Parking lock

Abstract

A gearwheel (10), in particular a parking interlock gear, includes an annular body (1). The annular body includes a first toothing (2), arranged on an outer circumference of the annular body, for engaging a locking pawl (20), and a second toothing (3), arranged on an inner circumference of the annular body, for the form-locking connection to a shaft (30).

Claims

1. A gearwheel (10) that is a parking interlock gear for a parking lock arrangement, comprising: an annular body (1) that includes a first toothing (2) configured for engaging a locking pawl (20), the first toothing (2) arranged on an outer circumference of the annular body (1), and a second toothing (3) configured for form-locking connection to a shaft (30), the second toothing (3) arranged on an inner circumference of the annular body (1), wherein the second toothing (3) is shaped such that, upon engagement of the locking pawl (20) into the rotating gearwheel (10), the gearwheel (10) turns relative to the shaft (30) and expands in a radial direction with respect to the shaft (30).

2. The gearwheel of claim 1, wherein the second toothing (3) comprises a plurality of teeth (5) with oblique tooth flanks (5a, 5b).

3. The gearwheel of claim 2, wherein an angle a is defined between two mutually adjacent tooth flanks (5a, 5b) for each of the plurality of teeth (5) of the second toothing (3), the angle a opening towards an axis (98) of the annular body (1), the angle a selected such that, after unloading of the parking lock arrangement when the gearwheel (10) turns relative to the shaft (30) and contracts in the radial direction with respect to the shaft (30), a self-locking of the shaft (30) is avoided and the gearwheel (10) returns to a neutral position.

4. The gearwheel of claim 3, wherein the angle a is no less than one hundred and forty degrees and no greater than one hundred and sixty-six degrees.

5. The gearwheel of claim 4, wherein the angle a is no less than one hundred and fifty degrees and no greater than one hundred and fifty-six degrees.

6. The gearwheel of claim 1, wherein the first toothing (2) and the second toothing (3) are radially acting toothings.

7. A parking lock arrangement, comprising: a shaft (30); and a gearwheel (10) arranged on the shaft (30), the gearwheel (10) including an annular body (1) with a first toothing (2) and a second toothing (3), the first toothing (2) configured for engaging a locking pawl (20), the first toothing (2) arranged on an outer circumference of the annular body (1), the second toothing (3) configured for form-locking connection to the shaft (30), the second toothing (3) arranged on an inner circumference of the annular body (1), wherein the second toothing (3) is shaped such that, upon engagement of the locking pawl (20) into the rotating gearwheel (10), the gearwheel (10) turns relative to the shaft (30) and expands in a radial direction with respect to the shaft (30).

8. The gearwheel of claim 1, wherein the tooth flanks (5a, 5b) on each of the plurality of teeth (5) of the second toothing (3) are planar or crowned.

9. The gearwheel of claim 1, wherein a lead angle β of each tooth flank (5a, 5b) of the plurality of teeth (5) is no less than twelve degrees and no greater than fifteen degrees.

10. The parking lock arrangement of claim 7, wherein the shaft (30) includes a third toothing (32), the second toothing (3) configured for form-locking connection to the shaft (30) at the third toothing (32).

11. The parking lock arrangement of claim 7, wherein the third toothing (30) comprises a plurality of teeth (34) with oblique tooth flanks (34a, 34b), the tooth flanks (5a, 5b) on each of the plurality of teeth (5) of the second toothing (3) are planar or crowned, and tooth flanks (34a, 34b) on each of the plurality of teeth (34) of the third toothing (34) are planar or crowned.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Advantageous example embodiments of the invention, which are explained in the following, are represented in the drawings. Wherein:

(2) FIG. 1 shows a gearwheel in a preferred example embodiment in an axial sectional view;

(3) FIG. 2 shows the example gearwheel from FIG. 1 in a perspective view;

(4) FIG. 3 shows the example gearwheel from FIG. 1 with a representation of the preferred angle of the second toothing;

(5) FIG. 4a shows oblique tooth flanks utilizable in the example gearwheel from FIG. 1; and

(6) FIG. 4b shows oblique tooth flanks utilizable in the example gearwheel from FIG. 1.

