Gearwheel pairing for a helical gearing, a helical gearing with such a gearwheel pairing, and a use of such a gearwheel pairing in helical gearings

Abstract

A gearwheel pairing for a helical gearing, comprising a helical gear with a first toothing segment, and a worm with a second toothing segment, wherein the first toothing segment and the second toothing segment can be brought into intermeshing and form an involute toothing when intermeshed, the materials of the first and the second toothing segments are chosen such that when intermeshed there results a plastic-metal material pairing, and the toothing segment made of plastic has a first normal tooth thickness and the toothing segment made of metal has a second normal tooth thickness, wherein the ratio of the first normal tooth thickness to the second normal tooth thickness is increased by 10 to 200% with respect to a reference profile.

Claims

1. A gearwheel pairing for a helical gearing, comprising: a helical gear with a first toothing segment; a worm with a second toothing segment; wherein the first toothing segment and the second toothing segment are arranged to intermesh and form an involute toothing when intermeshed; wherein materials of the first toothing segment and the second toothing segment are selected such that when the first toothing segment and the second toothing segment are intermeshed a plastic-metal material pairing results, and wherein one of the first toothing segment and the second toothing segment is made of plastic and has a first normal tooth thickness and another of the first toothing segment and the second toothing segment is made of metal and has a second normal tooth thickness, wherein a ratio of the first normal tooth thickness to the second normal tooth thickness is increased by a range with respect to a reference profile, wherein the range is 10 to 200% with respect to a reference profile, wherein the worm of the reference profile has a normal tooth thickness (sn) of 1.3096 mm and a profile shift coefficient (x) of −0.3053, and wherein the helical gear of the reference profile has a normal tooth thickness (sn) of 1.6633 mm and a profile shift coefficient (x) of 0.1647, resulting in a ratio Vsn of 0.7874.

2. The gearwheel pairing according to claim 1, wherein the toothing segment made of plastic has a root circle diameter which is increased by 5 to 40% with respect to the reference profile.

3. The gearwheel pairing according to claim 1, wherein the toothing segment made of plastic has a root circle diameter which is increased by 6 to 20% with respect to the reference profile.

4. The gearwheel pairing according to claim 1, wherein a normal meshing angle of the involute toothing differs by ±5° from the reference profile.

5. The gearwheel pairing according to claim 1, wherein a normal meshing angle of the involute toothing is reduced by 1 to 4° relative to the reference profile.

6. The gearwheel pairing according to claim 1, wherein the worm is connected to a drive shaft and the first toothing segment of the helical gear and the second toothing segment of the worm are intermeshed.

7. The gearwheel pairing according to claim 6, wherein the helical gear consists of metal, and is formed as a spindle nut and interacts with a spindle and the worm consists of plastic.

8. The gearwheel pairing according to claim 1, wherein the range is 15 to 120% with respect to the reference profile.

9. A method for using the gearwheel pairing as claimed in claim 1, comprising activating the gearwheel pairing to adjust a seat-length of a vehicle seat, wherein the gearwheel pairing is coupled to the vehicle seat.

10. A gear pairing, comprising: a helical gear with a helical toothing segment, the helical toothing segment comprising either a plastic toothing segment or a metal toothing segment; a worm with a worm toothing segment, wherein: the worm toothing segment comprises the plastic toothing segment if the helical toothing segment comprises the metal toothing segment; the worm toothing segment comprises the metal toothing segment if the helical toothing segment comprises the plastic toothing segment; and wherein the helical toothing segment and the worm toothing segment are arranged to intermesh with a plastic-metal material pairing and form an involute toothing when intermeshed; wherein the plastic toothing segment has a plastic normal tooth thickness; wherein the metal toothing segment having a metal normal tooth thickness, wherein a ratio of the plastic normal tooth thickness to the metal normal tooth thickness is increased by a range with respect to a reference profile, wherein the range is 10 to 200% with respect to a reference profile, wherein the worm of the reference profile has a normal tooth thickness (sn) of 1.3096 mm and a profile shift coefficient (x) of −0.3053, and wherein the helical gear of the reference profile has a normal tooth thickness (sn) of 1.6633 mm and a profile shift coefficient (x) of 0.1647 resulting in a ratio Vsn of 0.7874.

11. The gear pairing according to claim 10, wherein the plastic toothing segment has a root circle diameter which is increased by 5 to 40% with respect to the reference profile.

12. The gear pairing according to claim 10, wherein the plastic toothing segment has a root circle diameter which is increased by 6 to 20% with respect to the reference profile.

13. The gear pairing according to claim 10, wherein a normal meshing angle of the involute toothing differs by ±5° from the reference profile.

14. The gear pairing according to claim 10, wherein a normal meshing angle of the involute toothing is reduced by 1 to 4° relative to the reference profile.

15. The gear pairing according to claim 10, wherein the worm is arranged to be connected to a drive shaft.

16. The gear pairing according to claim 10, wherein the helical gear is formed as a metal spindle nut and interacts with a spindle and the worm is formed of plastic.

