GB2184199A - Diaphragm spring for pulled-type diaphragm spring clutch - Google Patents

Abstract

A diaphragm spring for a pulled-type diaphragm spring clutch is provided in the region radially outside the spring zone 9 with a circular zone of reduced wall thickness 10, the reduction being on the axially outer face of the spring and thus on the side loaded by tension stress. Furthermore in this zone, preferably radially within securing openings for screws 7, relief openings 13 are provided. These effect a more uniform introduction of moment into the diaphragm spring. <IMAGE>

Description

SPECIFICATION Diaphragm spring for pulled-type diaphragm spring clutch The invention relates to a diaphragm spring for a puiled-type diaphragm spring clutch, comprising a radially outer securing zone with which the diaphragm spring is firmly securableto a component, for example a fly-wheel, a spring zone radially in wardlyadjoining the securing zone and spring tongues radially inwardly adjoining the spring zone for the action of a releaser system.

A diaphragm spring of the above-stated formation is known forexamplefrom Fed. German Inspection Doc. No. 3,017,563. It is the problem of the present invention to optimalise diaphragm springsofthesta- ted construction style, as regards their life and spring characteristics.

This problem is solved in accordance with the invention in that the diaphragm spring comprises, in a circular zone radially outside the spring zone, a reduction of wall thickness, namely on the side remote from the side of action ofthe releaser system (arrow F).

By arrangement of a wall thickness reduction of a diaphragm spring in a circularzone radially outside the spring zone on the side remote from the side of action of the releaser system the object is achieved that the undesired effects of notch stresses can remain absent on this side of the diaphragm spring loaded by tension stresses. Furthermore it has appeared that by reduction of the wall thickness in the region outsidethe spring zone a substantially lower clamping-in moment is generated whereby the internal stresses introduced into the spring can be substantially reduced.Atthe same timethe pres- sure application force of the clutch, that is the force with which the clutch disc is pressed into engagement, is substantially increased.

Finally it has been found that a substantially hori zontal spring characteristic is achieved by the form- ation in accordance with the invention.

Further advantageous development possibilities are laid down in theSub-Claims.

The invention will next be explained in greaterdetail by reference to various examples ofembodi- ment. Individually: Figure 1 shows the upper half of a longitudinal section through a clutch with a diaphragm spring which possesses a reduction of wall thickness radially outside its spring zone; Figure2 shows the enlarged representation of the outer zone of a diaphragm spring with a reduction of wall thickness, having a small radial extent; Figure3showsthe partial elevation of a dia- phragm spring according to Figure 1; Figure4showsthe partial elevation of a dia- phragm spring with modified external contour; Figure 5shows the upper half of a longitudinal section through a diaphragm spring made in pot form; Figure 6shows a measured spring characteristic curve.

Figure 1 shows the longitudinal section through the upper half of a pulled-type diaphragm spring clutch in a representation of principle. The fly-wheel 4 is secured to a crank-shaft (not shown) of an internal combustion engine and rotates about the rotation axis 20. The fly-wheel 4 is made in pot form and carries on its side remote from the internal combustion engine a substantially flat diaphragm spring 1, which in the dismantled condition is slightly conical.

The diaphragm spring 1 is initially stressed in the direction towards the fly-wheel 4 and with this initial stress loads a presser plate 5 which is connected fast in rotation but axially displaceably with the fly-wheel 4 in a manner notfurther illustrated. A clutch disc 6 is clamped in between presser plate 5 and fly-wheel 4.

As may be seen forexamplefrom Figure 3 also, the diaphragm spring 1 comprises radially inwardly extending spring tongues 8 which extend outfrom the spring zone 9. Radially outwards a securing zone 10 adjoins the spring zone 9 and is provided with a plurality of securing openings 16 distributed on the circumference which are provided for the arrangement of securing screws 7. To disengage the clutch disc 6 a force is applied from the interior according to the arrow Fthrough a releaser system (notshown)to the ends ofthe spring tongues, so thatthe diaphragm spring 1 domes conically and liberates the presser plate 5 in the axial direction.

The securing zone 10 ofthe diaphragm spring 1 is made significantly thinner in material thickness in the zone radially outside the spring zone 9 than the other zones ofthe diaphragm spring 1. The inner side ofthe diaphragm spring 1 its made to extend substantially flatly radially outwards without modi fication of the surface structure, while the outer side is set back by the amount ofthe wall thickness reduc tion. The transition zone is rounded.This formation of the wall thickness reduction is advantageous be- cause on the inner side, which is loaded with compression stress, the cross-section is continued without interruption and on the outerside,which is loaded with tension stresses, a wall thickness reduction was effected in the direction towards the neutral fibres, so thatthe diaphragm spring is more heavily loaded in the region ofthe compression stresses.

