Helical gear pairing for a helical gear unit, pairing and use thereof

Abstract

A gear pairing for a helical gear unit or a spur gear unit, comprising a first gear with a first toothing portion, and a second gear with a second toothing portion, wherein the first gear has a first axis and the second gear has a second axis, which enclose a shaft angle, which is between 0 and 90°, the first toothing portion and the second toothing portion can be brought into meshing engagement and, when engaged, form an involute toothing, the materials of the first and second toothing portions are chosen so that, when engaged, a material pairing metal/plastic results, and the toothing portion made of plastic has a first helix angle and the toothing portion made of metal has a second helix angle.

Claims

1. A gear pairing for a helical gear unit, comprising: a first gear having a first toothing portion within which a number of first teeth are located and a first axis and wherein the first teeth have a front side and a back side; a second gear having a second toothing portion within which a number of second teeth are located and a second axis, wherein the first axis and the second axis enclose a shaft angle (χ) that is 90°; wherein the first teeth and the second teeth meshingly engage at only a single contact point located either on the front side or the back side of the first teeth such that a backlash is formed, the first teeth and the second teeth forming an involute toothing when engaged; wherein the first toothing portion is formed of a material selected from the group consisting of plastic or metal, and the second toothing portion is formed of the material selected from the group consisting of plastic or metal and which is different than the material of the first toothing portion such that when the first toothing portion and the second toothing portion meshingly engage, a material pairing of metal/plastic results, and wherein the toothing portion formed of plastic consists of a single plastic helix angle (β.sub.1) and the toothing portion formed of metal consists of a single metal helix angle (β.sub.2), wherein a difference (Δβ) between an absolute value of the plastic helix angle (|β.sub.1|) and an absolute value of the metal helix angle (|β.sub.2|) is for the helical gear unit with the shaft angle (χ) of 90°: Δβ=|β.sub.1|−|β.sub.2|=90°−χ±K≠90°−χ, wherein 0.5°≤K≤5°.

2. The gear pairing for the helical gear unit according to claim 1, wherein a reference profile has a reference helix angle (β.sub.r), wherein the plastic helix angle (β.sub.1) is different from the reference helix angle (β.sub.r), the metal helix angle (β.sub.2) is different from the reference helix angle (β.sub.r) or both the plastic helix angle (β.sub.1) is different from the reference helix angle (β.sub.r) and the metal helix angle (β.sub.2) is different from the reference helix angle (β.sub.r), the reference profile being defined as follows: TABLE-US-00003 Reference profile 1 Worm Helical gear Number of teeth z 2 13 Helix angle β.sub.r [°] 12.6608 12.6608 Normal pressure angle α].sub.n[°] 21.0000 21.0000 Normal module m.sub.n [mm] 0.9800 Pitch diameter d.sub.0 [mm] 8.94 13.06 Addendum factor h.sub.a 1.1255 0.8530 Dedendum factor h.sub.f 1.2214 1.2400 Profile modification factor x −0.3053 0.1647 Tip diameter d.sub.a [mm] 10.550 15.052 Root diameter d.sub.f [mm] 5.950 10.950

3. The gear pairing for the helical gear unit according to claim 1, wherein the first gear is formed as a worm gear and the second gear is formed as a helical gear and the helical gear or the worm are connected to a drive shaft; wherein the first toothing portion of the worm and the second toothing portion of the helical gear are meshingly engaged.

4. The gear pairing for the helical gear unit according to claim 3, wherein the helical gear is made of metal, is formed as a spindle nut and interacts with a spindle, and wherein the worm is made of plastic.

