Device for supplying electric current to the wound rotor of an electric machine.

Abstract

Device 1 for supplying current to the wound rotor of an electrical machine, characterized in that it has a first support element 30, carried by the rotor shaft 10, driven in rotation by the latter, a second complementary element 40 carried and driven in rotation by the first support element 30, these two support and complementary elements framing a fixed rotating element 60. The support elements 30, complementary 40 and fixed 60, made of insulating material, carry crown-shaped plates made of conductive material, preferably copper or copper alloy, respectively 31, 41 rotating and 61, 62 non-rotating.Between the crown-shaped plates 31, 61 on the one hand and 41, 62 on the other hand are interposed identical transmitter discs 50a, 50b, composed of an annular disc 51 made of insulating material, in which are inserted rollers 52, 53 transmitting current between the rotating crown-shaped plates 31, 41 and the non-rotating crown-shaped plates 61, 62. The rotating crown-shaped plates 31 and 41 have electrical connection tabs 31b and 41b and are connected to the rotor coils of the electric machine and the rotating crown-shaped plates 61, 62, fixed in rotation, have electrical connection tabs 61b, 62b and are connected to the external direct current supply device. Figure for the abstract: Fig.1.

Description

Title of the invention: Device for supplying electric current to the wound rotor of an electric machine. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an electric current supply device comprising a non-rotating central element, connected to an electrical energy source, framed by two rotating elements connected to the terminals of the coils of a rotor of an electric machine, and separated from the non-rotating central element by electrically conductive rolling bodies. STATE OF THE ART

[0002] the power supply of the rotor coils of an electrical machine uses a device comprising two friction contacts between rotating elements, rings generally made of copper also called collectors, carried by an insulating ring arranged on the rotor shaft, connected to the rotor coils and fixed elements, the brushes, also called "carbons" because of the high proportion of carbon, carried by an insulating structure fixed to the casing of the electrical machine.

[0003] Wound rotor electric machines have been adopted by very few electric car manufacturers.

[0004] However, this type of machine has the advantage of not requiring permanent magnets and therefore rare earths and the magnetic field generated by the rotor coils is adjustable.

[0005] On the other hand, the current supply of the coils has disadvantages: - an increase in the length of the machine; - the need to create a sealed chamber because the wear of the brushes releases dust; - wear of the brushes which may require maintenance; - small diameter collector rings to limit the tan- gentle contact with the brushes.

[0006] This last drawback obliges us to associate with the motor a conventional reducer with a remote differential. The small diameter rings do not, in fact, allow the association of the electric machine with a coaxial reducer, advantageous in packaging, because one of the transmission shafts, whose diameter is of the order of 25 to 30 mm, passes through the hollow shaft of the rotor. However, the external diameter of the collector rings is of the same order of magnitude as that of the transmission shaft.

[0007] A means of transmitting current other than the friction of a brush is known. This is conduction by the contact of a rolling body on a fixed body.

[0008] This is the method used for electric traction on rails. The motor of an electric train is supplied with energy by the single conductor cable of a catenary. The machine is subject to the potential difference between the catenary and the ground. The connection between the electric traction machine and the ground is made via the chassis, the bogie axle, the wheels and the rails. A brush device provides the electrical connection between the axle and the wheels in order to protect the wheel bearings. Such a device is described in publication EP 2 724 913.

[0009] A device for transmitting current by a rotating contact is described in publication FR 2 124 728 (utility certificate of 1972) entitled “rotating electrical contact”. The device is similar to an angular contact ball bearing whose inner and outer sheet metal rings each have a terminal and are insulated from the shaft and the housing. PRESENTATION OF THE INVENTION

[0010] The present invention relates to the supply of current to the coils of an electric machine rotor by two contacts, supply and return of the electric current, comprising the rolling bodies.

[0011] The rolling bodies are positioned on one or more diameters large enough to allow the production of a hollow rotor shaft and the passage of the transmission shaft of a coaxial type reducer.

[0012] The rolling bodies do not wear out and do not produce dust; there is no need to confine them in a sealed space.

[0013] Nevertheless, the current transmitted by a rolling body must remain of low intensity so as not to cause an electric arc to appear which could damage the rolling body itself and its raceways. The solution is the large multiplication of rolling bodies each transmitting, in parallel, a small fraction of the current.

[0014] According to a first characteristic, the device comprises an element made of insulating material mounted on the rotor shaft, driven in rotation by grooves, serving as a support for the entire device, carrying a crown-shaped track made of conductive material, copper or copper alloy, the latter having a terminal for first connection with the rotor coils.

[0015] According to a second characteristic, the device comprises a complementary element made of insulating material similar to the first on which it is mounted and driven in rotation by grooves, and also carrying a crown-shaped track made of conductive material, copper or copper alloy, the latter having a terminal for a second connection with the rotor coils.

