Energy storage and recovery system

Abstract

The invention relates to an energy storage and recovery system (ERS) coupleable to a prime mover and to an energy storage flywheel. The ERS has a hydrostatic arrangement with a first pumping element and a second pumping element. The pumping elements have a respective fluid displacement and a fluid coupling arrangement for the transfer of fluid power between the first and second pumping elements. The ERS also includes a differential device comprising at least three inputs, wherein a first driveshaft of the first pumping element is coupled to a prime mover in use, a first input of the a differential device is coupled to said prime mover in use, a second input of the differential device is coupled to a second driveshaft of the second pumping element, and the third input of the differential device is coupled to a flywheel in use.

Claims

1. An energy storage and recovery system (ERS) coupleable to a prime mover and to an energy storage flywheel, the ERS comprising: a hydrostatic arrangement having a first pumping element and a second pumping element, each pumping element having a respective fluid displacement and a fluid coupling arrangement for the transfer of fluid power between the first pumping element and the second pumping element, wherein at least one of the respective fluid coupling arrangements of the first and the second pumping elements may be selectively coupled to one or more hydraulic services for the transmission of fluid power between said at least one respective fluid coupling arrangement and the one or more hydraulic services; and a differential device comprising at least three inputs, wherein a first driveshaft of the first pumping element is coupled to a prime mover in use, a first input of the a differential device is coupled to said prime mover in use, a second input of the differential device is coupled to a second driveshaft of the second pumping element, and the third input of the differential device is coupled to a flywheel in use.

2. An ERS according to claim 1 in which the differential device is an epicyclic gearset.

3. An ERS according to claim 1, in which at least one of the pumping elements has a mechanism for varying its fluid displacement.

4. An ERS according to claim 3, wherein the first and second pumping elements have a mechanism for varying their respective fluid displacement.

5. An ERS according to claim 4, wherein both first and second pumping elements have a mechanism for varying and reversing flow for a given sense of speed of the respective driveshafts.

6. An ERS according to claim 1, wherein at least one of the pumping elements has a mechanism for varying and reversing flow for a given sense of speed of its driveshaft.

7. An ERS according to claim 1, wherein the first and the second pumping elements may be coupled via their respective fluid coupling arrangements for the transmission of fluid power between the two.

8. An ERS according to claim 7, further comprising a power-split arrangement in which only a portion of the power passing between the couple to said prime mover and the couple to said flywheel passes between the first and second pumping arrangements.

9. An ERS according to claim 1, wherein said first drive shaft is coupled to a carrier of an epicyclic, said second drive shaft is coupled to an annulus of said epicyclic and the flywheel is coupled to a sun of said epicyclic.

10. An ERS according to claim 9, wherein the epicyclic is a simple epicyclic.

11. An ERS according to claim 9, wherein there is a negative speed ratio between the sun and annulus with the carrier held stationary.

12. An ERS according to claim 1, wherein the respective fluid coupling arrangements of the first and the second pumping elements may be de-coupled so that transmission of fluid power between the two is not possible.

13. An ERS according to claim 1, adapted for transfer of vehicle kinetic energy to or from said flywheel.

14. An ERS according to claim 1, further comprising an energy storage flywheel coupled to the third input of the differential device.

15. An ERS according to claim 1, further comprising a prime mover coupled to said first driveshaft of the first pumping element and to a first input of the differential device.

16. A method of controlling a machine or vehicle comprising an ERS according to claim 1, the method comprising the following steps: a. determining a signal indicative of a power demanded by the current operating conditions of the machine or vehicle duty cycle; b. setting the prime mover power output to exceed that demanded by the current operating conditions of the vehicle or machine duty cycle; and c. varying the fluid displacement setting on one or both of the first and second pumping elements in order to effect power transfer from the prime mover to the flywheel.

17. A vehicle or machine operating according to claim 16.

18. A vehicle or machine according to claim 17 wherein the vehicle or machine is an urban passenger vehicle.

19. A vehicle or machine according to claim 17 wherein the vehicle or machine is one of a construction, industrial or agricultural vehicle.

