DEVICE FOR RECOVERING HYDRAULIC ENERGY BY CONNECTING TWO DIFFERENTIAL CYLINDERS

Abstract

Device for recovering hydraulic energy in a machine comprising at least a first differential cylinder-piston assembly having a differential cylinder with a separate rod and base side, at least a second differential cylinder-piston assembly having a differential cylinder with a separate rod and base side, and at least one hydraulic accumulator that can be hydraulically connected to at least one of the differential cylinder-piston assemblies, wherein the differential cylinder-piston assemblies are mechanically coupled to one another, and wherein the potential energy of at least one of the differential cylinder-piston assemblies retracting under a compressive load can at least partially be stored in the hydraulic accumulator.

Claims

1. A device for recovering hydraulic energy in a machine comprising: a first differential cylinder-piston assembly having a differential cylinder with a separate rod and base side; a second differential cylinder-piston assembly having a differential cylinder with a separate rod side and base side; and one hydraulic accumulator that is hydraulically connected to at least one of the differential cylinder-piston assemblies; wherein the differential cylinder-piston assemblies are mechanically coupled to one another; wherein a potential energy of at least one of the differential cylinder-piston assemblies is at least partially stored in the hydraulic accumulator; and wherein at least one of the differential cylinder-piston assemblies retracts under a compressive load.

2. The device according to claim 1, wherein the hydraulic accumulator is hydraulically connected to the differential cylinder-piston assemblies.

3. The device according to claim 1, wherein the device further comprises an assisting motor that directs the hydraulic energy stored in the hydraulic accumlator into a drivetrain of the machine wherein the assisting motor is hydraulically connected to the hydraulic accumulator via an assisting motor valve.

4. The device according to claim 1, wherein the device recovers the energy stored in the hydraulic accumulator by transferring the energy to at least one of the differential cylinder-piston assemblies.

5. The device according to claim 3, wherein the stored hydraulic energy is transferred simultaneously, alternately or sequentially to at least one of the drivetrain and at least one of the differential cylinder-piston assemblies.

6. The device according to claim 1, wherein the differential cylinder-piston assemblies operate in parallel.

7. The device according to claim 1, further comprising at least one operating pump for driving the differential cylinder-piston assembly.

8. The device according to claim 7, futher comprising a shut-off valve for isolating at least one of the differential cylinder-piston assemblies from a tank and from an operating pump.

9. A machine, having a device for recovering hydraulic energy in accordance with claim 1, wherein the machine is a wheel loader, a hydraulic excator or crane.

10. The machine according to claim 9, wherein the machine is operable without the loss of other functions in the event of a breakdown of the device for recovering hydraulic energy.

11. The device according to claim 1, further comprising at least one operating pump for driving the differential cylinder-piston assembly and at least one slide valve for controlling the hydraulic accumulator.

12. The device according to claim 1, further comprising at least one slide valve for controlling at least one of the hydraulic accumulators and the differential cylinder-piston assembly

13. The device according to claim 1, further comprising at least one tank.

14. The device according to claim 1, further comprising at least one hydraulic accumulator valve.

15. The device according to claim 1, wherein each of the differential cylinder-piston assemblies is associated with at least one brake valve.

16. The device according to claim 7, wherein the device has a shut-off valve for isolating at least one of the differential cylinder-piston assemblies from a tank and from an operating pump.

17. The device according to claim 4, wherein the stored hydraulic energy transferred simultaneously, alternately or sequentially to at least one of the drivetrain and at least one of the differential cylinder-piston assemblies.

Description

[0027] Further particulars and advantages of the invention are illustrated in the example embodiment shown in FIG. 1.

[0028] As can be seen in FIG. 1, a suitable precharging pressure can be applied to the high-pressure accumulator 20 when a machine or work machine with the inventive device is put into operation. To start the storage process, an external force must be applied to the differential cylinder 1 and the differential cylinder 4 thereby retracting the differential cylinders 1, 4. This causes pressures to build up on the base side 3 of the differential cylinder 1 and the base side 6 of the differential cylinder 4 which governs the amount of potential energy present. This potential energy can be taken up by means of the hydraulic accumulator 20.

