DE4328280C2 - worm gear - Google Patents

Description

The invention relates to a worm gear with worm and worm wheel.

Worm gearboxes have long been known in technology where they are widely used development areas. They are characterized by a low-noise Run as well as the possibility of realizing large translations in just one step.

The worm gear used for power transmission according to the state of the art The drives mostly consist of case-hardened and possibly ground steel snails and bronze worm wheels. Bronze wheels show compared to other wheel materials, particularly good running-in properties that the Reduction of manufacturing inaccuracies and the adaptation of the tooth flanks to favoring stagnant operating conditions. Also occurs with bronze worm gears practically no food. However, bronze is about ten times more expensive than steel and exhibits compared to steel materials, significantly lower strength values, which results in Bronze results in increased wear compared to steel materials. In "machines elements ", Volume III, 2nd edition (1986), Springer-Verlag, are on page 89 in Table 25/4 Material properties for worm gears with different material combinations specified. These material pairings also include worms made from operational ge hardened steel and worm wheels made of gray cast iron (GG) and cast iron with nodular graphite (GGG). The latter material pairings with worm wheels made of gray cast iron or from spheroidal graphite cast iron are considered only for low sliding speeds (hand operation). From the reference to manual operation it follows that these be Known material combinations as unsuitable for power transmissions.

The publication Langenbeck, E. Düser, P. Widmann, J. Greiner, H. Leibold: "Unter Searches for the choice of materials for worm gears "in Drive Technology, Volume 29 (1990), No. 3, pages 61 to 63, relates to the pairing of case-hardened blades cke / case hardened worm wheel. This material pairing is with one tooth The geometry has been optimized so that the gearbox is only in the  hydrodynamic range runs and does not allow operation in the mixed friction area.

The publication Hachenberg, K., H. Kowalke, J.M. Motz, K. Röhrig, W. Stiefer, H. P. Staudinger, P. Tölke, H. Werning, D. B. Wolters: "Ductile cast iron, cast iron with Ku gelgraphit ", Düsseldorf: Central casting use, reprint from" construct + gie ßen ", Volume 13 (1988), No. 1, pages 62, 63, relates only to cast iron Wheels in helical gear units, but not in worm gear units.

The invention has for its object material combinations for worm gears to find out which ones to extend in addition to cost advantages in the manufacture Lead lifetimes.

The lifespan of a worm gear is primarily determined by the load bearing capacity as well as determined by the wear resistance.

In order to differentiate between the two types of damage: the description of the invention assumed that the essential characteristic a feeding damage the sudden onset of material transfer from the partner with local lower strength on the partner with locally higher strength. This material Transfer is also due to an increase or a strongly fluctuating Ver marked the degree of loss during feeding. In contrast to that Wear a continuous flank removal from less hard or both contact partners for whom there is no increase in the degree of loss.

Particularly good results are achieved with a material combination which consists of a hardened steel worm made of 42CrMo4 and a worm wheel the ductile iron material GGG-40.

The preferred lubricant is a commercially available gear oil with high EP additives based on polyglycol with a kinematic viscosity ν ₄₀ of 460 mm ² / s and a kinematic viscosity ν ₁₀₀ of 82 mm ² / s as well as a classification with regard to load bearing capacity in the class GL5 the API classification (API = American Petroleum Institute).

The above object is achieved by a worm gear solved according to claim 1.

The invention is described below on the basis of exemplary embodiments and comparisons examples and described in more detail with reference to the drawing. In this shows:

Fig. 1 is a characteristic diagram of the Flankenabtrages per duty cycle for an annealed screw from the material 42CrMo4 and a wheel of the material GGG-40,

Fig. 2 for comparison, a map of the flank removal per load cycle for a case-hardened screw made of the material 16MnCr5 and a wheel made of bronze CuSn12Ni and

Fig. 3 is a graphical diagram in which for a variety of material pairing conditions the load bearing capacity is specified as a function of the input speed and the output torque.

The worm and worm gear materials examined are in the following table 1 together with their hardness, density and modulus values are given.

Plate 1

The test was carried out as follows:
After setting the best possible contact pattern, a test consisted of a sequence of individual test runs at different load levels that continued until damage occurred, the duration of a test run being set at 20 hours. In the first load stage, the output torque T _{2 was} 200 Nm, with each further load stage T _{2 was} increased by 50 Nm or 100 Nm.

After each test run, the worm wheel became the best Wear removed. The wear was ever because by weighing the worm wheel using a precision sions balance determined. Because the measured wear out load adjustment wear and normal operating wear wear, was usually every second Load level try again at this load level for so long catches up until a constant amount of wear (operating ver wear) resulted. This way the load adjustment wear can be largely eliminated for the evaluation. Wear on the screw occurred because of the much harder only a very small amount on and was therefore not determined.

