FR2879708A1 - INSTRUMENT BELT TENSIONER ROLLING DEVICE AND METHOD OF CONTROLLING THE SAME - Google Patents

Abstract

The belt tensioner roller device 9 is provided with a fixed support adapted to ensure the maintenance of the device on a motor block, a working eccentric 3 angularly movable relative to the fixed support 5, a roller 8 supported by the work eccentric and intended to be in contact with the belt, and a member adapted to exert a permanent force between the base plate and the work eccentric. The base plate comprises a sensor element 30 able to detect a predetermined wear limit of the belt directly as a function of the angular position of an encoder element mounted on the working eccentric, said encoder element being mounted opposite the sensor element with a radial air gap and comprising at least one bipolar permanent magnet angularly extending in a circumferentially limited manner around the axis 4a of rotation of the working eccentric 3.

Description

Instrumented belt tensioner roller arrangement and method of

associated control.

  The present invention relates to the field of automatic belt tensioner roller devices, in particular used to ensure an adequate tension of belts, for example internal combustion engine thermal engine timing belts.

  A belt tensioning roller device generally comprises a support intended to be fixed on the engine block, and a movable part that can move angularly with respect to the support. Said movable part is provided with an eccentric and a bearing on which is mounted a roller intended to be brought into contact with the belt. A spring exerts a permanent tension force between the support and the movable part, causing the roller to come into contact with the belt, with an adequate tension of the belt. The movable part is mounted on the support with a possibility of adjustment in order to adapt the tension force of the belt. For more details, reference may be made to FR-A-2 744 506 and FR-A-2 668 567.

  The tensioning roller device thus makes it possible to maintain the required tension of the belt within a certain tolerance range, despite the dimensional variations of the belt that can be generated by wear or by temperature variations.

  The failure of a belt, in particular of a motor vehicle engine timing belt can generate significant damage to said engine, and thus alter the operating curvature.

  For this purpose, document US-A-6 666 784 discloses a belt tensioner roller device provided with a fixed support mounted on a motor unit, an eccentric movable angularly with respect to said support, and a damping element disposed at the fixed support. Inside the damping element is mounted a belt wear detecting device provided with at least one magnet fixed on a movable member of the damping element and a sensor capable of detecting the linear position of the movable element, said linear position being related to the angular position of the eccentric relative to the fixed support.

  The device has the disadvantage of not allowing an accurate and reliable measurement of wear of the belt, said measurement being determined as a function of the linear position of a movable member of the damping device. Indeed, the device comprises a large number of intermediate elements that intervene in the kinematic chain between the movable element and the belt, which can thus generate significant inaccuracies in the measurements made. Moreover, this device has a relatively large axial size.

  The Applicant has also developed a belt tensioning roller device, which was the subject of the filing of a French patent application No. 01 14 669. The tensioner roller device is provided with a fixed support, d an eccentric working angularly relative to the fixed support, an encoder element mounted on the eccentric and comprising a multipole coding ring, a sensor element mounted on the fixed support and adapted to cooperate with said encoder element for measuring the angular displacement of the working eccentric, and a signal processing module emitted by the sensor element able to determine a wear information of the belt.

  Such a tensioner roller device, although it is particularly precise and effective in detecting displacements and angular oscillations of the eccentric with respect to the fixed support, has the disadvantage of including particularly expensive elements for a simple threshold measurement. belt wear, which may be incompatible with large-scale industrialization of tensioner roller devices.

  The present invention therefore aims to overcome these disadvantages by providing a belt tensioner roller device capable of detecting a predetermined wear limit of a belt particularly simple, accurate, reliable and economical way.

  For this purpose, the belt tensioning roller device is provided with a fixed support adapted to ensure the maintenance of the device on a motor block, a working eccentric movable angularly with respect to the fixed support, a roller supported by the work eccentric and intended to be in contact with the belt, and a member adapted to exert a permanent force between the fixed support and the work eccentric. The base plate comprises a sensor element capable of detecting a predetermined wear limit of the belt directly as a function of the angular position of an encoder element mounted on the working eccentric, said encoder element being mounted opposite the sensor element with a radial air gap and comprising at least one bipolar permanent magnet extending angularly in a circumferentially limited manner about the axis of rotation of the working eccentric.

