LOW VOLTAGE ELECTRIC-HYDRAULIC DRIVE SYSTEM FOR ELECTRIC TRANSPORTATION

Abstract

Disclosed is a hydraulic drive system for a vehicle, which system comprises a hydraulic motor, at least one hydraulic pump, at least one low voltage electric motor, at least one low voltage battery and at least one low voltage fuel cell.

Claims

1. A hydraulic drive system for a vehicle, wherein the system comprises a hydraulic motor, at least one hydraulic pump, at least one low voltage electric motor, at least one low voltage battery and at least one low voltage fuel cell.

2. The hydraulic drive system of claim 1, wherein the hydraulic motor is connected to at least a first hydraulic pump and a second hydraulic pump, the first hydraulic pump being connected to a first low voltage electric motor and the second hydraulic pump being connected to a second low voltage electric motor, and wherein (a) both the first low voltage electric motor and the second low voltage electric motor are connected to at least one low voltage battery and at least one low voltage hydrogen fuel cell; or (b) the first low voltage electric motor is connected to at least two low voltage batteries but is not connected to a low voltage fuel cell and the second low voltage electric motor is connected to at least two low voltage hydrogen fuel cells but is not connected to a low voltage battery.

3. The hydraulic drive system of claim 1, wherein the hydraulic motor is connected to at least one hydraulic pump which is connected to a low voltage electric motor which in turn is connected to at least one low voltage battery and at least one low voltage hydrogen fuel cell.

4. The hydraulic drive system of claim 1, wherein the at least one low voltage electric motor has a voltage of not higher than 100 V.

5. The hydraulic drive system of claim 1, wherein the at least one low voltage battery has a voltage of not higher than 100 V.

6. The hydraulic drive system of claim 1, wherein the at least one low voltage hydrogen fuel cell has a voltage of not higher than 100 V.

7. The hydraulic drive system of claim 2, wherein each of the first and second low voltage electric motors is connected to at least one low voltage battery and at least one low voltage hydrogen fuel cell.

8. The hydraulic drive system of claim 2, wherein the at least one first low voltage electric motor is connected to at least two low voltage batteries but is not connected to a low voltage hydrogen fuel cell and the at least one second low voltage electric motor is connected to at least two low voltage hydrogen fuel cells but is not connected to a low voltage battery.

9. The hydraulic drive system of claim 1, wherein the at least one low voltage hydrogen fuel cell is an alkaline fuel cell.

10. The hydraulic drive system of claim 1, wherein the system is capable of recovering breaking energy for charging the at least one low voltage battery.

11. An electric vehicle, wherein the vehicle comprises the hydraulic drive system of claim 1.

12. An electric vehicle, wherein the vehicle comprises at least two hydraulic drive systems each of which comprises a hydraulic motor connected to at least one hydraulic pump which in turn is connected to a low voltage electric motor, and wherein at least one low voltage electric motor comprised in any of the at least two hydraulic drive systems is connected to at least one low voltage battery and at least one low voltage electric motor comprised in any of the at least two hydraulic drive systems is connected to at least one low voltage fuel cell.

13. The vehicle of claim 11, wherein the vehicle is a bus.

14. The vehicle of claim 11, wherein the vehicle is a truck.

15. The vehicle of claim 11, wherein the vehicle is an all-wheel drive vehicle.

16. The vehicle of claim 11, wherein each wheel of the vehicle is connected to at least one hydraulic drive system which comprises a hydraulic motor, at least one hydraulic pump, at least one low voltage electric motor, at least one low voltage battery and at least one low voltage fuel cell.

17. The vehicle of claim 11, wherein at least two wheels of the vehicle are connected to different hydraulic motors.

18. The vehicle of claim 11, wherein at least all electric components and hydraulic pump(s) of the hydraulic drive system are protected from exposure to harsh environments.

19. The vehicle of claim 18, wherein at least all electric components and hydraulic pump(s) of the drive system are present in a water-proof compartment of the vehicle and/or are present in an elevated location of the vehicle.

20. A method of enabling an electric vehicle to operate with a low voltage battery, wherein the method comprises incorporating in the vehicle the hydraulic drive system of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention is further described in the detailed description which follows, in reference to the accompanying drawings by way of non-limiting examples of exemplary embodiments of the present invention. In the drawings:

[0032] FIG. 1 schematically represents the general design of a hydraulic drive system according to the present invention;

[0033] FIG. 2 is a schematic representation of a first embodiment of the hydraulic drive system according to the present invention;

[0034] FIG. 3 is a schematic representation of a second embodiment of the hydraulic drive system according to the present invention; and

[0035] FIG. 4 schematically represents the general design of another hydraulic drive system according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

[0036] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

[0037] FIG. 1 schematically represents the general design of a hydraulic drive system according to the present invention which comprises one hydraulic motor and more than one hydraulic pump. FIG. 1 shows a hydraulic motor which is connected (through a hydraulic accumulator not shown in FIG. 1) to N hydraulic pumps, three of which are shown in FIG. 1. Of course, according to the present invention it is also possible for the hydraulic motor to be connected to only one or only two hydraulic pumps. Each of the hydraulic pumps is connected to a separate low voltage motor. For example, a low voltage motor with 96 VDC will typically provide a power of 30 kW. If in FIG. 1 N=5, the total power of the hydraulic motor will be 150 kW (assuming there is no transmission loss). In other words, total hydraulic power=electric power x N. There is no electric motor available which delivers 150 kW from a 96 VDC power source.

