FR2879707A1 - Timing belt tensioning idler pulley device for use in internal combustion heat engine, has operating crank including reluctor unit for detecting predetermined wear limit of belt based on angular position of crank with respect to support - Google Patents

Abstract

The device has a fixed support (5) including a sensing unit and a magnetic unit that creates a magnetic field to proximity of the sensing unit. An operating crank (3) includes a reluctor unit, mounted relative to the sensing unit with an air-gap and cooperating with the magnetic unit, for detecting a predetermined wear limit of a belt (9) based on angular position of the crank with respect to the support. An independent claim is also included for a method for controlling wear of a belt.

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 belts (the distribution of internal combustion engine combustion engines of a motor vehicle.

  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 the engine, and thus alter the safety of operation.

  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 fixed support is provided with a sensor element and an associated magnetic element capable of creating a magnetic field in the vicinity of the sensor element, the eccentric comprising a target element, mounted facing the sensor element with a gap and cooperating magnetically with the magnetic element for detection by the sensor element, a predetermined wear limit of the belt according to the angular position of the working eccentric relative to the fixed support.

  Such a device has the advantage of allowing the detection of a predetermined wear threshold of the belt directly from the angular position of the working eccentric relative to the fixed support, with a limited number of parts and particularly simple. In addition, the target element being mounted directly on the working eccentric, the measurement is particularly accurate and reliable.

  Furthermore, the arrangement of the sensor element and the magnetic element at the fixed support facilitates not only the mounting of the device but also, during a possible failure of one of the elements, to simplify the necessary intervention by not requiring operations at the work eccentric level.

  Advantageously, the target element has means capable of allowing a modification of the magnetic field created as a function of the angular position of the working eccentric with respect to the fixed support.

  The target element by the nature of the material constituting it, by design, or by addition of additional means can thus have, depending on the angular position of said target element relative to the fixed support, characteristics likely to modify the magnetic field lines established by the magnetic element and detected by the sensor element.

  Preferably, the air gap between the target element and the sensor element is variable as a function of the angular position of the working eccentric with respect to the fixed support and / or the weight of material of the target element opposite the sensor element is variable as a function of the angular position of the working eccentric relative to the fixed support. The gap can be radial or axial.

  In a preferred embodiment, the target element is provided with a portion mounted substantially facing the sensor element with a constant air gap and a projection disposed on said portion and directed outwards towards the sensor element.

  Advantageously, the device comprises a sensor unit inside which is embedded the magnetic element and housed at least partly the sensor element.

  The arrangement of the magnetic element embedded inside the support block makes it possible to avoid any infiltration of external elements, for example metallic elements, close to its outer surface and capable of generating a variation in the emitted field. The detection of the wear of the belt is thus particularly precise.

  The target element can be attached or monobloc with the working eccentric.

  Preferably, the sensor element comprises a magnetosensitive cell. The use of such an element makes it possible to obtain a particularly simple and economical design device.

  In a preferred embodiment, the target element comprises a ferromagnetic material.

  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. , and 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 a sensor detecting a magnetic cooperation between a target element and an element magnetic.

  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 FIG. 2 is a perspective view of the device of FIG. 1; FIG. 3 is an axial sectional view of the device of FIG. 1, and FIG. detail of Figure 3.

  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 is in the form of an annular bushing comprising an axial portion 15 fixed by tight fitting in a bore 3a of the work eccentric 3, and able to slide on the outer cylindrical surface 2a of the eccentric 2. The axial portion 15 is extended, at one axial end, the side opposite the flange 13, by a radial portion 16 directed outwards. 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 extension 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 extension 3e, by an axial portion 3f extending axially in the direction of the base plate 17. The axial portion 3f here has an axial dimension substantially equivalent to that axial extension 3e and a substantially greater radial dimension. The portion 3f is truncated on a portion of its circumference, and extends angularly over a portion of a circle whose value is here substantially equal to 270.

  The eccentric 3 also includes a projection 3g disposed on the outer surface of the portion 3f and extending radially outwardly. The projection 3g has radial and circumferential dimensions respectively greater and smaller than those of the portion 3f. It is for example possible to provide a projection 3g having a circumferential dimension of between 20 and 30% of the circumferential dimension of the portion 3f.

  The radial surface 3b, the radial portion 3d, the axial extension 3e the axial portion 3f and the projection 3g of the eccentric 3 are monobloc. Advantageously, the eccentric 3 is made of ferromagnetic material such as a ferrous alloy, for example steel.

  The radial portion 3d, the axial extension 3e, and the radial portion 18d of the intermediate plate 18 define a housing in which is disposed the spring 6. One end 6a of the spring 6 is hooked on the base plate 17, the other end being secured to the work eccentric 3. Thus, the work eccentric 3 can rotate relative to the eccentric adjustment 2 while being subjected to a restoring 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 19b 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 complementary 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 211) 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 a sensor block 26 provided with a support 27, for example made of synthetic material, fixed at the level of the axial lug 17j, on the inner side.

  As illustrated more clearly in FIG. 4, the sensor unit 26 comprises a sensor element 28 and a magnetic element 29 respectively mounted semi-embedded and embedded inside the support 27.

  The sensor 28, for example a magnetosensitive cell, is flush with a cylindrical surface of small diameter of the support 27, so as to be mounted here facing the projection 3g of the eccentric 3, on the outside, with a small radial gap promoting the compactness of the device 1.

