Crane having a closed hydraulic circuit

Abstract

A crane, in particular a mobile crane, having a closed hydraulic circuit in which a hydraulic pump is hydraulically connected to at least one hydraulic motor via a feed and a discharge, and in which the feed is hydraulically connected to the discharge via at least one bypass which bypasses the at least one hydraulic motor, wherein the at least one bypass includes a continuously adjustable valve for variably controlling the fluid flow bypassing the at least one hydraulic motor. In addition, a corresponding control device and a corresponding crane control program for actuating a closed hydraulic circuit of a crane are provided.

Claims

1. A crane having a closed hydraulic circuit in which a hydraulic pump is hydraulically connected to at least one hydraulic motor via a feed and a discharge to provide fluid flow delivered to the at least one hydraulic motor, and in which the feed is hydraulically connected to the discharge via at least one bypass which bypasses the at least one hydraulic motor, wherein the at least one bypass comprises a continuously adjustable proportional valve, which is adapted to be proportionally opened and closed so as to variably control a fluid flow in the at least one bypass the continuously adjustable proportional valve being operatively coupled to an operator control member, and a control device which is in contact with the hydraulic pump and the at least one continuously adjustable proportional valve via at least one interface and is configured to actuate the hydraulic pump and the at least one continuously adjustable proportional valve during crane operations in a co-ordinated way, wherein the control device is configured to initiate: an acceleration of the at least one hydraulic motor by actuating the hydraulic pump to provide the fluid flow delivered to the hydraulic motor at a pressure that is higher than a pressure of a fluid flow received at the hydraulic pump from the at least one hydraulic motor; a coasting state of the at least one hydraulic motor by actuating the at least one continuously adjustable proportional valve to open, and by actuating the hydraulic pump to reduce the fluid flow delivered to the hydraulic motor, wherein a fluid flow delivered from the at least one hydraulic motor is directed through the at least one bypass; and deceleration initiated by a valve-controlled deceleration of the at least one hydraulic motor in the coasting state by actuating the at least one continuously adjustable proportional valve to proportionally close, wherein the continuously adjustable proportional valve is directly controlled by the operator control member to cause deceleration by causing a fluid flow received at the hydraulic motor from the at least one continuously adjustable proportional valve to be maintained at a lower pressure than the fluid flow delivered from the at least one hydraulic motor to the at least one continuously adjustable proportional valve.

2. The crane according to claim 1, wherein the at least one bypass comprises a closing valve which is configured to close the bypass to the fluid flow in at least one flowing direction.

3. The crane according to claim 2, wherein the at least one closing valve is a unidirectional valve.

4. The crane according to claim 1, wherein the at least one bypass comprises two bypasses such that the feed is hydraulically connected to the discharge via the two bypasses, wherein the two bypasses are connected in parallel and respectively comprise the continuously adjustable proportional valve and a closing valve for variably controlling the fluid flow in the at least one bypass for opposing slewing directions of the at least one hydraulic motor.

5. The crane according to claim 1, wherein the flow delivered to the hydraulic motor by the hydraulic pump is able to be variably adjusted.

6. The crane according to claim 1, wherein a volumetric displacement of the at least one hydraulic motor is able to be variably adjusted.

