Patent ID: 12247590

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG.1shows a schematic representation of a hydraulic system. A motor1can be recognized that drives two pumps3via a transfer case2. One of the two pumps3here has a pressure source P1that is directly connected to a steering control4so that the fluid pressure or fluid amount provided by the pressure source P1serves the actuation of the steering cylinder6.

In the present case, there is a total of eight pressure source P1-P8operable independently of one another and implemented by two pumps3,3arranged in tandem operation, of which each one has a plurality (four in the present case) of separately controllable pressure fluid outputs. Each of the total of eight pressure fluid outputs is here connected to its own, associated valve block input11that is either directly linked to a valve block output12or is guided to a valve V1-V7(=also switching valve).

In the present Figure, all the pressure fluid outputs P1-P8of the pumps3,3except for one are connected to a switching valve10. Only the pressure fluid output P1is directly connected to a valve block output12that is guided to the steering control4without a switch. In other words, it is thus ensured that the steering control4has the pump capacity of the pressure source P1permanently and independently of a switch position of the switching valves V1-V7in the switching valve block9. If a pump capacity going beyond this is required by the steering control, the switching valves V1and V2can be switched such that their associated pressure sources P2, P3likewise provide their power to the steering control4. Three pump sources P1, P2, P3are thus available overall as required to exercise the steering control4and to move the steering cylinders6.

The control valve block5in which the hydraulic consumers tilting51and lifting52, as well as further consumers53,54not mentioned by name, are arranged are arranged beside the switching valve block9on the right side ofFIG.1. With a corresponding valve setting of the switching valves V1to V7in the switching valve block9, the tilt control51can be linked to the pressure sources P2and P4to P8so that sufficient power is present for the tilt function for the actuation of the tilt cylinders7.

The situation is similar with the lifting control52that is likewise connectable to the associated pressure sources P3to P8with a corresponding position of the valves V2to V7. The lifting control52can here also forward pump capacity to the further consumers53,54that are not shown in detail for reasons of a simplified illustration.

The pump capacity of the plurality of pressure sources can accordingly also be guided to a respective consumer6,7,8by this hydraulic system in dependence on a current demand, with the disadvantages of a poor response behavior typically accompanying this being alleviated in that particularly sensitive consumers, for example the steering, are permanently and exclusively connected to a pressure source (the pressure source P1here).

FIG.2shows an implementation of the present invention in which not only the steering control4has an exclusive pump capacity, but also the lifting control52. In this respect, the pumps P7and P8are exclusively and unchangeably associated with the hydraulic consumer “lifting” to actuate the lifting cylinders8. In a similar manner as inFIG.1, is it also possible to add four further pressure sources P3to P6via a corresponding switching of the valves V3to V5so that challenging lifting work can also be accomplished.

The tilt control51can be connected to a total of four pressure sources P2to P4and P6with a corresponding valve position of the valves V1-V3and V5. It is likewise possible that the further consumers53and54are supplied via the tilt control51(and not, as shown inFIG.2, via the lifting control52).

The added value in accordance with the invention becomes clear inFIG.2in that the two pumps3,3that are in tandem operation can now each switch one of their pressure outputs P1, P5to the steering control4. The circumstance that the pumps3,3run in tandem operation is of subordinate significance for the invention since a separate operation of the pumps is likewise conceivable and does not stand in the way of the basic idea of the invention.

The pressure output P1of the left pump3is already fixedly connected to the steering control4so that the fluid flowing out of the pressure output P1is completely provided to the steering control.

There is furthermore the possibility via the valve V4to allow a further pressure source P5of the other hydraulic fluid pump3(the right pump3inFIG.2) to be assigned to the steering control4.

If, for example, the pressure outputs P1or P2can no longer deliver sufficient hydraulic fluid due to a pump defect or can only provide hydraulic fluid at very low pressure, it can be ensured via a switching of the valve V4that the steering control continues to be sufficiently supplied with hydraulic fluid.

The amounts and the pressure of the hydraulic fluid that is provided via the pressure output P2are at least sufficient for an emergency steering capability. In such a state, the usual steering comfort is admittedly not provided, but a safe steering and the maintenance of the maneuverability are ensured.

As a result, a more defect-tolerant steering is provided that continues to work reliably even on a failure of one of the two pumps3,3shown.

FIG.3shows a further abstract representation of the present invention. The switching block9is now shown in simplified form and now no longer shows the complete wiring of the pressure outputs of the pumps3,3, but only those of the pressure outputs P1and P5. The pressure output of the pressure source P1is here fixedly and unchangeably connected to the steering control4. The pressure output of the pressure source P5runs to a switching valve10that selectively connects the pressure output P5to the working hydraulics A (not shown) or to the steering control4.

It can additionally be recognized that each of the two hydraulic fluid pumps3,3have their own control units13,14that are connected to one another.

The two control units13,14are furthermore supplied with energy via different supply voltages15,16so that at least one of the two pumps3,3is still controllable on a failure of one of the two supply voltages15,16.

Furthermore, after the steering control4, that is directly before the steering cylinders, not shown, two pressure sensors19,20are present that provide a redundant measurement of the pressure applied there. Differing from the illustration, the pressure measured there by each of the sensors19,20is provided to the two control units13,14.

In addition, a further pressure sensor18, that measures the pressure entering into the steering control, is arranged directly after the switching block. This measured pressure is forwarded over a data line to the two control units13,14, with this being able to take place via an optional vehicle control.

It can thus be calculated in one or both of the control units13,14whether the pressure present at the valve block output12coincides with the individual pressure values of the possible plurality of pressure sources P1and P5switched to the steering control.

In addition, this value can be used if a pressure measurement of a pressure source P1or P5were to fail.