FR2748809A1 - BEARING SUPPORT - Google Patents

Abstract

A bearing support (1) for a transducer is made to receive a bearing arrangement (6) for a shaft (8), the angular position of which must be followed by measuring it with a transducer. To save weight and simplify assembly, the bearing support is made of a synthetic material, which has at least about the same coefficient of thermal expansion as the material from which the bearing arrangement is made. In addition, the bearing support is manufactured in the form of an injection molded part connected to the bearing arrangement by being injected around the latter.

Description

The invention relates to a bearing support for a transducer, the support

  bearing being produced for the reception of a bearing arrangement for the shaft whose angular position must be followed by measuring it by the transducer. In inductive transducers, as can be seen for example in documents DE-41 13 745 and DE-41 27 209, parts of the sensor which rotate with the shaft to be monitored and are thus fixedly fixed relative to this shaft must be very precisely positioned and guided, when high accuracy of measurement and resolution must

be obtained.

  In order to ensure this positioning and this precise guidance, the sensor itself and the shaft to be monitored are already assembled at the manufacturer to form a unit having a housing outside of which only protrudes the end of the shaft to be monitored by the sensor. and, at another location, a connecting cable for the power supply and the transmission of the measurement data leaves the housing. This unit can then be fixedly installed by devices

  appropriate mounting at the place of use.

  The bearing support of this unit thus plays an essential role, this being on the one hand equipped or connected with the above-mentioned mounting devices and on the other hand is made to receive a bearing arrangement, by means of which the shaft to be monitored is mounted and rotatably held. It is clear that in order to obtain high measurement accuracy and resolution of the transducer, high requirements must be placed on the solidity and stability of the bearing support as well as on the clearance tolerance and to the load capacity of the connection between it and the bearing arrangement, this connection having to withstand both thrust and traction forces acting in the direction of the longitudinal axis of the shaft as well as

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  reversal moments acting transversely to this direction. In order to be able to meet these requirements over the largest possible temperature range, in which such a transducer is used, the bearing support as well as the bearing arrangement have hitherto been made of steel with high precision, adapted to each other and linked together durably for example using

glued assemblies.

  The high weight of the bearing support made of steel, which represents up to 50% of the weight of the total sensor arrangement, the costly subsequent treatment by copper plating or nickel plating, as well as the mounting process comprising a series of stages of machining, whose automation as far as possible, requires an investment

  high in devices, however, constitutes disadvantages.

  In comparison with this, the invention aims to improve a bearing support of the aforementioned type so that by satisfying all the conditions mentioned relating to the load capacity and the accuracy, a significant reduction in weight and simpler mounting

  and less expensive can be obtained.

  To achieve this object, the invention provides that the bearing support is made of synthetic material, which has at least about the same coefficient of thermal expansion as the material from which the bearing arrangement is made, and that the support of bearing is manufactured as an injection molded part connected to the bearing arrangement by being injected around

this last.

  These characteristics according to the invention take advantage of the fact that today low-cost injection moldable synthetic materials can be obtained commercially, which after their treatment has a high resistance and whose coefficient of thermal expansion is equal to or is located in the same area as that of

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  materials used for the bearing. In this way it is obtained that the high adaptation precision between the bearing arrangement and the bearing support obtained during manufacture by injection of one around the other remains unchanged over a large temperature range. and due to variations in the ambient temperature, neither a loosening of the seat of the bearing arrangement in the bearing support nor the appearance of clamping force is achieved, which could affect the easy rotation of the tree in

the bearing arrangement.

  Due to the particularly high load-bearing capacity of steel, a bearing arrangement made of this material is preferably used in conjunction with a synthetic material reinforced with particles of carbon fibers, which have a very high resistance and whose coefficient of thermal expansion can be controlled by the amount of carbon and can be adjusted preferably in a range between 10 x 10-6 and 15 x 10-6 per degree Kelvin, which is very suitable for a coefficient of thermal expansion of types of steel conventionally used for such bearing arrangements, which is located at approximately 12 x 10-6 per K. The amount of carbon at the same time ensures good electrical conductivity

always wanted.

  Since the synthetic materials impregnated with carbon fiber particles have a comparatively weak adhesion on smooth upper surfaces, to obtain a reliable fixing which can be heavily loaded with the bearing arrangement in the bearing support, these two units are connected together in a suitable shape, which, due to the arrangements according to the invention, according to which the bearing support is injected around the bearing arrangement, is possible without

additional mounting effort.

  An essential point of view of the positioning of a tree to be monitored by a transducer resides in the fact of

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  be able to withstand as high reversing torques as possible acting on the shaft transversely to its axis of rotation without deformation or reduction in the capacity of easy rotation. For this purpose, the shaft is preferably mounted by means of two bearings arranged axially in spacing, in particular ball bearings whose axial distance should be on one side as large as possible, but which on the other hand, due to the low construction height often required for the transducer, most of the time it can exhibit only a fraction of the

  axial length of each of the two bearings.

