WO1985005421A1

WO1985005421A1 - Bellows for rigid coupling

Info

Publication number: WO1985005421A1
Application number: PCT/EP1985/000205
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: DE3417708A1; BR8507188A; JPS61502139A; ES543018A0; ES8607489A1; EP0211845A1

Abstract

The bellows for coupling with high pivoting, which is used at low temperatures, is made of thermoplastic elastomer based on polyetherester. The front flanks (3) of the first ply (1) viewed from the side opposite to the coupling (7), decrease more from the hollow (5) of the ply towards the crest (6) than the other flanks.

Description

Bellows for fixed joints

The invention relates to a bellows for fixed joints with a deflection of up to 50

Degree that consists of a thermoplastic elastomer based on polyetherester and has at least three folds.

Bellows for fixed joints, in particular for homokinetic joints, have been known for a long time and are generally made from natural or synthetic rubbers and their mixtures and polyurethane. The area of. Deflection was continuously increased because these bellows constructions are intended to protect cardan shafts of vehicle drives and the aim is to keep the turning circle of the vehicle as small as possible. Due to the requirement to withstand a deflection of up to 50 degrees, considerable demands are placed on the bellows, which are exacerbated by the fact that the bellows absorb grease inside and quite high speeds over a long period, in generally has to withstand a mileage of 150,000 to 200,000 km corresponding time of about 8 to 10 years.

Another requirement is the usability of the bellows under extreme weather conditions, i. H. 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 that high degrees of cold very often lead to the formation of cracks in the bellows. that is, vehicle joints equipped therewith were worn out by dirt entering through the crack after a short time. In order to solve the refrigeration problems, a new material had to be found that could withstand the stresses in the cold. A rather new proposal is therefore to use a thermoplastic elastomer based on polyether ester as a material, which has a high resistance to cold. However, compared to the rubber-based raw materials used to date, this material has only a very low elasticity and therefore has completely different properties during assembly and also in use as an axle boot, so that special steps have to be taken to make a bellows out of this material to design that meets the requirements.

The present application is therefore based on the task of a cold-resistant material, that is, a thermoplastic Elastomers based on polyetherester to create a bellows that withstands damage of 50 degrees and has a long service life even at the lowest temperatures, such as occur in regions of the Arctic Circle.

This object is achieved by a bellows for fixed joints with a deflection of up to 50 degrees, which consists of a thermoplastic elastomer based on polyetherester, has at least three folds with the characteristic feature that at least the front flank of the first fold and possibly the front flank the second fold, seen from the side facing away from the joint, has a taper ratio of the flank wall thickness from the base of the fold to the pleat tip of 15: 1 to 8: 1 and all other flanks have a ratio of the flank wall thicknesses of 6: 1 to 4: 1.

In many types of joints, in particular homokinetic joints, the side of the bellows facing away from the joint is generally the side that has the small axis diameter. The wrinkles in this area are also smaller. When the joint is flexed, the bellows is stretched on the outside of the bend and compressed on the inside of the bend. In the area of the small folds, it is often the case that there is a direct fitting in the inner area and a buckling in the outer area of the diffraction results that runs transversely to the fold arrangement and thus along the shaft. Rubber materials tolerate both buckling and slipping, particularly in the case of dynamic stress, but not materials that have a much lower elongation, such as polyether ester elastomers. With these, the overturning and also the kinking will certainly lead to the cuff breaking after a short time.

By increasing the number of folds one can counter the risk of kinking, but at the same time increases the likelihood that the inside of the diffraction will be put on the cuff, which further leads to the destruction of the cuff with these materials. According to the invention, this is put on by preventing the flanks of the bellows from tapering from the bottom of the fold to the tip of the fold, the tapering ratios of the flanks differing. The front flank of the first fold is always made stronger, so it offers considerable resistance to being pulled over. The opposite flank of the same fold has a much smaller wall thickness in the fold base. When the joint is flexed, it rests on the front flank without putting it on. The front flank of the second fold can thus lean against the rear flank of the first fold, which also means that no overturning occurs. A preferred embodiment of the invention provides that the flank wall thickness of the front flank of the first fold and possibly the second fold in the region of the flank base is between 2 and 3.5 mm. The flank wall thickness of the further folds is advantageously in the foot area between 1.2 and 2.2 mm. There is therefore a considerable difference in the wall thicknesses, ie all rear flanks are made thinner and therefore easier to deform, which ensures that the sleeve is not slipped on. In the area of the fold tips, the flank wall thickness is preferably between 0.2 and 0.4 mm, in order to ensure high elasticity while maintaining the required strength.

example

Made from a thermoplastic polyester elastomer

- Hytrel, a registered trademark of the Dupont company - bellows for a homokinetic joint with five folds were produced using the blowing process. The joint-side inside diameter of the cuff was 80 mm, the small inside diameter of the cuff was 25 mm, the wall thickness of the front flank, the first fold in the area of the fold base 2.5 mm, in the area of the fold tip 0.4 mm, the front flank of the second fold showed A thickness of 2.2 in the area of the fold base and a thickness of 0.35 mm in the area of the fold tip. All further

Flanks measured 1.6 mm in the area of the fold base and 0 3 mm in the area of the fold tip The bottom of the fold between the individual folds was provided with a relief groove. The folds were arranged at the following angles:

first fold, leading edge, angle 26 degrees, trailing edge, angle 23 degrees.

