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

Abstract

Current supply device 10 of the rotor of an electric machine consisting of: a first fixed element 200, made of insulating material, composed of a radial face 202, a tubular part 201 carrying lugs 203 for fixing to a housing 40 by means of screws 45 and centered on a shoulder 41 of the housing 40 by an internal diameter 201a; a second fixed element 300, made of insulating material, centered in the first fixed element 200; a rotating element 100, made of insulating material, carried by a rotor shaft 20; two current transmitting discs 400 interposed between the fixed elements and the rotating element; characterized in that the rotating element 100 is arranged in the tubular portion 201 of the fixed element 200 between the radial face 202 and the second fixed element 300, and the entire assembly of components is brought into contact and under pressure by a corrugated washer 320 pushing on the second fixed element 300, bearing against the first fixed element 200. Figure for the abbreviation: Fig. 1

Description

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

[0001] The present invention relates to an electric power supply device comprising a rotating central element, connected to the terminals of the rotor coils of an electric machine, framed and enclosed by two fixed elements connected to an external direct or alternating current power supply to the electric machine. STATE OF THE ART

[0002] The supply of the rotor coils of an electric machine uses a device comprising two friction contacts between rotating elements, generally copper rings 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 on the casing of the electric 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 to the coils presents some 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 and tear on the brushes which may require maintenance; - small diameter collector rings to limit the speed tangential contact with the brushes.

[0006] This last drawback forces us to pair the motor with a conventional gearbox with a remote differential. The small diameter slip rings do not allow the electric machine to be paired with a coaxial gearbox, which would be advantageous in terms of packaging, because one of the drive shafts, with a diameter of approximately 25 to 30 mm, passes through the hollow rotor shaft. However, the outer diameter of the slip rings is of the same order of magnitude as that of the drive shaft.

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

[0008] This is the method used for electric rail traction. The locomotive of an electric train is powered by the single conductor cable of an overhead contact line. The locomotive is subjected to the potential difference between the overhead contact line and ground. The connection between the electric traction locomotive and 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 to protect the wheel bearings. Such a device is described in publication EP 2 724 913.

[0009] A current transmission device using 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 lug 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 electric current, comprising the rolling bodies.

[0011] The rolling bodies are positioned on a diameter large enough to allow the creation of a hollow rotor shaft and the passage of the transmission shaft of a coaxial type reducer.

[0012] However, the current transmitted by a rolling body must remain of low intensity to avoid the appearance of an electric arc that could damage the rolling body itself and its running tracks. The solution is to multiply the rolling bodies, each transmitting, in parallel, a small fraction of the current.

[0013] The device, the object of the invention, comprises a central element made of insulating material mounted on the rotor shaft, driven in rotation by grooves, serving as a support for two ring-shaped plates made of conductive material, copper or copper alloy, and each of these plates has on its inner periphery, a tab for driving rotation by the central element and on which is soldered an electrically conductive wire for connection with the rotor coils.

[0014] The device includes a first fixed element, made of insulating material, of tubular shape surrounding the central rotating element, which has at one end a radial face which carries a ring-shaped plate made of conductive material, which has, on its outer periphery, a tab making it fixed like its supporting element and on which is soldered an electrically conductive wire for connection to the external electrical supply.

[0015] The device comprises a second fixed element made of insulating material closing the first hollow fixed element and thus forming a chamber containing the rotating element. This second The fixed element also carries a ring-shaped plate made of conductive material. This plate has, on its outer periphery, a tab that makes it fixed like its supporting element, and to which an electrically conductive wire is soldered for connection to the external power supply.

[0016] Between the conductive ring-shaped plate of the first fixed element and one of the ring-shaped plates of the rotating element is interposed an annular disc made of insulating or non-insulating material, carrying rolling bodies made of conductive material, copper or copper alloy, responsible for making a first electrical connection between the two ring-shaped plates.

[0017] Between the ring-shaped conductive plate of the second fixed element and the other ring-shaped plate of the rotating element, there is also an annular disc, identical to the previous one, made of insulating material or not, carrying rolling bodies made of conductive material, copper or copper alloy, responsible for making a second electrical connection between the two ring-shaped plates.