  It is thus customary to provide between the two bearings a spacer ring of corresponding thickness, which according to the state of the art has the same outside diameter or an outside diameter barely smaller than the two bearings, such so that it can be slid together with these into the through cylindrical bearing bore of a

  bearing support also made of steel.

  In comparison with this, this spacer ring has, according to a preferred embodiment of the invention, a different outside diameter, in particular the largest, than the two bearings, so that it projects radially beyond of their envelope surfaces. If such a bearing arrangement engaged on the shaft to be mounted and prestressed at this point is introduced into the injection molding form for the bearing support and a synthetic material is injected around, then one also obtains, when the support bearing has flush front surfaces with the free front surfaces of the two bearings and thus presents in this zone the shortest possible axial length, a connection adapted in shape between the bearing arrangement and the bearing support, which can also be supported significant forces acting in the direction of the shaft axis since the spacer ring, preferably made of steel, fully embedded with its area projecting from the material

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  Synthetic bearing support is no longer stressed by such forces than by shearing. If this load capacity is subject to lower requirements then the spacer ring may also have a smaller outside diameter than the two bearings. When injected around, a bead projecting radially inside the otherwise cylindrical opening surrounding the bearing arrangement is then created on the bearing support, the bead projecting between the two bearings

  and secures them against axial displacement.

  If synthetic materials with a higher treatment temperature are used for the injection around, then there is the danger that the bearing grease will become too hot when injected immediately around the bearing. In these cases, it is provided according to an advantageous variant that the bearing arrangement comprises a preferably metallic bearing bush, in which the

  bearings are mountable before or after injection around.

  These variants and advantageous and other possible embodiments of a bearing support according to

  the invention are set out in the claims

  dependent. The invention will be described hereinafter by means of embodiments with reference to the drawings, in which: - Figure 1 is an axial section through a first embodiment of a bearing support, in which the ring spacing disposed between the two bearings protrudes radially, and - Figure 2 is a section corresponding to the section of Figure 1 through a second embodiment in which the two bearings are surrounded by a sleeve

essentially cylindrical bearing.

  The bearing supports shown in the figures are respectively produced in the form of mounting flanges

  of essentially radial symmetry.

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  Each of the bearing supports 1, 1 'has a substantially cylindrical through central opening, in which a bearing arrangement 6, 6' comprising two ball bearings 3, 4 and a spacer ring 5, 5 'is positioned such that the shaft 8 mounted in the two bearings 3, 4, whose rotary movement must be followed by measuring it by a sensor not shown, extends coaxially to the axis of symmetry of the bearing support 1, 1 '

through this one.

  In the embodiment shown in Figure 1, the spacer ring 5 between the two ball bearings 3, 4 arranged axially one behind the other has an outside diameter such that it projects in the direction radial beyond the surface of the outer casing of the ball bearing and thus engages in a peripheral groove formed in the cylindrical internal surface of the through opening of the bearing support 1. This peripheral groove is produced during manufacture according to the invention of the arrangement shown automatically in that the bearing support 1 made of synthetic material reinforced with particles of carbon fibers is injected around the arrangement of

  bearing 6 already engaged on the shaft 8 and prestressed.

  The aforementioned preload is obtained in that the two rings of internal bearings 10, 11 are pressed against each other after introduction of the shaft 8 in the axial direction. This creates an O-shaped prestressed bearing arrangement. During the injection molding process, with which the bearing support 1 is produced, several stop or mounting pins 14 are simultaneously injected, of which only two are shown. in the figures. These mounting pins extend parallel to the axis of rotation of the shaft 8 and protrude with a large part of their length on the front surface of the

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  bearing support 1 located at the top in the figures. They serve to maintain in a defined position the parts not shown of the transducer which do not rotate together with the shaft 8. The ends of the mounting pins 14 embedded in the mass of synthetic material of the bearing support 1 can be provided for the obtaining a suitable connection in the form of a groove

  or an end thickening not shown.

  As can be seen in Figure 1, the front surfaces of the bearing support 1 beyond which the mounting pins 14 project, include an edge bead 15 projecting in the axial direction and extending over the entire the periphery, the cylindrical internal surface of which serves for an adjusted reception of a measurement chamber 18, which belongs to the measurement part of the transducer not shown and of which in FIG. 1 is shown only the part connected to the bearing support 1 serving as case back. On the cylindrical outer surface of the edge cord 15 is engaged a housing cover surrounding the transducer, also only the part directly adjacent to the support of

level 1 is shown.

