EP0972138A1

EP0972138A1 - Hydraulic control device

Info

Publication number: EP0972138A1
Application number: EP98919168A
Authority: EP
Inventors: Peter BÜTTNER; Armin Stellwagen
Original assignee: Mannesmann Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 1997-04-05
Filing date: 1998-03-27
Publication date: 2000-01-19
Anticipated expiration: 2018-03-27
Also published as: ATE239175T1; JP2001519010A; EP0972138B1; DE19714141A1; WO1998045603A1; US6250202B1; DE59808168D1

Abstract

A hydraulic control arrangement which has a directional control valve, a hydraulic pump and a two-way cartridge valve constructed as a seat valve. The directional control valve is connected to an inlet line and to a discharge line leading to a tank. Leading off from it is a load line leading to a hydraulic load. The hydraulic pump draws pressure medium from a tank and discharges it into the inlet line. The two-way cartridge valve is arranged in the inlet line and, in a closed position, isolates a second inlet line section leading off from the latter to the directional control valve from a first inlet line section running between the two-way valve and the hydraulic pump. A control piston of the two-way cartridge valve has an annular opening surface exposed to the pressure in the first inlet line section, a central circular opening surface exposed to the pressure in the second inlet line section, and a closing surface, which can be subjected to the pressure in the first inlet line section via a pilot valve in a first position of the latter and can be relieved from the pressure to the tank via the pilot valve in a second position of the latter. The two-way cartridge valve closes when an emergency off facility is triggered. To satisfy particularly high safety requirements, the invention makes provision for the second inlet line section to be relieved to the tank via the pilot valve in the first position of the latter.

Description

description

Hydraulic control arrangement

The invention is based on a hydraulic control arrangement which has the features from the preamble of claim 1.

Such a hydraulic control arrangement is e.g. B. from DE 196 19 860 AI known. There is shown a hydraulic control arrangement used on a die casting machine, in which a directional valve can shut off a consumer line leading from it to a pressure chamber of a hydraulic cylinder or can be connected to a drain line leading to a tank or to an inlet line. The feed line is fed by a hydraulic pump, which sucks pressure medium from the tank. A 2-way cartridge valve designed as a poppet valve is arranged in the inlet line, due to which a first inlet line section that runs between the hydraulic pump and the 2-way cartridge valve and a second inlet line section that goes from the 2-way cartridge valve to the directional valve goes off, can distinguish from each other. When the control piston of the 2-way cartridge valve is seated, the two supply line sections are separated from each other. A conventional 2-way cartridge valve with a directional function is used, the control piston of which has two opening surfaces acting in the opening direction, one of which is centrally located on the control piston, corresponds in diameter to the seat diameter and the pressure in the second supply contact line section is exposed. The second opening area is an annular area, the inside diameter of which corresponds to the seat diameter and the outside diameter of which corresponds to the guide diameter of the control piston and which can be acted upon by the pressure in the first inlet line section. The control piston also has a closing surface which is effective in the closing direction and is exposed to the pressure in a rear control chamber of the 2-way cartridge valve. The two opening areas together are as large as the closing area.

In a rest position, which it assumes under the action of a compression spring, a pilot valve connects the rear control chamber to the first inlet line section. In this position of the pilot valve, the 2-way cartridge valve, the control piston of which is usually still acted upon by a spring in the closing direction, is dependent on the pressure in the first inlet line section and on the pressure in the second inlet line section, which is normally not greater than the pressure in the first inlet line section not to open. By energizing an electromagnet, the pilot valve can be brought into a switch position in which it connects the rear control chamber on the control piston with the tank. Now the pressure prevailing in the first inlet line section and acting on the annular surface of the control piston is able to lift the control piston from the seat against the generally weak closing spring and to open the 2-way cartridge valve.

An emergency stop can be implemented with the valve described. In normal operation, the pilot valve's electromagnet is tils' excited and the 2-way cartridge valve open. In the event of an emergency, for example, an electrical switch can be actuated which interrupts the voltage supply for the electrical system, so that the electromagnet of the pilot valve is also disconnected from the voltage supply. The pilot valve comes into its rest position through the compression spring and connects the rear control chamber on the control piston to the first inlet line section, so that the 2-way cartridge valve closes and the flow of pressure medium to the directional control valve is leak-free.