[0029] To start the lowering process, the brake valve 7 of the differential cylinder 4 and the hydraulic accumulator valve 21 are opened. The volume flow moves out of the base side 6 of the differential cylinder 4, through the brake valve 7 of the differential cylinder 4 and the non-return valve 9, and into the rod side 5 of the differential cylinder 4 and the rod side 2 of the differential cylinder 1. The term differential cylinder-piston assembly 100, 400 encompasses, in this case, each differential cylinder 1, 4 and the corresponding separate rod 2, 5 and base sides 3, 6. The term may also encompass the respective pistons.

[0030] Any excess volume flow out of the base side 6 of the differential cylinder 4 can be led off to the tank 13 via the precharging valve 8. The volume flow moves out of the base 3 of the differential cylinder 1 and into the hydraulic accumulator 20 via the hydraulic accumulator valve 21. As a result of the take-up of the volume flow in the hydraulic accumulator 20 from the base side 3 of the differential cylinder 1, the pressure in the hydraulic accumulator 20 increases. The speed of retraction of the drive, consisting of the differential cylinder 1 and differential cylinder 4 or the respective differential cylinder-piston assemblies 100, 400, can be adjusted by proportional control of the hydraulic accumulator valve 21.

[0031] To stop the retracting movement of the differential cylinder 1 and differential cylinder 4, the brake valve 7 of the differential cylinder 4 and the hydraulic accumulator valve 21 are closed. The hydraulic accumulator 20 now contains the pressurised oil volume that was displaced out of the base side 3 of the differential cylinder 1 during the retracting movement of the linear drive. To reuse the hydraulic energy in the hydraulic accumulator 20 for an extension movement of the linear drive, the shut-off valve 22 is closed. Depending on the position of the slide valve 16, the base side 6 of the differential cylinder 4 is supplied with a volume flow from the operating pump 14. The operating pump is driven by the drive motor 17 via the transfer gearbox 18. To supply the hydraulic energy in the hydraulic accumulator 20 to the base side 3 of the differential cylinder 1, the hydraulic accumulator valve 21 is opened. The pressurised volume flow thereby moves out of the hydraulic accumulator 20 and into the base side 3 of the differential cylinder 1 via the hydraulic accumulator valve 21. When the discharge process for the hydraulic accumulator 20 has ended, the hydraulic accumulator valve 21 is closed and the shut-off valve 22 opened. Volume flow from the operating pump 14 now also moves into the base side 3 of the differential cylinder 1 via the slide valve 16 and the linear drive extends again. The volume flow exiting from the rod side 2 of the differential cylinder 1 and the rod side 5 of the differential cylinder 4 during the entire extension movement of the linear drive returns to the tank 13 via the slide valve 16.

[0032] Alternately or sequentially to the direct transfer to the linear drive, the energy of the pressurised oil volume in the hydraulic accumulator 20 after the storage process can be transferred again to the drivetrain of the machine. For this purpose, the assisting motor 15 is connected to the hydraulic accumulator 20 via the hydraulic assisting motor valve 19. The assisting motor 15 can be mounted directly on the transfer gearbox 18 of the machine and is driven by means of the fixed or prescribed rotational speed of the drive motor 17. Depending on the displacement of the assisting motor 15 and the particular operating state of the hydraulic accumulator 20, the energy is then transferred to the drivetrain. At the end of the energy transfer process, the assisting motor valve 19 is closed thereby disconnecting the hydraulic accumulator 20 and the assisting motor 15.

[0033] Depending on the size of the hydraulic accumulator 20, it is possible to store the potential energy of part of, or the entire stroke of the linear drive.

[0034] If the hydraulic accumulator 20 is designed to accommodate only part of the stroke of the differential cylinder 1, and the retracting movement needs to extend further than allowed by the design of the hydraulic accumulator 20, a brake valve circuit can be employed. For this purpose, the hydraulic accumulator valve 21 is closed at the end of the storage process while the brake valve 7 remains open. The brake valve 12 of the differential cylinder 1 is now opened. The volume flow exiting the base side 3 of the differential cylinder 1 flows into the rod side 2 of the differential cylinder 1 and into the rod side 5 of the differential cylinder 4 via the brake valve 12 and via the opened shut-off valve 22 and non-return valve 10. The excess volume flow is led off to the tank 13 via the precharging valve 11.

