HYDRAULIC SYSTEM WITH A SWITCH VALVE BLOCK FOR A HYDRAULICALLY ACTUATABLE WORKING MACHINE

Abstract

The present invention relates to a hydraulic system for a hydraulically actuable work machine that comprises a switching valve block having a plurality of valve block inputs for a respective connection to a pressure output of one or more hydraulic fluid pumps; having a plurality of valve block outputs for outputting a pressurized hydraulic fluid; and having at least one valve that is arranged between valve block inputs and valve block outputs and that is adapted to selectively produce a fluid connection between a first valve block input and a first valve block output or between the first valve block input and a second valve block output; a plurality of pressure sources, preferably a plurality of separately controllable pressure sources of which each one is connected to a respective valve block input; and a plurality of hydraulic consumers of which each one is connected to a respective valve block output. The system is characterized in that the first valve block output furthermore already has a fixed fluid connection, preferably a fixed exclusive fluid connection, to a second valve block input and in that the steering is connected to the first valve block output.

Claims

1. A hydraulic system for a hydraulically actuable work machine comprising a switching valve block having a plurality of valve block inputs for a respective connection to a pressure output of one or more hydraulic fluid pumps; a plurality of valve block outputs for outputting a pressurized hydraulic fluid; at least one valve arranged between valve block inputs and valve block outputs and adapted to selectively produce a fluid connection between a first valve block input and a first valve block output or between the first valve block input and a second valve block output; a plurality of pressure sources, preferably a plurality of separately controllable pressure sources of which each one is connected to a respective valve block input; and a plurality of hydraulic consumers of which each one is connected to a respective valve block output, wherein the first valve block output furthermore already has a fixed fluid connection, preferably a fixed exclusive fluid connection, to a second valve block input; and the steering is connected to the first valve block output.

2. A hydraulic system in accordance with claim 1, wherein the at least one valve is a switching valve that exclusively connects one valve block input to one of the plurality of valve block outputs.

3. A hydraulic system in accordance with claim 1, wherein the plurality of pressure sources are provided by at least two hydraulic fluid pumps that each have at least one pressure output, preferably at least one separately controllable pressure output.

4. A hydraulic system in accordance with claim 3, wherein the first valve block input is connected to a pressure output of the first hydraulic fluid pump and the second valve block input is connected to a pressure output of the second hydraulic fluid pump.

5. A hydraulic system in accordance with claim 3, wherein each of the at least two hydraulic fluid pumps have their own control unit preferably respectively connected to different voltage supplies.

6. A hydraulic system in accordance with claim 5, wherein the separate control units of the at least two hydraulic fluid pumps are connected to one another in order, on a defect event of that pressure source that is connected to the second valve block input and that represents the fixed and non-switchable fluid connection to the steering, to switch the valve independently of other control demands to the first valve block output to continue to ensure a fluid supply for the steering.

7. A hydraulic system in accordance with claim 5, wherein a sensor is present at every pressure output of an associated hydraulic fluid pump to determine the pressure that is applied there, said sensor being connected to the associated control unit of the at least two hydraulic fluid pumps so that they are able to detect an error event in dependence on the pressure applied there.

8. A hydraulic system in accordance with claim 5, wherein a sensor for sensing the load pressure is connected downstream of the first valve block output, preferably directly before a steering cylinder, which sensor is connected to the control units of the at least two hydraulic fluid pumps to preferably enable the steering to work in a pressure regulation mode.

9. A hydraulic system in accordance with claim 8, wherein two sensors for the respective sensing of the load pressure that are independent of one another are now arranged downstream of the first valve block output and are each connected to the control units of the at least two hydraulic fluid pumps, with the two sensors that are independent of one another preferably having different designs and/or different measurement ranges.

10. A hydraulic system in accordance with claim 6, wherein the control units are adapted to provide a constant pressure to the steering in the event of a failure.

