DE102009031190A1 - Controllable belt pulley device for use in motor vehicle, has inner drive element whose sliding path comprises coating, which possesses specific Vickers hardness under specific load and exhibits specific thickness - Google Patents

Abstract

The device (1) has an inner drive element (3), and a belt pulley (2) mounted on the inner drive element. A free-wheel (6) comprises multiple clamping elements i.e. cams (19), that are arranged between a sliding path (20) of the belt pulley and a sliding path (21) of the inner drive element. The free-wheel unidirectionally synchronizes the belt pulley and the internal drive element. The sliding path (21) comprises a coating (30), which possesses a Vickers hardness between 1.500 and 3.000 under a load of 0.05 kilograms and exhibits a thickness between 1 and 5 micrometer.

Description

The Invention relates to the field of freewheels.

Especially the invention relates to the field of switchable pulleys, which are equipped with freewheels, as they are for example at the drive pulleys of alternators in a motor vehicle be used.

such Switchable pulleys are known and are always more used to the harmful effects of acyclic behavior or to counteract if the engine slows down suddenly, which occur in internal combustion engines, especially at lower Speed and especially in diesel engines.

One Drive belt, which via a crankshaft pulley with the Motor is connected, namely suddenly can slow down while using an adjustment disc, for example a pulley of the alternator, due to inertia tends to continue to turn at the same speed.

in the Case of a rigid coupling between the crankshaft pulley and the generator shaft is the belt at these sudden Speed fluctuations subjected to very high loads.

such Fluctuations have harmful effects, such as unusually heavy wear of the belt with Risk of breakage, slipping of the belt on the pulley or vibration the belt ribs between the pulleys.

Around to mitigate these phenomena was between the adjusting disc and the output shaft inserted a freewheel, with which it is possible in case of a sudden slowdown the pulley to temporarily disengage it from the shaft.

From the document JP-A-2007278364 is known a switchable pulley having a rolling bearing for the bearing of the pulley on an inner gear shaft and a spring freewheel. To avoid premature abrasion between the spring and a slideway of the pulley with which it cooperates, a carbon coating similar to diamond is provided on both the spring and the slideway of the pulley.

It are also switchable pulleys of the type known two rolling bearings arranged on each side of the pulley are, and has a freewheel between the two rolling bearings is attached and provided with a plurality of clamping cam.

With such switchable pulleys occurs in a freewheeling operation a slip between the clamping cam and an inner track, on the the cams are sitting up. Is this contact zone badly lubricated, can cause premature wear of the cams to form flats occur on them, resulting in malfunctions of the freewheel and more generally the pulley can guide.

by virtue of The rotation of the inner web tends the fat to, ejected from the web to be, and the sliding contact between the cam and the inner race could be done under bad lubrication conditions.

task The present invention is therefore to eliminate this disadvantage.

task In particular, it is the object of the present invention to provide a simply designed, provide switchable pulley, the cheap to produce and components to be assembled includes and a good reliability having.

The switchable pulley device comprises an inner drive element, a pulley mounted on the inner drive element is, and at least one freewheel, with a plurality of clamping elements is provided between a slideway of the pulley and a slideway of the inner drive element are arranged, wherein the freewheel is intended to provide a unidirectional entrainment between to ensure the pulley and the inner drive element.

According to one general feature, the slideway of the inner drive element a coating that under a load of 0.05 kg a Vickers hardness, which is between 1500 and 3000 Hv, and a thickness that is between one and five microns, having.

The Coating advantageously has a coefficient of friction Steel above or equal to 0.2.

at One embodiment contains the coating amorphous carbon similar to diamond. In a variant For example, the coating may contain chromium nitride or titanium nitride.

In one embodiment, the coating is disposed directly on the slide track. Alternatively, the slideway carries at least one intermediate layer between itself and the coating. The Zwi can have titanium or tungsten.

The Clamping elements can also at least partially a Have coating that is identical to the coating of the inner Drive element is.

at In one embodiment, the device has a cage for the clamping elements and at least one elastic return element on which endeavors, the clamping elements in contact with the slideways at an engaged position and at a disengaged position to keep the freewheel.