  The front surface of the bearing support 1 facing the inside of the housing, beyond which the mounting pins 14 protrude, is covered by an electrically conductive plate 20, preferably made of metal, which has a central opening 21 through which the shaft 8 projects inwards. The diameter of this central opening 21 is approximately equal to the internal diameter of the outer bearing ring 23 of the ball bearing 3 so that the plate 20 projects with its internal edge beyond the through opening of the support of level 1 receiving the level arrangement and

  thus contributes to the fixing of the bearing arrangement.

  The anchoring of the plate 20 in the bearing support 1 is obtained in that the plate 20 has projections

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  peripherally spaced radials 25 of which only one is shown in the figures; these projections 25 extend through the edge bead 15 over a length such that they extend freely with their peripheral edges on its cylindrical outer surface and can thus come into electrically conductive engagement with

  the housing cover 17 which is arranged above.

  In this way, the plate 20 is suitably connected in shape with the bearing support 1 and forms with the cover 17 also made of electrically and magnetically conductive material a Faraday cage which protects the interior space of the housing in which is located the

  transducer against stray fields.

  From the previous description, we get that the

  plate 20 is also positioned before injection molding of the bearing body 1 together with the bearing arrangement 6 in the injection mold of the bearing body 1

  and is connected to it by injection around it.

  In the embodiment shown in Figure 2, the spacer ring 5 'has between the two bearings 3, 4 the same outside diameter as these and is surrounded together with them by a substantially cylindrical bearing bush 28 produced made of metal, in which the two bearings 3, 4 and the spacer ring 5 'can

  be arranged before or after the injection around.

  The bearing bush 28 has the advantage that it allows for injection around the use of synthetic materials having higher injection molding temperatures, because they prevent, by its thermal capacity, overheating of the bearing grease of the bearings

  3, 4 already introduced before the injection around.

  When the bearings 3, 4 and the spacer ring 5 'are already disposed in the bearing bush 28 before injection around it, the synthetic material injected around can then, as shown in Figure 2 , not only surround at least partially the

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  front surface of the bearing sleeve 28 located at the bottom in this figure but also. corresponding front surface of the bearing 4 and thus fix so

this level.

  If synthetic materials with even higher temperatures are used for injection around them, then the empty bearing sleeve is first injected around and the bearings 3, 4 with the shaft 8 and the spacer ring 'are introduced after cooling. In this case, contrary to what is shown in FIG. 2, the passage opening 29 of the material injected around must have the same internal diameter as the bearing bush 28, so that the two bearings 3, 4 can be engaged by the opposite front sides, to obtain the aforementioned O-shaped preload already mentioned. As can also be seen in FIG. 2, the bearing bush 28 made of metal has on its upper front side in this figure a radial flange 20 ′ , which fulfills the same function as the plate 20 described with reference to FIG. 1. This radial flange 20 ′ is produced with a comparatively large axial thickness, in order to increase the above-mentioned thermal capacity of the

bearing bush 28.

  Another peculiarity of the exemplary embodiment of FIG. 2 resides in the fact that here the mounting pins 14 ′ are produced from the same synthetic material as the bearing support 1 ′ and are manufactured

  together with this during the injection process.

  Also in this embodiment, an edge bead 15 'is provided which surrounds an edge 30 projecting in the axial direction of the flange 20' of the bearing bush 28. The opening 31 surrounded by the edge bead 15 ' has a frustoconical internal surface which widens from the cylindrical internal surface of the edge 30 towards

outside.

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  This arrangement has the advantage that the bearing bush 28 can be manufactured very precisely with its flange 28 'and the edge 30 as a rotating part and thus allows an even more adjusted positioning of the measurement chamber 28 omitted on the figure 2 (see figure 1). In both embodiments, the bearing support 1, 1 'can simultaneously serve as a mounting flange for the transducer as a whole. For this purpose, it comprises mounting bores 36 extending parallel to the shaft 8 from the external front surface and provided with an internal thread, a single bore being

shown in the figures.

  Except for the respective edge cord 15, 15 ', each of the bearing supports 1, 1' has an axial length which is substantially equal to the axial length of the bearing arrangement 6, 6 ', which in turn corresponds to the lengths axial of the two ball bearings 3, 4 as well as the thicknesses of the spacing rings 5, 5 ', and of the plate respectively of the edge 30. This gives a minimum axial construction length which it would not be possible to '' if the front surfaces of the ball bearings outside were injected around for the

  manufacture of a connection adapted in shape.

  In certain application cases, in which the protection of the transducer and its electronics are not subject to particularly high requirements, the electrical conductivity of the synthetic material used for the manufacture of the bearing support 1, 1 ′ is sufficient so that in the exemplary embodiment according to FIG. 1, one can dispense with the plate 20 and one can obtain an axial length reduced to the minimum value imposed by the

bearing geometry.