DETAILED DESCRIPTION

(7) Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

(8) FIG. 1 shows a gearwheel 10 in the form of a parking interlock gear of a parking lock arrangement (not represented in greater detail) of a vehicle transmission (not represented) and a locking pawl 20, which is engaged into a first toothing 2 of the parking interlock gear 10. The parking interlock gear 10 is arranged coaxially to an axis 98. The locking pawl 20 is arranged coaxially to an axis 99. The two axes 98, 99 are arranged axially parallel to one another.

(9) The parking interlock gear 10 includes an annular body 1. The annular body 1 includes the first toothing 2, arranged on the outer circumference of the annular body 1, for engaging the locking pawl 20. The annular body 1 also includes a second toothing 3, arranged on the inner circumference of the annular body 1, for the form-locking connection to a shaft (not represented). Both toothings 2, 3 are radially acting toothings. The first toothing 2 includes, in a known way, teeth 4 including straight-cut tooth flanks 4a, 4b. Appropriate recesses are present between adjacent teeth 4. The inner toothing 3 include teeth 5 including lateral flanks 5a, 5b. In contrast to the flanks 4a, 4b of the teeth 4 of the first toothing 2, the tooth flanks 5a, 5b of the teeth 5 of the second toothing 3 are oblique. There is an angle α between adjacent oblique tooth flanks 5a, 5b. The angle α is in a range of one hundred and fifty degrees and one hundred and fifty-six degrees (150°≤α≤156°) (see e.g., FIG. 3). In other words, the value of the lead angle of the tooth flank 5a, 5b is between twelve degrees and fifteen degrees (12°≤β≤15°).

(10) FIG. 2 shows the parking interlock gear 10 from FIG. 1 and a shaft 30 on which the parking interlock gear 10 is arranged, in a perspective representation. The shaft 30, which is a rotor shaft of an electric machine, includes a third toothing 32, which corresponds to or complements the second toothing 3 of the parking interlock gear 10. The third toothing 32 is therefore a radially acting toothing, i.e., a toothing extending in the radial direction, including teeth 34. The teeth 34 include oblique tooth flanks 34a, 34b. One tooth flank 34a rests against a tooth flank 5a, while one tooth flank 34b rests against a tooth flank 5b. The shaft 30, which, in the present case, is a rotor shaft of an electric motor (not represented in greater detail), therefore form-lockingly transmits, via mating surfaces 34a, 34b, onto the mating surfaces 5a, 5b and, therefore, onto the parking interlock gear 10.

(11) If the locking pawl 20 is engaged into the first toothing while the parking interlock gear 10 rotates, the parking interlock gear 10 turns relative to the shaft 30 and is expanded in the circumferential direction 97, i.e., in other words, the radius of the parking interlock gear 10 increases. In the process, the parking interlock gear 10 absorbs the shock energy while the parking interlock gear 10 cushions the torque shock. As a result, on the one hand, the load on the locking pawl 20 can be substantially reduced and, on the other hand, the arising torsional vibration can be damped by the friction of the inner toothing.

(12) Due to the friction of the second toothing, in addition, the arising torsional vibration is damped, whereby the subsequent torsional vibration of the torsional vibration system of the parking lock device subsides faster. During this process, the gearwheel is essentially under tension. Very generally, the invention therefore makes an optimal absorption of energy possible, i.e., a homogeneous energy distribution across the annular body via deformation of the ring.

(13) With respect to the present example, the torsional vibration system can be described in a simplified manner as follows: The rotor of the electric machine implements a torsional vibration. The torsion spring is formed from the elasticity of all components located in the power flow during the engagement of the pawl. These are mainly the elasticity of the appropriate parts of the connecting shaft(s), the elasticity of the parking interlock gear 10, the locking pawl 20, and the housing portions that absorb the forces from the pawl bearing. The oscillating mass consists essentially of the moment of inertia of the rotor of the electric machine.

