FR3002995A1 - BEARING ARRANGEMENT FOR A SHAFT, PARTICULARLY IN A VALVE UNIT, VALVE UNIT EQUIPPED WITH SUCH A BEARING ARRANGEMENT AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

The invention relates to a bearing arrangement for a shaft by means of at least one fulcrum, in particular in a motor vehicle valve unit, with a tube portion and a valve shaft supported on the tube portion. and a valve body secured thereto, such as a valve plate, in which the valve shaft can be rotated by an actuating means, and a valve unit equipped with such an arrangement. bearing and a method for making such a valve unit.

Description

The invention relates quite generally to a bearing arrangement for a shaft, so it is not limited to the application case described below by way of example and claimed, although it is applicable in a particularly advantageous manner, in particular by the example of a valve unit for a motor vehicle. The invention further relates to a method for forming such a bearing arrangement.

Such a valve unit may in this case consist of a tube portion and have a valve shaft, which is supported by at least one fulcrum provided on the tube portion. A valve body, such as a valve plate, is attached to the valve shaft and the valve shaft is rotatable or pivotable by means of an actuating means. Such devices are used in motor vehicles, in particular in the system of intake channels or exhaust gas, and in the latter case it is used for example in connection with the cutting of the cylinders, the recycling exhaust gases, with exhaust gas catalysts or to influence the noise produced by combustion or exhaust gases. As actuating means, cable drives, articulated links or motors, such as electric motors, are employed. In the latter case, such motors may be attached to the tube portion and form with the valve unit a pre-assembled unit. The valve shaft can, in this case, usually with the engagement of a clutch, rotate or pivot, either directly with the motor output shaft or indirectly through the output shaft of a gearbox installed downstream of the engine, and thus the flow of the corresponding flow means can be controlled. The bearing arrangement of the valve shaft can in this case be "flywheel", so be realized by means of a single fulcrum, in which it is then provided on the pipe of the exhaust gas, for the passage of the valve shaft, a bearing assembled tightly to the tube portion, in which is housed a plain bearing bushing for the support of the valve shaft. Such an embodiment is presented, for example, in DE 195 26 143. In devices, which have been disclosed in DE 10 2009 052 423, the exhaust valve is further mounted in a conical groove in the region opposite the bearing bushing inside the exhaust pipe. The single point of support and sealing is relatively expensive. More accurate bearing arrangements for the valve or exhaust valve shaft, however, are obtained by means of two bearing points with two plain bearings for the valve shaft, as known for example from the DE documents. 2008 005 992 Ul and DE 10 2006 048 713 A1, which however require two openings in the walls of the exhaust pipe and therefore two seals. In DE 20 2008 005 992 Ul, a fulcrum is provided as a seal, which furthermore has spring means and is therefore expensive. The other fulcrum is surrounded by a separate bearing housing, which is gas-tightly assembled to the tube portion. DE 10 2006 048 713 A1 discloses two bearings or spring seals. Such points of support and sealing are very expensive because of their self-adjustable constitution. The more stringent the requirements for tightness, durability and temperature resistance, or the more such temperature changes occur rapidly and rapidly, the greater the cost of the support points and the greater the cost. when expensive, especially for the materials to be used and the precision of the adjustments between the shaft and the plain bearings, and for the configuration of the seals. The object of the present invention is to configure the bearing arrangement for shafts or shafts, for example for valve units for motor vehicles, and hence such valve units, which are distinguished by economical manufacture and Simple, high sealing between shaft and plain bearing, long service life and economical manufacturing. In addition, the assembly must be simplified and cheaper. This object is achieved according to the present invention by the representation of a sliding bearing between the shaft and the bushing containing the plain bearing bush, the plain bearing bushing being deformed at least elastically. In this case, it may be interesting and sufficient for many application cases, particularly in connection with a configuration of a valve unit for motor vehicles, such as in exhaust valves, that the bearing bushing it is deformed only elastically by the application of an axial force on the plain bearing bushing and possibly the maintenance of a minimum pressure. Already by a radial expansion of the bearing which results radially inwards towards the shaft and radially outwards in the direction of the bearing, it is possible to provide a bearing arrangement with sufficient sealing by the choice of a bearing material suitable for this purpose.