20. A vehicle or machine according to claim 17 wherein the vehicle or machine is adapted for repeated cyclic operations.

21. A vehicle or machine according to claim 17 wherein the vehicle is one of a loading vehicle, a material shifting vehicle, an excavator and a wheeled loader.

22. A method of controlling a machine or vehicle comprising an ERS according to claim 1, the method comprising the following steps: a. determining a signal indicative of a power demanded by the current operating conditions of the machine or vehicle duty cycle; b. setting the prime mover power output to a level which is lower than that demanded by the current operating conditions of the vehicle or machine duty cycle; and c. varying the fluid displacement setting on one or both of the first and second pumping elements in order to effect power transfer from the flywheel to the prime mover.

23. A method of controlling a machine or vehicle comprising an ERS according to claim 1, the method comprising the following steps: a. determining a signal indicative of a power demanded by the current operating conditions of the machine or vehicle duty cycle; b. determining the direction to transfer power between the flywheel and the prime mover; b. setting the prime mover power output to a level which is lower or higher than that demanded by the current operating conditions of the vehicle or machine duty cycle dependent on the determined direction to power transfer; and d. varying the fluid displacement setting on one or both of the first and second pumping elements in order to effect power transfer from or to the flywheel to the prime mover dependent on the determined direction to power transfer.

24. A method of controlling a machine or vehicle comprising a ground engaging drive arrangement and an ERS according to claim 1, the method comprising the following steps: a. determining a signal indicative of a ground engaging drive arrangement torque request; b. varying the fluid displacement setting on one or both of the first and second pumping elements in order to effect power transfer from the flywheel to the ground engaging drive arrangement such that a portion of the torque request is satisfied; and c. setting the engine output such that substantially the remainder of the torque request is satisfied by said engine output.

25. A method of controlling a machine or vehicle comprising a ground engaging drive arrangement and an ERS according to claim 1, the method comprising the following steps: a. determining a signal indicative of a vehicle wheel torque request; b. setting the engine output such that the ground engaging drive arrangement torque request is exceeded by said engine output; and c. varying the fluid displacement setting on one or both of the first and second pumping elements in order to effect power transfer to the flywheel from the ground engaging drive arrangement such that substantially the remainder of the engine output is provided to said flywheel.

26. A method of controlling a machine or vehicle comprising a ground engaging drive arrangement and an ERS according to claim 1, the method comprising the following steps: a. determining a signal indicative of a ground engaging drive arrangement torque request; b. determining the direction to transfer power between the flywheel and ground the engaging drive arrangement; c. setting the engine output such that the output exceeds the torque request or vice versa dependent upon said determined direction; and d. varying the fluid displacement setting on one or both of the first and second pumping elements according to the determined direction, in order to control whether excess engine output is provided to the flywheel or torque from the flywheel is provided to said ground engaging drive arrangement where the engine output does not satisfy the torque request.

27. A vehicle or machine operating including an ERS according to claim 1.

Description

DESCRIPTION OF THE FIGURES

(1) The present invention will now be described in more detail with reference to the attached drawings in which:

(2) FIG. 1 shows an ERS coupled to an engine of a powertrain according to the invention, wherein the ERS is charging the flywheel when engine has surplus power;

(3) FIG. 2 shows an ERS coupled to an engine of a powertrain according to the invention, wherein the ERS is dis-charging the flywheel when engine has a deficit in power;

(4) FIG. 3 shows an ERS coupled to an engine of a powertrain according to the invention, wherein the engine pump only is used to power hydraulic services;

(5) FIG. 4 shows an ERS coupled to an engine of a powertrain according to the invention, wherein the engine pump only is used to recuperate or receive power from hydraulic services;

(6) FIG. 5 shows an ERS coupled to an engine of a powertrain according to the invention wherein one or both of the first and second pumping elements are used to receive or recuperate energy from the hydraulic services, delivering such energy to the engine and/or flywheel;

(7) FIG. 6 shows an ERS coupled to an engine of a powertrain according to the invention wherein the hydraulic services are powered using one or both of the first and second pumping elements, and the engine and/or flywheel; and

(8) FIG. 7 shows an ERS coupled to an engine of a powertrain according to the invention wherein the ERS is adapted for the recovery of vehicle kinetic energy in a vehicle.