From DE 44 20 459 AI a hydraulic control arrangement according to the load-sensing principle is known, which for emergencies also has a valve with which a second inlet line section can be separated from a first inlet line section. The isolating valve, which can be controlled with an electromagnetically actuated pilot valve, is obviously a slide valve which, in the rest position of the pilot valve, not only separates the two feed line sections from one another, but also connects the load signaling line to the tank and thus relieves the load. The pressure in the second supply line section is also reduced via the load signaling line, provided that the load-sensing directional valve is located at the side of its central position in a working position in which there is an opening cross section between the second supply line section and the load signaling line.

From DE 43 24 177 AI a hydraulic control arrangement according to the load sensing principle is known, in which a separating valve til after triggering an emergency stop signal, separates two supply line sections from each other, shuts off the load signaling line and connects a load signaling connection on the regulator of the variable displacement pump to the tank. The isolating valve is in turn a slide valve.

The aim of the invention is to further develop a hydraulic control arrangement with the features from the preamble of claim 1 so that high safety requirements are met with simple means.

This object is achieved according to the invention in that in a hydraulic control arrangement with the features from the preamble of claim 1 according to the characterizing part of this claim, the second inlet line section in the first switching position of the pilot valve can be relieved of this to the tank. In this way, it is ensured in every position of the directional valve that after the triggering of an emergency stop signal, no pressure is present in the second inlet line section. In this way, a force acting on the second opening surface, which tries to lift the control piston from its seat, falls away, so that the control piston is pressed onto its seat with a large excess force and closes very tightly. No pressure medium is locked into the second feed line section, which in an unfavorable case could relieve the load on a consumer and lead to a dangerous small movement of the hydraulic consumer. The increasing release of pressure from the second opening area with increasing closing travel of the control piston leads to a particularly quick closing of the 2-way cartridge valve and thus to an immediate stop of the inflow of pressure medium to the directional control valve.

A hydraulic control arrangement according to the invention is particularly advantageous if, according to claim 2, the directional control valve can be actuated hydraulically and the control oil is taken from the second feed line section for actuation. Due to the pressure relief of the second inlet line section, the control pressure drops, so that there is no longer any obstacle to the return of the control spool of the directional valve. When the directional valve is actuated electrohydraulically, it is not necessary to switch off the electrical pilot valves.

Several exemplary embodiments of a hydraulic control arrangement according to the invention are shown as circuit diagrams in the drawings. The invention will now be explained in more detail with reference to the figures of these drawings.

Show it

FIG. 1 shows a first exemplary embodiment which is based on the load-sensing principle, the pressure medium source being implemented by a constant pump with a load-sensing-controlled pressure compensator in the bypass to the tank,

Figure 2 shows a variable displacement pump with a load sensing controller 1 can be used instead of the constant pump and the bypass pressure compensator, and FIG. 3 shows a second exemplary embodiment with a constant pump as pressure medium source and directional control valves in a 6-way version with a circulation channel.

In the embodiment according to FIG. 1, a control block 10 contains two directional valve sections 11 and 12, each of which has a directional valve 13 with an inlet chamber 14, to which pressure medium from a hydraulic pump 18 can flow, an outlet chamber 15, which is connected to a tank 19, and has two consumer chambers 16 and 17 which are connected via consumer lines to a double-acting hydraulic consumer, not shown, for example to a differential cylinder. The control slide 27 of a directional control valve 13 can be adjusted in opposite directions in working positions from the middle position, in which the inlet chamber, the outlet chamber and the two consumer chambers are shut off, in the position between the inlet chamber 14 and the consumer chamber 16 or the consumer chamber 17 a metering orifice 20 is open and the other consumer chamber is connected to the drain chamber 15. A load holding valve 21 and an individual pressure compensator 22 are located upstream of the inlet chamber 14, and two control spaces 23 and 24 are adjacent to their control pistons. The control chamber 23 is connected to a load reporting chamber 25 of the directional control valve 13 and the control chamber 24 is connected to the inlet chamber 14 via the load holding valve. The load reporting chamber 25 is relieved of load in the central position of the control slide 27 and in each case in a lateral working position connected to the consumer chamber, which is supplied with pressure medium 20 via the measuring orifice. The regulating piston of the pressure compensator 22 is acted upon in the opening direction by a compression spring 26 and by the pressure prevailing in the control chamber 23 and in the closing direction by the pressure prevailing in the control chamber 24.

