WO1985005422A1

WO1985005422A1 - Bellows for fixed joints

Info

Publication number: WO1985005422A1
Application number: PCT/EP1985/000206
Authority: WO
Inventors: Siegfried Frank; Günter GLÜHMANN; Klaus Keinrad; Richard Zigelli
Original assignee: Feldmühle Aktiengesellschaft
Priority date: 1984-05-12
Filing date: 1985-05-07
Publication date: 1985-12-05
Also published as: BR8507187A; JPS61502138A; ES8607490A1; EP0211839A1; DE3417709A1; ES543019A0

Abstract

Bellows for fixed joints are made from a polyether ester thermoplastic elastomer and are intended to be used at low temperatures. Their fabrication length L exceeds the mounting length thereof l. The ratio between the width B of the folds (1, 2, 19, 20, 21) and their height H is equal or higher than 1. The front flanks (3) determine an angle $g(b) which is higher for the first fold (1) and lower for the last fold (2) than the angle $g(g) of the rear flanks (4).

Description

Bellows for fixed joints

The invention relates to a bellows for fixed joints with a high deflection, consisting of a thermo ^ -plastic elastomer based on polyetherester, which has a fixed production length and has at least three folds, each formed by an angled front and rear flank become.

Bellows for fixed joints, especially for homokinetic joints, have been known for a long time and are generally made from natural or synthetic rubbers and their mixtures. The range of the deflection was continuously increased because this bellows construction essentially protects the propeller shafts of vehicle drives and the aim is to keep the turning circle in the vehicle as small as possible. The requirement to withstand a deflection of up to 50 degrees places considerable demands on the bellows, which are exacerbated by the fact that the bellows in must absorb its inner fat and endure quite high speeds over a long period of 8 to 10 years.

Another requirement is the usability of the bellows under extreme weather conditions, ie it should be able to be used in the hot desert climate as well as in the cold polar region without any signs of aging. Practice has shown here that high degrees of cold very often lead to the formation of cracks in the bellows, ie that vehicle joints equipped with them were worn out after a short time by dirt entering the cracked bellows. In order to solve the refrigeration problems, a new material was developed. A thermoplastic elastomer based on polyetherester. This material has a high resistance to cold. However, the elastic elongation, which is approximately 400% and more in the previously used rubber-based materials, is considerably lower and is in the range of 25%. For the structural design, max. only 10% can be used. This means that completely different properties occur during assembly and also when using the axle sleeve, so that special steps have to be taken in order to design a bellows from this material that meets the high demands made. The present application is therefore based on the object, a bellows for Festge from a thermoplastic elastomer based on polyetherester _. to steer with high deflection without If the permissible low elastic expansion is exceeded, even at low temperatures, such as occur in areas around the polar circle, a dynamic deflection of 50 degrees survives without damage.

This object is achieved by a bellows for fixed joints with high deflection, consisting of a thermoplastic elastomer based on polyetherester, which has a fixed production length and has at least three folds, which are each formed by an angled front and rear flank, which is characterized by the combination of the following features: a) the manufacturing length L differs from the installation length 1, b) the ratio of the width B of the folds to the height H of the folds is equal to or greater than 1, c) the front flanks run at an angle β the back flanks at an angle> to the perpendicular to the center line of the bellows, the angle β being greater than or smaller than the angle j-9 at least in the first fold and in the last fold.

The first fold in the sense of the present application is understood to be the fold which is arranged on the side of the bellows facing away from the joint, generally on the side which has the small shaft diameter. The last fold is accordingly the fold that is in the immediate vicinity of the joint. When the joint is bent, the bellows is stretched on the outside of the diffraction angle and compressed on the inside of the diffraction angle. In the area of the small folds, that is to say in the area of the fold one, it is often the case that there is a direct slip in the inner area and that there is a kink in the outer area of the diffraction, which runs transversely to the fold arrangement and thus longitudinally to the shaft. The rubber materials that have been customary so far tolerate both the buckling and the slip. In the case of materials such as polyether ester elastomers, both the overturning and the buckling certainly lead to the cuff breaking after a short time.

To a certain extent, the risk of buckling can be countered by increasing the number of folds, but at the same time increasing the likelihood that the inside of the

Diffraction, the cuff is put on, which is just as harmful with these materials, as stated above. According to the invention, this problem is solved in that the folds have a relatively large fold width B during the manufacture of the sleeve, which fold is only reduced in the installed state. According to a preferred embodiment of the invention, the production length is 1.2 to 3.0 times the installation length. Due to the elongated production length, the folds can be produced with much greater accuracy than is the case would be if the bellows would have to be made with the small pleat width of the installation length. This trick also makes it possible to accommodate more folds in the same space.