The Coating is advantageously on the slide in a radial Area with respect to window of the cage provided, the intended to hold the clamping elements. This area has an axial dimension substantially equal to that the window is.

The Pulley advantageously has a single cage for the clamping elements. The cage is preferably integrally.

at An embodiment is at least one elastic restoring element placed between each clamping element and the cage.

The elastic return element is preferably radially between the cage and the inner drive element arranged.

at In one embodiment, the freewheel engages Cams on.

at In one embodiment, the device comprises at least one and preferably two rolling bearings, wherein the freewheel is arranged axially between the two rolling bearings.

The Switchable pulley device can be mounted on an alternator shaft be mounted to drive the alternator. The pulley can on a central shaft, in particular via a freewheel, be mounted. The drive shaft can be on the shaft of the alternator be mounted. A drive belt driven by the engine can sit on a perimeter of the pulley.

thanks of the freewheel, the pulley drives the central shaft when the engine accelerates or is in a substantially continuous speed range or slowing down very slowly. In a sudden Slowing down the engine and thus the pulley can become the Central axis of the switchable pulley device through the Freewheel continues to turn faster than the actual pulley, causing excessive stresses on the Drive belt can be avoided.

By the pulley device are in an engaged position and in a disengaged position of the freewheel, usually the Clamping elements in constant contact with the slideways which makes it possible, almost instantaneously from a freewheeling position to a position of the torque pickup and vice versa.

This is particularly advantageous when used in an alternator, the acyclic behavior is characterized by extremely fast fluctuations the rotational speed of the engine, which requires a good responsiveness of the device.

The Invention also allows the wear of the clamping elements, the perfectly lubricated on the outer track Clamping disk during the rotation of the device slide, limit, where the inner path of the inner drive element, at least partially coated with the coating under a load of 0.05 kg a Vickers hardness between 1500 and 3000 Hv and has a thickness between one and five microns. These two ranges of values allow good hardness and abrasion resistance values. Furthermore, it is possible by using a coating that has a coefficient of friction with steel greater than or equal to 0.2, operation under restricted lubrication conditions achieve, while at the same time an almost immediate transition from a freewheeling position to a position of the torque pickup and vice versa.

The The present invention will be more readily understood when reading the detailed description of an embodiment, the example given as by no means limiting and is illustrated by the attached drawing, wherein:

1 a sectional view of a switchable pulley device according to the invention;

2 a partial view in axial section along the axis II-II in 1 is; and

3 a perspective view of the switchable pulley device 1 is.

As in the 1 to 3 can be seen, includes the switchable pulley device 1 a pulley 2 , an internal drive element 3 , for example, a hollow shaft, two rolling bearings 4 and 5 as well as a freewheel 6 ,

The pulley 2 with a geometric axis 7 has an outer surface that has a grooved area 2a with annular grooves and an axial area 2 B , which at one axial end of the grooved area 2a is formed, is provided. The pulley 2 includes a cylindrical bore 2c extending over the entire length of the pulley 2 extends, except for chamfers (not designated), which are each arranged at one axial end, and two radial end faces 2d and 2e ,

The inner drive element 3 , which is in the form of a hollow shaft, has a cylindrical axial outer surface 3a on which a chamfer (not designated) is provided at each of the axial ends. The inner drive element 3 also has a hole 3b on, a part of 3c a thread for attachment to the end of an alternator shaft and for driving the shaft (not shown). Axially opposite to the hole 3b has the inner drive element 3 inside grooves 3d for clamping the element on the alternator shaft by means of a suitable tool cooperating with the grooves.

