Field of the invention

The invention relates to a capacitor module suitable for being a basic construction unit of a capacitive energy-storage. Furthermore, the invention relates to a mobile working machine comprising an electromechanical power transmission chain.

Background

An electromechanical power transmission chain comprises typically one or more electrical machines and an electronic power converter. The electromechanical power transmission chain can be a series transmission chain where one of the electrical machines operates as generator and the electronic power converter is arranged to convert the electrical voltages produced by the generator into electrical voltages having amplitudes and frequencies suitable for the one or more other electrical machines. The generator can be driven with a combustion engine that can be e.g. a diesel engine, an Otto-cycle engine, or a turbine engine. The other electrical machines can be, for example, electrical motors in wheels of a mobile working machine. The electronic power converter comprises typically an intermediate circuit, a converter stage between the generator and the intermediate circuit and one or more other converter stages between the intermediate circuit and the other electrical machines. It is also possible that the electromechanical power transmission chain is a parallel transmission chain where the generator is occasionally used as a motor that assists the combustion engine, especially when high output power is needed. In this case, the electronic power converter comprises typically an intermediate circuit, a converter stage between the generator and the intermediate circuit, and one or more converter stages between the intermediate circuit and one or more energy-storages.

The above-mentioned intermediate circuit is typically a capacitive energy-storage that comprises one or more capacitor modules and one or more heat-sink elements for cooling the one or more capacitor modules. A heat-sink element typically comprises cooling fins on its outer surface and/or cooling channels for conducting cooling fluid, e.g. water. Each capacitor module comprises an electrode structure for storing electrical energy in the form of electric charge polarization between the electrodes of the electrode structure. The electrode structure is inside a casing which can be made of for example aluminum. In many cases, the casing is fitted to an aperture of a heat-sink element.

A cooling arrangement of the kind described above is, however, not free from challenges. One of the challenges is related to a need to arrange a sufficiently good thermal contact between the casing and the heat-sink element.

Publication DE102005038409 describes a capacitor module that comprises an aluminum casing having a profiled form shaped by an extruder. The profiled form includes means of fastening such as grooves, holes, channels, ribs, and/or hooks. The profiled form may further comprise cooling channels for conducting cooling fluid.

Publication US201 1090614 describes a capacitor module that comprises a hous- ing element for receiving one or more capacitor units. One of the challenges is related to the need for sufficiently good thermal contacts between the housing element and the one or more capacitor units.

Publication EP2682963 describes a capacitor module for a mobile working machine. The capacitive module is encapsulated and comprises cooling ducts and wiring and piping lead-throughs. Thus, modular capacitive energy-storages of different sizes can be built by interconnecting capacitor modules described in EP2682963, and there is no need to build separately an encapsulation provided with cooling ducts.

Summary The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

In accordance with the invention, there is provided a new capacitor module that is suitable for being a basic construction unit of a capacitive energy-storage. A ca- pacitor module according to the invention comprises:

- an electrode structure for storing electrical energy in the form of electric charge polarization between electrodes of the electrode structure, and

- a casing made of electrically conductive material and containing the electrode structure. The casing is a heat-sink element that comprises cooling structures and a cavity containing the electrode structure. The capacitor module further comprises an electrically conductive lid closing the cavity. The cooling structures may comprise e.g. cooling fins and/or cooling channels for conducting liquid or gaseous cooling fluid. Thus, there is no need for a separate heat-sink element because the casing is not only a casing but also a heat-sink element. Furthermore, the casing is a single piece of the electrically conductive material. Therefore, there are no mutually interfacing material surfaces in the thermally conductive path from the walls of the cavity, i.e. from the inner surfaces of the casing, to the cooling structures. One of the electrodes of the electrode structure is electrically connected to the casing, and the electrically conductive lid is electrically insulated from the casing and electrically connected to another of the electrodes of the electrode structure.

In accordance with the invention, there is provided also a new mobile working machine. A mobile working machine according to the invention comprises: a combustion engine, and an electromechanical power transmission chain between the combustion engine and one or more wheels, chain tracks, and/or other actuators of the mobile working machine. The electromechanical transmission chain comprises a capacitive energy-storage comprising one or more capacitor modules according to the invention.