  Here is meant by a magnet extending angularly in a circumferentially limited manner around the axis of rotation of the working eccentric, a magnet having two distinct ends separated by a certain distance in the circumferential direction.

  In other words, in cross section, two straight lines passing through the center of the working eccentric and respectively by different ends of the magnet define an angular sector strictly less than 360.

  Such a device has the advantage of allowing the detection of a predetermined wear threshold of the belt simply from the angular position of the working eccentric relative to the fixed support, detected by the sensor, without it being necessary to provide additional elements, for example to process the information transmitted by said sensor. In addition, the encoder element being mounted directly on the working eccentric, the measurement is particularly accurate and reliable.

  Furthermore, the encoder element has a substantially reduced circumferential dimension with respect to the circumferential dimension of the working eccentric, which makes it possible to obtain a particularly economical tensioner roller device. In addition, the use of such an encoder element makes it possible to simplify the machining of the working eccentric as well as the mounting of said element on the eccentric.

  In a preferred embodiment, the encoder element extends angularly in a range between 0 and 10.

  Advantageously, the sensor element comprises a magnetosensitive cell. The use of such sensor and encoder elements provides a particularly simple and economical design device.

  Preferably, the sensor comprises a digital or linear magnetosensitive cell.

  The device may comprise a support block inside which the sensor element is housed at least in part.

  Preferably, the support comprises a base plate and a setting eccentric fixed to the base plate, the support block being fixed to the base plate.

  Advantageously, the support block comprises a wired link capable of communicating, to processing means of the device, information relating to the signals emitted by the sensor element.

  The invention also relates to a method for controlling the wear of a belt comprising the steps during which a permanent tension force is exerted between a fixed support and a moving element angularly relative to the fixed support and in contact with the belt. a wear limit of the belt is detected directly as a function of an angular displacement of the moving element relative to the fixed support, the angular displacement being detected by cooperation of encoder and sensor elements, said encoder element being mounted in view of the sensor element with a radial gap and extending angularly in a circumferentially limited manner around the axis of rotation of the working eccentric.

  The present invention will be better understood on reading the detailed description of an embodiment taken by way of non-limiting example and illustrated by the appended drawings, in which: FIG. 1 is a view in axial section of a tensioner device according to the invention, and - Figures 2 and 3 are perspective views of the device of Figure 1.

  As can be seen in Figures 1 to 3, the tensioner roller device, referenced 1 as a whole, comprises a fixed crew provided with a control eccentric 2, and a movable assembly pivotally mounted on the fixed crew and provided of a working eccentric 3. A smooth bearing bearing 4 is rigidly mounted by clamping in the work eccentric 3. An actuator comprising a spring 6 is mounted between said work eccentric 3 and a fixed support 5 comprising the eccentric 2, a roller 8 being mounted on the bearing 7, said roller 8 bearing on a belt 9.

  The adjustment eccentric 2, of generally cylindrical shape, comprises a bore 10, axis 10a, offset outwardly with respect to the geometric axis of said eccentric. The bore 10 allows the passage of a fastener such as a screw 11 for fixing said eccentric adjustment 2 on a motor block 12, shown schematically by a dotted line. The eccentric adjustment 2 can thus rotate angularly relative to the engine block 12 when the screw 11 is loosened, the screwing of said screw 11 causing the immobilization of the eccentric adjustment 2 on said block. The eccentric adjustment 2 comprises, at one axial end, a radial flange 13 directed radially outwards. The flange 13 substantially radially extends a radial bearing surface 14 of the adjusting eccentric 2 on the engine block 11 so as to increase the bearing surface of said block on the control eccentric 2.

  The sliding bearing 4, of axis 4a, is in the form of an annular bushing comprising an axial portion 15, fixed by tight fitting in a bore 3a of the working eccentric 3, and able to slide on the cylindrical surface 2 of the eccentric adjustment 2. The axial portion 15 is extended at an axial end, the side opposite the flange 13, by a radial portion 16 directed outwardly. The radial portion 16 bears against a radial front surface of the work eccentric 3.

