DE102008047724A1 - Sliding disc in a sprag clutch - Google Patents

Abstract

The invention relates to a sliding disk (8) made of sheet steel for the arrangement between an inner ring and an outer ring of a clamping body freewheel coupling (1), with a radially extending portion (9) and at its inner edge and outer edge adjoining axial sections (10, 11). each having an inner surface (13, 15) and an outer surface (14, 16), at least the outer surfaces (14, 16) having a Nitrocarburizing, enriched with nitrogen and carbon, wear and corrosion resistant edge layer. Furthermore, the invention relates to a method for producing such a sliding disk (8), wherein the sliding disk (8) is produced by deep drawing by means of a thermoforming tool from a Stahlblechronde and then the nitrocarburizing is performed.

Description

Field of the invention

The The invention relates to a sliding plate made of sheet steel for arrangement between an inner ring and an outer ring of a sprag one-way clutch with a radially extending portion and at its inner Border and outer edge adjoining axial sections, each with an inner surface and an outer surface. Furthermore, the invention relates a method of making the sliding washer and the use different types of steel for the sliding disk.

Background of the invention

A sliding disk of the type mentioned is, for example, from the DE 10 2005 046 799 A1 known. This sliding disk has a nickel-phosphor coating, whereby very good wear properties are achieved, which is given because of the use of steel as the base material of the sliding disk, the same coefficient of expansion as for the other steel components of the sprag clutch overrunning clutch. This nickel-phosphorus coating has proven itself, but is expensive to manufacture, albeit less expensive than the production of sliding plates made of a copper alloy, for example, in the DE 299 04 524 U1 is described.

Object of the invention

Of the Invention is therefore the object of a sliding disk for a freewheel clutch that is under changing conditions, in particular fluctuating temperatures, is operated, in terms of manufacturing costs to improve.

Summary of the invention

These The object is achieved by a sliding washer with the features of claim 1, by a method with the features of claim 10, and by the use of certain Steel grades for the production of the sliding disk according to Claim 13. Advantageous embodiments of the invention result from the dependent claims 2 to 9 and 11 and 12.

According to the invention at least the outer surfaces of the inner Edge and outer edge of the radially extending Section subsequent axial section of the sliding disk with one produced by nitrocarburizing, with nitrogen and carbon enriched, wear-resistant and corrosion-resistant surface layer Mistake.

The Nitrocarburizing is a thermochemical enrichment process the surface layer of a workpiece with nitrogen and carbon. This results in a nitriding layer consisting of a bonding layer and diffusion layer. Enriching the surface layer of a workpiece with nitrogen and carbon can be carburized by gas-nitruc, Salt bath nitrocarburizing or plasma nitrocarburizing perform. Gas nitrocarburizing is carried out at temperatures between 500 ° C and 600 ° C in a gas mixture containing nitrogen (eg ammonia) and carbon (eg, carbon dioxide) can give Runaway leads. The aim is to reduce the wear resistance and corrosion resistance from low- to medium-alloyed steels. In salt bath nitrocarburizing, components are made from low to medium alloyed Steels and cast iron in a molten salt at temperatures from 550 ° C to 630 ° C. As advantages of Procedure apply the short duration of treatment and the high generated Wear resistance and corrosion resistance. As Salzbadkomponenten serve alkali cyanates and alkali carbonates, the spent salts may be during the reaction be replenished. By means of plasma nitrocarburizing can be even high-alloyed steels harden in the surface layer. The components are used at temperatures of 350 ° C to 600 ° C treated with ionized gas. As a rule, no mechanical After treatment of the parts required.

Especially is the sliding washer according to the invention from nitrocarburiertem Sheet steel cheaper to produce than a sliding washer made of bronze-plated sheet steel, nickel phosphor-coated steel sheet or full bronze.

Preferably has a compound layer and a diffusion layer existing edge layer has a thickness of about 10 .mu.m, through the a wear-resistant composite layer is formed, which has a hardness of at least 400 HV and a mass fraction contains about 1% carbon and about 10-15% nitrogen. Since the nitrocarburizing takes place at a temperature of preferably 550 ° C, the delay of the sliding disk is minimal.

Of the high nitrogen content ensures very good wear and frictional properties, as evidenced by vibrational friction wear tests on samples of sliding discs made of different materials Has. The nitrocarburized samples of steel grade C16M or 16MnCr5 have hardly any compared to sliding discs made of brass or bronze Wear on. In addition, the running behavior constant without tarnishing or galling.