  As an alternative to a radially protruding spacer ring 5, it is also possible in this variant to use a spacer ring which has a considerably smaller outer diameter than the outer rings il- 2748809 of the ball bearings 3, 4. In this case , the bearing arrangement is ensured against axial displacement by a bead of synthetic material projecting inwardly which is obtained automatically during the injection around the bearing arrangement. As indicated by the thickened outer edge lines in the figures of the ball bearing 4, the outer ring 23 of this ball bearing has at its outer edge of the front surface a chamfer so that, during injection around with the synthetic material of the bearing body 1, a smaller edge protruding inwards its shape which also contributes to

  fixing the bearing arrangement.

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Claims (17)

Claims:   1.- Bearing support for a transducer, the bearing support being produced for the reception of a bearing arrangement for the shaft whose angular position must be followed by measuring it by the transducer, characterized in that the support of bearing (1; 1 ') is made of synthetic material, which has at least about the same coefficient of thermal expansion as the material from which the bearing arrangement (6; 6') is made, and in that the support bearing (1; 1 ') is manufactured in the form of an injection molded part connected to the bearing arrangement (6, 6') by being injected around this last.   2.- bearing support according to claim 1, characterized in that the bearing arrangement (6; 6 ') is made of steel and the coefficient of thermal expansion of the synthetic material used for the bearing support (1 1') is located in the area from 10 x 10-6 to 15 x 10-6 by Kelvin degree.   3.- bearing support according to claim 1 or 2, characterized in that the bearing arrangement (6; 6 ') and the bearing support (1; 1') are connected together so adapted in shape.   4.- bearing support according to one of claims   previous, characterized in that the bearing arrangement (6; 6 ') comprises two bearings (3, 4) arranged one behind the other in an axial direction, between which is arranged a spacer ring (5; 5 ').   5.- bearing support according to claims 3 and 4,   characterized in that the outside diameter of the spacer ring (5) is clearly different from that of the two bearings (3, 4).   6.- bearing support according to claim 5, characterized in that the spacer ring (5) comprises a 13 2748809   outer diameter significantly larger than that of the two bearings (3, 4).   7.- bearing support according to claim 3 or 4, characterized in that the bearing arrangement (6 ') comprises a bearing bush (28) in which the two bearings (3, 4) are mountable.   8.- bearing support according to one of claims   above, characterized in that it is mainly produced with a symmetry of revolution so that its axis of symmetry merges with the longitudinal axis of the shaft (8) which is mounted therein.   9.- bearing support according to one of claims   above, characterized in that it is produced in the form of a flanged bottom of the housing receiving the transducer and in that it comprises mounting pins (14; 14 ') projecting parallel to its axis of symmetry at -from one of its front faces to hold the parts of the   transducer fixedly fixed relative to the shaft (8).   10.- bearing support according to claim 9, characterized in that the mounting pins (14) are made of steel, are injected together with the bearing support during its injection molding, and comprise for obtaining a suitable connection in the form of a   groove in the area of its injected ends.   11.- bearing support according to claim 9, characterized in that the mounting pins (14 ') are made in one piece with the bearing support (1') during its injection molding.   12.- bearing support according to one of claims 9   to 11, characterized in that there is provided an electrically and magnetically conductive protective element (20; 20 '), approximately in the form of a plate, substantially covering the surface of the front face beyond which the mounting pins protrude (14; 14 '), and simultaneously injected into the bearing support (1; 1'), said protective element being, in the assembled state, in 14 2748809   electrically conductive connection with an electrically conductive housing cover (17) disposed on the support bearing (1; 1 ').   13.- bearing support according to claim 12, characterized in that the protective element (20) is surrounded by an edge bead (15) of the bearing support, said element passing radially through said edge bead in at least an angular segment area such that the element rests freely on the peripheral outer side of the edge cord (15) and can here engage in an electrically and magnetically conductive manner with the internal surface of the housing cover (17) engaged on the edge cord (15).   14.- bearing support according to claim 12, characterized in that the protective element (20 ') is formed by a flange extending substantially radially   connected in one piece with the bearing bush (28).   15.- bearing support according to one of claims 3   to 14, characterized in that the two bearings (3, 4) are ball bearings, which are prestressed so that after the engagement of the shaft (8) to be mounted in the two internal bearing rings ( 10, 11), these have been closed   pressing them one on the other in the axial direction.   16.- bearing support according to one of claims   previous, characterized in that the bearing support (1; 1 ') is made from a synthetic material having   good electrical conductivity.   17.- bearing support according to one of claims   previous, characterized in that the bearing support (1; 1 ') is made of a synthetic material reinforced with   carbon fiber particles.