Lower notch stresses occur in this zone.

Afurther measure for reducing the clamping in moments and thusforachieving lower stresses in the diaphragm spring is the arrangement of relief openings in the zone between spring zone 9 and securing zone 10. This constructive arrangement provides the most uniform possible introduction ofthe moments by way of the circumference. In this connection reference should be made especially to Figure 3.

Figure 3 shows the view ofthe diaphragm spring 1 from the outer side. Starting from the spring zone 9, the spring tongues 8 extend radially inwards and the securing zone 10 extends radially outwards. In the securing zone 10 several securing openings 16 are provided in distribution over the circumference, likewise for example three centring openings 22 distributed over the circu mference. The diaphragm spring 1 is provided with a reduction of wall thickness adjoining the radially outer limitation ofthe spring zoneS, which reduction was carried out by way of example by removal of material from the outer side or as early as in the hotorcold deformation.This reduction of wall thickness extends as far as the external circumference 12 of the diaphragm spring 1.

Moreover in this securing zone 10 radially outside the spring zone 9 and radially within the securing openings 16thereare provided relief openings 13 and 14 respectively. The relief openings 13 are situated radiallywithin the zone ofthe securing openings 16 and are circumferentially made larger than the relief openings 14. This ensures that the radial displace mentsofthediaphragm spring are de-coupled from the clamping points 16 in the spring zone 9, and local stress peaks are avoided.

Figure 2 showsthe radially outerzone of a dia- phragm spring 1 in enlarged representation. In this embodiment, in distinction from the diaphragm spring according to Figures 1 and 3,the wall thickness reduction is provided in a radially limited zone which extends between the radially outer end ofthe spring zone 9 andthe radially inner end ofthe securing zone 10, in the circumferential direction. Relief openings 13 for example according to Figure 3 -are likewise provided in this region ofthewall thickness reduction.

In Figure 4there is represented a further possible configuration of a diaphragm spring 2. In distinction from the diaphragm spring 1 according to Figure3 here the securing zone is not made closed in the circumferential direction, but the articulation to the flywheel is effected by lugs 11, each having a securing opening 16and a reliefopening 15. The reliefopen ing IS is arranged centrally radiallywithinthesecur- ing opening 16 and extends circumferentially over a iarge partofthe extent of the lug 11.Thecircum- ferential end zones of each relief opening 15 are here partially also drawn around the securing opening 16.

Furthermore by way of example three circumferentially distributed centring lugs 21 are provided each having a centring opening 22. The securing lugs and possibly also the centring lugs are reduced in wall thickness.

By arrangement of as manysecuring points as possible, distributed over the circumference, in the form ofthe lugs 11 and by corresponding formation ofthereliefopenings lSanextremelyuniform intro- duction of the moments into the diaphragm spring 2 is achieved. By reduction of the wall thicknesses radially outside the spring zone 9 on the outer side loaded by tension stress, a substantial improvement of the life and an increase ofthe pressure application forces are achieved.

Figure 5 showstheform of embodimentofadia- phragm spring 3which is used especially with aflywheel offlatformation and due to its potform grasps aroundthepresserplateandtheclutch disc. Forthis purpose the diaphragm spring 3 comprises a sub stantiallycylindricalzoneorpotshell 18whichcon- stitutes the connection between securing zone 10 and spring zone 9. Radially inwardsthe spring zone 9 is provided in the usual way with spring tongues 8.

Between the radially outer end ofthe spring zone 9 and the substantially cylindrical zone 18 an arcuate transition region 17 is provided which possesses the wall thickness reduction. In the arcuate transition re- gion 17the material ofthe diaphragm spring 3 is made slighter from the outer side and rounded atthe transition zones. Atthe same time relief openings 19 are provided in this zone. These relief openings 19 can also extend into the cylindrical region 18. Outof the cylindrical zone 18 the secu ri n 9 zo n extends in radial direction in the form of a potflangewith its securing openings 16 and the external circumfer ence 12.The function ofthis diaphragm spring 3 and the positive effects of the wall thickness reduction in the arcuatetransition zone 17 are in conformity with the forms of embodiment as described above.