11. A hydraulic system in accordance with claim 7, wherein a check valve is provided at each pressure output of the at least two hydraulic pumps; and the control units are adapted to monitor the functionality of the sensors at the pressure output in that the value of the sensor is used for the sensing of the steering supply pressure and in that pressures preferably measured by means of a check at connected pump outputs cannot be higher than the higher ranking steering supply pressure.

12. A hydraulic system in accordance with claim 7, wherein a sensor for sensing the load pressure is connected downstream of the first valve block output, preferably directly before a steering cylinder, which sensor is connected to the control units of the at least two hydraulic fluid pumps to preferably enable the steering to work in a pressure regulation mode; a check valve is provided at each pressure output of the at least two hydraulic pumps; and if one of the control units detects a failure of a sensor at the pressure output, a control of the pressure source linked to the failed sensor is continued while using the sensor for sensing the steering supply pressure, preferably in that it is assumed that the pressure value at the pump output corresponds to the higher ranking steering supply pressure.

13. A hydraulic system in accordance with claim 11, wherein the sensor for sensing the steering supply pressure is arranged directly after the valve block output.

14. A hydraulic system in accordance with claim 1, wherein the second valve block output is connected to working hydraulics, for example, to a tilt cylinder or to a lifting cylinder.

15. A work machine, in particular a wheeled loader, having a hydraulic system in accordance with claim 1.

16. A hydraulic system in accordance with claim 2, wherein the plurality of pressure sources are provided by at least two hydraulic fluid pumps that each have at least one pressure output, preferably at least one separately controllable pressure output.

17. A hydraulic system in accordance with claim 16, wherein the first valve block input is connected to a pressure output of the first hydraulic fluid pump and the second valve block input is connected to a pressure output of the second hydraulic fluid pump.

18. A hydraulic system in accordance with claim 17, wherein each of the at least two hydraulic fluid pumps have their own control unit preferably respectively connected to different voltage supplies.

19. A hydraulic system in accordance with claim 16, wherein each of the at least two hydraulic fluid pumps have their own control unit preferably respectively connected to different voltage supplies.

20. A hydraulic system in accordance with claim 4, wherein each of the at least two hydraulic fluid pumps have their own control unit preferably respectively connected to different voltage supplies.

Description

[0033] FIG. 1: a schematic representation of a hydraulic system;

[0034] FIG. 2: a schematic representation of a hydraulic system in accordance with the invention; and

[0035] FIG. 3: a schematic representation of a further embodiment of the hydraulic system in accordance with the invention in an abstract form.

[0036] FIG. 1 shows a schematic representation of a hydraulic system. A motor 1 can be recognized that drives two pumps 3 via a transfer case 2. One of the two pumps 3 here has a pressure source P1 that is directly connected to a steering control 4 so that the fluid pressure or fluid amount provided by the pressure source P1 serves the actuation of the steering cylinder 6.

[0037] In the present case, there is a total of eight pressure source P1-P8 operable independently of one another and implemented by two pumps 3, 3 arranged 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 input 11 that is either directly linked to a valve block output 12 or is guided to a valve V1-V7 (=also switching valve).

[0038] In the present Figure, all the pressure fluid outputs P1-P8 of the pumps 3, 3 except for one are connected to a switching valve 10. Only the pressure fluid output P1 is directly connected to a valve block output 12 that is guided to the steering control 4 without a switch. In other words, it is thus ensured that the steering control 4 has the pump capacity of the pressure source P1 permanently and independently of a switch position of the switching valves V1-V7 in the switching valve block 9. If a pump capacity going beyond this is required by the steering control, the switching valves V1 and V2 can be switched such that their associated pressure sources P2, P3 likewise provide their power to the steering control 4. Three pump sources P1, P2, P3 are thus available overall as required to exercise the steering control 4 and to move the steering cylinders 6.