Via a shuttle valve chain with shuttle valves 30, the highest pressure in a control chamber 23, ie the highest load pressure, is sent to an output LS of the control block 10 and via a load signaling line 31, in which a throttle 32 is arranged, to a bypass -Pressure compensator 33 reported, each so much pressure medium delivered by the hydraulic pump 18 can flow off to the tank 19 that a pump pressure which is set in a supply line section 34 extending from the hydraulic pump 18 and via which the pressure chambers 13 of the directional control valves 13 can be supplied a certain pressure difference lies above the reported highest load pressure.

The two directional control valves 13 can each be actuated electro-hydraulically, for which purpose two solenoid-operated pilot control valves 40 are integrated in each directional control valve section 11 or 12. In the rest position of a valve 40, an associated control chamber on the control slide 27 of a directional control valve 13 is relieved to a leakage oil channel 41, which leads through the directional control valve sections 11 and 12.

By energizing an electromagnet, a control chamber with a valve valve section 11 and 12 is also performed control pressure line 42 connected. The control oil is removed via a pressure reducing valve 43, which is contained in an end plate 44 attached to the directional valve section 12, from a channel which is guided through the two directional valve sections 11 and 12 and into the end plate 44 and which together with each of the inputs of the pressure compensator 22 guided branch lines is a second inlet line section 60. The pressure reducing valve 43 is set, for example, to a control pressure of 20 bar.

A safety block 51 is attached to the directional valve section 11 and has a 2-way cartridge valve 52, an associated pilot valve 53 and a number of pressure medium channels. The control piston 54 of the 2-way cartridge valve 52 is a differential piston, which is guided axially with a piston section 55 and can sit axially with a piston section 56 of smaller diameter on a seat 57 in order to close an axial outlet 58. The first inlet line section 34 is connected to the radial inlet 59 and thus to the annular space around the piston section 56. The second supply section 60 extends from the axial outlet 58 and continues in the directional valve sections 11 and 12 as a continuous channel. In the closing direction, a force acts on the control piston 54, which is generated by a control pressure in a rear control chamber 61 on a closing surface 62, which is equal to the cross-sectional area of the large piston section 55, and the force of a relatively weak closing spring 63. A pressure in the first inlet line section 34 acts on an annular surface 64 and a pressure in the second inlet line section 60 on a circular surface 65, which is equal to the cross-sectional area of the small piston section 56, in the opening direction of the control piston 54. The sum of the two surfaces is 64 and 65 equal to the size of the area 62.

The pilot valve 53 is a 4/2-way valve which ^assumes' r 69 under the action of a Druckfede a rest position in which it cooperates with the first inlet line section 34 connects the rear control chamber 61 on the control piston 54 and the second inlet line section 60 via a channel 70 for Relieved tank 19. The pilot valve 53 can be brought into a switching position by actuating an electromagnet 71, in which it connects the rear control chamber 61 to the channel 70, i.e. relieves the load on the tank and, since it is a standard component, the first inlet line section 34 with the second inlet line section 60 connects.

In normal operation, the electromagnet 71 is excited so that the pilot valve 53 assumes the second switching position. Since there is tank pressure in the rear control chamber 61, the pump pressure acting on the annular surface 64 can lift the control piston 54 off the seat, so that pressure medium can get from the first inlet line section 34 into the second inlet line section 60 with almost no pressure loss. If all the directional control valves 13 are in their central position, tank pressure is present in the load signaling line 31 and the pressure compensator 33 regulates a pressure of, for example, 20 bar in the feed line sections a, which is equivalent to the force of a pressure spring 35 which acts on the regulating piston of the pressure compensator together with the pressure in the closing direction in the load signaling line 31. If a directional control valve is now brought into a working position, the load pressure is reported to the pressure compensator 33, which closes the bypass to the tank 19 to such an extent that a pump pressure which is 20 bar above the load pressure builds up in the feed line 34, 60. If both directional control valves are actuated, the highest load pressure is reported to the pressure compensator 33.

