EP0733743B1 - Flow distribution device, independent of the load pressure, for control valves in mobile working machines - Google Patents

Abstract

A regulator valve formed as compensator, is located between the pilot opening (4-6) of a slide valve and a working cylinder (1-3). The valve has an axially movable regulator piston (10,14,15), with two sides associated with first and second pressure chambers (17,22,23,9,24,25). The first chamber charges the piston with spring pressure (18) and the pressure from the working cylinder is charged with the highest load pressure. The second chamber is fitted into the feed line to the slide valve, and has a pilot opening (19,26,27) to the working cylinder, which is controlled by the piston edge of the regulator piston. A return valve (12,30,31) is located between the pressure chambers of each compensator.

Description

The invention relates to a device for load pressure independent flow distribution at a Control spool for mobile construction and work machines.

With spool valves based on the principle of flow pressure independent flow distribution (LUDV) there are different ways of tapping and forwarding the so-called Load sensing (LS) signal. On the one hand, there is the possibility of using a complex signal system of signaling lines integrated in the slide sections, the load-sensing signal forward to the pump controller. On the other hand, there is the possibility in the compensator piston to install additional pistons equipped with a relatively weak spring are. The compensator pistons can also be designed so that they have a control opening forward the load sensing signal. The first version is complex, while the latter two are so sensitive to signaling that over the control edges with the small oil flows a pressure-accurate forwarding of the load-sensing signal is not always guaranteed. This causes inaccurate activation of the pump controller which in turn negatively affects overall control, i.e. the control of individual or multiple consumers.

The prior art is represented, for example, by US-A-5067389.

The object of the invention is to provide a device for flow distribution independent of load pressure with a spool for mobile construction and work machines to further develop that there is a cost-effective, simple and trouble-free solution, in which the required oil flow is reliably and accurately passed on to the pump controller becomes.

This goal is achieved by a device for load flow independent flow distribution for a spool valve for mobile construction and work machines, with at least two downstream consumers is operatively connected and by at least one controllable Delivery pump provided flow according to the load pressure independent Principle of correspondingly controllable piston-type compensators one or more the consumer makes available and the highest of those due to the consumer Press the regulator of the feed pump is reported, the compensators on the one hand a pressure chamber that can be connected to the respective consumer and, on the other hand, one Include spring space, the consumer can be connected to the spring space via corresponding channels are and in the connecting line at least one occupying two defined positions Closure element is used.

Advantageous further developments of the subject matter of the invention can be found in the subclaims. In addition to spherical closure elements, geometrically different shapes can also be used Elements such as Cone, find use.

The subject of the invention is applicable to any number of consumers who Via a flow distribution that works according to the principle of load pressure independent Control spool can be controlled. Significant advantage of a spherical or conical closure element compared to a piston is that the spherical or conical closure element knows only two defined positions, namely 'open' or 'closed', while when using a piston due to the constantly changing direction changes only a so-called snapping on the control edges, which is ultimately in the reflects unfavorable delivery of the required oil flow. This disadvantage is caused by the Closure element according to the invention effectively eliminated, since it is now possible by a sufficient cross-section released through the ball or cone position "open" Deliver oil flow to the pump controller and the other compensators.

The object of the invention is shown in the drawing using an exemplary embodiment and is described as follows.

The single figure shows a schematic diagram of the schematic structure of a controller with a any number of consumers; in this example designed as a cylinder 1,2,3. The Cylinders 1,2,3 are controlled by a spool valve, which works on the principle of flow pressure-independent flow distribution is built, of which only the control openings 4,5,6 are shown. These control openings 4, 5, 6 can be changed by the driver.

Assuming that the cylinder 1 is subjected to the highest load pressure p _z1 , the variable displacement pump 7 will output the delivery flow with a pressure higher by the load-sensing differential pressure Δp _{LS of} its regulator 8. The following applies: p _p = p _z1 + Δp _LS .

Due to the reduced pump pressure in the control opening 4 pump pressure, which acts in the pressure chamber 9, the compensator 10 designed as a piston, the slide section of which is assigned to the cylinder 1, is activated so that its oil flow can flow to this cylinder 1. At the same time, the cylinder pressure p _z1 , which has to serve as an LS signal, transports itself through transverse channels 11 in the compensator piston 10 by lifting the closure element 12, which is spherical here, via line 13, on which the other compensator pistons 14, 15 are also connected in parallel , to pump controller 8. As already explained, geometrically differently shaped closure elements, such as cones, can also be used. This pressure acts via a longitudinally extending connecting channel 16 in the spring chamber 17. Thus, the load pressure p _z1 and the equivalent pressure of the spring 18 counteract the pressure in the chamber 9, so that the compensating piston 10 adjusts itself automatically so that via the throttling point that forms 19 the _{flow rate is} reduced to the load pressure p _z1 . The pressure drop at the throttle point 19 corresponds to the equivalent pressure of the spring 18 (this is relatively low, 1 to 8 bar).

