DE2052303A1 - Hydraulic system for grading machines, loading machines, excavators and the like - Google Patents

Description

Applicant: RHEINSTAHL HANOMAG AG, 3000 Hannover-Linden, Hanomagstr. 9 Hydraulic system for grading machines, loading machines, excavators and the like.

The invention relates to a hydraulic system for graders, loading machines, Excavator and the like. With at least two sets of hydraulic pressure in the middle ! Consumers and upstream control devices, and at least a hydraulic feed pump assigned to each consumer group.

In the case of hydraulically operated implements of the aforementioned type one strives on the one hand a sensitive control of the tools and on the other hand - if necessary - to achieve a very quick reaction and the implementation of faster work movements in order to achieve the work performance of devices to increase. However, this is not achieved at all or in an unsatisfactory manner with the known devices. For hydraulic excavators, where the hydraulic units for the bucket are the pressure medium consumers, the hub, the stick and the rotary and travel drive have to be loaded, the ideal control is aimed at the working pressure regulation.

The known hydraulic systems for hydraulic excavators work without working pressure control. Rather, either with a pressure build-up in the control

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piston of the control units worked, whereby the circulation channel is continuously blocked when the control piston moves. If the control unit is free to flow, the pressure-limiting valve is relieved when the control valve is in the neutral position, so that additional oil circulation occurs. If the working pressure is at an average pressure of approx. 150 bar and if fine control is to be carried out, the oil circulation must be completely closed in order to achieve the pressure of 150 bar. However, the supply to the consumer advises * is fully open. In order to achieve fine control, it would be necessary that either the inlet to the consumer or the outlet of the consumer is throttled.

Should the fine control through the outlet throttling and the circulation throttle are made, the circulation channel must be completely closed. The discharge throttling is already in operation and is no longer effective, when the full pressure has already been built up. A fine control can thus do not take effect in order to sensitively set a consumer in motion. The pressure and the full oil amount are on the consumer, so that this is driven at full speed.

Also fine control of the lifting cylinder in known hydraulic systems can not. The piston area of the lifting cylinder is always under load, either only under the weight of the design or under the Dead weight and additional load. If the piston surface is pressurized, so the Kolenne then executes when the pressure is reached. A discharge throttling then taking effect would lead to an increase in pressure drive in the piston rod space. For this reason, the outlet throttling is allowed will not take effect. This means that there is no fine control.

Fine control can only be achieved when lowering the display will. The discharge throttle takes effect when lowering. As soon

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the control piston is out of the overlap area, the lowering speed can be varied accordingly via the throttle path « The circulation throttle is partially, or the greater the speed is completely closed.

Fine control is not possible with the SHe! Cylinder either. Through the

horizontally arranged stick cylinder, external forces occur in the piston -

Rod space due to the weight of the spoon. Becomes the piston area

of the stick cylinder is applied, the discharge throttle must be fully opened otherwise a higher pressure will occur in the piston rod space. If the rod space is pressurized, the piston rod retracts, when full pressure is reached «The outlet throttle is in this case not effective.

The conditions described also apply to the control of the Bucket cylinder · Even with oil motors under load, the discharge throttle is opened first when actuated. The full pressure must be can be built up, the circulation throttle is completely closed. Of the The engine is charged with the full amount of oil and runs with full Speed so that fine control cannot be achieved.

The invention is therefore based on the object, avoiding the Disadvantages of the known devices to create a hydraulic system for devices of the type mentioned, which as a working pressure control works and with which both fine control and fast driving of the pressure medium users can be achieved.

According to the invention, this object is achieved in that the feed pumps of the individual groups can be connected together to one or the other group of printing center consumers.

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According to the invention, consumers within the group are printed one or the other or more diners with the forcing pumps connectable. Behind the control units for the individual pressure in the middle (Consumers are directional valves or controlled check valves. The control devices are preferably electro-magnetic trainable controllable valves.

The concept of the invention is in an exemplary embodiment in the form of a hydraulic circuit diagram for a hydraulic excavator explained in more detail. It is a flow-controlled double pump system, in which two single pumps with total power control are used. The pump 1 is the pressure medium consumers spoon L, Hub H, and drive F and the pump 2 the pressure center I consumers Handle S, turning D and the travel drive F assigned, which work together with the total power controller 3. The den Pumps 1 and 2 downstream pressure control valves 4 and 5 are used to protect the pumps, with Sn neutral position the pressure relief valves 4 and 5 by relieving the control lines 6 and 7 are circulation valves. The arrangement of the pressure relief valves 4 and 5 near the two pumps 1 and 2 results from the short lines low oil heating and low flow resistance. This also results in a low drive power in the neutral position of pumps 1 and 2, namely the drive power can be reduced to approx. 1/10 of the normal drive power, which is reflected in Noticeable savings in fuel and the amount of oil in the tank power.

For the sensitive control of the pressure consumers L, H, F, S, D, F two monoblock control units are provided, each with three control units have, and indeed has {every control unit per consumer connection

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Shock reloading valve so that consumers do not get too high with external Forces (pressure) are loaded. The shock valve causes a Secondary protection, while the recharging valve vacuum occurs should prevent.

