FR2878010A1 - MAGNETIC COUPLING DEVICE BETWEEN TWO ELEMENTS - Google Patents

Abstract

Coupling device 22 between a driving element intended to drive a driven element in rotation, the driven element being mounted on the driving element by means of a bearing comprising two concentric rings 24, 25 between which is disposed at least one row of 'rolling elements 26 in contact with raceways formed on said rings, the passage of the torque between the driving element and the driven element being effected by a coupling involving magnetic fields, the bearing comprising a magnetized ring 28 fixed on one of the rings of the bearing and a ring 29 fixed on the other ring of the bearing, said rings being arranged opposite one another with an air gap and cooperating magnetically.

Description

Magnetic coupling device between two elements.

  The present invention relates to the field of magnetic couplings used to transmit torque between a driving element and a driven element. This type of device is used for example in the case of cooling fans of motor vehicle alternators. However, we seek more and more, for reasons of comfort, to reduce the noise of all origins in engines and their accessories.

  A cooling fan of the engine alternator is generally rotated by the alternator shaft, itself driven by a pulley cooperating with a drive belt. The rotational speed of the alternator shaft is directly proportional to the rotational speed of the motor. As a result, if the fan rotor is rigidly coupled to the alternator shaft, the aerodynamic noise generated by the fan becomes extremely important at high rotational speeds. On the other hand, the air flow of the high speed fan is often too high compared to the flow required to ensure efficient cooling. This results in a significant waste of energy.

  The magnetic coupling devices between the fan and the drive member of the fan allow, beyond a certain speed of rotation of the driving part linked to the motor, to partially decouple the fan, so that the speed of rotation of the fan fan is limited, while the rotation speed of the driving part continues to grow. Such partial fan decoupling occurs when the aerodynamic drag torque of the fan becomes greater than the driving magnetic torque between the driving element and the fan. There is then a relative rotation between the fan and the alternator shaft, which allows the engine to run at high speed without the fan turns too fast and produce too much aerodynamic noise. Such devices are known in particular from GB 2 102 216 and US 4 446 391.

  The main disadvantage of these devices lies in their size and in the large number of elements to be assembled by the manufacturer of the alternator on the rotor and on the fan, which is detrimental in terms of cost and production time .

  The invention proposes to remedy these drawbacks.

  The invention provides a compact magnetic coupling device, simple structure, whose production can be easily automated and reasonable cost.

  The coupling device between a driving element and a driven element is intended to rotate the driven element, mounted on the driving element by means of a bearing. The bearing comprises two concentric rings between which is disposed at least one row of rolling elements in contact with the raceways formed on said rings. The passage of torque between the driving element and the driven element is effected by coupling, involving magnetic fields. The bearing comprises at least one magnetized ring fixed on one of the rings of the bearing and at least one ring fixed on the other ring of the bearing. The rings are arranged opposite one another with an air gap and cooperate magnetically. Such a device can be mounted between a fan and a shaft in a simple manner, for example by fitting operations.

  Advantageously, the rings are arranged between the axial bearings of the bearing rings. The bearing is particularly compact.

  In one embodiment, the device comprises support frames of the rings. The armatures may have an L-shaped section with a portion fitted on a ring and a radial portion respectively supporting the rings. Reinforcements and rings can help seal the bearing by forming a labyrinth seal.

  Alternatively, the reinforcements may consist of a circular ring extending axially over a certain length. The structure of the frames is particularly simple.

  In one embodiment, the rings are arranged protruding from a front surface of the bearing rings. The rings may have a large section allowing the generation of high magnetic fields. The reinforcements may be in the form of annular cups provided with a fitting portion on the rings and a stop portion on the front surface of the rings. This guarantees an excellent axial positioning of the rings, one with respect to the other.

  In one embodiment, the device comprises two magnetized rings. The magnetized rings can be made in the form of plasto-ferrite having circumferentially alternating magnetic poles.