Second fold, front flank, angle 32 degrees,

Trailing edge, angle β 27 degrees.

Third fold, front flank, angle 34 degrees,

Trailing edge, angle 29 degrees.

Fourth fold, front flank, angle 33 degrees,

Trailing edge, angle 28 degrees.

Last fold, leading edge, angle 31 degrees,

Trailing edge, angle β 35 degrees.

The width to height ratio was:

first fold = 1.0

second fold - 1.18

third fold = 1.2

fourth fold = 1.14

fifth fold = 1.15

The 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 continuously adjustable in the speed range 0 ... 3500 min. 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 so that every change in shape of the cuff was visible and measurable and could be captured photographically. The deformation at each speed level 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 ΔB = 95 + 5 ºC by means of an adjustable heating fan.

The table shows the dimensional deviations in the corresponding folds.

Diameter - enlargement

The tested cuff did not expand until n = 2400 min ^-1 . Only from n = 2400 min ^-1 to n =

A slight widening occurred at 3200 min ^-1 . The bellows showed no signs of damage and no grease escaped.

Heat testing

The bellows was brought to a temperature of 100 ° C. The axle boot test bench was set to a flexion angle of 20 degrees and the homokinetic joint with 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 to 1,100 rpm over a period of 15 minutes. 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 1100 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 ºC, joint deflection 15 degrees, speed 1,000 rpm, running time 200 hours, b) temperature -35 ºC, joint deflection 15 degrees, 300 starts from 0 to 1,000 rpm, c) temperature 45 ºC, joint deflection 30 degrees, speed 250 rpm, running time 4 hours, d) temperature -35 ºC, joint deflection 30 degrees, 30 starts from 0 to 250 rpm, e) temperature 90 ° C, joint deflection 42 degrees, speed 20 rpm / min., running time 4 hours, f) temperature -35 ºC, joint deflection 42 degrees, 15 starts from 0 to 20 rpm, g) temperature -40 ºC, 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 7 homokinetic joints with the bellows according to the invention in different flexion positions,

characters

8 and 9 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 3.20 mm in the region of the fold base 5 and tapers towards the fold tip 6 towards 0.60 mm. The front flank 3 of the second folds 2 has a wall thickness of 2.40 mm in the region of the fold base 5 and tapers to 0.40 mm. The rear flank 4 of the first fold 1 and also the rear flank 4 of the further fold 2 have the same dimension in the area of the fold base 5, namely 1.50 mm and taper to 0.60 or 0.40 mm. The fold base 5 at the front flank 3 of the third fold 21 is 1.80, the fourth fold 20 1.65 and the fifth fold 19 1.40 mm. The corresponding rear flanks 4 have a thickness of 1, 50 or 1.35 or 1.30 mm in the fold base 5. They taper to a total of 0.40, 0.25 and 0.20 mm.

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 α 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 angle α is 10 degrees. The first contact of the folds occurs with one another, the fifth fold 19 and the fourth fold 20, in FIG

4, the diffraction angle α 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 α is 37.5 degrees, which gives the fourth touch, that is to say that the second fold 2 is now also in contact with the first fold 1. 6 shows a diffraction of 40.5, in FIG. 7 that of 50 degrees. All wrinkles touch each other continuously.

Figures 8 and 9 show a homokinetic joint according to the prior art, i. H. a homokinetic joint 7, which according to FIG. 8 has a diffraction angle α of 42.0 and according to FIG. It is shown that at 42.0 degrees diffraction the first fold 1 has already been slipped over, and at a diffraction angle α of 50.0 degrees, the last fold 19 also slips over itself. In addition, the buckling 22 can be clearly seen in the practically stretched area.

Claims

1. bellows for fixed joints with a deflection of up to 50 degrees, which consists of a thermoplastic elastomer based on polyetherester and has at least three folds, characterized in that at least the front flank (3) of the first

Fold (1) and possibly the front flank (3) of the second fold (2), seen from the side facing away from the joint (7), a taper ratio of the flank wall thickness from the fold base (5) to fold tip (6) from 15: 1 to 8 : 1 and all other flanks (8) have a ratio of the flank wall thicknesses of 6: 1 to 4: 1.

2. Bellows according to claim 1, characterized in that the flank wall thickness of the front flank (3), the first fold (1) and possibly the second fold (2) in the region of the fold base (5) between 2.0 and 3.5 mm lies.

3. Bellows according to one of claims 1 and 2, characterized in that the flank wall thickness of the further folds (8) in the region of the fold base (5) is between 1.2 and 2.2 mm.

4. Bellows according to one of claims 1 to 3, characterized in that the flank wall thickness in the region of the fold tip (6) is between 0.2 and 0.4 mm.