  The magnetic element 29 may for example comprise a permanent magnet provided with two magnetic poles of opposite polarities, north and south, extending axially inside the support 27 so that one of the poles is oriented in the direction of the sensor element 28, the other being directed outwards. The magnetic element 29 is axially aligned with the sensor 28, and offset radially outwardly relative to said sensor by being mounted at a short radial distance so as to further increase the compactness of the device 1. The magnetic element 29 creates a field magnetic sensor which is detected by the sensor 28, said field being able to be modified according to the angular position of the working eccentric 3 with respect to the sensor unit 26.

  The projection 3g and the sensor and magnetic elements 28, 29 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 27 also comprises a wire link 30 capable of communicating information relating to the electrical signals emitted by the sensor 28 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 27 of the sensor unit 26.

  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.

  When mounting the device 1, the projection 3g of the working eccentric 3 can be mounted substantially opposite the sensor 28, the gap between said eccentric and the sensor 28 is thus low. The sensor 28 thus detects a first magnetic field created by the magnetic element 29, the projection 3g being also subjected to the field lines of the magnetic element 29.

  During wear of the belt 9, the working eccentric 3 will move angularly with respect to the eccentric adjustment 2. The projection 3g will no longer be opposite the sensor 28 and the axial portion 3f of the eccentric working 3 will come opposite the sensor 28, thus causing a large variation of the air gap between said eccentric and the sensor 28. Such gap variation thus generates a modification of the magnetic field lines initially established between the element 29 and the projection 3g of the working eccentric 3, this modification of the field lines being detected by the sensor 28. In other words, the sensor 28 detects a second magnetic field different from the first.

  The axial portion 3f and the projection 3g of the working eccentric 3 thus form a target element cooperating magnetically with the magnetic element 29 to enable detection of the wear of the belt 9. In fact, it suffices that a modification brutal magnetic field detected by the sensor 28 is operated by the processing means of the device as a signal corresponding to a state of wear of the belt 9, and that the signal is transmitted to an alarm module (not shown) of the device 1, which can be for example made in the form of a light and / or sound mounted at the table (the edge of the motor vehicle to prevent the driver from achieving the predetermined level of wear and the need replace the belt.

  Of course, it is also conceivable to design a device 1 in which a large gap between the working eccentric 3 and the sensor block 26, ie the axial portion 3f opposite the sensor element 28, corresponds to an adequate voltage of the belt 9 and a reduced gap, ie the projection 3g opposite the sensor element 28, translate a predetermined wear state of said belt.

  The axial portion 3f and the projection 3g thus make it possible to obtain a target element having means capable of allowing a modification of the field created by the magnetic element, and detected by the sensor 28, as a function of the angular position of the eccentric working 3 with respect to the adjustment eccentric 2 of the fixed support 5.

  This modification of the emitted magnetic field is obtained here by the projection 3g directed radially toward the sensor block 26.

  In alternative embodiments, it is also conceivable to provide an axial portion 3f provided with at least one material recess in the form of windows or notches, for example, so that the local absence of ferromagnetic material can provoke in passing the sensor 28, a sudden modification of the field emitted by the magnetic element 29, said modification being detected by said sensor 28. It could also be envisaged to add, for example on the outer surface of the axial portion 3f, an element having different magnetic characteristics.

  The device thus makes it possible, in operation, to recover signals corresponding to the state of wear of the belt in a particularly reliable, economical and inexpensive manner, and in a particularly small radial space.

Claims (11)

  1 / belt tensioner roller device (9) provided with a fixed support adapted to maintain the device on an engine block, a working eccentric (3) angularly movable relative to the fixed support (5), d a roller (8) supported by the working eccentric and intended to be in contact with the belt, and a member able to exert a permanent force between the fixed support and the working eccentric, characterized in that the fixed support is provided with a sensor element (28) and an associated magnetic element (29) adapted to create a magnetic field in the vicinity of the sensor element (28), the eccentric comprising a target element, mounted opposite of the sensor element with an air gap and cooperating magnetically with the magnetic element, for the detection by the sensor element of a predetermined wear limit of the belt according to the angular position of the working eccentric relative to fixed support.   2 / Apparatus according to claim 1, characterized in that the target element has means adapted to allow a modification of the magnetic field created according to the angular position of the working eccentric (3) relative to the fixed support.   3 / Apparatus according to claim 1 or 2, characterized in that the mass of material of the target element facing the sensor element (28) is variable depending on the angular position of the working eccentric relative to the fixed support.   4 / Apparatus according to any one of the preceding claims, characterized in that the gap is variable depending on the angular position of the working eccentric (3) relative to the fixed support.   5 / Apparatus according to any one of the preceding claims, characterized in that the target element is provided with a portion (3f) mounted substantially opposite the sensor element with a constant air gap and a projection (3g) disposed on said portion and directed outwardly towards the sensor element.   6 / Apparatus according to any one of the preceding claims, characterized in that the air gap is radial or axial.   7 / Apparatus according to any one of the preceding claims, characterized in that it comprises a sensor block (26) inside which is embedded the magnetic element (29) and housed at least partly the sensor element ( 28).   8 / Apparatus according to any one of the preceding claims, characterized in that the target element is attached or monobloc with the working eccentric.   9 / Apparatus according to any one of the preceding claims, characterized in that the sensor element comprises a magnetosensitive cell.   10 / Apparatus according to any one of the preceding claims, characterized in that the target element comprises a ferromagnetic material.   11 / A method for controlling the wear of a belt comprising the steps in 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 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 a sensor detecting a magnetic cooperation between a target element and an element magnetic.