DETAILED DESCRIPTION

(9) With reference to FIGS. 1 to 6, an engine (or other prime mover) 11 is coupled to a first pumping element 4 which has an associated driveshaft 10 coupled to the carrier 7 of a simple epicyclic gearset 5. A second pumping element 3 which has an associated driveshaft 9 is coupled via a gear to an annulus 8 of epicyclic 5. A sun 6 is coupled to flywheel 2.

(10) FIG. 1 shows the case where the first pumping element 4 is coupled to second pumping element 3, their respective fluid coupling arrangements arranged for transfer of fluid at pressure, and hence hydrostatic power, between them. By varying the displacement of one or both pumping elements using the fluid displacement mechanism 18, the CVT ratio can be adjusted in order to drive power into the flywheel. In this example, the torque applied to the carrier 7 will be opposite to that applied to the annulus 8. Hence in order to transfer power in a parallel fashion, as required by a power-split arrangement, the annulus should be driven in an opposite sense to the carrier 7.

(11) This is readily accomplished with a hydrostatic CVT as the driveshaft 9 of the second pumping element 3 can be made to rotate in any desired direction with respect to the driveshaft 10 of the first pumping element 4 by configuring the fluid connections between the pumping elements appropriately, as is known. In this example, the pumping element 4 is configured to drive carrier 7, whilst the second pumping element 3 is configured to drive the annulus 8. This may be achieved by progressively decreasing the fluid displacement of the first pumping element 4 with respect to the first pumping element 3. This tends to increase the speed of the flywheel 2, thus transferring energy to it from the engine, or in the case of KERS, from the ground engaging member such as the wheels or tracks of a machine or vehicle. If the displacement of the first pumping element 4 reaches zero then substantially no power passes through the CVT and the power-split arrangement achieves its highest efficiency.

(12) FIG. 2 shows the case where energy is transferred in the opposite sensei.e. from the flywheel 2 back to the engine 11 side. This may be achieved in this example by increasing the fluid displacement of the first pumping element 4 with respect to the second pumping element 3, this slowing down the flywheel 2 and extracting energy from it.

(13) FIGS. 3 and 4 show a case where the flywheel 2 may have insufficient state of charge to supply energy to the engine or to the vehicle or machine. In this case, the pumping elements 3 and 4 may be decoupled so that the engine 11 alone supplies power to hydraulic services (labelled), or so that energy from the hydraulic services may be used to support the prime mover 11.

(14) FIGS. 5 and 6 show the cases where power is received from (FIG. 5) or supplied to (FIG. 6) the hydraulic services. As the torques in the epicyclic 5 are related by gains related to the speed ratio between the sun and the annulus when the carrier is stationary, the sense of the speeds of the driveshaft 9 of second pumping element 3 may be set by suitably adjusting the fluid displacement mechanism for this pumping element such that power is taken in from the hydraulic service. Alternatively or additionally, a valve arrangement (not shown) intervening between the hydraulic services and the second (or first) pumping element may allow the speed and torques to be suitably reversed in order to achieve the correct sign of speed and torque at the epicyclic (in this case, annulus 8). In this configuration a portion of the power is passed through each pumping element 3, 4 towards, or away from, the flywheel 2.

(15) FIG. 7 shows an ERS in a vehicle (such as an urban passenger vehicle 19, a construction vehicle 20, an industrial vehicle 21, an agricultural vehicle 22, a loading vehicle 23, a material shifting vehicle 24, an excavator 25 or a wheeled loader 26). Engine 11 is coupled to ERS 1, which is optionally coupled to transmission 12. The output of transmission 12 is coupled to prop-shaft 14 which drives final drive 17. The final drive 17 is coupled to the vehicle wheels 15. Thus an ERS 1 mounted on or close to the engine 11 may also serve as a vehicle kinetic energy recovery system.