[0035] This control of the brake valve 12 of the differential cylinder 1 and the brake valve 7 of the differential cylinder 4 also occurs whenever it is desired to retract the linear drive when operating without an accumulator system or with a defective accumulator system, whereby accumulator system refers to the hydraulic accumulator 20 and the accumulator valve 21.

[0036] To retract the linear drive during the machine cycle, and to direct the volume flow of the operating pump 14 by suitably controlling the slide valve 16 on the rod side 2 of the differential cylinder 1 and the rod side 5 of the differential cylinder 4, the shut-off valve 22 is kept open. This directs the volume flow exiting from the base side 3 of the differential cylinder 1 and the base side 6 of the differential cylinder 4 into the tank 13 via the slide valve 16.

[0037] The circuit contains at least one operating pump 14 and at least one slide valve 16. All kinds of hydraulic accumulators 20 employing a variety of energy storage media, for example nitrogen, can be used. Conceivable are embodiments as gas accumulators, piston accumulators, membrane accumulators or spring accumulators as well as different combinations of accumulator embodiments.

[0038] The valves shown can be used as single 2/2-way valves or also as multiple valves on a valve rod. Proportional and/or switching control of the individual valves is likewise possible.

[0039] The inventive device differs from the prior art in that the potential energy of the equipment can always first be stored in the hydraulic accumulator, and then reused. In this case it is possible to use either a recovery motor, or alternatively or in addition to this the energy can also be transferred directly back into the hydraulic cylinder.

[0040] The invention is characterised by an arrangement of at least two hydraulic differential cylinders that are mechanically coupled to each other, whereby the areas of the base and rod side are configured in such a way that the area of one base side is greater than or equal to the area of the two rod sides.

[0041] The invention is characterised in that a large part of the potential energy present when a hydraulic linear drive is retracted under a compressive load can be stored with the help of one or more hydraulic accumulators.

[0042] The invention is further characterised in that only one of the two differential cylinders can be connected to the hydraulic accumulator for the specific purpose of storing energy.

[0043] The invention is characterised in that a large part of the externally impressed or applied force during the lowering process is taken up by the differential cylinder that is connected to the hydraulic accumulator.

[0044] The invention is characterised in that the energy stored while retracting the hydraulic linear drive or cylinder can be directly released by exactly one or at least one of the hydraulic differential cylinders while extending the hydraulic linear drive. This can occur by appropriately connecting the single or multiple hydraulic accumulators to suitable valves. In doing so, it is advantageous that no intermediate conversion of the energy occur and no conversion losses arise.

[0045] The invention is characterised in that the energy stored while retracting the hydraulic linear drive can be transferred directly back into the drivetrain of the machine. This is achieved by connecting a hydraulic motor to the relevant hydraulic accumulator so that the energy contained in the hydraulic accumulator can be transferred to the drivetrain of the machine to assist the primary drive source, for example a diesel motor or electric motor.

[0046] The invention is further characterised in that the stored energy can be directly reused by transferring it into the linear drive and/or utilising it via the hydraulic motor. This method of reuse can be used either individually or serially.

[0047] The invention is further characterised in that the hydraulic linear drive can be retracted and extended without the single or multiple hydraulic accumulators and hydraulic valves for storing potential energy being activated. This is achieved within the hydraulic circuit by suitable parallel connection of the hydraulic linear drive.

[0048] The invention is further characterised in that the energy storage and release by means of the hydraulic linear drive is possible over the entire, or only a part of the full travel distance.

[0049] The invention is also characterised in that it can be integrated into the drivetrain of a machine without affecting the functioning of the drivetrain in such a way that it depends on the invention to function fully. This means that the machine can be operated flawlessly even without the functionality of the invention.