The tests were all carried out with injection lubrication and an oil injection temperature of 80 ° C.

The operating wear (mg / h), which has been determined on different materials, cannot be used for a direct comparison if the materials have different densities. The density of the investigated bronze CuSn12Ni is 8.8 kg / dm ³ , whereas the density of the investigated material 42CrMo4 is 7.8 kg / dm ³ . The operational wear could, however, be converted into a flank abrasion δ _NL per load cycle via the flank surface and material density as well as the drive speed, ie into a layer thickness erosion, which is therefore independent of the respective material. Figs. 1 and 2 show for the material pairings 42CrMo4 / GGG-40 (Fig. 1) or 16MnCr5 / CuSn12Ni (Fig. 2) maps the Flankenabträge thus determined, depending weils for lubrication with the best for the particular combination of materials suitable Lubricant that had been determined by preliminary tests.

The map shown in Fig. 1 relates to a fiction, according worm gear with a worm from the vergue ended steel material 42CrMo4 and a wheel from the spheroidal cast material GGG-40. In contrast, the map ge according to FIG. 2 relates to a material combination not according to the invention with a worm made of case-hardened steel (16MnCr5) and a bronze wheel (GZ-CuSn12Ni). In Figs. 1 and 2, the drive speed are respectively plotted n is _1, the output torque T ₂ and the Flankenabtrag (logarithmic mixed).

From Figs. 1 and 2 it can be seen that for both material / lubricant combinations at all drive speeds the flank removal per load cycle (LS) increases with increasing load. The quantitative comparison of the maps according to FIGS. 1 and 2 shows that wheels made of GGG-40 in cooperation with a worm made of 42CrMo4 sometimes have significantly lower flank abrasion than bronze wheels in cooperation with a worm made of a case-hardened steel material according to FIG. 2 GGG-40 wheels initially reduce the flank abrasion with increasing drive speed, but then increase again from drive speed of 500 min ^-1 . A comparison of FIGS. 1 and 2 makes it clear that the flank removal, ie the operational wear in the material pairing according to the invention ( FIG. 1) is practically lower in all operating conditions than in the comparison material pairing according to FIG. 2.

The results of the load bearing capacity tests are shown in FIG. 3.

Fig. 3 allows a comparison of the load bearing capacity of the material pairing according to the invention [screw 42CrMo4, (tempered) / wheel GGG-40] with other material pairings not according to the invention. For these comparative tests, a worm made of the case-hardened steel material 16MnCr5 was combined with wheels made of GGG-40, GGG-60, GG-25 and 42CrMo4. Further, FIG. 3 includes the catalog torque according to the company publication "MUTAX worm and" TGW Thyssen no. 1-750. This catalog moment was determined on a worm made of case-hardened steel material 16MnCr5 in combination with a bronze wheel GZ-CuSn12Ni.

As shown in Fig. 3, the seizure capacity with lubrication with the oil S3 / 460 decreases with increasing drive speed n ₁ for all investigated material combinations. It is important that the highest seizure capacities according to FIG. 3 are achieved with the material combination according to the invention, that is to say with a worm made of 42CrMo4 (tempered) and wheels made of GGG-40. The load carrying capacities determined on this material combination nation according to the invention lie far above the catalog moment for bronze wheels. Comparatively high feeding capacities were also achieved with case-hardened worms and wheels made of GGG-40 and GGG-25. Here, too, there were large safety clearances from the catalog torque, especially at lower screw speeds. On the other hand, wheels made of GGG-60 or 42CrMo4 failed due to seizure even under loads below the catalog torque.

The lubricant S3 / 460 mentioned above is a commercially available gear oil. It is a polyglycol with a high-alloy EP additive. The kinematic viscosity ν _{40 of} this gear oil is 40 mm ² / s, and the kinematic viscosity ν _{100 of} this gear oil is 82 mm ² / s. Furthermore, this gear oil is classified in the GL5 class of the API classification (American Petroleum Institute) with regard to load bearing capacity.

Claims (2)

1. worm gear for power transmission with worm and worm wheel, characterized in that for the worm one of the following tempering steels (according to DIN 17200):
34Cr4; 25CrMo4; 34CrMo4; 42CrMo4; 50CrMo4; 30CrMoV9; 36CrNiMo4; 34CrNiMo6 and 30CrNiMo8
used in tempered condition and that one of the following gray cast iron materials (according to DIN 1691) is used for the worm wheel:
GG-25; GG-30; GG-35 and GG-40
or one of the following ductile iron materials (according to DIN 1693):
GGG-38; GGG-40; GGG-42 and GGG-50
is used together with a gear oil with high EP additives based on polyglycol with a classification with regard to load bearing capacity in class GL5 of the API classification. 2. worm gear according to claim 1, characterized net that the screw from the tempered steel material 42CrMo4 and the worm wheel made of nodular cast iron GGG-40 exists.