In other cases, it may also be advantageous to provide a bearing arrangement in which the bearing sleeve is permanently deformed or stamped, especially in the direction of plastic deformation. In other words, here there is a targeted change of the bearing bushing to another geometry, beyond the yield strength of the material used, but within the capacity of shape change and before that there is a breakage by shearing or separation. This can be done in a particularly simple way by inserting the bearing bushing into the bushing and the shaft into the bearing bushing - or the bearing and the shaft together into the bearing bushing - and performing the plastic deformation of the bearing bushing. inside the pad. This can be done in a simple way by applying a targeted pressure on the bearing in the axial direction and / or by the displacement for example of a pressure punch over a given axial distance, the strain rate to be determined by the shape-changing capacity of the bearing bushing, the differences to be filled between the diameters or the volumes between the bushing, the bushing and the shaft, the necessary sealing of the bearing arrangement, therefore the permissible leakage when using such a bearing arrangement or seal, for example in a motor vehicle valve unit, such as an exhaust valve, the necessary flexibility or hardness of the device. It may in this case be advantageous for the bushing to be plastically deformed between 40 and 80%, preferably between 55 and 70%, and more preferably between 58 and 65% of its shape changing capacity. It has proved advantageous for such a bearing bush to use one which contains at least porous material, in particular a porous bearing material, such as graphite, in particular soft graphite, for which it is suitable. It has been found particularly advantageous to adapt the corset to a certain extent to the graphite body in order to give the components, which by their nature are soft, a certain stability or a certain stability of shape. For this purpose, an insert or support in a lattice is particularly suitable, for which it can also be provided a fabric, a nonwoven or a similar structure, for example in wire - or otherwise - the bearing material can also be introduced into such a structure. The inherently insoluble shape graphite is thus brought into a constant shape and this compound body can, as described above, be plastically deformed and maintain this deformation by the insert or support. In this case, it will be advantageous in the majority of cases to operate the deformation in a targeted manner as a function of the stroke and the pressure within limits such as destruction, disintegration or erosion of the graphite structure is avoided. Although such a valve unit with a bearing arrangement with sealing function formed in this way by plastic deformation of the bearing - or seal with bearing function - already provides, by a configuration with only one point of support for the valve shaft, significant advantages over the devices known hitherto, this type of units with two points of support, at least one of which is realized according to the invention, provides further advantages relative to comparable units known from the state of the art, in particular a simpler mounting when, according to another characteristic of the invention, the fulcrum having the embossed bearing is provided on the side of the unit valve facing the actuating means. In this case, the other point of support can be formed by a sliding bearing - which also takes up the axial support of the shaft - and which is sealed, after the introduction of the shaft from below, so from the opposite side of the actuation - before or after formation of the deformed bearing arrangement - by welding or soldering or the like or by means of a sealing cap. This may be advantageous for embodiments in which the shaft is pulled or squeezed by springs towards the actuating means. On the other hand, the bearing point formed by deformation can however also provide the function of an axial bearing, in which the shaft pushed with a shoulder, a bead or the like in the direction of the actuating means can press against an edge zone or a bead of the bearing bushing in the inner region of the valve unit. The shaft can however also bear axially in the outer region of the valve unit, in that the shaft, provided at this point with a washer or the like, can be pushed elastically against the edge region of the valve. smooth bearing. In some cases, it is also advantageous if the plain bearing is formed by deforming the bearing bushing beyond the yield point, thus further destroying the geometrical shape as described above. The invention further relates to a method of manufacturing a bearing arrangement according to any one of the claims and to units or assemblies equipped with it, in which the geometric shape of the bearing housing is modified in a housing and in the presence of a shaft, deformed permanently, and therefore deformed plastically, in particular cold-worked or deformed plastically cold or even destroyed. The invention will be explained in more detail with reference to FIGS. 1 to 3, in which FIG. 1 shows the invention in connection with an exhaust valve, elevational view; Fig. 2 shows the exhaust valve 10 in section along the line II-II; Fig. 3 shows an enlarged detail III of Figure 2 before the realization of the fulcrum according to the invention. The exhaust valve A is shown in the form of a prefabricated unit, with an exhaust pipe 1, which is introduced, for example welded, into an exhaust gas system. Lower and upper bearing points 2, 3 with bearing bushes 2a, 3a and bearing elements 4, 5 housed therein serve to support the valve shaft 6. The two bearings are assembled by examples welded to the pipe 1 in a gas-tight manner. The bearing element 4 of the lower fulcrum 2a is a sliding bearing with an axial bearing function, for which the shaft 6 is supported by a bead 6a against the lower end face of the bearing 4, in particular under the action of an axial spring force.