[0018] The second fixed element has a peripheral overthickness whose inner diameter accommodates a wave washer type spring, put under tension by a flat washer stopped by a ring housed in a groove of the first fixed element, which allows axial pressure to be applied to all the elements and ensures permanent contact of the rolling bodies with the two tracks. DETAILED DESCRIPTION OF THE INVENTION

[0019] These features, objectives and advantages of the present invention will become apparent from the detailed description that follows and from the accompanying drawings given by way of non-limiting examples and on which:

[0020] [Fig. 1] is a cross-sectional view of the entire device mounted on the rotor shaft;

[0021] [Fig.2] is a front view of the annular transmitting disk supporting bodies rolling and a cut according to AA;

[0022] [Fig.3] is a cross-sectional view of the entire device passing through the first fixed connection and BB cut in the plane of the conductive crown-shaped plate;

[0023] [Fig.4] is a cross-sectional view of the entire device passing through the second fixed connection and the CC section in the plane of the conductive ring-shaped plate;

[0024] [Fig.5] is a front view of the device on the side of the fixing on the housing showing the exit of the two fixed conductors;

[0025] [Fig.6] is a cross-sectional view of the entire device passing through the first rotating connection and the DD section in the plane of the conducting ring-shaped plate;

[0026] [Fig.7] is a cross-sectional view of the entire device passing through the second rotating connection and the EE section in the plane of the conductive ring-shaped plate;

[0027] [Fig.8] is a front view of the device on the side opposite the mounting face and showing the output of two rotating conductors.

[0028] Fig. 1 shows in cross-section the entire device 10 carried by the hollow rotor shaft 20. It is composed of a first fixed element 200, made of insulating material, containing, in its tubular part 201, the other components of the device 10.

[0029] This fixed element 200 has around its tubular part 201 lugs 203 for fixing to the casing 40 of the electric machine by means of screws 45. It is centered by its inner diameter 201a on the shoulder 41 of the casing.

[0030] Opposite the fixing face, the first fixed element 200 is partially closed by a radial face 202 open in its center.

[0031] On the inner side of the radial face 202 is fixed, for example by gluing, a ring-shaped plate 210 made of conductive material, preferably copper or copper alloy.

[0032] Inside this first fixed element 200 is arranged a rotating element 100 having a cylindrical part 101 and a discoid part 102.

[0033] The rotating element 100, carried by the rotor shaft 20, has drive splines 101a, cooperating with the splines 21 of the rotor shaft. This rotor shaft 20 is guided by the ball bearing 30, held on the shaft by the retaining ring 32 and placed under slight preload by the spring washer 31 arranged between its outer ring and the housing 40.

[0034] The rotating element 100 carries on either side of its discoidal part 102 two ring-shaped plates 110 and 120, made of conductive material, preferably copper or copper alloy.

[0035] A second fixed element 300 encloses the rotating element 100 in the first fixed element 200. This second fixed element 300 is mainly in the shape of a disc with a cylindrical part 302 centered by its outer diameter 302a in the first fixed element 200.

[0036] Internally the fixed element 300 has an overthickness 301. This overthickness, open in its center, allows the rotor shaft 20 to pass freely and its outer diameter centers the ring-shaped plate 310, made of conductive material, preferably copper or copper alloy.

[0037] Between the rotating and fixed crown-shaped plates 110 on the one hand, and the rotating and fixed plates 120 on the other, are interposed free-rotating and centered transmission discs 400 by their outer diameter with a substantial clearance in the part tubular 201 of the first fixed element 200 and by the internal diameter with a substantial clearance in the cylindrical part 101 of the rotating element 100.

[0038] The cylindrical part 302 accommodates an elastic wave washer 320 centered in the inner diameter 302b. This wave washer 320 is put under tension by the washer 321 stopped by the stop ring 322, implanted in a groove cut in the diameter 201a of the first fixed element 200.