In a dangerous situation, it should be possible to interrupt the flow of pressure medium from the hydraulic pump 18 to the directional control valves 13 from one or more points of a machine which is equipped with the hydraulic control arrangement shown, for example a skip truck. For this purpose, electrical switches (not shown in more detail) are mounted at the said points, which in a rest position allow the connection of the electromagnet 71 of the pilot valve 53 to a power supply. By switching one of the electrical switches, the power supply to the electromagnet 71 is interrupted, so that the pilot valve 53 comes into its rest position under the action of the compression spring 69. As a result, the rear control chamber 61 is acted upon by the pressure prevailing in the first inlet line section 34, so that the installation valve 52 closes. The second inlet line section 60 is relieved to the tank, so that the pressure at the opening surface 65 drops rapidly during the closing process. This leads to a quick closing process. Since the opening surface 65 is finally completely relieved of pressure, the control piston engages 54 a large excess force in the closing direction, so that the control piston 54 is seated firmly on its seat and shuts off the second inlet line section 60 without leakage against the first inlet line section 34. The relief of the second inlet line section 60 also allows the control pressure in the control pressure line 42 to drop, so that the directional valves return to the central position even when a pilot valve 40 remains switched.

In the middle position of the directional control valve 13, the load signaling line 31 is relieved to the tank, so that the pump 18 leads to the tank at a low pressure of 20 bar via the pressure compensator 33.

In the embodiment according to FIG. 2, a variable displacement pump 75 with a load sensing controller 76 is used instead of a constant pump 18 and a bypass pressure compensator 33. All other components are identical to those from FIG. 1, so that a further description of the embodiment according to FIG. 2 is unnecessary.

The version according to FIG. 3 also has a control block 10 with two directional valve sections 11 and 12 and an end plate 44. Each directional valve section 11 now contains a 6-way throttle valve 80 of a generally known type with a circulation channel and with a load holding valve 81. The directional valves 80 are electro-hydraulic operable using pilot valves 40. Control oil is taken from the pressure reducing valve 43 accommodated in the end plate 44 from an inlet channel which extends through the directional valve sections 11 and is part of the second inlet line section 60 and into a control pressure channel 42 delivered. So that a control pressure can be built up starting from the central position of the directional control valves 80, the circulation channel is prestressed by a check valve 82.

The same safety block 51 as in the embodiment according to FIG. 1 is attached to the directional valve section 11, so that reference can be made to the corresponding description of FIG. 1.

A constant pump 18 is used as the pressure medium source and is protected by a pressure limiting valve 83. The pump 18 draws in pressure medium from a tank 19 and discharges it into a first inlet line section 34, which is connected to the radial inlet 59 of the cartridge valve 52. The second inlet line section 60 in turn goes from the axial outlet 58 of the cartridge valve 52.

In normal operation, the built-in valve 52 is open, so that the pressure medium conveyed by the hydraulic pump 18 is either completely returned to the tank via the circulation channel or, after actuating a directional control valve, reaches all or part of a hydraulic consumer. In an emergency, actuation of an electrical switch de-energizes the electromagnet 71, so that the pilot valve 53 comes into its rest position and the built-in valve 52 closes. The second inlet line section 60 is separated from the first inlet line section 34 and relieved to the tank. As in the exemplary embodiment according to FIG. 1, the control pressure coincides. The directional control valves 80 reach their central position.

Claims

claims

1. Hydraulic control arrangement with a directional valve (13, 80), which is connected to an inlet line (34, 60) and an outlet line leading to a tank (19) and from which a consumer line leads to a hydraulic consumer, with a hydraulic pump (18, 75), can be sucked in by the pressure medium from the tank (19) and discharged into the feed line (34, 60) and with a 2-way built-in valve (52) designed as a seat valve, which is located in the feed line (34 , 60) is arranged and, in a closed position, separates a second inlet line section (60) going from it to the directional control valve (13, 80) from a first inlet line section (34) running between it and the hydraulic pump (18, 75) and the one control piston (54), with an annular opening area (64) exposed to the pressure in the first inlet line section (34), with a central circular opening area (65) exposed to the pressure in the second inlet line section (60), and m it has a closing surface (62) which, in a first switching position of a pilot valve (53), can be acted upon by the pressure in the first inlet line section (34) and in a second switching position of the pilot valve (53) can be relieved to the tank (19) , characterized in that the second inlet line section (60) in the first switching position of the pilot valve (53) can be relieved via this to the tank (19).

2. Hydraulic control arrangement according to one of the preceding claims, characterized in that the directional control valve (13, 80) can be actuated hydraulically and the control oil for actuating supply is taken from the second inlet line section (60).