  In one embodiment, the device comprises an electrically conductive non-magnetic ring. The non-magnetic ring can be made of copper or aluminum. The coupling is ensured by the interaction between the magnetic flux of the magnets and the eddy currents induced in the non-magnetic ring when said non-magnetic ring moves relative to the magnets. Two magnetized rings supported by one of the rings can surround a ring supported by the other ring, including a non-magnetic ring.

  Alternatively, the device comprises a hysteresis ring, for example made of anisotropic magnetic material.

  The gap can be radial or axial.

  A fan may comprise means provided with blades and a coupling device as described above attached to said means. The outer ring of the bearing can be fitted into a bore of the wheel provided with blades.

  An alternator may comprise a rotating part, a non-rotating part and a fan mounted via said coupling device on said rotating part.

  It is also proposed a rolling bearing comprising at least two concentric rings, between which are arranged a plurality of rolling elements in contact with the raceways formed on said rings, and at least one magnetized ring fixed on one of the rings. of rolling and arranged opposite another ring fixed on the other ring of the bearing with an air gap for magnetically coupling without contact, in rotation, said two rings.

  Such a rolling bearing can be applied to any type of mechanical member, in which it is desired to transmit a torque and a rotational movement between a driving element and a driven element, with a possible speed differential between the two elements and a possible speed limitation of the driven element. This is ensured in a simple and particularly compact way with said rolling bearing.

  The present invention will be better understood on reading the detailed description of some embodiments taken by way of non-limiting examples and illustrated by the accompanying drawings, in which: FIG. 1 is an axial sectional view of a part of FIG. an alternator; Figure 2 is a half-view in axial section of a rolling bearing; FIG 3 is a partial front elevational view of a magnetic ring; FIG. 4 is an external partial view of the two magnetic rings of the rolling bearing of FIG. 2; - Figures 5 to 9 are half-views in axial section of different embodiments of the rolling bearing; and FIG. 10 is a view similar to FIG. 4 of the rings of FIG. 9.

  As can be seen in FIG. 1, the alternator 1, of which only one end portion is shown, comprises a rotating part 2 and a non-rotating part 3. The rotating part 2 comprises a shaft 4, a non-visible rotor in the drawing and a grooved pulley 6 in which passes a drive belt 7 provided to be driven by a driving pulley secured to the crankshaft with thermal engine not shown. A spacer 5 mounted on the shaft 4 ensures the precise axial positioning of the rotor relative to the bearings that support it. The non-rotating part 3 comprises a casing 8, for example made of light alloy.

  Between the shaft 4 and the casing 8, is disposed a rolling bearing 9, of conventional type, provided with a rotating inner ring 10 whose bore is fitted with clamping on the shaft 4, an outer ring no rotating 11 whose cylindrical outer surface is fitted into a cylindrical bore of the casing 8, a row of rolling elements 12, here balls, arranged between the races of the inner and outer rings 10, a cage 13 maintaining the circumferential spacing of the rolling elements 12, here made of sheet metal, and two seals 14 and 15 mounted in annular grooves of the outer ring 11 and rubbing by flexible lips on an outer cylindrical bearing surface of the inner ring 10. The seals 14 and 15 are symmetrical with respect to a radial plane passing through the center of the rolling elements 12 and are provided with a frame covered with a soft material e, for example an elastomer. The races of the inner and outer rings 11 are formed by machining with chip removal to give them the desired depth. The outer ring 11 is held axially relative to the casing 8, in one direction by a radially inwardly projecting bead 16 forming part of the casing 8, and in the other direction by a flange 17 fixed to the casing 8 by means appropriate.

  The rotating part 2 further comprises a fan 18 in the form of a ring of blades 19 extending outwards and inclined substantially helically, and an annular central portion 20 forming a means supporting the blades 19. The means 20 comprises an annular axial portion of small diameter 21 provided with a bore. A coupling device 22 is arranged radially between the shaft 4 and the axial portion 21 of the central portion 20 of the fan 18 and axially between the rotor 5 and an annular spacer washer 23 in contact with a front radial surface of the inner ring 10. Bearing 9. Axial clamping can be ensured.