  The fixed support 5 also comprises a base plate 17 provided with a tubular axial guide portion 17a, here having a small axial dimension and defining a bore coming into contact with the outer surface 2a of the adjusting eccentric 2 The axial portion 17a is extended outwards, from an axial end, on the side of the flange 13, by a radial portion 17b bearing against said flange 13. The radial portion 17b is extended axially, from a zone of larger diameter, on the opposite side to the axial portion 17a, by an axial portion 17c which extends radially outwards, from its free end, by a radial portion 17d situated axially substantially at the level of the collar 13.

  The radial portion 17d comprises, at its outer edge, radial protuberances 17e to 17h extending radially outwardly the radial portion 17d. The radial protuberances 17e and 17f, of small circumferential dimensions, are extended, from their outer edge, respectively by first and second axial tabs 17i and 17j. The axial tabs 17i and 17j extend substantially axially in the direction of the eccentric adjustment 2. The said axial tabs 17i and 17j are substantially angularly opposed to each other.

  The radial protuberances 17g and 17h have a circumferential dimension substantially greater than that of the radial protuberances 17e and 17f. Said radial protuberances 17g and 17h are circumferentially offset, in the clockwise direction, with respect to the protuberance 17e. The radial protuberances 17g and 17h join together to form a fork, and make it possible to immobilize the plate 17 relative to the engine block 12. It is for example possible to provide a pin (not shown) attached to the block motor 12 and projecting radially through a space 17k formed between the radial protuberances 17g and 17h.

  The axial portions 17a and 17c, the radial portions 17b and 17d, the radial protuberances 17e to 17h, and the axial tabs 17i and 17j of the base plate 17 are in one piece. Advantageously, the base plate 17 is made by cutting, stamping and bending, from a sidewall made of thin sheet steel.

  The support 5 also comprises an intermediate plate 18 substantially in register with the base plate 17. The intermediate plate 18 is fitted axially and centered on said base plate 17, on the side of the adjusting eccentric 2. The intermediate plate 18, advantageously made of sheet steel, comprises an axial portion 18a, of tubular shape, defining a bore coming into contact with the outer surface of the axial portion 17a of the base plate 17. The axial portion 18a is extended towards the outside, from an axial end, a radial portion 18b extending from an area of larger diameter, the opposite side to the axial portion 18a, by an axial portion. The axial portion 18c extends from its free end, by a radial portion 18d in contact with the radial portion 17d of the base plate 17. The axial portions 18a, 18c and the radial portions 18b, 18d of the intermediate plate 18 are monoblocks.

  The working eccentric 3 comprises a radial surface 3b arranged axially opposite the base plate 17, a cylindrical outer surface 3c extending over most of its length from the front radial surface 3b, a portion radial 3d extending outwardly from the end of the cylindrical outer surface 3c, and an axial portion 3e extending from the free end of the radial portion 3d, axially opposite the front radial surface 3b. The working eccentric 3 is extended locally, at the axial portion 3e, by an axial extension 3f extending axially towards the base plate 17.

  The axial extension 3f here has an axial dimension substantially equivalent to that of the axial portion 3e and a substantially greater radial dimension. The circumferential dimension of the axial extension 3f is relatively small, said extension extending angularly between 30 and 40.

  The radial surface 3b, the radial portion 3d, the axial portion 3e and the axial extension 3f of the eccentric 3 are in one piece.

  The radial portion 3d, the axial portion 3e, and the radial portion 18d of the intermediate plate 18 define a housing in which the spring 6 is arranged. One end 6a of the spring 6 is hooked on the base plate 17, the other end being integral with the working eccentric 3. Thus, the working eccentric 3 can rotate about the axis 4a, with respect to the eccentric adjustment 2, while being subjected to a return torque exerted by said spring 6.