The lower fulcrum is closed gas-tight to the outside by means of a lid 7. A bracket 8, which is welded to the tube 1 by means of U-shaped arms, serves at the same time as a metal plate. 9 held on it for the support of the actuating means B, here a cable control. A helical spring 10 is supported on the one hand by an end 10a on an extension 9a directed upwardly of the retaining plate 9 and on the other hand by its other end 10b on a extension 12a directed downwards by a washer. lower 12. The washer 12, which is integral in rotation with the shaft 6, forms with a washer 13, on which it is fixed, the cable pulley for the core of the cable control B. The spring 10 is configured in such a way that it keeps the valve fixed on the shaft 6 in an open position, when the cable control is correspondingly released by a drive motor. In this position, the spring moves the extension 12b of the washer 12 against the extension 9b acting as a stop of the holding plate 9. The spring 10, a pressure spring, exerted by the washer 12, the shaft 6 and the bead 6a provided on it an axial prestressing on the front face of the bearing element 4. The open position of the panel 11, and thus the rest position, is represented in both FIG. 1 and FIG. in a strongly marked position. According to another characteristic of the invention, the panel 11 is here flatter with respect to the pipe 2, so it is elliptical in shape. It has a configuration deviating from the usual circular shape, in the present embodiment therefore with the large half-axis disposed horizontally. Such an embodiment is particularly - but not exclusively - advantageous in connection with valve drives, which are self-locking and in which, when no energy is required for adjustment, the energy supply is cut off. in order to save energy. In this case, drive motors may be self-locking by nature, for example braked or blocked or the like, or an assembly placed downstream of the drive motor may be provided, such as a gearbox with self-locking mechanism. blocking, like a worm drive, in the force transmission path. However, such drives have the disadvantage that, in the event of a power failure, if the panel is in the closed position, it can not be moved from this position, and the internal combustion engine stops. in an uncontrolled way. This can also happen when with the closed panel - which of course undergoes thermal expansion faster and stronger than the exhaust pipe, because it is directly in the stream of hot gases - it occurs a sudden cooling of the exhaust pipe, for example by the action of splashing water and it therefore occurs seizure of the panel especially in motorcycles, with catastrophic consequences.

In Figure 1, it can be seen that the panel 11 - shown in phantom in the closed position 11a - is of flatter shape with respect to the tube 1, at least approximately elliptical, with its small half-axis in the direction of the axis 6, so that here too, in case of failure of the actuators, a minimum flow or a targeted leak is still guaranteed (e). It has been found that a minimum leak of up to 30% may be advantageous, it is advantageously between 20 and 30%, and more preferably between 20 and 25%. However, this effect can also be obtained when the tube and / or the valve have a shape deviating from the circular shape and there is provided between them a targeted minimal leak, which is (clearly) above the slot resulting from the usual manufacturing tolerances. In this case, at least in the embodiments in which valve clogging may occur due to sudden cooling of the exhaust pipe when the valve is thermally expanded, it is advantageous to make the slot between the tube and the valve sufficiently large in the regions of the panel which are close to the shaft or axis. The support of the valve on the tube in the closed position of the valve can be achieved by the stop of the latter on at least one region further from the shaft. The configuration of the fulcrum 3 will be explained in more detail in connection with Figure 3, which shows a detail III of Figure 2.