[0016] According to a third characteristic, the device comprises a central element made of insulating material arranged between the first two, centered on the carrier element, im moved in rotation by a pin carried by the motor casing, and carrying on either side a crown-shaped track made of conductive material, copper or copper alloy, each having a connection terminal with an external direct current power supply device.

[0017] According to a fourth characteristic, between the track of the rotating carrier element and a first track of the central fixed element is interposed an annular disc made of insulating material supporting rolling bodies made of conductive material, copper or copper alloy, responsible for making a first electrical connection, and between the track of the rotating complementary element and the second track of the central fixed element is interposed a second annular disc made of insulating material, identical to the first, supporting rolling bodies made of conductive material, copper or copper alloy, responsible for making a second electrical connection.

[0018] According to another characteristic, the rotary complementary element carries in a circular groove a spring of the corrugated washer type, put under tension by a washer stopped by a ring housed in a groove of the carrier element, which allows axial tensioning of all the elements and guarantees the contacts of the rolling bodies with their two tracks. DETAILED DESCRIPTION OF THE INVENTION

[0019] These characteristics, aims and advantages of the present invention will appear on reading the detailed description which follows and with regard to the appended drawings given as non-limiting examples and in which:

[0020] [Fig-1] is a left view of the entire device mounted on the rotor shaft and a section along AA;

[0021] [Fig.2] is a front view of the annular disc supporting rolling bodies and a section along BB;

[0022] [Fig.3] is a left view of the rotating carrier element and a section along CC;

[0023] [Fig.4] is a front view of the fixed element in rotation and three sections along DD, E- E and FF;

[0024] [Fig.5] is a left view of the rotating complementary element, without the spring and the elements holding it and a section along GG.

[0025] Section AA of [Fig. 1] shows a part of the transmission shaft 20, passing through the hollow rotor shaft 10 carrying the electric current supply device 1.

[0026] The power supply device 1 is composed of a first support element 30, made of insulating material, for the other elements of the power supply device 1.

[0027] This support element 30, carried by the rotor shaft 10, is axially supported on the shoulder 10a, is driven in rotation by the grooves 10b and is held axially by the stop ring 11.

[0028] On this support element 30 is fixed, for example by gluing, a plate 31 in the form of a crown made of conductive material, preferably copper or copper alloy.

[0029] On the support element 30 is mounted a complementary element 40, having the same function, also made of insulating material and driven in rotation by the grooves 30a.

[0030] The support element 30 and the complementary element 40, integral in rotation, frame a fixed element in rotation 60, made of insulating material.

[0031] The fixed element 60 in the form of a crown, is centered on the support element 30, has a protrusion 60a which cooperates with a pin 70, for locking in rotation, planted in the casing 71 of the electric machine.

[0032] On the complementary element 40 is attached a crown-shaped plate 41 made of conductive material, preferably copper or copper alloy.

[0033] The fixed element 60, made of insulating material, carries on either side the crown-shaped plates 61 and 62 made of conductive material.

[0034] Between the crown-shaped plates 31, 61 on the one hand and 41, 62 on the other hand are interposed identical transmitting discs 50a and 50b, made of insulating material, the first 50a centered by its external diameter in the support element 30, the second 50b centered by its external diameter in the complementary element 40, free to rotate and carrying cylindrical current-transmitting rollers.

[0035] The support element 30 and the complementary element 40 carry on their crown-shaped plate 31, 41 tabs 31b and 41b for connection to the rotor coils.

[0036] The crown-shaped plates 61, 62 carried by the fixed element 60 each have a tab 61b, 62b for connection to the external current supply device.

[0037] The complementary element 40, the fixed element 60, as well as the transmitting discs 50a, 50b are pressed against each other and against the support element 30 by a spring of the corrugated washer type 42, mounted in a circular groove 40b of the complementary element 40, put under tension by the washer 43 held by the stop ring 44 engaged in a groove of the support element 30.

[0038] [Fig.2] is a front view of the transmitter discs 50a or 50b. They are similar to those of the needle thrust bearings, but play a very different role. They are composed of an annular disc 51 made of insulating material which has, on two concentric circles, a large number of rectangular openings in which are inserted rollers 52, 53, all identical cylindrical, made of conductive material, copper or copper alloy, with a diameter greater than the thickness of the annular disc 51.

[0039] These rollers are subjected to a very low axial load which ensures the contact of the largest possible proportion of rollers 52,53 with on the one hand the shaped plates crown 31,61 (transmitter disc 50a) and on the other hand the crown-shaped plates 41,62 (transmitter disc 50b) in order to transmit the current from the fixed element 60, connected to an external power supply, to the support element 30 and the complementary element 40 in rotation, connected to the rotor coils.