7. The crane of claim 1, wherein the operator control member is a brake pedal.

8. The crane of claim 1, wherein the operator control member is a joystick.

9. A control device for actuating a closed hydraulic circuit of a crane, the hydraulic circuit having a hydraulic pump hydraulically connected to at least one hydraulic motor via a feed and a discharge to provide a fluid flow delivered to the at least one hydraulic motor, and in which the feed is hydraulically connected to the discharge via at least one bypass which bypasses the at least one hydraulic motor, wherein the at least one bypass comprises a continuously adjustable proportional valve, the continuously adjustable proportional valve being operatively coupled to an operator control member, wherein the control device is in contact with the hydraulic pump and the at least one continuously adjustable proportional valve via at least one interface, and wherein the control device is configured to initiate: an acceleration of the at least one hydraulic motor by actuating the hydraulic pump to provide the fluid flow delivered to the hydraulic motor at a pressure that is higher than a pressure of a fluid flow received at the hydraulic pump from the at least one hydraulic motor; a coasting state of the at least one hydraulic motor by actuating the at least one continuously adjustable proportional valve to open, and by actuating the hydraulic pump to reduce the fluid flow delivered to the at least one hydraulic motor, wherein a fluid flow delivered from the at least one hydraulic motor is directed through the at least one bypass; and deceleration initiated by a valve-controlled deceleration of the at least one hydraulic motor in the coasting state by actuating the at least one continuously adjustable proportional valve to proportionally close, wherein the continuously adjustable proportional valve is directly controlled by the operator control member to cause deceleration such that a fluid flow received at the at least one hydraulic motor from the at least one continuously adjustable proportional valve is maintained at a lower pressure than the fluid flow delivered from the at least one hydraulic motor to the at least one continuously adjustable proportional valve.

10. The control device of claim 9, wherein the operator control member is a brake pedal.

11. The control device of claim 9, wherein the operator control member is a joystick.

12. A crane having a closed hydraulic circuit comprising: a hydraulic pump hydraulically connected to at least one hydraulic motor via a feed and a discharge to deliver a fluid to the at least one hydraulic motor; a first bypass hydraulically connecting the feed to the discharge; a first proportional valve arranged in the first bypass being operatively coupled to an operator control member; a second bypass hydraulically connecting to the feed to the discharge; and a second proportional valve arranged in the second bypass being operatively coupled to the operator control member, a control device which is in contact with the hydraulic pump and the first and second proportional valves via at least one interface and is configured to actuate the hydraulic pump and the first and second proportional valves during crane operations in a coordinated way; wherein the at least one hydraulic motor is operable in an acceleration state for a first slewing direction and a second slewing direction and in a coasting state for the first slewing direction and the second slewing direction, wherein the control device is configured to initiate the acceleration state and the coasting state; wherein in the acceleration state for the first slewing direction, the hydraulic pump is configured to deliver the fluid to the at least one hydraulic motor at a first volumetric flow, the first proportional valve is open, the second proportional valve is closed, and wherein the fluid in the feed is at a higher pressure than the fluid in the discharge, and wherein in the coasting state for the first slewing direction, the hydraulic pump is configured to deliver the fluid to the at least one hydraulic motor at a second volumetric flow less than the first volumetric flow, the first proportional valve is open, the second proportional valve is closed, and the fluid is directed into the first bypass in a first flow direction, wherein to initiate deceleration during the coasting state, the first proportional valve is directly controlled by the operator control member and is proportionally closed so as to variably reduce a fluid flow in the first bypass to decelerate the at least one hydraulic motor, and the fluid in the discharge to be maintained at a higher pressure than the fluid in the feed.

13. The crane of claim 12, further comprising a first closing valve arranged in the first bypass, wherein in the acceleration state for the first slewing direction, the first closing valve is closed to prevent the fluid flow through the first proportional valve in a second flow direction opposite to the first flow direction.

14. The crane of claim 13, wherein in the coasting state for the first slewing direction, the first closing valve is open to permit the fluid flow through the first bypass to the at least one hydraulic motor.

15. The crane of claim 12, wherein in the coasting state for the first slewing direction, the at least one hydraulic motor is further decelerated in response to the hydraulic pump delivering the fluid flow to the at least one hydraulic motor at the second volumetric flow.

16. The crane of claim 12, wherein in the acceleration state for the second slewing direction, the hydraulic pump is configured to deliver the fluid to the at least one hydraulic motor at the first volumetric flow, the first proportional valve is closed, the second proportional valve is open, and the discharge is a load side of the at least one hydraulic motor, and wherein in the coasting state for the second slewing direction, the hydraulic pump is configured to deliver the fluid to the at least one hydraulic motor at the second volumetric flow less than the first volumetric flow, the first proportional valve is closed, the second proportional valve is open, the feed is the load side of the at least one hydraulic motor, and the fluid is directed into the second bypass in a second flow direction, wherein, as a consequence of an actuation of the operator control member by an operator, the second proportional valve is proportionally closed so as to variably reduce a fluid flow in the second bypass to decelerate the at least one hydraulic motor.