After the introduction of the shaft 6 with the plain bearing 4 from below through the bearing bush 2a and with its upper region through the bearing bush 3a and the introduction of the bearing body 5 shown in broken lines, which is placed relatively freely between the shaft 6 and the pad 3a, the latter is stamped by the application of a predetermined force F, for example by means of a directory punch, until it reaches the shaded gray form 5a, and that a plastic discharge of the material has occurred and that the bearing element 5 is sealingly applied to the shaft 6 as well as to the sleeve 3a and that the shaft 6 is also supported. The rate of plastic deformation is also determined by, in addition to the pressure to be applied, the axial stroke of which the bearing bushing is stamped by the punch, both of which must be taken into account in order to guarantee a sufficient permanent deformation of the body. Bearing here in soft graphite and reinforced by a wire mesh, without compromising the holding of the bearing body.

Claims (20)

REVENDICATIONS1. Bearing arrangement for a shaft by means of at least one fulcrum, in particular in a motor vehicle valve unit with a pipe portion and a valve shaft supported on the pipe portion and a valve body attached thereon, as a valve plate, in which the valve shaft can be rotated by an actuating means, characterized in that the fulcrum is formed by means of a bearing housing provided on the tube portion, such as a bushing and a bearing bushing housed between the latter and the shaft and deformed at least elastically. 2. Valve unit, in particular according to claim 1, characterized in that the bearing bushing is plastically deformed. 3. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing sleeve is plastically deformed after insertion between the bearing and the shaft. 4. Valve unit, in particular according to any one of the preceding claims, characterized in that the sleeve is plastically deformed both radially outwards in the direction of the pad and radially inward towards the shaft. 5. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing bushing is plastically deformed by applying a pressure in the direction of the axis thereof. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing bush is permanently deformed within its shape changing capacity. 7. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing bushing is plastically deformed between 40 to 80% of its shape-changing capacity. 8. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing bushing is plastically deformed between 55 and 70%, preferably center 58 and 65% of its shape-changing capacity. 9. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing sleeve simultaneously represents the seal between the tube portion and the shaft. 10. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing bush is composed of a porous metal. 11. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing bush is made of a porous bearing material. Valve unit, in particular according to one of the preceding claims, characterized in that the bearing bush contains at least graphite. 13. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing sleeve is composed of soft graphite. 14. Valve unit, in particular according to any one of the preceding claims, characterized in that the bearing bush comprises a brace. 15. Valve unit, in particular according to any one of the preceding claims, characterized in that the brace is a wire mesh embedded in the bearing material. 16. A valve unit for a motor vehicle with a tube portion and a valve shaft supported thereon by two fulcrums and a valve body secured thereto, such as a valve plate, wherein the valve shaft can be rotated by an actuating means, the bearing points are respectively formed by means of a bearing housing in the form of a bearing fixed to the tube part, which each form a smooth bearing andat least that which is turned towards the actuating means contains a bearing sleeve, which is plastically deformed therein. 17. Valve unit, in particular according to claim 16, characterized in that the valve shaft is introduced into the bearing points by the opposite side of the actuating means. 18. Valve unit, in particular according to claim 17, characterized in that the fulcrum located opposite the fulcrum with the deformed bearing bush is closed gas-tight. 19. A method of forming a plain bearing for a shaft by means of a bearing bush housed in a bushing, characterized in that the bearing bushing is plastically deformed after insertion thereof between the bushing and the bushing. 'tree. 20. Process for forming a sliding bearing for a shaft, in particular according to claim 19, characterized in that the bearing sleeve is plastically deformed between 40 to 80%, preferably between 55 and 70%, and more preferably between 58 and 70%. and 65% of its fitness change capability.