5. The gear pairing for the helical gear unit according to claim 3, wherein 1°≤K≤3°.

6. A gear pairing for a helical gear unit, comprising: a first gear having metal teeth and a first axis and wherein the metal teeth have a front side and a back side; a second gear having plastic teeth and a second axis, wherein the first axis and the second axis enclose a shaft angle (χ) that is between 0° and 90°; wherein the metal teeth and the plastic teeth meshingly engage at only a single contact point located either on the front side or the back side of the first teeth such that a backlash is formed, the first teeth and the second teeth forming an involute toothing when engaged; wherein the metal teeth and the plastic teeth meshingly engage to a metal to plastic pairing; wherein the plastic teeth consists of a single plastic helix angle (β.sub.1) and the metal teeth consists of a single metal helix angle (β.sub.2), wherein a difference (Δβ) between an absolute value of the plastic helix angle (|β.sub.1|) and an absolute value of the metal helix angle (|β.sub.2|) is for the helical gear unit with the shaft angle (χ) of 45 to 90°: =|β.sub.1|−|β.sub.2|=90°−χ±K≠90°−χ, and is for the helical gear unit with the shaft angle (χ) of 0 to 45°: Δβ=|β.sub.1|−|β.sub.2|=−χ±K≠0°−χ, wherein 0.5°≤K≤5°, wherein a reference profile has a reference helix angle (β.sub.r), wherein the plastic helix angle (β.sub.1) is different from the reference helix angle (β.sub.r), and wherein the metal helix angle (β.sub.2) comprises the reference helix angle (β.sub.r) TABLE-US-00004 Reference profile 1 Worm Helical gear Number of teeth z 2 13 Helix angle β.sub.r [°] 12.6608 12.6608 Normal pressure angle α].sub.n[°] 21.0000 21.0000 Normal module m.sub.n [mm] 0.9800 Pitch diameter d.sub.0 [mm] 8.94 13.06 Addendum factor h.sub.a 1.1255 0.8530 Dedendum factor h.sub.f 1.2214 1.2400 Profile modification factor x −0.3053 0.1647 Tip diameter d.sub.a [mm] 10.550 15.052 Root diameter d.sub.f [mm] 5.950 10.950

Description

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

(2) FIG. 1a) shows a view of a worm of a proposed gear pairing,

(3) FIG. 1b) shows a view of a helical gear of a proposed gear pairing, wherein the worm and the helical gear can be brought into meshing engagement with one another,

(4) FIG. 2a) shows a view of a first spur gear of a proposed gear pairing,

(5) FIG. 2b) shows a view of a second spur gear of a proposed gear pairing, wherein the first spur gear and the second spur gear can be brought into meshing engagement with one another,

(6) FIG. 3 shows a schematic representation of a helical gear unit with a proposed gear pairing, and

(7) FIG. 4 shows a schematic representation of a spur gear unit with a proposed gear pairing.

(8) FIG. 1a) shows a first gear 10 according to a first embodiment of the present application, which is configured as a worm 12 and made entirely of plastic. Worm 12 has a first toothing portion 14 within which a number of teeth 16 are located. The first toothing portion 14 has a first helix angle β.sub.1.

(9) FIG. 1b) shows a second gear 18 according to a first embodiment of the application. The second gear 18 is formed as a helical gear 20 and made entirely of metal. The helical gear 20 has a second toothing portion 22, within which a number of teeth 16 are located. The second toothing portion 22 has a second helix angle β.sub.2.

(10) As defined, below, the first helix angle β.sub.1 is always associated with the toothing portion made of plastic and the second helix angle β.sub.2 is associated with the toothing portion made of metal, irrespective of whether the relevant toothing portion is arranged on the first gear 10 or the second gear 18.

(11) Worm 12 and helical gear 20 form a gear pairing 24, in which the first toothing portion 14 and the second toothing portion 22 can be brought into meshing engagement with one another and form an involute toothing 26 (see FIG. 3).

(12) Not shown is a reference profile, which also has a worm and a helical gear, which form a gear pairing 24 (see Table 1). In the case of the reference profile, the first helix angle β.sub.1 and the second helix angle β.sub.2 are equal in terms of absolute value, so that they both form a reference helix angle β.sub.r of the same absolute value. Both the worm 12 shown in FIGS. 1a) and 1b) and the helical gear 20 shown, and the worm and the helical gear of the reference profile are designed for a helical gear unit, which forms a shaft angle χ of 90° (see FIG. 3).

