connection A _] _, B] _) would then not be supplied with sufficient pressure medium, so that the caterpillar drive turns. This is prevented by the interconnection device 30 in the following manner.

Due to the pressure drop in the first circuit 2 and the corresponding reduction in the pump pressure, the pressure compensator 40 is brought into its control position, so that the two circuits 2, 4 are connected to one another. By connecting these two circles, the pupa pressure in the second circle 4 also drops, so that the pressure compensator 42 assigned to this circuit also opens accordingly, so that the two circles 2, 4 are connected to one another via both pressure compensators 40, 42. I.e. , a kind of LUDV single-circuit system is set, which is operated in under-saturation - the crawler device goes straight ahead and the connected consumer (boom) is supplied with pressure medium.

In the exemplary embodiment described above, the interconnection valve arrangement 38 works automatically and binds the two circles 2, 4 in the event of one or both circles being under-saturated. It may now be necessary for the operator to arbitrarily interconnect both circuits in order, for example, to ensure optimal supply to one of the consumers. However, it may also be necessary to lock the two circles against each other in order to prevent interconnection.

These variants can be realized in a comparatively simple way by the fact that the two control Lines 46, 48 are not led directly to the control surface of the pressure compensators 40, 42 (spring chamber) acting in the opening direction, but in each case via a control valve 54, as shown in FIG. 3.

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

When the electrically operated control valve 54 is switched to the switching position (a), the load pressure present in the respective circuit 2, 4 is switched through to the control line 46 (48) - the interconnection valve arrangement 38 works in the same way as explained with reference to FIGS. 1 and 2 has been .

When the control valve 54 is switched to the position marked with (b), the pressure port P is connected to the control port s, so that the higher of the two pump pressures is effective in the spring chamber and the associated ordered pressure compensator 40 (42) is held in the open position by the force of the spring 44. I.e. The system is then operated as a single-circuit system in which the consumers are supplied with pressure medium by both pumps.

A hydraulic dual-circuit brake system for controlling consumers of a mobile device, for example a caterpillar device, is disclosed. The two hydraulic circuits can be interconnected via an interconnection valve arrangement, with a device, for example non-return valves, ensuring that when the circuits are interconnected, a higher load pressure with low pressure medium requirement in one of the circuits is not reported in the other circuit with a lower load pressure , In a preferred variant, the interconnection valve arrangement has two pressure compensators, each of which is acted upon by the pump pressure and the load pressure in the associated circuit and which are connected upstream of check valves.

LIST OF REFERENCE NUMBERS

Excavator control first circuit second circuit directional control valve pressure balance pilot valve pilot valve pressure line pressure line work performance work performance tank line pressure relief valve pressure relief valve load pressure signaling line load pressure signaling line LS flow control valve LS flow control valve intermediate disk interlocking valve arrangement pressure balance pressure compensator spring control line control line check valve check valve check valve control valve shuttle valve

Claims

claims

1. Hydraulic two-circuit system for controlling consumers of a mobile device, in particular a caterpillar device, each hydraulic circuit

(2, 4) is assigned to a variable displacement pump, via which the assigned consumers can be supplied with pressure medium, and the two circuits (2, 4) can be connected to one another via an interconnection valve arrangement (38) such that the variable displacement pump of one circuit (2, 4 ) Promotes pressure medium in the other circuit (4, 2) so that this circuit (4, 2) can be supplied with pressure medium via both variable displacement pumps, and the variable displacement pumps are each controlled as a function of the load pressure in the assigned circuit (2, 4), characterized in that the interconnection valve arrangement (38) has two valve devices (40, 42; 50, 52), each of which is assigned to one of the circuits (2, 4) and via which, depending on the load pressure and the pump pressure in the assigned circuit (2 , 4) the connection to the other circuit (4, 2) can be controlled, the connection of the line sections carrying the load pressure being designed in such a way that the load pressure from the other circuit (4, 2) is not in dan z associated circle (2, 4) can be reported.

2. Two-circuit system according to claim 1, wherein the interconnection valve arrangement (38) two pressure compensators

(40, 42), one of which has a pressure compensator (40) of the pump pressure acting in one of the circles (2) in the closing direction and the load pressure in the opening direction and the other pressure compensator (42) accordingly of the pump pressure and the load pressure in the other circuit (4 ) is acted upon, and via the pressure and LS lines gen (14, 16; 28, 30) of the two circuits (2, 4) can be connected, check valves (50, 52) are provided in the LS lines (28, 30), which control oil flow from the circuit> (2, 4) with the higher load pressure in the circuit (4, 2) with the lower load pressure.

3. Two-circuit system according to claim 1 or 2, wherein the pressure compensators (40, 42) each have a spring (44) effective in the opening direction, the spring force of which is less than the pressure drop at the pump.

4. Two-circuit system according to one of the preceding claims, wherein the interconnection valve arrangement (38) is received in an intermediate plate (36) of a valve block.

5. Two-circuit system according to one of the preceding claims, with a locking device (54) for locking the interconnection valve arrangement, so that either a two-circuit or single-circuit system is adjustable.

6. Two-circuit system according to claim 2 and 6, wherein the locking device each has a pressure compensator (40, 42) assigned control valve (54), via which a spring chamber of the pressure compensator (40, 42) optionally with the load pressure in the associated circuit (2, 4 ), with which the tank pressure or the higher of the pump pressures can be applied.

7. Two-circuit system according to claim (6), wherein the control valve (54) is an electrically operated 4/3 way valve. Two-circuit system according to one of the preceding claims, wherein the consumers are undercarriage drives for two chains of a caterpillar device and further units for the equipment of the caterpillar device, such as, for example, a spoon, stick, boom and a slewing gear.