Electrical coupling device for a machine

An electrical connecting device for a machine includes a fitting element (2) to be fitted in an aperture (1a) of a wall element (1), at least one connecting element (3) which has a first end (3a) with a first connection unit (3b) for an electric cable which is situated outside the wall element (1), a second end (3c) with a second connecting element (3d) for an electric cable which is situated within the internal space, and an intermediate portion (3e) to be fitted in an aperture (2c) which runs through the fitting element (2); a sealing (5) makes a tight connection between the connecting element (3) and the fitting element (2) in the aperture (2c). The fitting element (2) is made integrally from a first material. The connecting element (3) is made integrally from a second material. The connecting element (3) and the fitting element (2) are provided with mutually cooperating surfaces (2c1, 2c2, 3e1, 3e2) which define a predetermined fitting position for the connecting element (3) in the aperture (2c).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. §§371 national phase conversion of PCT/SE2013/051423, filed Dec. 2, 2013, which claims priority of Swedish Patent Application No. 1251397-4, filed Dec. 10, 2012, the contents of which are incorporated by reference herein. The PCT International Application was published in the English language.

BACKGROUND TO THE INVENTION AND PRIOR ART

The present invention relates to an electrical connecting device for a machine.

Electrical machines may be cooled by oil which is distributed freely within an internal space of the machine. Such an electrical machine may be situated in a hybrid vehicle in which it serves alternately as a motor and a generator. Electrical machines of this kind need a connecting device which transfers electrical energy between its stator windings situated within the oil-filled space and a source for storage of electrical energy situated outside the oil-filled space. The connecting device has an internal connection for electric cables which are connected to the electrical machine's stator windings and an external connection for electric cables which are connected to the energy storage source. The internal connection is suited to being in contact with oil, whereas the external connection needs to be kept dry and free from oil. Any oil reaching the external connection would make this part of the connecting device difficult to service. Oil also tends to creep in between the conductors and insulation of electric cables. The oil may thus reach the energy storage source and connecting electrical components via the electric cables and cause problems.

EP 1 541 831 refers to an electric motor and a pump situated in a housing which contains hydraulic oil. An electrical connecting device is situated in an aperture of the housing. The connecting device comprises a platelike element fastened in the housing.

The platelike element has three holes for respective contact pins made of electrically conductive material. Each contact pin is fitted on the platelike element by means of a screw-type portion and a nut. The threaded portion and the nut constitute a threaded connection which in a tightened state has also the function of providing a tight connection between the platelike element and the contact pin in the respective hole.

U.S. Pat. No. 7,494,362 refers to a connecting device for transfer of high voltage between an electric cable situated on the outside of a casing of an electric motor unit and an electric cable situated on the inside of the casing. The contact device comprises a connection unit situated in an aperture in the casing. The connection unit comprises a plurality of components, in particular an electrically conductive means, an internal casing and an external casing. The connection unit is provided with an O-ring which serves as a seal in the space between the hole and the connection unit. The connection unit has a threaded portion by means of which it is screwed firmly in a cuplike retainer fastened to the inside of the casing. Such a connecting device is of relatively complicated configuration.

SUMMARY OF THE INVENTION

The object of the present invention is to propose an electrical connecting device for a machine, the device being of relatively simple configuration with few components and which at the same time provides a good seal and is easy to fit.

This object is achieved with the arrangement herein.

The fitting element is thus manufactured integrally from a first material which has, with advantage, good resistance to oil and also has with advantage electrically insulating characteristics. It may be a plastic material with the characteristics indicated above.

The connecting element is manufactured integrally from a second material which has good electrical conductive characteristics. The second material is appropriately a metal material, which may with advantage be brass. The connecting element and the fitting element are configured with mutually cooperating surfaces which define a predetermined fitting position for the connecting element positioned in the hole which runs through the fitting element. Such a solution makes it possible for the connecting element and the fitting element to be fitted in an intended firm fitting position relative to one another in which they are locked together by their shapes. This obviates any need to use separate components for fixing the connecting element and the fitting element in the intended fitting position relative to one another. If the electrical machine is oil-cooled, it is also important to prevent oil from leaking out via the hole which runs through the fitting element. It is therefore appropriate to provide a sealing means between the connecting element and the fitting element in the hole. Because the connecting element is kept in a fixed fitting position in the hole, there will be no relative movements between the connecting element and the fitting element, making it easier to achieve a tight connection with a sealing means. The connecting device according to the invention comprises a small number of components which can be manufactured at low cost. Few components also make the connecting device easy to assemble.

In one embodiment of the invention the fitting element and the connecting element have mutually cooperating surfaces which define a predetermined rotational position for the connecting element within the hole. Providing the intermediate portion of the connecting element and the hole which runs through the fitting element with matching cross-sectional shapes which are not circular in at least one region gives the connecting element a firm rotational position relative to the fitting element. Such a cross-sectional shape may with advantage be semicircular. A semicircular shape results in a planar surface of the connecting element being in contact with a planar surface which defines the hole. The result is two relatively large planar surfaces which ensure that the connecting element is kept in a desired rotational position.