The mobile working machine comprises preferably, but not necessarily, a liquid cooling system configured to cool both a hydraulic system of the mobile working machine and the electromechanical power transmission chain. The mobile working machine can be, for example, a tractor, a bucket charger, a road drag, a bulldozer, or any other working machine having wheels and/or chain tracks or any other means for moving.

A number of exemplifying and non-limiting embodiments of the invention are de- scribed in accompanied dependent claims.

Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in connection with the accompanying drawings.

The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.

Brief description of the figures

Exemplifying and non-limiting embodiments of the invention and their advantages are explained in greater detail below in the sense of examples and with reference to the accompanying drawings, in which: figures 1 a and 1 b illustrate a capacitor module according to an exemplifying and non-limiting embodiment of the invention, figures 2a and 2b illustrate a capacitor module according to an exemplifying and non-limiting embodiment of the invention, and figure 3 shows a schematic illustration of a mobile working machine according to an exemplifying and non-limiting embodiment of the invention.

Description of the exemplifying embodiments

Figure 1 a shows a capacitor module according to an exemplifying and non-limiting embodiment of the invention. Figure 1 b shows a view of a section taken along a line A-A shown in figure 1 a. The section plane is parallel with the xz-plane of a coordinate system 190. The capacitor module comprises an electrode structure 101 for storing electrical energy in the form of electric charge polarization between electrodes of the electrode structure. The electrode structure 101 may comprise e.g. a first foil, a second foil, and dry dielectric material between the first and second foils. It is also possible that the electrode structure 101 comprises an anode foil, a cathode foil, and porous filler material between the anode and cathode foils so that the filler material is impregnated with liquid electrolyte. In this case, the capacitor module is an electrolytic capacitor. Furthermore, it is also possible that the electrode structure 101 constitutes an electric double-layer capacitor "EDLC" which is often called a "super capacitor". The capacitor module comprises a casing 102 made of electrically conductive material, e.g. aluminum. The casing 102 is a heat-sink element comprising cooling structures and a cavity that contains the electrode structure 101 as illustrated in figure 1 b. Therefore, the casing 102 acts not only as a casing but also as a heat-sink element for cooling the electrode structure 101 . Furthermore, the casing 102 is a single piece of the electrically conductive material. Thus, the thermally conductive path from the walls of the cavity to the cooling structures is free from mutually interfacing material surfaces. The heat transfer is effective because there are no mutually interfacing material surfaces on the above-mentioned thermally conductive path. The cooling structures of the casing 102 may comprise for example cooling fins on an outer surface of the casing and/or cooling channels for conducting liquid or gaseous cooling fluid. Liquid cooling fluid can be e.g. water, and gaseous cooling fluid can be e.g. air. In figures 1 a and 1 b, one of the cooling fins is denoted with a reference number 104. In figure 1 b, one of the cooling channels is denoted with a reference number 105. Connection tubes 108 of the cooling channels are schematically depicted in figure 1 a. In the exemplifying capacitor module illustrated in figures 1 a and 1 b, one of the electrodes of the electrode structure 101 is electrically connected to the casing 102 and the other of the electrodes is electrically connected to a terminal element 107 which is electrically insulated from the casing 102. Therefore, in this case, the casing 102 acts also as an electrical pole of the capacitor module. It is, however, also possible that each of the electrodes of the electrode structure 101 is electrically connected to a respective one of terminal elements which are electrically insulated from each other and from the casing.