(13) In the embodiment shown in FIG. 1a), worm 12 corresponds to the worm of the reference profile, so that the first helix angle β.sub.1 is equal to the reference helix angle β.sub.r.

(14) However, the second helix angle β.sub.2 of helical gear 20 is larger than the reference helix angle β.sub.r, so that helical gear 20 deviates from the helical gear of the reference profile. However, the deviations are limited to the second helix angle β.sub.2 and the quantities dependent of the second helix angle β.sub.2 in an involute toothing 26. Otherwise, helical gear 20 is constructed in the same way as helical gear 20 of the reference profile. However, to ensure a perfect engagement, especially the tip diameter must be kept constant. As a result, it may be necessary to adapt other quantities that are not dependent on the second helix angle β.sub.2. The second helix angle β.sub.2 is larger than the first helix angle β.sub.1, so that the difference Δβ between the first helix angle β.sub.1 and the second helix angle β.sub.2 assumes negative values.

(15) For the difference Δβ, the following applies:
Δβ−β.sub.1−β.sub.2

(16) In FIG. 2a), the first gear 10 is configured according to a second embodiment as a first spur gear 28 and made entirely of plastic. The first spur gear 28 also has the first toothing portion 14, within which a number of teeth 16 are located. The first toothing portion 14 has the first helix angle β.sub.1.

(17) In FIG. 2b), the second gear 18 is formed according to a second embodiment of the application as a second spur gear 30. The second spur gear 30 is made entirely of metal. The second spur gear 30 has the second toothing portion 22, within which a number of teeth 16 are located. The second toothing portion 22 has a second helix angle β.sub.2.

(18) The first spur gear 28 and the second spur gear 30 form a gear pairing 24 in which the first toothing portion 14 and the second toothing portion 22 can be brought into meshing engagement with one another in (see FIG. 4).

(19) Not shown is a reference profile, which also has a first spur gear and a second spur gear, which form a gear pairing. In the case of the reference profile, the first helix angle β.sub.1 and the second helix angle β.sub.2 are equal in terms of absolute value, so that they both form a reference helix angle β.sub.r of the same absolute value. It should be noted that in spur gears, the two helix angles β.sub.1, β.sub.2 have opposite signs, so that the corresponding gear pairing 24 includes a left-beveled gear 10 and a right-beveled gear 18.

(20) Again, the first gear 10 corresponds to that of the reference profile so that the first helix angle β.sub.1 is equal to the reference helix angle β.sub.r. However, the second helix angle β.sub.2 of the second gear 18 is larger than the first helix angle β.sub.1, so that the difference Δβ between the absolute value of the first helix angle β.sub.1 and the absolute value of the second helix angle β.sub.2 assumes negative values.

(21) FIG. 3 shows a helical gear unit 32 with reference to a schematic representation, which comprises helical gear 20 and worm 12. Helical gear 20 and worm 12 are in meshing engagement with one another and together form a gear pairing 24, which forms an involute toothing 26. Since the helical gear 20 is made of metal and the worm 12 is made of plastic, when engaged, material pairing metal/plastic results.

(22) In the example shown, worm 12 is connected to a drive shaft 34 which can be rotated by a motor, not shown, about a first axis A.sub.1. Helical gear 20 is formed as a spindle nut 36 having an internal thread and which is rotatable about a second axis A.sub.2. By means of the internal thread, spindle nut 36 is connected to a spindle 38 with the longitudinal axis L of the spindle 38 being perpendicular to the plane of FIG. 3. Not shown is a housing in which gear pairing 24 is arranged. First axis A.sub.1 and second axis A.sub.2 form a shaft angle χ of 90°.