17. The gear pairing according to claim 10, wherein the range is 15 to 120% with respect to the reference profile.

18. A gear pairing, comprising: a helical gear with a helical toothing segment, the helical toothing segment comprising either a plastic toothing segment or a metal toothing segment; a worm with a worm toothing segment, wherein: the worm toothing segment comprises the plastic toothing segment if the helical toothing segment comprises the metal toothing segment; the worm toothing segment comprises the metal toothing segment if the helical toothing segment comprises the plastic toothing segment; and wherein the helical toothing segment and the worm toothing segment are arranged to intermesh with a plastic-metal material pairing and form an involute toothing when intermeshed; wherein the plastic toothing segment has a plastic normal tooth thickness; wherein the metal toothing segment having a metal normal tooth thickness, wherein a ratio of the plastic normal tooth thickness to the metal normal tooth thickness is increased by a range with respect to a reference profile, wherein the range is 15 to 120% with respect to a reference profile; wherein a normal meshing angle of the involute toothing is reduced by 1 to 4° relative to the reference profile; and wherein the plastic toothing segment has a root circle diameter which is increased by 6 to 20% with respect to the reference profile, wherein the worm of the reference profile has a root circle diameter d.sub.f of 5.950 mm, and wherein the gear of the reference provide has a root circle diameter d.sub.f of 10.950 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The subject matter of the present application will be explained more closely below with reference to the accompanying drawings showing exemplary embodiments in which:

(2) FIG. 1 shows a cross section view through a helical gear according to one embodiment of the present disclosure as compared to a helical gear based on a reference profile,

(3) FIG. 2 shows a cross section view through a worm according to one embodiment of the present disclosure as compared to a worm based on a reference profile,

(4) FIG. 3 shows an enlarged representation of the feature A of the worm as defined in FIG. 2, and

(5) FIG. 4 shows a basic diagram of a helical gearing with a worm as represented in FIG. 1 and a helical gear as represented in FIG. 2.

DETAILED DESCRIPTION

(6) FIG. 1 shows a cross section view through a helical gear 10 according to one embodiment of the present disclosure as compared to a helical gear 10P based on a reference profile. The continuous line describes the helical gear 10 according to the present disclosure, while the broken line shows a helical gear 10P which is in series production by the applicant.

(7) The helical gear 10 shown is made entirely of metal. The helical gear 10 has a first toothing segment 12, within which there are a number of teeth 14. Radially inward, the first toothing segment 12 is bounded by a root circle with a root circle diameter d.sub.f2, while the first toothing segment 12 is bounded radially outward by a tip circle with a tip circle diameter d.sub.a2.

(8) Furthermore, the teeth 14 of the helical gear 10 have a normal tooth thickness s.sub.n2, which designates the thickness of the teeth 14 on a pitch circle with the pitch circle diameter d.sub.02 of the helical gear 10. The distance between two neighboring flanks of the teeth 14 is known as the gap width e.sub.2. The index 2 in the above given quantities of the helical gear 10 indicates that the helical gear is made of metal.

(9) FIG. 2 shows a cross section view through a worm 16 according to one embodiment of the present disclosure as compared to a worm 16P based on a reference profile of the applicant. The continuous line describes the worm 16 according to the present disclosure, while the broken line shows a worm 16P which is in series production by the applicant.

(10) The worm 16 shown is made entirely of plastic. The worm 16 has a second toothing segment 18, within which there are a number of teeth 20. Radially inward, the second toothing segment 18 is bounded by a root circle with a root circle diameter d.sub.f1, while the second toothing segment 18 is bounded radially outward by a tip circle with a tip circle diameter d.sub.a1. The index 1 in the above given quantities indicates that the worm 16 is made of plastic.

(11) FIG. 3 shows the feature A of the worm 16 represented in FIG. 2 in enlarged form. As can be seen from FIG. 3, the teeth 20 of the worm 16 have a normal tooth thickness s.sub.n1, which designates the thickness of the teeth 20 on a pitch circle with the diameter d.sub.01 of the worm 16.

(12) FIG. 4 shows a helical gearing 22 by a basic diagram. The helical gear 10 and the worm 16 are intermeshing and together form a gearwheel pairing 24, forming an involute toothing 26. Since the helical gear 10 consists of metal and the worm 16 consists of plastic, a plastic-metal material pairing results from the intermeshing.

(13) The worm 16 in the example shown is connected to a drive shaft 28, which can be placed in motion by an engine, not shown. The helical gear 10 is fashioned as a spindle nut 30, having an internal thread 32. By the internal thread 32, the spindle nut 30 is connected to a spindle 34, the longitudinal axis L of the spindle 34 running perpendicular to the plane of the drawing in FIG. 4. Not shown is a housing in which the gearwheel pairing 24 is arranged.

(14) In the example depicted, the helical gearing 22 is especially suitable as a seat length adjustment in vehicles. The spindle 34 is mounted in rotationally locked manner in the vehicle. If the worm 16 is turned by the drive shaft 28 due to a corresponding activation of the engine, the rotation of the worm 16 is transmitted with the corresponding transmission ratio to the spindle nut 30. Consequently, the spindle nut 30 and the entire helical gearing 22 move along the longitudinal axis L of the spindle 34. This movement is used to adjust the length of the respective seat.