[0039] The control valve block 5 in which the hydraulic consumers tilting 51 and lifting 52, as well as further consumers 53, 54 not mentioned by name, are arranged are arranged beside the switching valve block 9 on the right side of FIG. 1. With a corresponding valve setting of the switching valves V1 to V7 in the switching valve block 9, the tilt control 51 can be linked to the pressure sources P2 and P4 to P8 so that sufficient power is present for the tilt function for the actuation of the tilt cylinders 7.

[0040] The situation is similar with the lifting control 52 that is likewise connectable to the associated pressure sources P3 to P8 with a corresponding position of the valves V2 to V7. The lifting control 52 can here also forward pump capacity to the further consumers 53, 54 that are not shown in detail for reasons of a simplified illustration.

[0041] The pump capacity of the plurality of pressure sources can accordingly also be guided to a respective consumer 6, 7, 8 by 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 P1 here).

[0042] FIG. 2 shows an implementation of the present invention in which not only the steering control 4 has an exclusive pump capacity, but also the lifting control 52. In this respect, the pumps P7 and P8 are exclusively and unchangeably associated with the hydraulic consumer “lifting” to actuate the lifting cylinders 8. In a similar manner as in FIG. 1, is it also possible to add four further pressure sources P3 to P6 via a corresponding switching of the valves V3 to V5 so that challenging lifting work can also be accomplished.

[0043] The tilt control 51 can be connected to a total of four pressure sources P2 to P4 and P6 with a corresponding valve position of the valves V1-V3 and V5. It is likewise possible that the further consumers 53 and 54 are supplied via the tilt control 51 (and not, as shown in FIG. 2, via the lifting control 52).

[0044] The added value in accordance with the invention becomes clear in FIG. 2 in that the two pumps 3, 3 that are in tandem operation can now each switch one of their pressure outputs P1, P5 to the steering control 4. The circumstance that the pumps 3, 3 run 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.

[0045] The pressure output P1 of the left pump 3 is already fixedly connected to the steering control 4 so that the fluid flowing out of the pressure output P1 is completely provided to the steering control.

[0046] There is furthermore the possibility via the valve V4 to allow a further pressure source P5 of the other hydraulic fluid pump 3 (the right pump 3 in FIG. 2) to be assigned to the steering control 4.

[0047] If, for example, the pressure outputs P1 or P2 can 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 V4 that the steering control continues to be sufficiently supplied with hydraulic fluid.

[0048] The amounts and the pressure of the hydraulic fluid that is provided via the pressure output P2 are 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.

[0049] As a result, a more defect-tolerant steering is provided that continues to work reliably even on a failure of one of the two pumps 3, 3 shown.

[0050] FIG. 3 shows a further abstract representation of the present invention. The switching block 9 is now shown in simplified form and now no longer shows the complete wiring of the pressure outputs of the pumps 3, 3, but only those of the pressure outputs P1 and P5. The pressure output of the pressure source P1 is here fixedly and unchangeably connected to the steering control 4. The pressure output of the pressure source P5 runs to a switching valve 10 that selectively connects the pressure output P5 to the working hydraulics A (not shown) or to the steering control 4.

[0051] It can additionally be recognized that each of the two hydraulic fluid pumps 3, 3 have their own control units 13, 14 that are connected to one another.

[0052] The two control units 13, 14 are furthermore supplied with energy via different supply voltages 15, 16 so that at least one of the two pumps 3, 3 is still controllable on a failure of one of the two supply voltages 15, 16.

[0053] Furthermore, after the steering control 4, that is directly before the steering cylinders, not shown, two pressure sensors 19, 20 are present that provide a redundant measurement of the pressure applied there. Differing from the illustration, the pressure measured there by each of the sensors 19, 20 is provided to the two control units 13, 14.

[0054] In addition, a further pressure sensor 18, 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 units 13, 14, with this being able to take place via an optional vehicle control.

[0055] It can thus be calculated in one or both of the control units 13, 14 whether the pressure present at the valve block output 12 coincides with the individual pressure values of the possible plurality of pressure sources P1 and P5 switched to the steering control.

[0056] In addition, this value can be used if a pressure measurement of a pressure source P1 or P5 were to fail.