(23) In the example shown, the helical gear 32 is particularly suitable as a seat-length adjustment in vehicles. The spindle 38 is non-rotatably mounted in the vehicle. If worm 12 is rotated via drive shaft 34 as a result of a corresponding activation of the motor, the rotation of worm 12 is transmitted to spindle nut 36 with the corresponding gear ratio. As a result, spindle nut 36 and the entire helical gear unit 32 move along longitudinal axis L of spindle 38. This movement is used for the longitudinal adjustment of the seat in question.

(24) FIG. 4 shows a spur gear 40 with reference to a schematic representation, which comprises the first spur gear 28 and the second spur gear 30. The first spur gear 28 and the second spur gear 30 are in meshing engagement with one another and together form a gear pairing 24, which forms an involute toothing 26. Since the first spur gear 28 is made of plastic and the second spur gear 30 is made of metal, when engaged, a material pairing metal/plastic results.

(25) The first spur gear 28 is connected to a drive shaft 42 and the second spur gear 30 is connected to an output shaft 44. The first spur gear 28 and the drive shaft 42 are rotatable about a first axis A.sub.1. The second spur gear 30 and the output shaft 44 are rotatable about a second axis A.sub.2. Spur gear unit 40 comprises a housing 46 in which drive shaft 42 and output shaft 44 are supported in a manner not shown in detail. The first axis A.sub.1 and the second axis A.sub.2 are parallel to one another, so that the shaft angle χ is 0° and therefore is not marked.

(26) In the following, the relationships of the major quantities of involute toothings 26 are listed. The most important quantities are:

(27) d.sub.0 pitch diameter (mm)

(28) d.sub.a tip diameter (mm)

(29) d.sub.f root diameter (mm)

(30) e gap width (mm)

(31) h tooth height (mm)

(32) h.sub.a addendum factor

(33) h.sub.f dedendum factor

(34) m.sub.n normal module (mm)

(35) p pitch (mm)

(36) s.sub.n normal tooth thickness (mm)

(37) x profile modification factor (−)

(38) z number of teeth (−)

(39) α.sub.n normal pressure angle (°)

(40) β helix angle (°)

(41) These quantities are related to one another as follows:

(42) The following relationships apply to the pitch diameter d.sub.0:

(43) $d_0=z\frac{m_n}{\cos \beta }$

(44) The following relationships apply to the root diameter d.sub.f:
d.sub.f=d.sub.0−2*m.sub.n*h.sub.f+2*x*m.sub.n

(45) For the tip diameter, the following applies:
d.sub.a=d.sub.0+2*m.sub.n*h.sub.a+2*x*m.sub.n

(46) For the normal module, the following applies:

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

(48) For the tooth height h, the following applies:
h=2.25*m.sub.n

(49) Table 1 shows a comparison of the essential values of the proposed involute toothing 26 compared to a reference profile for a helical gear unit 32 produced in series by the applicant and thus known, based on two exemplary embodiments, wherein worm 12 is made of plastic and helical gear 20 is made of metal and together form gear pairing 24. In all cases, the helical gear units have a shaft angle χ of 90°.

(50) From Table 1 it can be seen that, in the reference profile, the first helix angle β.sub.1 of the worm is equal to the second helix angle β.sub.2 of the helical gear. In the first exemplary embodiment, worm 12 corresponds to the worm of the reference profile, so that the first helix angle β.sub.1 corresponds to the reference helix angle β.sub.r. Compared to the first helix angle β.sub.1 the second helix angle β.sub.2 of helical gear 20 is increased by a correction value K of about 3°.

(51) In the second exemplary embodiment, helical gear 20 corresponds to the helical gear of the reference profile, so that the second helix angle β.sub.2 corresponds to the reference helix angle β.sub.r. Compared to the second helix angle β.sub.2, the first helix angle β.sub.1 of worm 12 is reduced by a correction value K of about 3°.