17. The crane of claim 12, wherein the operator control member is a brake pedal.

18. The crane of claim 12, wherein the operator control member is a joystick.

Description

(1) In the following, a preferred embodiment of the present invention is described in more detail by referring to the enclosed figure. The invention can comprise any of the features described here, individually and in any expedient combination.

(2) FIG. 1 shows a hydraulic circuit diagram of a closed hydraulic circuit 1 of a crane, in which two hydraulic motors 3, 9 can be supported on the regulatable hydraulic pump 2 both via their shared feed 4 and via their shared discharge 5. It should be noted at this juncture that if the slewing direction of the motors 3, 9 is reversed, the feed 4 performs the function of the discharge, while the discharge 5 performs the function of the feed 4.

(3) In addition to the hydraulic motors 3, 9 which are connected in parallel, the circuit 1 comprises two bypasses 6A, 6B in opposite directions, which are connected in parallel and bypass the two motors 3, 9. The hydraulic fluid can only flow anti-clockwise through the bypass 6A due to the unidirectional valve 8A and only clockwise through the bypass 6B due to the unidirectional valve 8B. Each of the bypasses 6A, 6B is thus responsible for exactly one slewing direction of the slewing mechanism of the crane (not shown), and the hydraulic fluid flows through it as soon as the proportional valve 7A, 7B assigned to it is opened. As can be seen in FIG. 1, the proportional valves 7A, 7B are held in their closed base position by means of a spring and can be non-incrementally opened by means of an operating member which is not indicated in greater detail. The valves can however also be designed inversely, i.e. opened when there is no flow and then proportionally closed. Depending on the degree to which the respective proportional valve 7A, 7B is open, a portion of the hydraulic fluid will flow through the relevant bypass 6A, 6B and will consequently not be available to drive the motors 3, 9.

(4) In the following, different operational states of the hydraulic circuit shown in FIG. 1 are described in more detail.

(5) In an open hydraulic circuit 1, when the joystick is moved, the proportional valve 7A (and/or 7B) assigned to the slewing direction is opened, wherein the hydraulic pump 2 which is configured as an axial piston pump increases the volumetric flow of hydraulic fluid by pivoting out, and the slewing mechanism accelerates as in known closed circuits. Hydraulic fluid does not flow through the proportional valve 7A (and/or 7B), since the higher pressure in the feed 4 acts to close the unidirectional valve 8A.

(6) When coasting, the proportional valve 7A continues to be open, whereupon the hydraulic pump 2 pivots in and thus reduces the volumetric flow of hydraulic fluid delivered. The load side of the hydraulic motors 3, 9 changes, and circumferential coasting arises, similar to the coasting in previous closed circuits. When controlled in the opposite direction, the proportional valve 7A (and/or 7B) is closed using a ramp function, which increases the pressure in the discharge 5. This ramp function can be controlled or regulated. Once the resting position has been reached, the proportional valve 7B (and/or 7A) of the opposing bypass 6B (and/or 6A) is opened, and the hydraulic pump 2 drives in the other slewing direction. The crane accelerates in the opposite direction.

(7) The brake pedal (not shown) is coupled to the two valves 7A, 7B, wherein slewing direction recognition defines which of the valves 7A, 7B is to be operated. The corresponding proportional valve 7A, 7B is proportionally closed, and the pump is pivoted in, which reduces the volumetric flow of hydraulic fluid delivered. The braking pressure increases, and the slewing mechanism slows. In order to re-accelerate, the proportional valve 7A, 7B is controlled to open and the hydraulic pump 2 is pivoted out (increasing the volumetric flow). As soon as the driving load pressure is higher than the pressure in the respective discharge 5, the unidirectional valve 8A, 8B closes.