(14) FIG. 3 shows the parking interlock gear 1, wherein, additionally, the preferred angle α is indicated; the preferred angle α is between one hundred and fifty degrees (150°) and one hundred and fifty-six degrees (156°) in the present example case.

(15) In addition, the lead angle β is represented. The angle β is spanned, on the one hand, by a tangent that extends through the point P1 and by a connecting line that extends through the points P1 and P2. The point P1 is the point at which adjacent tooth flanks 5a, 5b intersect and which intersection point has the shortest distance r1 to the axis 98 of the parking interlock gear 10. P2 is the point at which adjacent tooth flanks 5a, 5b intersect and which intersection point P2 has the greatest distance r2 to the center of the parking interlock gear 10. This angle β is the so-called lead angle and the value is between twelve degrees and fifteen degrees (12°≤β≤15°).

(16) The relationship between the angles α and β is expressed as a formula as follows:
α=180−2β

(17) FIGS. 4a and 4b show the characteristics of the oblique tooth flanks of the type that can be utilized in the embodiments according to FIGS. 1 through 3. In FIG. 4a, the teeth 5 include oblique and planar tooth flanks 5a, 5b. The tooth flanks 34a, 34b of the teeth 34, however, are designed to be oblique and crowned. This is reversed in FIG. 4b: the tooth flanks 34a, 34b of the teeth 34 are designed to be oblique and planar, while the tooth flanks 5a, 5b of the teeth 5 are designed to be oblique and crowned.

(18) The invention was comprehensively described and explained with reference to the drawings and the description. The description and the explanation are to be understood as an example and not to be limiting. The invention is not limited to the disclosed embodiments. Other embodiments or variations result for a person skilled in the art within the scope of the utilization of the present invention and within the scope of a precise analysis of the drawings, the disclosure, and the following claims.

(19) In the claims, the words “comprise” and “comprising” do not rule out the presence of further elements or steps. The indefinite article “a” does not rule out the presence of a plurality. A single element or a single unit can carry out the functions of several of the units mentioned in the claims. The mere mention of a few measures in multiple various dependent claims is not to be understood to mean that a combination of these measures cannot also be advantageously utilized.

(20) Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. In the claims, reference characters corresponding to elements recited in the detailed description and the drawings may be recited. Such reference characters are enclosed within parentheses and are provided as an aid for reference to example embodiments described in the detailed description and the drawings. Such reference characters are provided for convenience only and have no effect on the scope of the claims. In particular, such reference characters are not intended to limit the claims to the particular example embodiments described in the detailed description and the drawings.

REFERENCE CHARACTERS

(21) 1 annular body

(22) 2 first toothing, outer toothing

(23) 3 second toothing, inner toothing

(24) 4 tooth, teeth of the first toothing

(25) 4a, 4b tooth flanks

(26) 5 tooth, teeth

(27) 5a, 5b tooth flanks, mating surface

(28) 6 recess(es) of the first toothing

(29) 7 recess(es) of the second toothing

(30) 10 gearwheel, parking interlock gear

(31) 20 locking pawl

(32) 30 shaft, rotor shaft

(33) 32 third toothing

(34) 34 tooth, teeth of the third toothing

(35) 34a, 34b tooth flanks, mating surface

(36) 97 direction of rotation of shaft, gearwheel; direction of expansion (circumferential direction)

(37) 98 axis of the gearwheel, shaft

(38) 99 swivel axis of the locking pawl

(39) P1 point of the inner toothing having the shortest distance to the center

(40) P2 point of the inner toothing having the greatest distance to the center

(41) t tangent

(42) d connecting line between P1 and P1

(43) r1 radius, distance between center and P1

(44) r2 radius, distance between center and P2