[0039] This corrugated washer 320, resting on the first fixed element 200, presses the second fixed element 300 on the transmitting disc 400, itself under pressure on the rotating element 100, itself under pressure on the second transmitting disc 400, pressed on the ring-shaped plate 210. This ensures the best possible transmission of the electric current between the opposite ring-shaped plates 110,210 and 120,310.

[0040] [Fig.2] is a front view of the transmitting disc 400. It is similar to a needle bearing, but plays a very different role. It consists of an annular disc 401 made of insulating or metallic material (preferable for mechanical strength) which has, on a circle, a large number of rectangular openings in which are inserted identical cylindrical rollers 402 made of conductive material, copper or copper alloy, with a diameter greater than the thickness of the annular disc 401.

[0041] The choice of a very large number of rollers 402 is the way to share the electric current and to limit it, for each contact, to a low intensity level reducing the risks of electric arc and damage.

[0042] The choice of short cylindrical rollers is a way to limit friction due to sliding, since the ends of the rollers, being on different radii, theoretically have different rotational speeds. As this is not possible, compensation is achieved through sliding, which can cause slight wear over time. To limit this effect, the transmission discs are lubricated during assembly (conductive grease). Since the discs are enclosed by the fixed elements 200,300, the grease will remain confined.

[0043] The rollers could be replaced by balls. This has a negative impact on the contacts, which become point contacts instead of linear contacts. Modifying the tracks to accommodate two point contacts would impose a constraint on the positioning of the opposing ring-shaped plates, one fixed and the other rotating, located on either side of the transmitting disk. However, by design, the fixed ring-shaped plates 210, 310 are centered on the fixed elements 200, 300 supported by the housing 40, and the rotating ring-shaped plates 110, 120 are centered on the rotating element 100 supported by the rotor shaft 20. Installing an adjustment device does not seem realistic. The rollers provide the fixed ring-shaped plates with a degree of eccentricity relative to the rotating ring-shaped plates.

[0044] [Fig.3] is a cross-sectional view of the entire device 10 passing through the first fixed connection and the BB section in the plane of the crown-shaped conducting plate 310.

[0045] The crown-shaped plate 310, supported by the second fixed element 300, has a tab 311 on its outer periphery. This tab occupies a suitably shaped area 204 around the tubular portion 201 of the first fixed element. This tab 311 also prevents the crown-shaped plate 310 from rotating.

[0046] On this tab 311 is attached, for example by welding, a conductor 312 passing through a first guide 205 carried by the fixed element 200, then a second guide 42 carried by the housing 40 and held by a plate 43 and a screw 44.

[0047] [Fig-4] is a cross-sectional view of the entire device 10 passing through the second fixed connection and the CC cut in the plane of the crown-shaped conductive plate 210.

[0048] The crown-shaped plate 210, carried by the first fixed element 200, has on its outer periphery a tab 211. This tab 211 occupies a suitably shaped area 206 in the periphery of the tubular part 201, and also ensures that the crown-shaped plate 210 does not rotate.

[0049] On this tab 211 is attached, for example by welding, a conductor 212 passing through a first guide 207 carried by the fixed element 200 and then a second guide 42 carried by the housing 40 and held by the plate 43 and the screw 44.

[0050] [Fig.5] is a front view of the device 10 on the fixing side on the housing showing the relative positions of the conductors 212,312 in the guides 205,207 housed in the adapted forms 204,206 in the tubular part 201 of the first fixed element.

[0051] [Fig.6] is a cross-sectional view of the entire device 10 passing through the first rotating connection and the section DD in the plane of the crown-shaped conducting plate 120.

[0052] The ring-shaped plate 120, carried by the discoidal part 102 of the rotating element 100, has, on its inner periphery, a tongue 121. This tongue occupies a groove adapted 101c in the cylindrical part 101. This tongue 121, moreover, ensures the rotation of the ring-shaped plate 120.

[0053] On this tab 121 is attached, for example by welding, a conductor 122 passing through the cylindrical part 101 in the bore 101b, and exiting the device 10.

[0054] [Fig.7] is a cross-sectional view of the entire device 10 passing through the second rotating connection and the EE section in the plane of the crown-shaped conducting plate 110.