In another embodiment of the invention the fitting element and the connecting element have mutually cooperating surfaces which define a predetermined axial fitting position for the connecting element within the hole. The fitting element is preferably provided with a hole running through it which has a region with a reduced cross-sectional shape. When the connecting element reaches this region, it will not be possible for it to be inserted further into the hole. The mutually cooperating stop surfaces are with advantage situated in a transitional region in which the fitting element and the connecting element change from a circular cross-section to a non-circular cross-section.

In another embodiment of the invention the sealing means is configured to being fitted in a recess which extends round the connecting element. Such a sealing means is with advantage an O-ring. O-rings are annular gaskets made of elastic material. When the connecting element with the O-ring is inserted in the hole, the O-ring is compressed, causing it to exert a pressure on the connecting element and the surfaces which define the hole. A suitably compressed O-ring provides a very good seal in the radial space between the connecting element and the surfaces which define the hole. A further advantage of an O-ring is that said compressive force counteracts any outward movement of the connecting element from the hole. Such a compressive force is often sufficient to keep the connecting element in the intended fitting position in the hole.

In another embodiment of the invention the intermediate portion of the connecting element comprises a region which has a circular cross-section and a region which has a non-circular cross-section. In this case an O-ring may be placed in a recess in the region which has the circular cross-section. The region of the intermediate portion which has the non-circular cross-section will keep the connecting element in a specific rotational position relative to the fitting element when the connecting element has reached the specific fitting position. Such an intermediate portion thus provides a firm rotational position for the connecting element relative to the fitting element while at the same time making it possible to fit an O-ring and achieve good sealing of the hole.

In another embodiment of the invention the ends of the connecting element have connection units in the form of threaded holes which may have an axial extent and have in an end surface at an end of the connecting element an aperture which has a circular cross-section. Each threaded hole may be provided with a radial extent and have in a planar surface at an end of the connecting element an aperture which has a circular cross-section. This makes it easy for an electric cable provided with a suitable cable lug to be screwed firmly into such a threaded hole at the ends of the connecting element by means of a screw. It is however possible to provide the connecting element with substantially any suitable kind of connection unit for electric cables.

In another embodiment of the invention the fitting element has running through it at least two holes to accommodate respective connecting elements. The fitting element preferably has running through it three holes to accommodate respective connecting elements in order to be able to transfer electric current in three phases. It is possible to use only one fitting element which has running through it a number of holes which corresponds to the number of electric cables which are to be connected in the connecting device.

In another embodiment of the invention the connecting element has a housing which encloses the first connection unit and the first end of the connecting element. The connecting components at the first end of the connecting element are thus provided with good protection from dirt, moisture and mechanical deformation. The housing has with advantage an openable or removable cover which may be fastened by screws or the like so as to be easy to remove, e.g. for servicing of the connecting device.

In another embodiment of the invention the housing and the fitting element are manufactured in the form of a composite unit. They may be made of different materials and thereafter be fastened together in a suitable way. They may for example be adhesively bonded together. The connecting element may thereafter be inserted in the hole to the specific fitting position. The connecting device may then be fitted as a unit in the aperture in the wall element. In this case, the connecting device will be very easy to fit.

FIG. 1depicts part of a wall element1of an electrical machine. The electrical machine is oil-cooled and the wall element defines a closed internal space which contains oil.

Such an electrical machine may be situated in a hybrid vehicle in which it serves alternately as a motor and a generator. An electrical connecting device is adapted to transferring electrical energy, via an aperture1ain the wall element1, between the electrical machine's windings (not shown) which are situated within the closed space and externally situated electric cables (not shown) which are connected to a hybrid energy store (not shown). The hybrid energy store may comprise a hybrid battery with associated electronic components. The electric cables which are connected to the connecting device, the electrical machine's windings and the hybrid energy store do not appear in drawings, since they do not form part of the connecting device.

The electrical connecting device comprises a fitting element2configured to being fitted in the aperture1ain the wall element1. The shape of the fitting element2corresponds to that of the aperture1aso that it fully covers the aperture in the fitted state. The fitting element is made integrally from oil-resistant material with electrically insulating characteristics. The fitting element is with advantage made of plastic material which has these characteristics. The fitting element has a first side2asuited to being located outside the wall element1, and a second side2bsuited to being located inside the wall element1. The fitting element has running through it three holes2csuited to accommodating respective connecting elements3of the connecting device.