Figure 2a shows a capacitor module according to an exemplifying and non-limiting embodiment of the invention. Figure 2b shows a view of a section taken along a line A-A shown in figure 2a. The section plane is parallel with the xz-plane of a coordinate system 290. The capacitor module comprises electrode structures 201 a, 201 b, and 201 c for storing electrical energy. Each of the electrode structures 201 a, 201 b, and 201 c may comprise e.g. a first foil, a second foil, and dry dielec- trie material between the first and second foils. It is also possible that each of the electrode structures 201 a, 201 b, and 201 c comprises an anode foil, a cathode foil, and porous filler material between the anode and cathode foils so that the filler material is impregnated with liquid electrolyte. In this case, the capacitor module is an electrolytic capacitor. Furthermore, it is also possible that each of the electrode structures constitutes an electric double-layer capacitor "EDLC". The capacitor module comprises a casing 202 that is a single piece of electrically conductive material, e.g. aluminum. The 202 casing is a heat-sink element that comprises cooling structures and cavities that contain the electrode structures 201 a, 201 b, and 201 c as illustrated in figure 2b. The cooling structures of the casing 202 may com- prise for example cooling fins on an outer surface of the casing and/or cooling channels for conducting liquid or gaseous cooling fluid. In figures 2a and 2b, one of the cooling fins is denoted with a reference number 204. In figure 2b, one of the cooling channels is denoted with a reference number 205. Connection tubes 208 of the cooling channels are schematically depicted in figure 2a. Therefore, the cas- ing 202 acts not only as a casing but also as a heat-sink element for cooling the electrode structures 201 a, 201 b, and 201 c. In the exemplifying capacitor module illustrated in figures 2a and 2b, a first one of the electrodes of each of the electrode structures 201 a, 201 b, and 201 c is electrically connected to the casing 202. The capacitor module further comprises an electrically conductive lid 206 arranged to close the cavities as illustrated in figure 2b. The lid 206 is electrically insulated from the casing 202 with the aid of a layer of electrically insulating material 209. A second one of the electrodes of each of the electrode structures 201 a, 201 b, and 201 c is electrically connected to the electrically conductive lid 206. Therefore, the casing 202 constitutes one electrical pole of the capacitor module and the lid 206 constitutes the other electrical pole of the capacitor module.

The casing 202 can be manufactured as a single piece of electrically conductive material e.g. by casting or extrusion and/or machining. It is, however, also possible that a casing for two or more electrode structures can be constructed by welding together casings each being designed for a single electrode structure. Figure 3 shows a schematic illustration of a mobile working machine 320 according to an exemplifying and non-limiting embodiment of the invention. In this exemplifying case, the mobile working machine is a bucket charger but the mobile working machine could as well be a tractor, a road drag, a bulldozer, or any other working machine having wheels and/or chain tracks or any other means for moving. The mobile working machine comprises a combustion engine 321 that can be e.g. a diesel engine, an Otto-cycle engine, or a turbine engine. The mobile working machine comprises an electromechanical power transmission chain 322 between the combustion engine 321 and wheels of the mobile working machine. In figure 3, two of the wheels are denoted with reference numbers 328 and 329. The electro- mechanical transmission chain comprises a generator 321 the rotor of which is mechanically connected to the shaft of the combustion engine. The electromechanical transmission chain comprises an electronic power converter 327 and electrical motors at the hubs of the wheels of the mobile working machine. In figure 3, two of the electrical motors are denoted with reference numbers 330 and 331 . The electronic power converter 327 is arranged to convert the electrical voltage produced by the generator 326 into electrical voltages having amplitudes and frequencies suitable for the electrical motors. The electromechanical transmission chain further comprises a capacitive energy-storage 323 comprising one or more capacitor modules. Each of the capacitor modules comprises one or more electrode structures for storing electrical energy and a casing that is a single piece of electrically conductive material and contains the one or more electrode structures. The casing is a heat-sink element that comprises cooling structures, e.g. cooling fins and/or cooling ducts, and one or more cavities containing the one or more electrode structures.

A mobile working machine according to an exemplifying and non-limiting embodiment of the invention comprises a liquid cooling system 324, and the casing of at least one capacitor module comprises cooling ducts connected to the liquid cooling system 324. The liquid cooling system 324 can be arranged to cool also the other parts of the electromechanical power transmission chain 322, and/or a hydraulic system 325 of the mobile working machine, and/or the combustion engine 321 . A mobile working machine according to an exemplifying embodiment of the invention comprises a battery element 332 which, together with the capacitive energy- storage 323, can be used for responding to peak power needs exceeding the maximum power of the combustion engine 321 .

The specific examples provided in the description given above should not be con- strued as limiting the applicability and/or interpretation of the appended claims.