DE1960464A1 - Worm drive with cylindrical worm - Google Patents

Description

Dr. Gerhard Stade, 1 Berlin 30, Regensburger Str.5a

Worm drive with cylindrical worm

There are known worm drives with a cylindrical worm. In all worm drives, the shape of the worm gear flanks is determined by the shape of the screw flanks. The worm meshes with the worm wheel. Both form the worm drive. The drive power is generated by the rolling tooth flanks of the worm drive transmit the worm wheel.

Worm drives are known to have a trapezoid, straight flank profile of the worm teeth in the longitudinal center section of the worm (Trapezoidal screws) or a trapezoidal-convex flank profile (involute screws). There are also worm drives known with a trapezoidal-concave flank profile of the worm teeth, known as hollow flank worms will.

The screw flanks are usually milled and then Ground to achieve a higher surface quality. Around

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To be able to produce reproducible and interchangeable screws in large series, the screw flanks and so that the flanks of the worm gear cutters are also surfaces that arise when grinding with grinding wheels, which are caused by Dressers can be shaped in such a way that they always produce the same profile regardless of their diameter.

The known involute worm gears meet this requirement. Their advantage is the reproducible, exact production, which is why they are preferred in practice. Their downside is but the lack of flank contact, which is only along a line of contact between the tendon tooth flanks and the Worm gear tooth flanks takes place.

The lines on the flank surface are used as contact lines of a worm gear, along which the worm tooth flank and the worm gear tooth flank at the touch the current angular position of the worm wheel. When turning the worm, that is a rotation of the worm wheel causes the position and shape of these lines of contact to change.

In the case of involute worm drives, the result on each worm gear tooth flank is as mentioned, a single line of contact that must transmit the power. This line of contact is essential straight forward. The desired lubricating pressure between the touching tooth flanks cannot arise here. Therefore involute worm drives have a power loss that is caused by the friction that occurs between the tooth flanks of the worm and the worm wheel is conditional.

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- 3 The same disadvantages occur with trapezoidal screws.

The hollow flank tendons show a better carrying behavior compared to the trapezoidal and involute snails. Through the hollow Due to the worm tooth shape, the tooth flank profiles nestle under load in a somewhat larger contact area, although here too there is only one contact line in the main area every tooth flank is present. Due to the hollow tooth shape of the worm, the line of contact runs convex to the tooth base of the worm wheel. This promotes the formation of lubrication pressure and the power loss compared to the involute worm drive less. Despite these certain advantages, the hollow flank worm drive has the decisive disadvantage that the It is extremely difficult to produce screws that are identical to one another.

For reasons of manufacture, involute worm drives are therefore preferred, especially when replacing them.

The invention has set itself the task of improving the flank shape of the worm so that it is larger in the worm drive Can transmit torques and power than before, and an economical production of the same screws for to enable replacement construction.

To solve this problem, the invention proposes that the screw flanks have a cycloid shape in the frontal section of the worm.

Due to the cycloid shape of the screw flanks, we nestle against one another, which is also better than the hollow flank screw of the tooth flank profile is achieved because the tooth flanks of the worm and the worm wheel come into contact along two lines of contact takes place during the entire tooth engagement. In addition, in every phase of the engagement of the screw flank and

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1960A64

Schneekenradflanke through the lines of contact oil chambers in which the hydrodynamic lubrication required is located Oil pressure builds up, the build-up of which is supported by the capillary action of the flanks nestling closely together.

The progress achieved by the invention enables the transmission of greater torques and powers than with the well-known snails.

Cycloid worm drives can be reproducibly produced by milling and grinding so that they are identical to one another Have cycloid screws produced interchangeably in large series.

The pitch line of the cycloid worm advantageously coincides with its outer cylinder. As a result, the two lines of contact and the line of action run roughly in the axial section of the worm symmetrical to the center of the tooth.

Further details of the invention can be seen from the following description with reference to the figures, namely show:

Fig. 1 shows a known involute worm drive in the axial section with the line of action drawn,

FIG. 2 shows an end section of the involute worm drive according to FIG. 1 with lines of contact drawn on the tooth flank of the worm wheel,

3 shows the lines of contact of the tooth flanks of the involute worm drive 1 and 2 during the entire procedure in successive phases,

4 the generation of cycloid flanks schematically,

5 shows a cycloid worm gear consisting of a worm and a worm wheel with drawn line of action,

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6 shows an end section of the cycloid worm drive according to FIG. 5 with lines of contact drawn on the Tooth flank of the worm wheel and

7 shows the lines of contact of the cycloid worm drive according to FIGS. 5 and 6 during the entire engagement in successive ones Phases.

FIGS. 1 to 3 illustrate the prior art on an involute worm drive.

The involute worm 1 is in meshing engagement with the worm wheel 2. The screw axis is denoted by 3. 4 is the pitch line of the involute worm at a distance of 5 from the worm axis. The rolling line 4 goes through the center point 6 of the common tooth height. 7 denotes the line of action between the Involute flanks 8 and 9 of the teeth of the worm and the worm wheel. Those present during the meshing Lines of contact are denoted by 10. They arise during the rotation of the worm on the flank surface 9 and set in chronological sequence represents those lines along which the worm tooth flank 8 and the worm gear tooth flank 9 in the touch the current angular position of worm wheel 2. In each time interval of rotation results on the worm gear tooth flank 9 only a single line of contact 10 which transmits the torque and the power and is essentially straight runs.