The rolling bearing 4 , coaxial with the axis 7 lies, includes an inner ring 8th and an outer ring 9 , between which a number of rolling elements 10 , here in spherical form, are housed a cage 11 for obtaining the circumferential space of the rolling elements 10 , and a seal 12 ,

The inner ring 8th includes a cylindrical bore 8a that with the outside surface 3a of the inner drive element 3 connected and by two opposite radial side surfaces 8b and 8c is limited, as well as a stepped cylindrical outer surface 8d on which a circular circumferential groove 8e is formed, which has a concave inner profile in cross-section, which is a raceway for the rolling elements 10 can form, the groove is directed outwards.

The outer ring 9 includes a cylindrical outer surface 9a into the hole 2c the pulley 2 is pressed in and through the end faces 9b and 9c is limited, and a cylindrical stepped bore 9d in which an annular circumferential groove 9e is formed, which has a concave inner profile in cross-section, which elements a career for the Wälzele 10 can form, which is directed to the outside. The hole 9d here comprises two annular grooves (not designated), with respect to a plane passing through the center of the rolling elements 10 runs, symmetrical to each other. Inside the annular groove, located on the outside of the rolling bearing 4 is the seal 12 attached to the cylindrical outer surface 8d of the inner ring 8th slides to form a seal. The seal 12 is radially between the inner ring 8th and the outer ring 9 arranged and axially between the rolling elements 10 and the radial surfaces 8b and 9b The Rings 8th and 9 assembled. The surfaces are axially at the same height as the radial end face 2e the pulley 2 ,

Accordingly, the rolling bearing 5 , coaxial with the axis 7 runs, an inner ring 13 that with the outside surface 3a of the inner drive element 3 connected, and an outer ring 14 that in the hole 2c the pulley 2 is pressed between which a number of rolling elements 15 , here in spherical form, are housed a cage 16 for obtaining the circumferential space of the rolling elements 15 , and a metal gasket 17 , The rolling bearing 5 is identical to the rolling bearing 4 and is arranged symmetrically with respect to this, relative to a radial plane passing through the center of the pulley 2 runs. The rolling bearing 5 is axially slightly recessed in relation to the radial end face 2d the pulley 2 ,

The rolling bearings 4 and 5 So are at each axial end of the pulley 2 arranged, with the freewheel 6 is mounted axially between them. The freewheel 6 thus experiences a protection against the ingress of foreign elements by the bearings 4 and 5 and in particular by the seals 12 and 17 ,

The freewheel 6 includes a plurality of clamping elements or cams 19 between two slideways 20 and 21 are arranged in a rotating cylindrical shape. The cams 19 are "engaging", that is to say, under the effect of centrifugal force during rotation of the freewheel, they usually tilt in the direction that their blocking between the two slideways 20 and 21 favored to facilitate an almost immediate transition of the freewheeling operation in the operation for torque tapping.

The slideway 20 is right through the hole 2c the pulley 2 educated. The slideway 21 is directly through the axial outer surface 3a the wave 3 educated.

In other words: the pulley 2 can be made with a completely axial inner surface of a particularly simple shape, with the exception of the Endfasen 2d and 2e , The pulley 2 can therefore be produced at low production costs. This inner surface forms an outer bearing surface or a large diameter bearing surface for the cams 19 ,

On the opposite side is the slideway 21 on the outside surface 3a the wave 3 educated. The outer rotary profile of the shaft 3 has the same diameter over its entire length. The Finishing can be done in a single pass on a grinder and it is possible to use the slideway 21 with small diameter or as inner bearing surface for the cams 19 of the freewheel 6 standard and inexpensive to obtain.

The freewheel 6 also includes a generally annular cage 22 , which may be made of a metallic material, in particular of steel, or of a plastic, such as polyamide.

The cage 22 includes an axial section 23 and two radial sections 24 . 25 , The radial section 24 extends an axial end of the axial section 23 located near the camp 4 located radially outward while the radial section 25 an axial end of the axial section 23 located near the camp 5 is extended radially inward. The free ends of the radial sections 24 and 25 stay at a distance from the hole 2c the pulley 2 or from the outer surface 3a of the inner drive element 3 ,

The cage 22 also includes a plurality of windows 26 in the axial section 23 are arranged and a receiving seat for the cam 19 form. The window 26 are arranged at a uniform distance from each other in the circumferential direction. The cage 22 allows the cams 19 circulating at regular intervals. It may be made of a metallic material, in particular of steel, or of a plastic, such as polyamide.