  An axial stop member in the form of a ring 19 comprises an inner surface 19a, mounted for example by crimping on a cylindrical outer surface 2b of the adjusting eccentric 2, at an axial end on the side opposite to the flange 13, delimited by two radial surfaces 19b and 19c, and a cylindrical outer surface 19d. The radial surface 19h forms an axial stop surface for the control eccentric 3 bearing on said surface 19b, via the axial portion 16 of the bearing 4. The surfaces 19a and 2b have a complementarity of shape and are capable of ensuring an angular connection between the ring 19 and the adjusting eccentric 2. The ring 19 can thus allow the angular adjustment of the adjusting eccentric 2 before tightening the screw 11.

  The bearing 7 with deep grooves and radial lateral faces, has a low manufacturing cost, and comprises an inner ring 20, an outer ring 21, between which are housed a row of rolling elements 22 made here in the form of balls, a cage 23 for maintaining the circumferential space of the rolling elements 22, and two seals 24 and 25 metal.

  The inner ring 20 is of massive type. Solid ring means a ring whose shape is obtained by machining with chip removal (turning, grinding) from tubes, bars, forged blanks and / or rolled. The inner ring 20 comprises a bore 20a of cylindrical shape, in contact with the outer surface 3c of the eccentric adjustment 3, and delimited by two radial lateral surfaces 20b and 20c opposite, the radial surface 20c being in contact with the radial portion 3d, and an outer cylindrical surface 20d from which is formed a circular groove 20e having in cross section a concave internal profile adapted to form a raceway for the rolling elements 22, said groove being oriented outwards.

  The outer ring 21, also of massive type, comprises an outer cylindrical surface 21a delimited by front surfaces 21b and 21c, and a bore 21d of cylindrical shape from which is formed a circular groove 21e having in cross section a concave internal profile suitable forming a raceway for the rolling elements 22, facing inwards. The outer cylindrical surface 21a here comprises two annular grooves symmetrical to each other with respect to a plane passing through the center of the rolling elements 22. Inside said grooves are mounted the seals 24 and 25, coming close to portions of the cylindrical outer surface 20d of the inner ring 20 forming narrow passages. The seals 24, 25 are arranged radially between the inner and outer rings 20, 21. The seal 24 is mounted axially between the rolling elements 22 and the radial surfaces 20b and 21b of the rings 20 and 21, the seal 25 being mounted axially between the rolling elements 21 and the radial surfaces 20c, 21c of said rings.

  The roller 8 comprises a stepped bore overmolded on the outer cylindrical surface 21a of the ring 21. Of course, it is also conceivable to design a roller 8 mounted by fitting on an outer cylindrical surface of an outer ring of the bearing 7 devoid of grooves ring. The bearing 7 thus ensures the freedom of rotation of the roller 8 relative to the working eccentric 3, and the recovery of radial forces.

  The device 1 also comprises an encoder or target element formed here in the form of a permanent magnet 26 fixed inside a housing 27 formed at the axial extension 3f of the adjusting eccentric 3 so that a portion of the magnet 26 is substantially outwardly displaced with respect to the outer surface of the axial extension 3f. The magnet 26 has a reduced circumferential dimension with respect to the circumferential dimension of the axial extension 3e of the control eccentric 3. The magnet 26 extends angularly in a relatively small range, advantageously between 5 and 10.

  The device 1 also comprises a sensor unit 28 provided with a support 29, for example made of synthetic material, fixed at the level of the axial lug 17j, on the inside, and a sensor element 30 mounted semi-embedded to the Inside said support 29. The sensor 30 is flush with a cylindrical surface of small diameter of the support 29, so as to be mounted facing the magnet 26, the outer side of said magnet, with a small radial gap promoting the compactness of the device 1 The sensor 30 may advantageously comprise a magneto-sensitive, digital or linear cell. A digital cell reacts to a magnetic flux in all or nothing. A linear (or analog) cell provides an electrical signal whose voltage is proportional to the magnetic flux.

  The magnet 26 and the sensor 30 are thus arranged radially between the spring 6 and the periphery of the rotating part of the roller 8, and axially between the base plate 17 and the bearing 7, which allows a great compactness of the device 1 .

  The support 29 also comprises a wire link 31 capable of communicating information relating to the electrical signals emitted by the sensor 30, to processing means (not shown) of the device 1. Said processing means may for example comprise an electronic unit produced under the shape of a printed circuit board supporting electronic circuits. The processing means may, for example, be mounted at the support 29 of the sensor unit 28.