The arrangement of the angles and J> and their assignment to the front and rear flanks is particularly important. The choice of these angles in conjunction with the ratio of the width to the height of the folds results in a very specific position of the flanks in relation to one another, as a result of which the front flanks are longer than the rear flanks and, accordingly, the force acting on the bellows during flexion transfer the joint to the back flanks with a larger lever arm. The rear flanks are folded in, the front flanks are pushed against one another essentially in their predetermined position. There is therefore no minimal slipping on, but rather the flanks lie against one another, which is particularly favored by the fact that the angle at the last fold is equal to or smaller than the angle, i. H. that the folding takes place only in the area between the front flank of the first and the rear flank of the last fold, without these being significantly deformed.

According to the invention, the ratio of the width to the height of the folds is equal to or greater than 1. This ratio favors in terms of production technology that the wall thickness distribution from the bottom of the fold to the tip of the fold is achieved to the extent required for the function of the cuff. The formation of transverse folds during axial displacement and diffraction is prevented.

The ratio B to H is preferably between 1: 1 to 1: 0.65.

According to a preferred embodiment of the invention, the angle β is 1.15 to 1.35 times the angle j.

In connection with the above-mentioned ratio of width to height of the folds, the size of the angles and Λ * ensures that the folds deform evenly when they are axially deformed from the production state into the installed state; which in turn is advantageous for the deformation behavior when bending the cuff.

Example Bellows for a homokinetic joint with five folds were produced from a thermoplastic polyester elastomer - Hytrel, registered trademark of the Dupont company - by the blowing process. The inner diameter of the sleeve was 80 mm, the small one

Inner diameter of the cuff 25 mm. The folds were arranged at the following angles: first fold, front flank, angle 26 degrees,

Trailing edge, angle if 23 degrees. Second fold, leading edge, angle & 32 degrees,

Trailing edge, angle »27 degrees. Third fold, front flank, angle ß 34 degrees,

Trailing edge, angles 29 degrees. Fourth fold, front flank, angle ß 33 degrees,

Trailing edge, angle * 28 degrees.

Last fold, leading edge, angle ß 31 degrees, trailing edge, angle J _* »35 degrees.

The width to height ratio was:

first fold -fi- = 1.0

H

second fold-g- = 1.18

H

third fold-g- = 1, 2 H

fourth fold-§- = 1.14

H

fifth fold- | - = 1.15 H

The production length of the bellows between the bundles was 130 mm, the installation length 84 mm. The following tests were carried out on these bellows:

1. deformation behavior during the static deflection,

2. Rotation test up to n = 3200 min

3. Functional test when exposed to heat,

4. Functional test when exposed to cold. The axle boot test rig consisted of two columns that were adjustable at an angle to each other, between which a drivable, homokinetic fixed joint with a bellows was applied. The length of the bellows was 84 mm. There was 30 g of fat in the joint and 50 g in the bellows. "Molykote VN 2461 C" was used as fat.

The rotary test bench was equipped with a drive that was infinitely variable in the speed range 0 ... 3500 min ^"1. The central axis of the test mandrel, on which the test specimen was tightly mounted with tensioning straps, was set exactly to the zero point of the 2 mm grid. The flash frequency of a stroposcope was adjusted to the speed in such a way that every change in shape of the cuff was visible and measurable and could be photographically recorded.The deformation in each speed step was measured after a run of t = 15 min.

The diameter changes of the cuff were determined at the speed levels 1600; 1800; 2000; 2200; 2400; 2600; 2800; 3000; 3200 min ^"1 compared to the actual dimensions before the test. The test mandrel was kept at a constant temperature of 95 = 5 + 5" C by means of an adjustable heating fan. The table shows the dimensional deviations in the corresponding folds.

Diameter - enlargement

0 The tested cuff did not expand until n = 2400 min ^-1 . Only from n = 2400 min ^"1 to n = 3200 min ~ ¹ did a slight widening occur. The bellows showed no damage and no grease escaped.

Heat testing

The bellows was brought to a temperature of 100 ° C. The axle cuff test stand was set to a flexion angle of 20 degrees and the horaokinetic joint at a speed of 140 rpm. powered for 240 hours. Two bellows were subjected to this test. After 240 hours, no grease had escaped, and no damage to the bellows could be found.

Cold test

Four bellows were brought to a temperature of -40 ° C. The flexion angle of the homokinetic joint in the axle boot test bench was set to 18 degrees and the speed during a running time of 15 minutes to 1,100 rpm. held. Thereafter, during a standing time of 60 minutes, the bellows was cooled back down to -40 ^° C., then moved again at a speed of 1,100 revolutions for 15 minutes. After 20 load changes of this kind, all four pieces showed no grease leakage and no damage. Lifetime and fatigue strength

Two test specimens were exposed to the following loads in turn:

a) temperature 45 ° C, joint deflection 15 degrees, speed 1,000 rpm, running time 200 hours, b) temperature -35 ^β C, joint deflection 15 degrees, 300 starts from 0 to 1,000 rpm, c) temperature 45 ° C, joint deflection 30 degrees, speed 250 rpm. , Running time 4 hours, d) temperature -35 ° C, joint deflection 30 degrees, 30 starts from 0 to 250 rpm. , e) temperature 90 ° C, joint deflection 42 degrees, speed 20 rpm, running time 4 hours, f) temperature -35 ° C, joint deflection 42 degrees, 15 starts from 0 to 20 rpm, g) temperature - 40 ° C, joint deflection 50 degrees, 30 starts from 0 to 250 rpm.