The freewheel 6 also has a spring 27 on, which is in the form of an annular, rolled-up metal strip, which is joined to one another with the ends or with partial coating. The feather 27 is inside the cage 22 mounted and in particular radially between the outer surface 3a of the drive element 3 and the axial section 23 of the cage 22 arranged. The feather 27 is located axially between the radial sections 24 and 25 of the cage 22 ,

The feather 27 also has cells or windows 28 on, those of the cage 22 correspond to the cams 19 to mount. Therefore, the windows are 28 arranged at a uniform distance over the circumference.

The feather 27 is also with at least one elastic return element 29 per cam 19 provided, which is designed in the form of a tab, which originated from the edge of a window and is provided on a for this purpose on the associated cam 19 to lie upright surface to exert a tilting moment with which the cams 19 in contact with the slides 20 and 21 should be kept. In a static position practice the reset elements 29 one radial to the pulley 2 out directed force.

In a variant, a single return element connected to each cam could be used to exert a force to make permanent contact with the slideways 20 and 21 maintain. It would be possible, for example, for each of the cams 19 an elastic return spring, which is between the cam 19 and the cage 22 is arranged to assemble.

To the abrasion between the cams 19 and the slideway 21 of the inner drive element 3 To limit, this has a coating 30 on. The coating 30 has a thickness between 1 and 5 microns and a Vickers hardness, which is at a load of 0.05 kg between 1500 and 3000 Hv. With such value ranges of the coating 30 At the same time good hardness and abrasion resistance values can be achieved for the slideway 21 achieve. The friction coefficient of the coating 30 with steel is advantageously greater than or equal to 0.2, to the friction between the slideway 21 and to limit the cam and allow operation under limited lubrication conditions.

In one embodiment, the coating contains 30 amorphous carbon similar to diamond. Amorphous carbon similar to diamond is known internationally as DLC. The DLC coatings offer numerous advantages, especially their self-lubricating properties, their abrasion, adhesion and corrosion resistance. As a variant, the coating can 30 Chromium nitride or contain titanium nitride.

The coating 30 gets on the slideway 21 of the inner drive element 3 applied in the form of a hard layer. The coating 30 can be applied in a manner known per se by conventional industrial techniques, such as vacuum deposition or gas phase deposition.

The coating 30 can jump on the slide 21 can be applied, which then represents a substrate and can be made of steel 100C6, for example. Alternatively, the coating 30 be placed on one or more liners, previously on the slideway 21 be applied. Such intermediate layers may comprise, for example, titanium or tungsten.

The coating 30 So it's on the slideway 21 of the inner drive element 3 applied that they are the axial bearing surface of the web, the with the cams 19 to cooperate, covered. The coating 30 is on the slideway 21 in a radial area with respect to the windows 26 and 28 provided, in an axial zone which is substantially equal to the window and continues in the circumferential direction. In this way, the amount of coating to be applied is reduced.

To further limit the risk of premature wear, it is also possible to additionally provide on the cams 19 to apply a coating to the coating 30 is identical to them completely or at least partially on the section that is using the slideway 21 cooperates, to cover.

The operation of the freewheel 6 is the following. At a stabilized speed or at an acceleration of the pulley 2 tend the cams 19 under the effect of centrifugal force and by contact with the slideways 20 and 21 to tilt in a first direction, which makes it possible, by tilting between the two slideways blocking with the two slideways 20 and 21 the pulley 2 and the inner drive element 3 to obtain. The freewheel 6 works as a torque cam, ie it is engaged and transmits a drive torque between the pulley 2 and the inner element 3 ,

With a sudden slowdown of the pulley 2 in contrast, the cams tend 19 to tilt in a second direction opposite to the first, causing the release or release of the cams 19 caused. The freewheel 6 then transmits no more torque and allows temporary relative rotation of the pulley 2 with respect to the inner drive element 3 , The freewheel 6 thus ensures a unidirectional coupling between the pulley 2 and the drive element 3 ,