  It is thus possible, with the device 1, from a predetermined relative angular position between the working eccentric 2 and the adjusting eccentric 3 to emit a signal corresponding to a state of wear of the belt 9, the signal being transmitted an alarm module (not shown) of the device 1, which may for example be in the form of a light and / or audible indicator mounted at the dashboard of the motor vehicle to warn the driver of damage the predetermined level of wear and the need to replace the belt. By way of example, it will be possible to choose the position at which the magnet 26 arrives opposite the sensor 30 as a belt wear limit position. Of course, it is also conceivable to design a device 1 such that the position of the magnet corresponds to a starting position relative to a new belt, the distance of the magnet relative to the sensor 30 causing in this case the signal wear alarm.

  When mounting the belt tensioning device 1, a first step consists in adjusting the tension of the belt 8. To do this, the screw 11 is placed without tightening, so that the eccentric adjustment 2 is movable in rotation with respect to the block 12, and the support 5. It is rotated, by means of an operating key cooperating with the ring 19, the eccentric adjustment 2 relative to the base plate 17. The roller is thus brought 8 is in contact with the belt 9. The eccentric 2 is continued to rotate, which, by reaction of the belt 9 on the roller 8, causes the working eccentric 3 to rotate relative to the support 5 with a increasing the tension of the spring 7, which exerts a resistant torque between the support 5 and the work eccentric 3 tending to push the roller 8 continuously against the belt 9. The device 1 is designed so that the roller 8 exerts on the crown 9 an effort generating adequate tension in said 9. The carrier 5 is then immobilized on the engine block 12 by means of the screw 11.

  In operation, when the roller 8 is rotated by the belt 9, the sensor allows, as a function of the angular position of the working eccentric 3 and the eccentric adjustment 2, to recover the signals corresponding to the wear condition of the belt 9 in a particularly reliable, precise and economical manner by means of a particularly compact tensioning roller.

Claims (9)

  1 / Belt tensioner roller device (9) provided with a fixed support (5) adapted to maintain the device on an engine block and comprising a base plate (17), a working eccentric (3) angularly movable relative to the fixed support (5), a roller (8) supported by the working eccentric and intended to be in contact with the belt, and a member adapted to exert a permanent force between the plate of base and work eccentric, characterized in that the base plate (17) comprises a sensor element (30) adapted to detect a predetermined wear limit of the belt directly as a function of the angular position of an encoder element mounted on the working eccentric, said encoder element being mounted facing the sensor element with a radial air gap and comprising at least one bipolar permanent magnet extending in an angularly limited manner in the circumferential direction about the axis (4a ) rotation of the eccentric working (3).   2 / Apparatus according to claim 1, characterized in that the encoder element extends angularly in a range between 0 and 10.   3 / Apparatus according to claim 1 or 2, characterized in that the sensor element comprises a magnetosensitive cell.   4 / Apparatus according to claim 3, characterized in that the magnetosensitive cell is digital.   5 / Apparatus according to claim 3, characterized in that the magnetosensitive cell is linear.   6 / Apparatus according to any one of the preceding claims, characterized in that it comprises a support (29) inside which is housed at least in part the sensor element.   7 / Apparatus according to claim 6, characterized in that the fixed support comprises a base plate (17) and a control eccentric (2) fixed on the base plate, the support (29) being fixed on the base plate .   8 / Apparatus according to claim 6 or 7, characterized in that the support block comprises a wire link (31) adapted to communicate information relating to the signals transmitted by the sensor element to the device processing means.   9 / method for controlling the wear of a belt comprising the steps during which a permanent tension force is exerted between a fixed support and a moving element angularly relative to the fixed support and in contact with the belt, characterized in that a limit of wear of the belt is detected directly as a function of an angular displacement of the moving element relative to the fixed support, the angular displacement being detected by cooperation of encoder and sensor elements, said encoder element being mounted facing the sensor element with a radial gap and extending angularly in a circumferentially limited manner around the axis of rotation of the working eccentric.