(52) TABLE-US-00001 TABLE 1 Comparison of helical gear units (shaft angle χ = 90°) Reference First exemplary Second exemplary profile embodiment embodiment Helical Helical Helical Worm gear Worm gear Worm gear Number of teeth z 2 13 2 13 2 13 Helix angle β [°] 12.6608 12.6608 12.6608 15.6631 9.6584 12.6608 Normal pressure angle 21.0000 21.0000 21.0000 22.5371 22.2422 21.0000 α.sub.n [°] Normal module m.sub.n [mm] 0.9800 0.9800 0.9800 Pitch diameter 8.94 13.06 8.94 13.23 11.68 13.06 d.sub.0 [mm] Addendum factor h.sub.a 1.1255 0.8530 1.1255 0.8621 1.0588 0.8530 Dedendum factor h.sub.f 1.2214 1.2400 1.2214 1.2309 1.2882 1.2400 Profile modification factor x −0.3053 0.1647 −0.3053 0.0669 −1.6365 0.1647 Tip diameter 10.550 15.052 10.550 15.052 10.550 15.052 d.sub.a [mm] Root diameter 5.950 10.950 5.950 10.950 5.950 10.950 d.sub.f [mm]

(53) Table 2 shows a comparison of the essential values of the proposed involute toothing 26 compared to a reference profile for a spur gear unit 40 produced in series by the applicant and thus known, based on one exemplary embodiment, wherein the first spur gear 28 is made of metal and the second spur gear 30 is made of plastic and together form a gear pairing 24. As defined, the first helix angle β.sub.1 is associated with the toothing portion made of plastic, and the second helix angle β.sub.2 is associated with the toothing portion made of metal. In this respect, in Table 2, the first spur gear 28 has the second helix angle β.sub.2, and the second spur gear 30 has the first helix angle β.sub.1.

(54) From Table 2 it can be seen that, in the reference profile, the first helix angle β.sub.1 of the second spur gear is equal to the second helix angle β.sub.2 of the first spur gear. In the first exemplary embodiment, the first spur gear 28 made of metal corresponds to the first spur gear of the reference profile, so that the second helix angle β.sub.2 corresponds to the reference helix angle β.sub.r. Compared to the second helix angle β.sub.2 of the first spur gear 28 made of metal, the first helix angle β.sub.1 of the second spur gear 30 made of plastic is increased by a correction value K of 1°.

(55) TABLE-US-00002 TABLE 2 Comparison of spur gear units (shaft angle χ = 0°) First exemplary Reference profile embodiment First Second First Second spur spur spur spur gear gear gear gear Number of teeth z 36 36 36 36 Helix angle β [°] 23.0000 23.0000 23.0000 24.0000 Normal pressure 20.0000 20.0000 20.0000 20.8619 angle α.sub.n [°] Normal module m.sub.n [mm] 1.4600 1.4600 Pitch diameter 57.10 57.10 57.10 57.53 d.sub.0 [mm] Addendum factor h.sub.a 1.0300 1.0300 1.0300 1.0235 Dedendum factor h.sub.f 1.2200 1.2200 1.2200 1.2265 Profile modification −0.3000 −0.0700 −0.3000 −0.2125 factor x Tip diameter 59.231 59.902 59.231 59.902 d.sub.a [mm] Root diameter 52.661 53.332 52.661 53.332 d.sub.f [mm]

LIST OF REFERENCE NUMERALS

(56) 10 first gear

(57) 12 worm

(58) 14 first toothing portion

(59) 16 teeth

(60) 18 second gear

(61) 20 helical gear

(62) 22 second toothing portion

(63) 24 gear pairing

(64) 26 involute toothing

(65) 28 first spur gear

(66) 30 second spur gear

(67) 32 helical gear unit

(68) 34 drive shaft

(69) 36 spindle nut

(70) 38 spindle

(71) 40 spur gear unit

(72) 42 drive shaft

(73) 44 output shaft

(74) 46 housing

(75) β.sub.1 first helix angle

(76) β.sub.2 second helix angle

(77) β.sub.r reference helix angle

(78) A.sub.1 first axis

(79) A.sub.2 second axis

(80) K correction value

(81) L longitudinal axis