Each of the connecting elements3is made integrally from an electrically conductive material which may be brass. Each of them has a first end3awhich has a cylindrical shape and a circular cross-section. The first end3ais provided with a connection unit in the form of a threaded axial hole3bwhich has an aperture in an end surface of the first end3a. An undepicted externally situated electric cable provided with a suitably shaped cable lug may be fastened to the end surface by means of a screw or the like. Each of the connecting elements3has a second end3cwhich has a semicylindrical shape and a consequently semicircular cross-section. The second end3cis provided with a connection unit in the form of a threaded radial hole3dwhich has an aperture in a planar surface3e2. An undepicted internally situated electric cable provided with a suitably shaped cable lug may be fastened to the planar surface3e2by means of a screw or the like. Each of the connecting elements3has an intermediate portion3esuited to being situated within the hole2cwhich runs through the fitting element when the connecting element3is in a fitted state. The intermediate portion3ehas a region with a circular cross-section and a region with a semicircular cross-section. The intermediate portion3ehas an annular depression3fin the circular region to serve as a seat for a sealing means in the form of an O-ring5. The region with semicircular cross-section comprises part of the planar surface3e2.

The electrical connecting device also comprises a housing4which has an internal space appropriate to enclosing the first end3aand the first connection unit3bof the connecting element3and connecting electric cable ends. The housing4has three holes4afor leading in the electric cables which are to be connected to the connecting device in the housing. The holes4aare provided with screw-type cable fittings for sealing and electrical screening connections. The housing is provided with a contact surface4bappropriate to coming into contact with the wall element1in a fitted state. The housing is provided with holes4cfor screws or the like for fitting the housing to the wall element. The electrical connecting device thus comprises a fitting element2, three connecting elements3, a housing4and three O-rings5.

FIG. 2is a cross-sectional view in a vertical plane through the connecting device when the latter is in a fitted state, andFIG. 3is a section through the connecting device in a horizontal plane. It may be seen that the holes2crunning through the fitting element2have a circular cross-section at an aperture in the first side2a. The holes2chave a continuously circular cross-sectional shape up to a stop surface2c1. Thereafter they have a semicircular cross-sectional shape up to an aperture on the second side2b. Each connecting element3has a circular cross-sectional shape at the first end3aand a semicircular cross-sectional shape at the second end3c. The intermediate portion3ehas a transition between the circular cross-sectional shape and the semicircular cross-sectional shape. The transition is defined by a stop surface3e1.

The electrical connecting device may be fitted in the following way. The fitting element2is fastened in the aperture1aof the wall element1. The wall element has in this case an internal stop surface1bfor the fitting element2when the latter reaches a desired fitting position in the aperture1a. The stop surface1bmay where appropriate be provided with a sealing means to ensure a tight connection between the fitting element and the wall element. The second ends3cof the respective elements3are thereafter each inserted in a hole2cwhich runs through the fitting element, via the apertures on the first side2a. When the connecting element's second end3creaches the semicircular region of the hole2c, it has to be kept in a specific rotational position to enable it to be inserted further through the hole2c. The connecting element3has here to be kept in a rotational position such that its planar surface3e2will be parallel with a corresponding planar surface2c2which defines the hole2cwhere it has a semicircular cross-sectional shape. The connecting element's first end3cmay thereafter be inserted further through the hole2cand out on the second side2bof the fitting element. The movement will end when the connecting element's stop surface3e1reaches the hole's stop surface2c1. The connecting element3will then have reached an intended fitting position in the hole2c. In this position the connecting element's second end3cwill protrude a suitable distance into the enclosed space defined by the wall element1, while at the same time the connecting element's first end will be in a desired position outside the wall element1. The planar surface3e2of the connecting element and the planar surface2c2which defines the hole2cwill be in contact with one another. The surfaces2c2,3e2will thus prevent any turning of the connecting element3. In the fitting position the connecting element may therefore neither be turned nor be inserted further in the hole2c. The O-ring5will also exert compressive force on the connecting element3and the surrounding surfaces of the fitting element2. The O-ring5will thus provide a good seal so that oil cannot leak out through the hole2c. The compressive force of the O-ring5means that a certain amount of force would be required to draw the connecting element3back from the specific fitting position. The O-ring5thus also helps to keep the connecting element3in the specific fitting position.

Finally, the housing4is fastened to the wall element1by means of screws6placed in the holes4c. The housing has an openable cover4dwhich is with advantage fastened to the housing by means of undepicted screws or a suitable snap device. When the cover is in place, the housing4serves as a tight enclosure for the connecting element's first end3aand connecting cable ends. The connections of the connecting device to the external electric cables may thus be protected from dirt, moisture and mechanical action.

FIG. 4depicts an alternative embodiment of the connecting device. In this case the fitting element2and the housing4constitute a preassembled unit. The housing has in this case an internal wall4e. The connecting element3is thereafter fitted in the fitting element2. In this case the connecting device may be fitted as a composite unit in an aperture1ain a wall element1of an electrical machine and be fastened by means of screws placed in the holes4c.

The invention is in no way limited to the embodiments to which the drawings refer, but may be varied freely with the scopes of the claims.