HYDRAULIC CONTROL CIRCUIT FOR CRANE SLEWING GEAR

Abstract

The present disclosure relates to a hydraulic control circuit for crane slewing gear having directional valves arranged in work lines and controllable separately for the inflow and outflow to the hydraulic motor for the carrying out of a rotational movement of the slewing gear, wherein an inflow valve serves the control of the oil inflow from a hydraulic pump via the work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor can be relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via an outflow valve into the tank.

Claims

1. A hydraulic control circuit for crane slewing gear having directional valves arranged in work lines and controllable separately for inflow and outflow to a hydraulic motor for carrying out a rotational movement of the slewing gear, wherein an inflow valve is provided for control of oil inflow from a hydraulic pump via a work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor is relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via the outflow valve into the tank.

2. The hydraulic control circuit in accordance with claim 1, wherein at least one inflow pressure maintenance valve is provided before the inflow valve in the direction of flow to ensure a load pressure-independent oil quantity in the inflow to the hydraulic motor.

3. The hydraulic control circuit in accordance with claim 1, wherein at least one outflow pressure maintenance valve is provided before the outflow valve in the direction of flow to keep the pressure difference over the outflow valve constant and to ensure a load pressure-independent oil quantity in the outflow.

4. The hydraulic control circuit in accordance with claim 1, wherein the outflow valve is opened and/or closed proportionally and is changeable between freewheeling and clamped operating modes of the hydraulic control circuit by a proportional opening and closing of the outflow valve.

5. The hydraulic control circuit in accordance with claim 3, wherein the outflow valve is controlled by a larger volume flow than the inflow valve, whereby the outflow pressure maintenance valve is completely opened and the control circuit is switched into the freewheeling operating mode.

6. The hydraulic control circuit in accordance with claim 2, wherein a pressure regulation valve is connected to the inflow pressure maintenance valve to limit or fully prevent an increase in the pressure at the inflow pressure maintenance valve caused by closing the outflow valve.

7. The hydraulic control circuit in accordance with claim 6, wherein the load pressure taken up at the inflow valve is influenced by the pressure regulation valve.

8. The hydraulic control circuit in accordance with claim 3, wherein the outflow pressure regulation valve is deactivated via an adding valve.

9. The hydraulic control circuit in accordance with claim 8, wherein a braking torque is built up in the freewheeling operating mode by restricting the outflow valve, with a restriction actuation of the outflow valve taking place by a movement of a joystick opposite to the direction of rotation and/or by actuating a foot brake pedal.

10. The hydraulic control circuit in accordance with claim 1, wherein all or at least some of the valves are controlled via on-board electronics having an integrated BUS interface.

11. A slewing gear having at least one hydraulic control circuit, the hydraulic control circuit having directional valves arranged in work lines and controllable separately for inflow and outflow to a hydraulic motor for carrying out a rotational movement of the slewing gear, wherein an inflow valve is provided for control of oil inflow from a hydraulic pump via a work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor is relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via the outflow valve into the tank.

12. A crane having a hydraulic control circuit, wherein the hydraulic control circuit has directional valves arranged in work lines and controllable separately for inflow and outflow to a hydraulic motor for carrying out a rotational movement of the slewing gear, wherein an inflow valve is provided for control of oil inflow from a hydraulic pump via a work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor is relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via the outflow valve into the tank.

13. The hydraulic control circuit in accordance with claim 2, wherein the at least one inflow pressure maintenance valve is a three-way pressure maintenance valve.

14. The hydraulic control circuit in accordance with claim 7, wherein the influence of the pressure regulation valve is such that no higher pressure is present before the outflow pressure maintenance valve than a set pressure value of the pressure regulation valve.

15. The hydraulic control circuit in accordance with claim 8, wherein the outflow pressure regulation valve is deactivated in a manner that feedback of the outlet pressure of the pressure maintenance valve is interrupted by the adding valve.

16. The hydraulic control circuit in accordance with claim 10, wherein the BUS interface is a CAN interface.

17. The crane in accordance with claim 12, wherein the crane is a mobile crane or a crawler mounted crane.

18. The crane in accordance with claim 12, further comprising a slewing gear.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0025] FIG. 1 shows a hydraulic circuit diagram of the hydraulic control circuit in accordance with the present disclosure for the control of crane slewing gear.