The load pressure P _{z1 of} the cylinder 1 is also fed to the further compensator pistons _{14, 15} via the line 13. This pressure is also present in the spring spaces 22, 23 of the compensators 14 and 15 via the connecting channels 20, 21 running in the longitudinal direction. In the pressure chambers 24, 25, the same pump pressure p _{p is} reduced by the pressure drop through the control openings 5, 6, the pressure drops in the control openings 4, 5, 6 of all consumers 1, 2, 3 being the same in accordance with the LUDV principle. As a result, the pressure in the pressure chambers 24, 25 is reduced by the throttle openings 26, 27 which are set according to the pressure compensator principle to the pressures p _z2 and p _z3 in the cylinders 2, 3 which are lower than the pressure p _z1 in the cylinder 1. Since only the cylinder pressures p _z2 and p _z3 prevail in the transverse channels 42, 44 leading to the ball seats 28, 29, the spherical closure elements 30, 31 are pressed onto their seats 28, 29 by the higher pressure p _z1 controlled via the line 13 pressed so that oil flow from line 13 to cylinders 2 and 3 is prevented. In this example, the spherical closure element 12 is lifted from its valve seat 32 as a result of the higher pressure prevailing in this compensator piston 10 and bears against a stop 33 of a closure element 34 inserted from above into the compensator piston 10, which at the same time guides the spring 18 in the spring chamber 17. The spherical closure element 12, 30, 31 can thus be moved back and forth between its two defined positions 32, 33, 28, 35, 29, 36, depending on the higher pressure which occurs at the respective compensator 10, 14, 15. As already explained, each compensator piston 10, 14, 15 is provided with channels 37, 38, 39 running in the longitudinal direction and in each case two channels 11, 41, 42, 43, 44, 45 running transversely thereto. In the respective end element 34, 46, 47, channels 16, 20, 21 are also incorporated in the longitudinal direction for connecting the cylinders 1, 2, 3 with the associated spring chamber 17, 22, 23.

• die Querschnitte in den Load-Sensing-Meldeleitungen 11,42,44 sowie die von den kugelförmigen Verschlußelementen 12,30,31 freigegebenen Querschnitte 37,38,39 können ohne nennenswerten Druckabfall den durch den Pumpenregler 8 und/oder durch die Entspannungsblende 48 in den Tank 49 abfließenden Ölstrom durchleiten.
• die Signalgabe ist absolut präzise und zuverlässig, da das kugelförmige Verschlußelement 12,30,31 lediglich zwei definierte Stellungen 32,33;28,35 sowie 29,36 (offen - geschlossen) aufweist und der LS-Strom nicht über Steuerkanten sich einregelnder Kolben abfließt.
• die Leitungsführung ist stark vereinfacht.

The advantages of the subject of the invention are characterized by the following features:

• the cross-sections in the load-sensing signal lines 11, 42, 44 and the cross-sections 37, 38, 39 released by the spherical closure elements 12, 30, 31 can be reduced by the pump regulator 8 and / or through the expansion orifice 48 without significant pressure drop Pass tank 49 through the flowing oil flow.
• the signaling is absolutely precise and reliable, since the spherical closure element 12, 30, 31 only has two defined positions 32, 33, 28, 35 and 29, 36 (open - closed) and the LS current does not flow out via control edges of the regulating pistons .
• the routing is greatly simplified.

Claims (9)

1. Device for load-independent flow distribution in a control valve for mobile construction and working machines, which valve is in operative connection with at least two downstream loads (1, 2, 3) and, in accordance with the load-independent principle, by way of suitably activatable piston-like compensators (10,14,15) makes available to one or more of the loads (1, 2, 3) the delivery flow provided by at least one controllable delivery pump (7), and each time the highest of the pressures present at the loads (1 or 2 or 3) is relayed to the controller (8) of the delivery pump (7), wherein the compensators (10, 14, 15) at one side contain a pressure chamber (9, 24, 25) which is arranged to be connected to the relevant load (1, 2, 3) and at the other side contain a spring chamber (17, 22, 23), the loads are arranged to be connected by way of corresponding ducts (11, 37, 16; 42, 38, 20; 44, 39, 21) to the spring chamber (17, 22, 23) and at least one sealing element (12, 30, 31) occupying just two defined positions (32, 33; 28, 35; 29, 36) is inserted in the connecting line (37, 16; 38, 20; 39, 21).
2. Device according to claim 1, characterised in that the sealing element (12, 30, 31) is a sphere.
3. Device according to claim 1, characterised in that the sealing element has a conical seating surface.
4. Device according to one or more of claims 1 to 3, characterised in that each compensator (10, 14, 15) contains at least one longitudinally running duct (37, 16; 38, 20; 39, 21) and at least two ducts (11, 41; 42, 43; 44, 45) running transversely thereto, wherein the longitudinally running closeable duct (37, 16; 38, 20; 39, 21) connects the loads (1, 2, 3) and the respective spring chambers (17, 22, 23) to one another, when one of the compensators (10 or 14 or 15) is displaced, one of the transversely running ducts (11 or 42 or 44) transmits the pressure signal present at the compensator to the longitudinally running duct (37 or 38 or 39), and a further transversely running duct (41 or 43 or 45) transmits this signal via a line (13) on the one hand to the spring chambers (22, 23 or 17, 22 or 17, 23) of the further compensators (14, 15; 10, 14; 10, 15) and on the other hand to the controller (8) of the pump (7).
5. Device according to one or more of claims 1 to 4, characterised in that the sealing element (12, 30, 31) is inserted between the ducts (11, 41; 42, 43; 44, 45) running transversely to the longitudinal duct (37, 38, 39).
6. Device according to one or more of claims 1 to 5, characterised in that the sealing element (12, 30, 31) is movable between a cylinder chamber side valve seat (32, 28, 29) and a spring chamber side stop (33, 35, 36).
7. Device according to one or more of claims 1 to 6, characterised in that the stop (33, 35, 36) is formed by an end face of a closing element (34, 46, 47) inserted in the compensator (10, 14, 15), which closing element serves at the same time as guide means for the spring (18).
8. Device according to one or more of claims 1 to 7, characterised in that the duct (16, 20, 21) leading to the spring chamber (17, 22, 23) runs through the closing element (34, 46, 47).
9. Device according to one or more of claims 1 to 7, characterised in that the duct leading to the spring chamber (17, 22, 23) runs inside the wall of the compensator (10, 14, 15).

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