[0040] The choice of a very large number of rollers 52,53 is the way of sharing the electric current and limiting it, for each contact, to a low intensity electric level reducing the risks of electric arcing and damage.

[0041] The choice of short cylindrical rollers is the way to limit sliding friction because the ends of the rollers, being on different radii, have theoretically different rotation speeds. This not being possible, compensation is made by sliding which can cause slight wear during use.

[0042] The level of slippage, and the damage that it can cause, will be reduced by installing this device 1 in the rotor and stator compartment of an electrical machine whose windings are cooled by oil spray. Thus, the device 1 will be in an oil mist that is not detrimental to the transmission of current by the rollers.

[0043] the rollers can be replaced by balls. This has an impact on the contacts which become point contacts instead of linear contacts. It is possible to arrange tracks on the crown-shaped plates 31, 61, 41, 62 to improve the contact with the rolling bodies, by adding circular grooves. This makes it possible to move to two point contacts per ball. The tracks are obviously more delicate and expensive to produce. Finally, the diameter of the balls must be greater than that of the rollers and increases the axial size of the device.

[0044] [Fig.3]is a left-hand view of the support element 30 and a section along CC. This view shows that the crown-shaped plate 31 has on its periphery four rotational drive notches 31a and a folded tab 31b, visible on the CC section, for transmitting current (forward or return) to the rotor coils of the electrical machine. The left-hand view also shows an opening 30b allowing the passage of the tab 41b, visible in [Fig.l], linked to the track 41 carried by the complementary element 40.

[0045] [Fig.4]is a front view of the fixed element 60 and three sections along DD, EE and FF. This front view shows that the crown-shaped plate 61 has four anti-rotation notches 61a relative to its supporting fixed element 60 and a tab 61b for electrical connection with the external power supply. It also shows the electrical connection tab 62b linked to the crown-shaped plate 62 and the angular orientations of these two tabs.

[0046] Section DD shows that the crown-shaped plates 61 and 62 have identical anti-rotation notches 61a and 62a.

[0047] Section EE shows the curved shape of the tongue 61b of the crown-shaped plate 61.

[0048] Section FF shows the curved shape of the tab 62b as the crown-shaped plate 62.

[0049] [Fig.5] is a front view of the complementary element 40 made of insulating material and a section along GG.

[0050] This complementary element 40 carries the crown-shaped plate 41 provided with four rotational drive notches 41a and a tongue 41b for connection to the rotor coils which passes under the fixed element 60 and passes through the support element 30 at the opening 30b, as shown in the left-hand view of [Fig.3].

[0051] This complementary element 40, mounted on the support element 30, is driven in rotation by the grooves 40a which cooperate with the grooves 30a.

[0052] This complementary element 40 has a circular groove 40b for receiving the spring for lightly pressing all the elements of this current transmission device.

Claims

Claims

1. Device (1) for supplying current to the wound rotor of an electrical machine comprising a first support element (30), carried by the rotor shaft (10), driven in rotation by the latter, a second complementary element (40) carried and driven in rotation by the first support element (30), these two support and complementary elements framing a fixed rotating element (60) characterized in that the support elements (30), complementary (40) and fixed (60), made of insulating material, carry crown-shaped plates made of conductive material, preferably copper or copper alloy, respectively (31), (41) rotating and (61), (62) non-rotating and that between the crown-shaped plates (31), (61) on the one hand and (41), (62) on the other hand are interposed identical transmitter discs (50a), (50b), composed of an annular disc (51) made of insulating material, in which rollers are inserted (52),(53) cylindrical in conductive material,which allows the electric current to be transmitted from the fixed rotating crown-shaped plates (61), (62) to the rotating crown-shaped plates (31), (41).

2. Power supply device (1) according to claim 1, characterized in that the crown-shaped plates (31), (41) each have four notches (31a), (41a) for driving rotationally respectively to the rotating support element (30), to the rotating complementary element (40) and that the crown-shaped plates (61), (62) each have four notches (61a), (62a) for driving by the fixed element (60), thus also making them fixed.

3. Power supply device (1) according to claim 1, characterized in that the crown-shaped plates (31), (41), (61), (62) conducting electrical current, each have a respective electrical connection tab (31b), (41b), (61b), (62b).

4. Current supply device (1) according to the preceding claim characterized in that the tabs (31b) and (41b) are connected to the rotor coils of the electric machine and that the tabs (61b) and (62b) are connected to the external direct current supply device.

5. Power supply device (1) according to claim 1, characterized in that the fixed element (60) has a U-shaped protrusion (60a).

6. Current supply device according to the preceding claim, characterized in that the protrusion (60a) of the fixed element (60) cooperates with a pin (70) planted in the casing (71) of the electrical machine, providing rotational locking.

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