  As best seen in Figure 2, the coupling device 22 is in the form of a rolling bearing provided with an inner ring 24, an outer ring 25, a row of rolling elements 26 here balls, a cage 27 for maintaining the circumferential spacing of the rolling elements 26 and coupling rings 28 and 29. The inner ring 24 and outer 25 have raceways in the form of deep groove for the rolling elements 26 and are provided with radial front surfaces. The bore of the inner ring 24 is fitted on the shaft 4 and in contact on one side with the spacer 5 and on the opposite side with the spacer washer 23. The inner ring 24 has an outer surface in the form of a cylindrical bearing, on one side and the other of the raceway. The outer ring 25 has an axial outer surface fitted into the axial portion 21 of the central portion 20 of the fan 18. The radial front surfaces of the outer ring 25 are aligned on the radial end surfaces of the inner ring 24. The outer ring 25 has a cylindrical bore, on both sides of the raceway. The cage 27 comprises a bead disposed on one side of the rolling elements, while the coupling rings 28 and 29 are arranged on the opposite side.

  In addition, the coupling device 22 comprises reinforcements 30 and 31 respectively supporting coupling rings 28 and 29.

  In the embodiment illustrated in FIG. 2, the armatures 30 and 31 are in the form of L-section cups. The armature 30 comprises an axial portion fitted on the outer cylindrical surface of the inner ring 24 and a portion radial adjacent rolling elements 26 and extending outwardly. The armature 31 comprises an axial portion fitted into the bore of the outer ring 25 and a radial portion extending inwardly and substantially aligned with the radial end surfaces of the inner and outer rings 24 and 25.

  As best seen in FIGS. 3 and 4, the coupling rings 28 and 29 are in the form of a circumferential alternation of magnetized segments of opposite polarity, for example made from plasto-ferrite which can be magnetized after manufacturing. The angular sector occupied by each of the individual magnets is constant and identical for the coupling rings 28 and 29. In this way, the magnets of a polarity of the ring 28 tend to come opposite the magnets of opposite polarity. the ring 29. The rings 28 and 29 supported respectively by the radial portions of the frames 30 and 31, extend over most of the radial gap between the inner and outer rings 24 and 25 are separated by a small air gap axial. The axial size of the bearing is retained. The rings 28 and 29 are thus integral in rotation respectively of the inner and outer rings 24 and 25 tend to be positioned relative to each other in the position illustrated in FIG. 4, as long as a torque greater than their attraction Mutual does not alter such relative positioning. When the limit torque is crossed, the rings 28 and 29 begin to rotate relative to each other.

  Such a coupling device can be produced extremely simply, by providing a sealed bearing without magnetic coupling rings. The magnetic coupling rings provide a labyrinth seal on one side of the bearing. On the side of the cage 27, the tightness can be ensured by narrow passage, by providing a spacer washer 23 which comes close to the outer ring 25.

  In the embodiment illustrated in FIG. 5, the coupling device 22 differs from that illustrated in FIG. 2 in that the reinforcements 32, 33 for supporting the coupling rings consist of a simple circular ring made of axially extending sheet metal. over a certain length and having a small thickness, said armatures being respectively fitted on the corresponding surfaces of the inner and outer rings 24 and 24. The coupling rings 28, 29 are separated by a small radial air gap and are flush with the radial front surface of the inner rings. 24 and outer 25 so as not to increase the axial size of the bearing. Such a coupling device is even simpler than that illustrated in FIG.

  In the embodiment illustrated in FIG. 6, the coupling rings 28 and 29 are separated by an axial air gap and have a radial dimension that is clearly greater than the space available between the inner and outer rings. The coupling rings and 29 are disposed in axial projection with respect to said rings 24 and 25 and are supported by reinforcements 34 and 35, respectively, of suitable shape.