(15) As explained, the gear pair comprising the intermeshing worm 16 and the helical gear 10 forms an involute toothing 26. In FIG. 3, the normal meshing angle α.sub.n of the proposed involute toothing 26 is contrasted with the normal meshing angle αP of the reference profile of the applicant.

(16) In the following, the relations of the most important quantities of involute toothings 26 are given. The most important quantities are:

(17) d.sub.0 Pitch circle diameter (mm)

(18) d.sub.a Tip circle diameter (mm)

(19) d.sub.f Root circle diameter (mm)

(20) e Gap width (mm)

(21) h Tooth height (mm)

(22) h.sub.a Tooth tip height factor

(23) h.sub.f Tooth root height factor

(24) m.sub.n Normal modulus (mm)

(25) p Pitch (mm)

(26) s.sub.n Normal tooth thickness (mm)

(27) x Profile shift coefficient (−)

(28) z Number of teeth (−)

(29) α.sub.n Normal meshing angle (°)

(30) γ,β Pitch angle or helix angle (°)

(31) These quantities stand in the following relations to each other:

(32) For the normal tooth thickness s.sub.n:

(33) $s_n=m_n*\left(\frac{\pi }{2}+x*\sin {\alpha }_n\right)$

(34) For the pitch circle diameter d.sub.0 the following relations apply:

(35) $d_0=z\frac{m_n}{\cos \beta }=z\frac{m_n}{\sin \gamma }$

(36) For the root circle diameter d.sub.f the following relations apply:
d.sub.f=d.sub.0−2*m.sub.n*h.sub.f+2*x*m.sub.n

(37) For the tip circle diameter:
d.sub.a=d.sub.0+2*m.sub.n*h.sub.a+2*x*m.sub.n

(38) For the normal modulus:

(39) $m_n=\frac{p}{\pi }=\frac{s+e}{\pi }\approx \frac{2s}{\pi }$

(40) It should be noted that the gap width e and the normal tooth thickness s of the reference profile are approximately the same for both the toothing segment made of plastic and the toothing segment made of metal, which is not the case for the proposed involute toothing 26. For the tooth height h we have:
h=2.25*m.sub.n

(41) For the ratio Vsn we have:

(42) $V_{\mathrm{sn}}=\frac{s_{n1}}{s_{n2}}$

(43) The following table shows a comparison of the important values of the proposed involute toothing 26 relative to the reference profile which is produced in series by the applicant and is thus known, with the aid of two sample embodiments. Here, the worm 16 is made of plastic and the helical gear 10 is made of metal.

(44) TABLE-US-00001 values per values sample values sample reference profile embodiment 1 embodiment 2 worm gear worm gear worm gear Number of teeth z 2 13 2 13 3 20 Pitch angle or helix angle 12.6608 12.6608 12.9000 12.9000 11.8500 11.8500 γ, β [°] Normal meshing angle 21.0000 20.0000 17.0000 αB[°] Normal modulus m.sub.n 0.9800 0.9868 0.6278 [mm] Pitch circle diameter d.sub.0 8.94 13.06 8.84 13.16 9.17 12.83 [mm] Tooth tip height factor h.sub.a 1.1255 0.8530 0.4927 1.4728 1.3465 1.3900 Tooth root height factor 1.2214 1.2400 1.6177 0.6401 1.5100 1.4665 h.sub.f Profile shift coefficient x −0.3053 0.1647 0.3736 −0.5155 −0.1839 −0.0461 Normal tooth thickness s.sub.n 1.3096 1.6633 1.8184 1.1798 0.9156 0.9684 [mm] Ratio Vsn 0.7874 1.5413 0.9455 Tip circle diameter d.sub.a 10.550 15.052 10.550 15.050 10.631 14.517 [mm] Root circle diameter d.sub.f 5.950 10.950 6.385 10.880 7.045 10.930 [mm]

(45) The normal meshing angle α.sub.n, the normal tooth thickness s.sub.n and the root circle diameter d.sub.f are the quantities of the proposed involute toothing which are specifically changed. These quantities are shown highlighted in the table. The other values indicated in the table change by virtue of the connection among the different quantities per the formulas.

LIST OF REFERENCE SYMBOLS

(46) 10 Helical gear 10P Known helical gear 12 First toothing segment 14 Teeth 16 Worm 16P Known worm 18 Second toothing segment 20 Teeth 22 Helical gearing 24 Gearwheel pairing 26 Involute toothing 28 Drive shaft 30 Spindle nut 32 Internal thread 34 Spindle A Cutout d.sub.0 Pitch circle diameter d.sub.a Tip circle diameter d.sub.f Root circle diameter e Gap width h Tooth height h.sub.a Tooth tip height factor h.sub.f Tooth root height factor L Spindle longitudinal axis m.sub.n Normal modulus p Pitch s.sub.n Normal tooth thickness V.sub.sn Ratio of s.sub.n1 to s.sub.n2 x Profile shift coefficient z Number of teeth α.sub.n Normal meshing angle αP Known normal meshing angle β,γ Pitch angle or helix angle