DE4328280A1 - Worm gear pair - Google Patents

Abstract

A worm gear pair consists of a worm of a hardened chromium-molybdenum steel, if desired with additions of vanadium and/or nickel, preferably of the steel material 42CrMo4 (hardened) and also of a worm wheel of grey cast iron or of cast iron containing spheroidal (nodular) graphite, preferably of the spheroidal-graphite-containing iron material GGG-40.

Description

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

Worm gears have long been known in the art, where they have opened up many areas of application. she are characterized by a quiet running and by the ability to do large translations in just one stage realize.

The state of the art for power transmission set worm gears mostly consist of insert gears hardened and, if necessary, ground steel screws and bronze worm wheels. Bronze wheels are particularly good in comparison to other wheel materials running properties that reduce the manufacturing inaccuracies and adapting the tooth flanks to changing ones Favor operating conditions. It also occurs with snails wheels made of bronze practically no food. Bronze is ever yet about ten times more expensive than steel and points Steel materials have significantly lower strength values, what makes for bronze compared to steel materials increased wear results. In "machine elements", volume III, 2nd edition (1986), Springer-Verlag, are on page 89 in Table 25/4 material parameters for worm gear units with different material pairings specified. To this Material pairings also include worms made of mission-hardened material tetem steel and worm wheels made of gray cast iron (GG) and cast iron with spheroidal graphite (GGG). The latter pair of materials with worm wheels made of gray cast iron or cast iron Spheroidal graphite are considered only for small sliding speeds marked (manual operation). From the note on hand operation follows that these known material pairings have proven unsuitable for power transmission.

The invention has for its object material combinations for worm gears to find which ones at cost Advantages in the production of extended life take lead.

The service life of a worm gear is primarily Li never from the load bearing capacity as well as from the wear capacity ability determined.

To differentiate between the two types of damage: eating and ver Wear is there in the present description of the invention assumed that the essential characteristic of a feed the sudden transfer of material from Partner with less local strength on the partner with locally higher strength. This material transfer is also by an increase or by a strong fluctuating course of the degree of loss during feeding featured. In contrast, wear is a constant Nuclear flank removal from the less hard or both Contact partners with whom there is no increase in the degree of loss can be determined.

The above object is achieved according to the invention solved that for the snail one of the following remuneration steels according to DIN 17200:

34Cr4; 25CrMo4; 34CrMo4; 42CrMo4; 50CrMo4; 30CrMoV9; 36CrNiMo4; 34CrNiMo6 and 30CrNiMo8

used in the tempered state and that for that Worm gear of one of the following gray cast iron materials according to DIN 1691:

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.

Particularly good results are obtained with a pair of materials achieved, which from a tempered steel screw from the Material 42CrMo4 and a worm wheel made of nodular cast iron Material GGG-40 is made.

Preferred as a lubricant is a commercially available gear oil with high EP additives based on polyglycol with a kinematic viscosity ν₄₀ of 460 mm² / s and a kinematic viscosity ν ₁₀₀ of 82 mm² / s as well as a classification in terms of load bearing capacity in class GL5 of the API Classification (API = American Petroleum Institute).

The invention is described below with reference to exemplary embodiments play as well as comparative examples and with reference to the Drawing described in more detail. 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 lot of material pairings the bearing capacity depending on the drive speed and from the torque is specified.

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

Table 1

The test was carried out as follows:

An attempt was made after setting the best possible wear picture from a law that continues until damage occurs sequence of individual test runs in different Load levels, the duration of a test run being 20  h was set. In the first load stage the Ab was drive torque T₂ 200 Nm at each additional load level T₂ was increased by 50 Nm or 100 Nm.

After each trial 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 ver 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 for the evaluation can be largely eliminated. 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 / dm³, whereas the density of the investigated material 42CrMo4 is 7.8 kg / dm³. However, the operational wear could be converted into a flank removal δ _NL per load cycle via the flank surface and material density as well as the drive speed, ie into a layer thickness reduction, 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 tion for the respective Werkstoffpaa best suitable lubricant, which 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 pairing 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 n₁, the output torque of T₂ 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 ablation 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 in 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, i.e. with a worm made of 42CrMo4 (hardened and tempered) and wheels made of GGG-40. The load carrying capacities determined on this material combination according to the invention are 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 42CrNo4 failed due to seizure even under loads below the catalog torque.

The S3 / 460 lubricant mentioned above is a commercially available gear oil. It is a polyglycol with a high-alloy EP additive. The kinematic viscosity ν₄₀ of this gear oil is 40 mm² / s, and the kinematic viscosity ν _{100 of} this gear oil is 82 mm² / 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 (3)

1. worm gear 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 is used in the tempered state and that one of the following gray cast iron materials (according to DIN 1691) GG-25; GG-30; GG-35 and GG-40 or one of the following nodular cast iron materials (according to DIN 1693) GGG-38; GGG-40; GGG-42 and GGG-50 is used. 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. 3. Use of the worm gear according to claim 1 or 2 with a commercially available gear oil with high EP additive based on polyglycol with one class in terms of eating capacity in the GL5 class API classification.