[0038] FIG. 2 schematically represents an embodiment of the hydraulic drive system of the invention which is a hybrid at the hydraulic level. Specifically, FIG. 2 shows a hydraulic motor which is connected (through a hydraulic accumulator not shown in FIG. 2) to N hydraulic pumps each of which is connected to a separate low voltage electric motor which in turn is connected (through an electric motor controller not shown in FIG. 2) to two low voltage batteries (only one such hydraulic pump/electric motor is shown in FIG. 2) and to M hydraulic pumps each of which is connected to a separate low voltage electric motor which in turn is connected (through an electric motor controller not shown in FIG. 2) to two low voltage fuel cells (only one such hydraulic pump/electric motor is shown in FIG. 2). Both N and M can independently have values of 1, 2, 3, 4, 5, 6 or even higher. It is, of course, possible for an electric motor to be connected to only one or to more than two (e.g., three or four) low voltage batteries or low voltage fuel cells. Further, if N and/or M are at least 2 it is possible for the electric motors in each of the two groups to be connected to a different number of fuel cells/batteries. Further and as already mentioned, each and every battery/fuel cell may also independently be connected to more than one electric motor.

[0039] FIG. 3 schematically represents an embodiment of the hydraulic drive system of the invention which is a hybrid at the electric level. Specifically, FIG. 3 shows a hydraulic motor which is connected (through a hydraulic accumulator not shown in FIG. 3) to N hydraulic pumps each of which is connected to a separate low voltage electric motor which in turn is connected (through an electric motor controller not shown in FIG. 3) to one low voltage battery and one low voltage fuel cell (only two such hydraulic pump/electric motor combinations are shown in FIG. 3). N can have values of 1, 2, 3, 4, 5, 6 or even higher. In other words, it is, of course, also possible for a hydraulic motor to be connected to only one hydraulic pump. It further will be appreciated that it is not necessary for an electric motor to be connected to only one battery and only one fuel cell. On the contrary, each of the electric motors in this embodiment can independently be connected to more than one battery (e.g., two or three batteries) and/or to more than one fuel cell (e.g., two or three fuel cells). Additionally and as already mentioned, each and every battery/fuel cell may also independently be connected to more than one electric motor.

[0040] While not shown in the instant drawings, the embodiments of the hydraulic drive system of the invention illustrated in FIGS. 2 and 3 may also be combined. In other words, a corresponding system would comprise at least one electric motor which is connected to at least one battery and at least one fuel cell and would also comprise at least one electric motor which is connected to only one or more batteries and/or at least one electric motor which is connected to only one or more fuel cells.

[0041] FIG. 4 schematically represents the general design of another hydraulic drive system of the invention. Specifically, FIG. 4 shows a group of M hydraulic motors (four of which are shown in FIG. 4), each of which being connected to a (at least one) hydraulic pump which in turn is connected to a low voltage electric motor. The total number of hydraulic pumps/electric motor combinations is N (three of these N combinations are shown in FIG. 4). M is a number of 2, 3, 4 or even higher, whereas N equals at least M, but can also be higher than M. Preferably, N=M. For example, for N=M=4 each of the four hydraulic motors could be connected to one of the four wheels of an electric vehicle. Assuming, for example, that in this case each hydraulic motor is responsible for one wheel of a hydraulic bus, the electric bus can have a 4-wheel drive and the size of each hydraulic motor can be smaller than that of a hydraulic motor which is connected to all four wheels. Further, in the embodiment shown in FIG. 4 each of the electric motors can be connected to (i) only one or more low voltage batteries or to (ii) only one or more low voltage fuel cells or to (iii) both one or more batteries and one or more fuel cells. It only is required that at least one of the electric motors is connected to at least one low voltage battery and at least one of the electric motors is connected to at least one low voltage fuel cell. For example, in the embodiment with four hydraulic pumps for four wheels it is conceivable that each of the two hydraulic pumps for the front wheels or the rear wheels is connected to hydraulic pumps and electric motors which are connected to both at least one low voltage battery and at least one low voltage fuel cell, whereas the remaining two hydraulic pumps are connected to hydraulic pumps and electric motors which are connected to only one or more low voltage fuel cells or to only one or more low voltage batteries. Alternatively, the first group of hydraulic pumps may indirectly be connected to only one or more low voltage batteries, whereas the second group of hydraulic pumps may be indirectly connected to only one or more low voltage batteries.