Du e to th e above-described formation of diaphragm springs ofthe pulled-constructiontype not only is a significant lengthening of life achieved but furthermore a spring characteristic curve is achieved which is unaccustomed for ordinary diaphragm springs and especiallyfavourable.The spring characteristic curve of the diaphragm springs as represented and described extends substantially horizontally according to Figure 6 and possesses an extremely slight hysteresis. The horizontally extending spring characteristic curve hasthe greatadvan- tage overthe ordinary spring characteristic curves of diaphragm springs of possessing constant actuation forces overthe entire release distance and the wear distance of a clutch. The release distanceA ofthe release device acting on the radially inner ends ofthe spring tongues 8 in clutch disengagement is entered in Figure6 on the abscissae axis to the right.

On the abscissae axis to the left there is entered the wear distance V, that is the distance which the radially innerends ofthe spring tongues 8travel when the clutch disc 6 becomesthinner dueto wear.

The spring force Fa with which the clutch disc is pressed is entered on the ordinate axis. The release force F is correspondingly proportional.

Claims (17)

1.) Diaphragm springfora pulled-typediaphragm spring clutch, comprising a radially outer securing zone (10) with which the diaphragm spring is firmly securableto a component (4), such forexample as a fly-wheel (4), a spring zone (9) radially inwardly adjoining the securing zone (10) and spring tongues (8) for the engagement of a releaser system (F) radially inwardly adjoining the spring zone (9), characterised inthatthediaphragm spring (1,2,3) possesses a reduction of wall thickness in a circular zone radially outside the spring zone (9), namely on the side remote from the side of action of the releaser system (arrow F).

2.) Diaphragm spring according to Claim 1,char acterised in thatthe zone ofwall thickness reduction extends in the radial direction from the outer end of the spring zone (9) as far as the external circumference (12) ofthe diaphragm spring (1).

3.) Diaphragm spring according to Claim 2, characterised in that relief openings (13, 14, 15) are provided in a zone radially outside the spring zone (9) and radiallywithin the securing zone (10).

4.) Diaphragm spring according to Claim 3, characterised in that the relief openings (13, 14) are provided preferably radially within securing openings (16).

5.) Diaphragm spring according to one of Claims 1 to 4, characterised in thatthe securing zone (10) consists of a plurality of lugs (11) distributed overthe circumference and protruding radially beyond the spring zone (9).

6.) Diaphragm spring according to Claim 5, characterised in that the lugs (11) possess a reduction of wall thickness.

7.) Diaphragm spring according to Claim 5 or6, characterised in that each ofthe lugs (11) possesses at least one relief opening (15).

8.? Diaphragm spring according to Claim 7, characterised in that the relief openings (15) extend in the circumferential direction over at least 50% ofthe circumferential extent ofthe lugs (11).

9.) Diaphragm spring according to Claim 7 or8, characterised in that the relief openings (1 5) extend around securing openings (16) provided in the lugs (11), in arcuate or Uform radially inwards and laterally of these securing openings.

10.) Diaphragm spring according to Claim 1, which is of pot-shaped formation with a securing zone (10) made as pot flange, a pot shell (18) and a pot bottom formed by the spring zone (9) and the spring tongues (8), characterised in that the wall thickness reduction is provided in an arcuatetransition zone between the spring zone (9) and the pot shell (18).

11.) Diaphragm spring according to Claim 10, characterised in that relief openings (19) are provided in a zone radially outside the spring zone (9) and radiallywithin the securing zone (10).

12.) Diaphragm spring according to Claim 11, characterised inthatthe relief openings (19) are arranyed in the arcuatetransition zone (17).

13.) Diaphragm spring according to one of Claims 1 to 12, characterised in that the wall thick ness reduction amounts to about 30% to about 70%, preferably about 50%, ofthe full wall thickness ofthe diaphragm spring.

14.) Diaphragm spring according to one of Claims 1 to 13, characterised in that the wall thick ness reduction is formed by swarfless deformation in production.

15.) Diaphragm spring according to one of Claims 1 to 13, characterised inthatthewallthick- ness reduction is formed byswarf- removing mach ining.

16.) Diaphragm spring according to one of Claims 1 to 15, characterised in that the zone of redu ced wall thickness adjoins the spring zone (9) by way of a transitional rounding.

17.) Adiaphragm spring as claimed in claim 1 substantially as described with reference to the ac companying drawings.