  The armature 34 comprises an axially-shaped push-fit portion 34a fixed on an outer cylindrical bearing surface of the inner race 24, and a radial double portion 34b bent at 180, in contact with the radial front surface of the inner race. and extending the fitting portion 34a, first radially inward, then outward. The double radial portion 34b forms a fitting abutment of the armature 34 on the inner ring 24 and thus ensures accurate axial positioning. The armature 34 is extended by an axial portion 34c, of the same diameter and concentric with the fitting portion 34a and by a radial portion 34d supporting the magnetic ring 28 and extending outwardly from the end of the axial portion 34c opposed to the rolling elements 26.

  The armature 35, of annular shape, has a T-section with a radial portion 35a, a double axial portion 35b and a radial portion 35c. The radial portions 35a and 35c form the bar of the T and are located in the same radial plane. The radial portion 35a is in contact with the radial front surface of the outer ring 5. The radial surface 35a also serves as axial abutment for fitting on the outer ring 25. The double radial portion 35b is folded to 180, the fold being formed the side of the rolling elements 26, and fitted into the bore of the outer ring 25 and provides the junction between the two radial portions 35a and 35c. The radial portion 35c is inward from the double radial portion 35b.

  The magnetic ring 29 is supported both by the radial portions 35a and 35c while being integral. Such an arrangement makes it possible to benefit from a large surface area vis-à-vis between the magnetic rings and to obtain a high limit torque.

  In the embodiment illustrated in Figure 7, the coupling device 22 comprises two magnetized rings integral with the outer ring 25 and a ring 36 integral with the inner ring 24. More specifically, the ring 36 is in the form of a C-section cup completely disposed between the rings 24 and 25, with a small diameter axial portion 36a fitted on an outer cylindrical surface of the inner ring 24, a radial portion 36b in the vicinity of the rolling elements 26 and an axial portion large diameter 36c extending opposite the rolling elements 26 from the end of large diameter of the radial portion 36b.

  The ring 36 may be made of electrically conductive non-magnetic material, for example aluminum or copper or an alloy of such metals.

  The outer ring 25 supports a magnetic ring 29 via a reinforcement 33, of a shape identical to the embodiment illustrated in FIG. 5, but of reduced axial length to allow a certain axial space to remain between said magnetic ring 29 and the radial front surface of the outer ring 25. The magnetic ring 29 is disposed with a slight radial air gap with respect to the large-diameter axial portion 36c of the ring 36. The outer ring 25 also supports a radially arranged magnetic ring 37 between the axial portions 36a and 36c of the ring 36 with a slight radial gap relative to the axial portion 36c of large diameter. The ring 37 is supported by a frame 38, for example made of steel. The armature 38 has an outer surface fitted into the bore of the outer ring 25 in the vicinity of the armature 33, a body 39 extending radially inward occupying most of the radial space between the bore the outer ring 25 and the small diameter axial portion 36a of the armature 36 while being substantially aligned with the radial end faces of the inner and outer rings 24 and an axial portion 40 disposed within and in contact direct from the magnetic ring 37 and in the vicinity of the small diameter axial portion 36a of the ring 36. The body of the armature 38 passes between the large-diameter axial portion 36c of the armature 36 and the radial plane passing through. by the front surfaces of the rings 24 and 25.

  The rotational coupling can be provided by the interaction between the magnetic fluxes of the magnets of the magnetic rings 29 and 37 and the eddy currents induced in the non-magnetic ring 36 when said non-magnetic ring 36 has a relative movement with respect to the two rows of poles of the magnetized rings 29 and 37.

  It can also be provided that the ring 36 is made of an anisotropic magnetic material, for example an Al-Ni-Co alloy to form a hysteresis ring.

  In the embodiment illustrated in FIG. 8, the outer ring supports a non-magnetic or hysteretic ring 41 in the form of an L-section cup with an axial portion fitted into the bore of the outer ring 25 and a radial portion extending inwardly. The inner ring 24 supports two magnetic rings 42 and 43, arranged on one side and the other of the ring 41 with a small axial gap. The magnetic rings 42 and 43 are supported by armrests 44 and 45, similar in shape, annular L-section, with a short axial portion fitted on the outer cylindrical surface of the inner ring 24 and a radial portion extending towards the outside. outside and supporting the magnetic rings 42 and 43, respectively. The magnetic ring 42 is disposed on the side of the radial portion opposite to the axial portion of the frame 44. On the contrary, the magnetic ring 43 is disposed on the same side of the radial portion as the axial portion of the frame 45 Such an arrangement makes it possible to use armatures of identical shape while offering a seal by labyrinth seal and excellent compactness.