The sliding disks generally have slightly conical outer surfaces after production on the radially extending portion adjoining axia len sections. Idle wear tests on such sliding disks show that the conicity can cause a lubricant film interruption. In this case, a mixed friction state prevails in the load zone, which leads to the temperature rise and to an increase in wear. Since the oil in freewheel is thrown radially outward on contact with a rotating sliding disk, the sliding disk can run dry in the load zone, whereby a further increase in temperature and an increase in wear occur.

Around To avoid this is at least the outer surface of the adjoining the inner edge of the radial section axial portion with a plurality preferably evenly spaced, provided axially extending oil grooves, wherein the number of oil grooves results from that in one zone the sliding disc with minimum load at least three oil grooves available. This means that nine oil grooves for Sliding discs with one for common sprag freewheel clutches suitable diameter are usually sufficient, reducing the surface pressure in the remaining areas of the sliding washer not essential increases.

The Width of the oil grooves can be about 3 mm and their depth about 0.6 mm, whereby an adequate oil supply of Contact surface in the load zone and a hydrodynamic Lubricant structure are guaranteed. This oil also causes sufficient cooling of the highly stressed Inner race of the sliding disc.

The Manufacturing the lubrication grooves is easy and cost neutral by training of associated webs in the Integrate thermoforming tool, wherein by a circular segment-shaped Cross section of the oil grooves the wear of the thermoforming tool is minimized.

The Sliding disk with the features listed above can be advantageously by deep drawing a Make thermoforming tool from a Stahlblechronde, after which the Nitrocarburizing is performed.

As already mentioned, the oil grooves in the Deep drawing through the thermoforming tool into the outer surface of the adjoining at the inner edge of the radial portion, bring in axial section, thereby reducing the tool costs slightly increase, but not the production costs.

The Nitrocarburizing the sliding disk can also be used with the Carbonitriding combine, reducing wear and tear Frictional properties are further improved.

Also carbonitriding is one of the thermochemical processes through which the boundary layer of components with carbon and nitrogen Enriched and the mechanical properties of the component edge layer be improved. The temperatures during carbonitriding are generally between 760 ° C and 900 ° C, d. H. higher than nitrocarburizing. The effect of Carbonitriding is based on carbon diffusion and simultaneously Nitrogen diffusion. By enrichment of nitrogen, the Hardening temperature and the critical cooling rate lowered, so that can be deterred milder. Both factors reduce the risk of default. With a subsequent tempering treatment becomes the desired surface hardness set. For carbonitriding are unalloyed and low-alloyed case-hardened steels as well as free-cutting steels and structural steels. These are generally steels with carbon contents below 0.2%. Carbonitriding serves to the surface layer of steel workpieces and tools much higher hardness and the workpieces or To give tools better mechanical properties. By Carbonitriding results in increased wear resistance with simultaneous delay.

Accordingly The steel grades DC03, DC04, C16M, 16MnCr5 are particularly suitable advantageous for producing a sliding disk with one with nitrogen and carbon enriched, wear and corrosion resistant Use edge layer.

Short description of the drawing

following an embodiment of the invention with reference to a Drawing explained in more detail. Herein shows

1 in an exploded view, a sprag free-wheel clutch,

2 a sectional view of a sliding disk of the sprag free-wheel clutch according to 1 , and

3 a front view of the sliding disk according to 2 ,

Detailed description the drawings

In 1 are essential functional elements of a sprag clutch 1 visible with the exception of an inner ring and an outer ring. A plurality of clamping bodies 2 is arranged in the annular gap space between the outer ring and the inner ring or a shaft. The leadership of the clamp body 2 serves a made of plastic cage 3 with recesses 4 for each egg NEN clamping body 2 , Radially inside the cage 3 is a against this biased spring band 5 with spring tongues 6 which the individual clamping body 2 anfedern. In this case, each clamp body 2 acted upon by a force in the direction of its clamping position.

On surrounding shelves 7 of the cage 3 is each a sliding disk 8th snapped. The sliding disk 8th serves to produce a sliding bearing between the inner ring and the outer ring of the sprag clutch 1 and is formed as a deep-drawn formed sheet steel part.

Like from the 2 and 3 closer, the slide disc has 8th a radially extending portion 9 and at these subsequent, axially extending sections 10 and 11 on. Overall, the sliding washer has 8th in the longitudinal section thus cut the shape of a bent into a circle U-profile.

The axially extending, radially inner portion 10 has an inner surface 13 and an outer surface 14 on while the radially outer axial section 11 an inner surface 15 and an outer surface 16 having. The outer surface 14 causes a sliding bearing to the inner ring and the outer surface 16 a sliding bearing to the outer ring of the sprag free-wheel clutch 1 ,

The radially inwardly facing outer surface 14 is the highly stressed inner race of the sliding disc, which requires special lubrication and cooling. For this reason, the outer surface indicates 14 regularly spaced, axially extending oil grooves 12 the number of which is sized to provide at least three grooves in the minimum load zone to provide oil to the contact surface, to aid in hydrodynamic lubrication film buildup, and to cool the highly stressed inner race of the slip disk. The width of the oil grooves is about 3 mm and the depth about 0.6 mm.