After this test, no grease leakage or damage to the bellows that could impair the function were found. A slight abrasion was seen in the area where the folds touched. The first contact between the fifth and fourth fold occurred at a deflection angle of 10 degrees, the second contact between the fourth and third fold occurred at a deflection of 17.5 degrees, and the third contact between the third and second fold occurred at a deflection of 22.5 degrees 37.5 degrees the fourth contact between the second and first fold, from 40.5 degrees all folds are in continuous contact. The invention is based on the

Drawings explained:

1 shows a constant velocity joint with bellows in partial section, FIG. 2 shows the front view of the bellows in partial section,

characters

3 to 6 homokinetic joints with the bellows according to the invention in different flexion positions,

characters

7 and 8 a homokinetic joint with a

State-of-the-art rubber bellows at various flexion angles.

The homokinetic joint 7 consists of a fixed area 9, in which the shaft 10 is pivotally mounted. The shaft 10 has two annular beads 11, which serve to receive the small collar 12 of the bellows 13. The collar 12 of the bellows 13 is held on the shaft 10 in the area between the annular beads 11 by a tensioning band 14. Similarly, the large collar 15 of the bellows 13 is attached to the

Fixed area 9 of the homokinetic joint 7 in an annular groove 16 also with a tensioning strap 14. The front flank 3 of the first fold 1 has a wall thickness of 3.5 mm in the region of the fold base 5 and tapers towards the fold tip 6 to 0.4 mm. The first flank 3 of the further folds 2, 19, 20, 21 point in the region of the

Fold base 5 has a wall thickness of 1.3 mm and also tapers to 0.4 mm. The rear flank 4 of the first fold 1 and also the rear flanks 4 of the further folds 2, 19, 20, 21 have the same dimensions.

The front flank 3 of the first fold 1 runs at an angle of 26 degrees with respect to the vertical 23, the rear flank 4 of the first fold at an angle »* of 23 degrees. The angles β of the second fold 2, the third fold 21 and the fourth fold 20 run at 32, 34 and 33 degrees. The associated angles are 27, 29 and 28 degrees. The last fold 19 has an angle β of 31 and an angle * of 35

Degrees on.

In the area of the fold base 5, a circumferential relief groove 17 is arranged between the individual folds, through which the upsetting and stretching of the bellows is facilitated.

By deflecting the shaft 10, the bending angle β is formed between the extension of the center line 18 of the fixed region 9 of the homokinetic joint 7 and the angled shaft 10. In Figure 3, this flexion angle OC is 10 degrees. The first touch of the folds occurs one below the other, it touches the fifth fold 19 and the fourth fold 20, in FIG

4, the diffraction angle t * is 22.5 degrees, the fourth fold 20 has touched the third fold 21 and the third fold 21 lies against the second fold 2 for the first time. According to figure

5 the angle is 37.5 degrees, which results in the fourth touch, i. H. that now the second fold 2 is also present on the first fold 1. Figure 6 is at 40.5 diffraction

Degrees. All wrinkles touch each other continuously.

Figures 7 and 8 show a homokinetic joint according to the prior art, i. H. a constant velocity joint 7, which according to FIG. 7 has a diffraction angle o of 22.5 and according to FIG. 8 that of 40.5 degrees. It can be seen that at 22.5 degrees diffraction, the overlapping of the first fold 1 already occurs, which is accomplished at a diffraction angle C of 40.5 degrees. In addition, the fold 22 can be clearly seen in the practically stretched area.

Claims

Bellows for fixed joints with high deflection, consisting of a thermoplastic elastomer based on polyetherester, which has a defined production length and has at least three folds, each formed by an angled front and rear flank, characterized by the combination following features:

a) the production length L differs from the installation length 1, b) the ratio of the width B of the folds (1, 2, 19, 20, 21) to their height H is equal to or greater than 1, c) the front flanks (3) run at an angle p, the rear flanks (4) at an angle J> to the vertical (23) of the center line (18) of the bellows (13), the angle p being larger at least in the first fold (1) and in the last Fold (2) is equal to or less than the angle. 2. Bellows according to claim 1, characterized gekenn¬ characterized in that the production length L is 1,

2 to 3.0 times the installation length 1.

3. Bellows according to one of claims 1 or 2, characterized in that the ratio of pleat width B to pleat height H is 1: 1 to 1: 0.65.

4. Bellows according to one of claims 1 to 3, characterized in that the angle ß is 1.15 to 1.5 times the angle] S.