The family of contact lines 10 shown in FIG. 2 is shown in FIG. 3 in the individual phases. Here, the worm and thus the worm wheel are rotated by the same angle of rotation. The lines of contact 10 result one after the other,

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ο q 4. c e 7 ο

10, 10, 10, 10, 10 °, 10 and 10.

The invention is illustrated in FIGS.

Fig. 4 illustrates the creation of cycloid snails. The flanks of cycloid snails are in the frontal section of the snail real cycloids. These arise on the circular disk 11 with the outer circle 12 and the root circle 13 when the tool 14 with the Outer circle 15 and the foot circle 16 on the circular disk 11 rolls. Here, the foot circle 16 rolls on the. Outer circle 12 and the Tool tip 17 describes the cycloid during rolling: 18. The tool tip 17 therefore lifts so much material from the circular disk 11 that a gap is created through the Cycloid flanks 19 and 20 is limited. One fictionally ranks extremely thin tool disks together in such a way that their tool tips lie on a helical line, this creates a generating tool screw, which would produce a snail with flanks that would be cycloid-shaped in the frontal section. If you lead the tip of a So grind dressing diamonds of a worm grinder along the generating helix of the tool tips 17 the flanks of the grinding wheel dressed in this way exactly the flanks of a cycloid snail.

Screws are identical to screws. The production of cycloid screws by grinding is the subject of the earlier German patent application P 19 39 919.0 of August 1, 1969.

FIGS. 5 to 7 illustrate the engagement behavior of the tooth flanks of a cycloid screw drive a.

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The cycloid worm 21 meshes with the worm wheel 22. The screw axis is denoted by 23. 24 is the pitch line of the cycloid worm at a distance of 25 from the Screw axis. The pitch line 24 of the cycloid worm 21 coincides with its outer cylinder 26. 27 denotes the Line of action between the tooth flanks 28 and 29 of the teeth of the cycloid worm 21 and of the worm wheel 22. The line of action 27 runs symmetrically to the center of the tooth. It shows that in each rotational position of the worm wheel two points of contact "in the axial section between the flanks of the cycloid worm and Worm wheel are present. The lines of contact that exist during tooth engagement are denoted by 30. They arise during the worm rotation on the flank surface 29 of the worm wheel and represent those lines in chronological order represents, along which the worm tooth flank 28 and the Touch worm wheel tooth flank 29 at the current angular position of worm wheel 22. In each time interval of the Rotation, there are always two lines of contact 30 on the worm gear tooth flank 29, which represent the torque and the power transfer.

The family of contact lines 30 shown in FIG. 6 is shown in FIG. 7 in the individual phases. The cycloid worm and the worm wheel are each rotated by the same angle of rotation. ^{The contact lines 30 10} and 30 ¹¹ , 30 ²⁰ and 30 ² \ 30 ³ ° and 30 ³¹ , 30 ⁴ ° and 30 ⁴¹ , 30 ⁵ ° ^{and 30 51} , 30 ⁶ ° ^{and 30 61} , 30 ™ and 30 ^{? 1} result one after the other , 30 ⁸ ° and 30 ⁸¹ . At the current angular position of the worm wheel, two of these lines of contact transfer the torque and the power to it, both of which can be considerably greater than before.

The lines of contact 30 and 30 of Fig. 7a are strongly curved

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and lie in the right and left side areas of the tooth flanks. During the rotation of the worm wheel according to FIGS. 7b to 7d

20 21 30 31

hike the contact lines 30 and 30 ', 30 and 30,

40 41

30 and 30. towards each other and form a narrowing

12 3 4

Oil chambers 31, 31, 31 and 31. On further rotation from the position according to FIG. 7d into that according to FIG. 7e, the lines touch, as shown in dashed lines in FIG. 7e, and then move up and down away from one another. This movement is illustrated in Figures 7e to 7h. This now forms two oil chambers 31 and 31 , 31 and 31, 31 and

71. ί? 0 Rl

31, 31 and 31. These oil chambers narrow in the direction of the

Worm root 32 and worm wheel root 33 (Fig. 6),

4th
The oil chamber 31 of Fig. 7d goes continuously into the oil

50 51

chambers 31 and 31 of FIG. 7e.

The oil pressure required for hydrodynamic lubrication is built up in the narrowing oil chambers the capillary action of the closely clinging flanks is supported.

In contrast to this, oil chambers cannot form in involute screws 7 according to FIGS. 1 to 3.

Claims;

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Claims (2)

Patent claims: L) worm drive with cylindrical worm, characterized in that that the screw flanks have a cycloid shape in the frontal section of the screw. 2. worm drive according to claim 1, characterized in that that the pitch line of the worm with the outer cylinder of the d Snail collapses. 209808/0701