[0055] The crown-shaped plate 110, carried by the discoidal portion 102 of the rotating element 100, has a tab 111 on its inner periphery. This tab occupies a suitable shape lOld in the cylindrical part 101 and ensures, moreover, the rotation of the crown-shaped plate 110.

[0056] On this tab 111 is attached, for example by welding, a conductor 112 passing through the cylindrical part 101 in the adapted shape lOld, and exits the device 10.

[0057] [Fig-8] is a front view of the device 10 on the radial face side 202, opposite the face of the fixing on the housing and showing the exit of two rotating conductors 122 and 112 in the bore 101b and the adapted shape lOld. This view also shows the tab 111.

Claims

Demands

1. Current supply device (10) for the rotor of an electric machine comprising: • a first fixed element (200), made of insulating material, consisting of a radial face (202), a tubular part (201) carrying lugs (203) for fixing to a housing (40) by means of screws (45) and centered on a shoulder (41) of the housing (40) by an inner diameter (201a); • a second fixed element (300), made of insulating material, centered in the first fixed element (200); • a rotating element (100), made of insulating material, carried by a rotor shaft (20); • two current transmitting discs (400) interposed between the fixed elements and the rotating element;characterized in that in the tubular part (201) of the fixed element (200) the rotating element (100) is arranged between the radial face (202) and the second fixed element (300) and the whole of the components is brought into contact and under pressure by a corrugated washer (320) pushing on the second fixed element (300) bearing against the first fixed element (200).;

2. Current supply device (10) for the rotor of an electric machine according to claim 1 characterized in that on the radial face (202), inner side of the fixed element (200) is attached, for example by bonding, a ring-shaped plate (210): • made of conductive material, preferably copper or copper alloy; • provided with a tab (211), housed in a suitable form (206) in the cylindrical part (201), making the ring-shaped plate (210) fixed, and on the tab (211) is fixed a conductor (212) which, first, runs along the cylindrical part (201) in a guide (207) housed in the suitable form (206) and then passes through a guide (42) carried by the housing (40).

3. Current supply device (10) for the rotor of an electric machine according to claim 1 characterized in that on the second

4.

5. fixed element (300), side oriented radial face (202), a ring-shaped plate (310) is attached, for example by gluing: • made of conductive material, preferably copper or copper alloy; • equipped with a tab (311), housed in a suitable form (204) in the cylindrical part (201), making the ring-shaped plate (310) fixed, and on the tab (311) is fixed a conductor (312) which, first, runs along the cylindrical part (201) in a guide (205) housed in the suitable form (206) then passes through a guide (42) carried by the housing (40). Current supply device (10) for the rotor of an electric machine according to claim 1 characterized in that on the rotating element (100) are attached, for example by gluing, on either side of its discoid part (102) two ring-shaped plates (110), (120): • made of conductive material, preferably copper or copper alloy; • each equipped with a tab (111),(121) housed in the adapted forms (101d),(110c) of the cylindrical part (101), making the crown-shaped plates (110),(120) rotatable and on these tabs are fixed the conductors (112),(212) passing the first in the adapted form (111d), and the second in a bore (101b) in the rotating element (100), so as to be able to be connected to the coils of the rotor. Current supply device (10) for the rotor of an electric machine according to claims 1 to 4, characterized in that between the ring-shaped plates (110), (210) on the one hand and (120), (310) on the other hand are intercalated the transmitting discs (400) composed of an annular disc (401) made of insulating or metallic material (preferable for mechanical strength) and which has, on a circle, a large number of rectangular openings in which are inserted identical cylindrical rollers (402) made of conductive material, copper or copper alloy, of diameter greater than the thickness of the annular disc (401).

6. Current supply device (10) for the rotor of an electric machine according to claims 1 and 5 characterized in that the set of components, to ensure at best the transmission of electric current between the opposite crown-shaped plates 110,210 and 120,310 is put under pressure by a corrugated washer (320) implanted in a diameter (302b) of the second fixed element (300) on which rests a washer (321) held by a retaining ring (322) implanted in a groove of the first fixed element (200).

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