  In the embodiment illustrated in Figure 9, the magnetic rings 42 and 43 are supported by the outer ring 25 through the frames 44 and 45. The ring 41, non-magnetic or hysteresis, is supported by the inner ring 24.

  The arrangement of the various rings illustrated in FIGS. 8 and 9 is found in FIG. 10, in which it can be seen that the amagnetic or hysteresis ring 41 is disposed at a very short axial distance from the magnetic rings 42 and 43 which tend to see their opposite poles align axially.

  The maximum torque transmissible by the coupling device depends on the materials chosen to make the magnets, their magnetization, the area of the surfaces facing each other, and the value of the gap. It is thus possible to calibrate, by construction or adjustment, the maximum torque that can be transmitted between the driving element and the driven element. The maximum torque can be predefined, so that at a given rotational speed of the fan, the aerodynamic drag torque of the fan will exceed the maximum transmittable torque. There will then be a relative rotation between the fan rotor and the drive shaft. The fan speed will stop increasing according to the torque-speed curve of a fan that is monotonically increasing. The coupling device is compact and can easily be placed inside an alternator. It provides both a reduction of fan noise and a reduction in power consumption by limiting the torque transmitted to the fan.

  The coupling device is in the form of a single bearing with deep groove rings or with sheet metal rings equipped with magnetic rings.

Claims (15)

  1-Coupling device (22) between a driving element for rotating a driven element, the driven element being mounted on the driving element by means of a bearing comprising two concentric rings (24, 25) between which is disposed at least one row of rolling elements (26) in contact with raceways provided on said rings, the passage of torque between the driving element and the driven element being effected by coupling involving magnetic fields, characterized in that the bearing comprises at least one magnetized ring (28) fixed on one of the rings of the bearing and at least one ring (29) fixed on the other ring of the bearing, said rings being arranged facing one of the other with a gap and cooperating magnetically.   2-Device according to claim 1, characterized in that said rings are arranged between axial bearings of the bearing rings.   3-Device according to claim 1 or 2, characterized in that it comprises reinforcements (30, 31) for supporting the rings.   4-Device according to claim 3, characterized in that said armatures have an L-shaped section with a portion fitted on a ring and a radial portion respectively supporting the rings.   5-Device according to claim 3, characterized in that the armatures consist of a circular ring extending axially over a certain length.   6-Device according to any one of the preceding claims, characterized in that the rings are arranged projecting relative to a front surface of the bearing rings.   7-Device according to claim 6, characterized in that reinforcements are in the form of annular cups provided with a fitting portion on the rings and a stop portion on the front surface of the rings.   8-Device according to any one of the preceding claims, characterized in that it comprises two magnetized rings.   9-Device according to any one of the preceding claims, characterized in that it comprises an electrically conductive non-magnetic ring.   10-Device according to any one of claims 1 to 8, characterized in that it is made of anisotropic magnetic material.   11-Device according to any one of the preceding claims, characterized in that two magnetized rings supported by one of the rings surround a ring supported by the other ring.   12-Device according to any one of the preceding claims, characterized in that the air gap is radial or axial.   13-Fan (18) comprising means (20) provided with blades (19) and a device according to any one of the preceding claims, fixed on said means (20).   14-Alternator (1) comprising a rotating part (2), a non-rotating part (3) and a fan (18) according to the preceding claim, mounted via said device on said rotating part.   15-rolling bearing comprising at least two concentric rings, between which are arranged a plurality of rolling elements (26) in contact with the raceways formed on said rings, characterized in that it comprises at least one magnetized ring (28) fixed on one of the rolling rings and disposed opposite another ring (29) fixed on the other ring of the bearing with an air gap for magnetically coupling without contact, in rotation, said two rings.