At least the outer surfaces 14 and 16 the axial cuts 10 and 11 , preferably the entire surface of the sliding disk, are provided by nitrocarburizing with a nitrogen and carbon enriched, wear and corrosion resistant edge layer. This surface layer has a hardness of at least 400 HV and a mass fraction of C. 1% carbon and 10 to 15% nitrogen.

Nitrocarburizing (standard M6) can also be combined with carbonitriding (standard designation X6) in order to improve the wear and friction properties even further without a significant distortion of the sliding disk due to this thermochemical treatment 8th entry. For producing the sliding washer according to the invention 8th It is preferable to use steel grades DC03, DC04, C16N, 16MnCr5.

The illustrated embodiment shows a longitudinal section C-shaped sliding disk 8th However, the optimized sliding washer for a sprag freewheel in sigma form, which is in the DE 10 2006 023 564 A1 described by the same applicant, very well suited as a sliding washer according to the invention, which is stiffness-optimized and has a lower distortion due to the thermochemical treatment.

The oil grooves 12 for the oil passage at the edge of the sliding disk 8th are with regard to the lubricant supply and cooling of the highly stressed inner raceway surface of the sliding disk 8th optimal, but may result in increased surface pressure. However, this is associated with no disadvantage, since the enriched with nitrogen and carbon surface layer overstressing the sliding disk 8th prevented. By the inventive thermo-chemical treatment of the sliding disk 8th thus come the benefits of axial oil grooves 12 fully effective.

1

Sprag one-way clutch

2

clamping bodies

3

Cage

4

recess

5

spring band

6

spring tongue

7

shelf

8th

sliding disk

9

radial section

10

axial section

11

axial section

12

oil grooves

13

palm

14

outer surface

15

palm

16

outer surface

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

• DE 102005046799 A1 [0002]
• - DE 29904524 U1 [0002]
• - DE 102006023564 A1 [0030]

Claims (13)

Sliding washer ( 8th ) made of sheet steel for the arrangement between an inner ring and an outer ring of a sprag clutch ( 1 ), with a radially extending portion ( 9 ) and at its inner edge and outer edge subsequent axial sections ( 10 . 11 ) each having an inner surface ( 13 . 15 ) and an outer surface ( 14 . 16 ), characterized in that at least the outer surfaces ( 14 . 16 ) have a generated by nitrocarburizing, enriched with nitrogen and carbon, wear and corrosion resistant edge layer. Sliding disk according to claim 1, characterized that of a bonding layer and a diffusion layer existing edge layer has a thickness of about 10 microns. Sliding disk according to claim 1 or 2, characterized the surface layer has a hardness of at least 400 HV. Sliding disc according to one of claims 1 to 3, characterized in that the edge layer has a mass fraction contains about 1% carbon and 10 to 15% nitrogen. Sliding disc according to one of claims 1 to 4, characterized in that the outer surface ( 14 ) located at the inner edge of the radial section ( 9 ) subsequent section ( 10 ) spaced, axi al extending oil grooves ( 12 ) having. Sliding disc according to claim 5, characterized in that the number of oil grooves ( 12 ) shows that in the minimum load zone at least three oil grooves ( 12 ) available. Sliding disc according to claim 5 or 6, characterized in that the outer surface ( 14 ) nine oil grooves ( 12 ) having. Sliding disc according to one of claims 5 to 7, characterized in that the width of the oil grooves ( 12 ) about 3 mm and the depth is about 0.6 mm. Sliding disc according to one of claims 5 to 8, characterized in that the oil grooves ( 12 ) have a circular segment-shaped cross-section. Method for producing a sliding disk according to one of claims 1 to 9, characterized in that the sliding disk ( 8th ) by deep drawing by means of a deep-drawing tool made of a Stahlblechronde and then the nitrocarburizing is performed. Method according to claim 10, characterized in that the oil grooves ( 12 ) during deep drawing by the thermoforming tool in the outer surfaces ( 14 ) located at the inner edge of the radial section ( 9 ) subsequent axial section ( 10 ) are introduced. Method according to claim 10 or 11, characterized in that the sliding disk ( 8th ) is subjected to treatment by nitrocarburizing (M6) and carbonitriding (X6). Use of one of the steel grades DC03, DC04, C16M, 16MnCr5 for producing a sliding washer according to one of the claims 1 to 12.