In this disengaged position, the elastic return elements 29 between the only cage 22 and the cam 19 are arranged, the inclination sliding contact between the cams 19 and the slideway completely lubricated by the centrifugation 20 the pulley 2 which tends to cause the lubricant, for example, grease, to be blown outward. During the temporary state between the transition from the engaged position to the disengaged position or vice versa, the relative arrangement of the elastic return elements allows 29 and the cage 22 it also, a sliding contact between the cams 19 and the slideway 21 maintain.

In the disengaged position, there is a relative displacement between the slide 21 of the inner drive element 3 and the cam 19 with contact. The provision of the coating 30 on the area of the outer surface 3a in contact with the cams 19 allows the abrasion between the cams 19 and the slideway 21 Significantly reduce and improve the sliding conditions of the cams on the web in a poorly lubricated by the Zentrifugie ren, Thus, the premature formation of flats on the sole of the cams 19 avoided, which would lead in the long term to the failure of the device.

The coating 30 Therefore, in this frictional region, it allows the device to operate under restricted lubrication conditions while reducing the coefficient of friction between the cams 19 and the slideway 21 is reached in order to limit the wear of these elements.

Further, the use of a coating 30 having amorphous carbon similar to diamond or chromium nitride or titanium nitride, is particularly advantageous in that its implementation is relatively simple with conventional industrial processes.

thanks The invention thus provides a switchable pulley device available, which allows the wear to limit the Klemmnocken, which on an outer Trajectory of the pulley, which during rotation of the device completely lubricated, and slide on an inner track of the drive shaft, which at least partially has a self-lubricating coating and at the same time has a high abrasion resistance.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 2007278364 A [0008]

Claims (12)

Switchable pulley device with an internal drive element ( 3 ), a pulley ( 2 ) mounted on the inner drive element ( 3 ) is mounted and at least one freewheel ( 6 ), which is provided with a plurality of clamping elements ( 19 ) provided between a slideway ( 20 ) of the pulley and a slideway ( 21 ) of the inner drive element ( 3 ) are arranged, wherein the freewheel is intended to unidirectional entrainment between the pulley ( 2 ) and the inner drive element ( 3 ), characterized in that the slideway ( 21 ) a coating ( 30 ) which, under a load of 0.05 kg, has a Vickers hardness of between 1,500 and 3,000 Hv and a thickness of between 1 and 5 μm. Device according to claim 1, in which the coating ( 30 ) has a coefficient of friction with steel above or equal to 0.2. Device according to claim 1 or 2, in which the coating ( 30 ) contains amorphous carbon similar to diamond. Device according to claim 1 or 2, in which the coating ( 30 ) Contains chromium nitride. Device according to claim 1 or 2, in which the coating ( 30 ) Contains titanium nitride. Device according to one of the preceding claims, wherein the coating directly on the slideway ( 21 ) is arranged. Device according to one of claims 1 to 5, wherein the slideway ( 21 ) between itself and the coating ( 30 ) carries at least one intermediate layer. Apparatus according to claim 7, wherein the intermediate layer made of titanium or tungsten. Device according to one of the preceding claims, in which the clamping elements ( 19 ) at least in one area have a coating which is identical to the coating of the slideway ( 12 ). Device according to one of the preceding claims, comprising a cage ( 22 ) for the clamping elements and at least one elastic return element ( 29 ), which endeavors to bring the clamping elements in contact with the slideways ( 21 ) to hold at a coupled position and a disengaged position of the freewheel. Device according to Claim 10, in which the coating ( 30 ) on the slideway ( 21 ) in a radial area with respect to windows ( 26 ) of the cage ( 22 ) is provided, which are intended, the clamping elements ( 19 ), this region having an axial dimension approximately equal to that of the windows. Generator comprising a shaft and a switchable pulley device according to one of the preceding claims, comprising the shaft is mounted.