Each monoblock control unit consists of a pressure valve 8.1 and the the three pressure medium consumers of the first group associated control slides 8.2, 8.3, 8.4 and the corresponding other control slides 9.2, 9.3, 9.4 and the pressure valve 9.T of the other group.

The two monoblock control units are followed by the directional control valves "

10, 11, 12 and 13, 14, 15 and the check valves 16, 17, 18 and 19,20,21.

The possibility of sensitive Ans expensive ns of a consumer, for example of the hydraulic cylinder on Lö ffel L is explained below t

To extend the bucket cylinder, the control slide 8.2 and the directional valve 10 are actuated at the same time. The directional control valve 10 switches immediately to the end position. The working pressure in the line B 1 is passed through the return valve 16 and the control line St 1 to the pressure valve 8.1. This has a constant spring preload of approx. 15 bar. Thus %

the working pressure + 15 bar on the pressure valve 8.1. Has the control piston of the control spool 8.2 covered approx. 20% of the stroke, the Control line 6 blocked. The pressure relief valve 4, which previously Circulation valve is activated. Pump 1 is now delivering the oil against the working pressure applied to the pressure valve 8.1 + 15 bar into the tank T. If the control piston is actuated further, the connection from P 1 to the consumer connection B 1 is established via the non-return valve.

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The opening of the passage cross-section on the control piston takes place via throttle cross-sections, which more or less depending on the control piston stroke can be opened wide, via the existing pressure relief valve 4 constant spring preload of 15 bar is created at the open throttle cross-section a constant pressure vessel Ie of 15 bar. The throttle cross-section is designed in such a way that approx. 1/3 of the pump delivery rate is sensitively regulated will. This ensures that the entire fine control path is available when the working pressure is high. The fine control travel amounts to approx. 60% of the entire control piston stroke

If several consumers that are connected to a pump circuit are controlled, the highest working pressure is set at the pressure valve 8.1. The constant pressure gradient is no longer available to every consumer. Rather, the pressure gradient of 15 bar is available to the most heavily loaded consumer, with the pressure gradient of the lower loaded consumer the difference between the most heavily loaded consumer and the lower loaded one Consumer corresponds. The fine control path becomes shorter for the less loaded consumers.

The highest utilization of the work performance occurs when for the actuation of only one consumer the automatic interconnection of both pumps takes place. For example, the pump is switched on 1 to pump 2 when the stick cylinder S is actuated. In the same way the pump 2 is switched on when the spoon cylinder L and the lifting cylinder H is applied. In the case of mobile excavators, " the pump 2 switched on while driving.

If, for example, the bucket cylinder L is retracted, the function is the interconnection Both pumps 1 and 2 as follows. The control slide 8.2 and the directional control valve 10 are connected to the line A 1, and at the same time the WegeveWtiI 22 is switched. The control lines 6 and 7 are locked. The pressure relief valve 4 and 5 are in function set. The pump 1 delivers to the spoon cylinder L, at the same time delivers

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and the pump 2 via the Lefrung _v P 2 by the Monoblocksteuergertlt via the line P 3 and the check valve 23 in the line PI.

By optionally switching on the directional control valve 22, the oil can circulate are interconnected. There are double oil circuits either the piston surface or the piston rod side or the piston surface and the piston rod side are available. With mobile excavators the circuit can be made in such a way that the double oil circuit is only used for driving forwards or for driving forwards and backwards is available.

If one consumer is charged a second one When the consumer is switched on, the oil amount is divided accordingly. If a simple * speed is required when actuating the consumer, so the directional control valve 22 is switched off.

The working pressure control according to the invention has the advantage that a sensitive control of all consumers is possible, with only one control unit being required for each consumer. In addition, the interconnection is Both pump circuits are possible on each consumer, with both pump circuits also being switched for only one direction of movement can be. This regulation is applicable to all circuit

types of control units applicable. It is advantageous that the fine control "

tchon at ca * starts 20% of Steuerkolbenhubes and actuation de $ spool it is very light, so that it can be for example directly electromagnetically actuated. Any desired speed can be driven in the range of 1/3 of the pump delivery rate.

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Claims (4)

20b2303 Patent claim (1. - Hydraulic system for grading machines, loading machines, excavators and the like. with at least two groups of hydraulic pressure medium consumers and upstream control devices and at least one hydraulic feed pump assigned to each consumer group, characterized in that that the feed pumps (1 and 2) of the individual consumer groups (L, H, F and S, D, F) together to one or the other Group of pressure center consumers (L, H, F, S, D, F) can be connected are. 2. Hydraulic system according to claim 1, characterized in that within the group of pressure medium consumers (L, H, F, S, D, F) one or the other or more pressure medium consumers can be connected to the feed pumps (1 and 2). 3. Hydraulic system according to claim 1 and 2, characterized in that behind the control units (8.2, 8.3, 8.4, 9.2, 9.3, 9.4) of the individual Pressure medium consumers (L, H, F, S, D, F) Directional valves (10, 11, 12, 13, 14, 15) or controlled check valves (16, 17, 18, 19, 20, 21) are provided. 4. Hydraulic system according to claim 1 to 3, characterized in that the Control devices are designed as electromagnetically controllable valves. 209818 / (U09