DETAILED DESCRIPTION

[0026] A main component of the hydraulic control circuit is the main pump 2 for driving the slewing gear. This main pump 2 is driven via an engine, in particular a diesel engine of a crane. The hydraulic motor 1 that is supplied with the required operating pressure from the main pump 2 via the work lines A, B serves the carrying out of the rotational movement of the slewing gear. Depending on the direction of rotation of the slewing gear, either work line A or, alternatively, work line B is acted on by the desired pressure level while the hydraulic motor is relieved via the pressure-free work line A, B toward the tank.

[0027] The hydraulic control circuit in accordance with the present disclosure offers a slewing gear control that works in both directions, driving or driven, regulated both by quantity and by pressure. All conceivable control demands can thereby be covered by only one single hydraulic slewing gear control. This is achieved in that the pressure inflow of the hydraulic motor is controllable via a single inflow valve 5 and the pressure outflow is controllable via an outflow valve 9. In addition, a load-independent oil quantity can be ensured both in the inflow 15 and in the outflow 16 by integration of the inflow pressure maintenance valve 10 and of the outflow pressure maintenance valve 8.

[0028] The exact operating mode of the hydraulic control circuit will be described in more detail in the following. The slewing gear direction is connected via the inflow valve 5. In the neutral position, as shown in the single FIGURE, both work lines A, B are blocked via the directional check valves 6, 7 and by the outflow valve 9 toward the tank. The slewing gear is fixed by it in addition to the stop brake. If the outflow valve 9 is controlled to open, the slewing gear can move freely. The neutral position is generally also conceivable with an open outflow valve 9; then with a reverse control. It can be recognized that the two work lines A, B are combined to form a common outflow line 16 via the check valves 6, 7. The use of a common outflow valve 8 for both directions of rotation is thereby made possible at all.

[0029] The inflow valve 5 is brought into the first or third switch position to carry out a rotational movement, whereby either the work line A or the work line B is acted on by the required system pressure of the main pump 2. The integration of the three-way pressure maintenance valve 10 provides a load-independent oil quantity in the inflow 15 through the inflow valve 5. A system pressure limitation is achieved via the valves 17. The two check valves 18 serve as re-suction valves.

[0030] At the same time, the inflow valve 5 switches the outflow line of the hydraulic motor 1 free via the directional check valves 6, 7 and the outflow valve 9 to the tank. The integration of the outflow pressure maintenance valve 8 provides that the pressure difference over the outflow valve 9 is always constant such that the outflow quantity only depends on the opening of the outflow valve 9 itself. The outflow valve 9 is for this purpose a proportionally switchable outflow valve 9 with a variable adjustable flow quantity.

[0031] The function of the outflow pressure maintenance valve 8 can be taken out of operation via the adding valve 12 in that the return of the outlet pressure is interrupted. This is in particular desirable for the “freewheeling” mode in order here to be able to introduce a possible braking torque onto the slewing gear by a direct restriction of the outflow valve 9. A mechanical brake 3 can additionally also be available for applying a braking torque onto the slewing gear.

[0032] To avoid the pump pressure of the main pump 2 quickly reaching the maximum system pressure on the closing of the outflow valve 9 in the “clamped” mode, a pressure regulation valve 11 purely hydraulically prevents an increase of the pump pressure at the three-way pressure maintenance valve 10. The pressure regulation valve 11 for this purpose influences the load pressure picked up at the inflow valve 5 such that no higher pressure arises at the outflow pressure maintenance valve 8 than the pressure value set at the pressure regulation valve 11. A reduction of the diesel engine speed of the drive unit through the main pump 2 is thus avoided and no unnecessarily high pump pressure is produced, which helps save fuel and costs and reduces noise.

[0033] In the “clamped” mode, the slewing gear is delayed in a quantity regulated manner and with great precision by closing the outflow valve with an active outflow pressure maintenance valve 8. The switchover of the different operating modes is achieved in that the quantity regulation is deactivated in the outflow in the “freewheeling” mode. In this mode, the outflow valve 9 is opened further until the regulation pressure difference of the pressure maintenance valve 8 can no longer be reached at the outflow valve 9. The pressure maintenance valve 8 thus opens fully and is thus out of operation. It is thus possible to change continuously between the modes “freewheeling” and “clamped” by a proportional opening and closing of the outflow valve 9.