EP1883759A1

EP1883759A1 - Crown gear and differential arrangement comprising a crown gear

Info

Publication number: EP1883759A1
Application number: EP06724163A
Authority: EP
Inventors: Werner Krude; Ralf Leuschen; Michael Engelmann
Original assignee: GKN Driveline International GmbH
Current assignee: GKN Driveline International GmbH
Priority date: 2005-05-24
Filing date: 2006-04-08
Publication date: 2008-02-06
Also published as: KR20080011707A; DE102005024455A1; US20100075795A1; JP2008545927A; CN101228366A; DE102005024455B4; CN101228366B; WO2006125495A1

Abstract

The invention relates to a crown gear (2) which can be applied to a front gear (20) which is in contact with the toothing, in addition to a differential arrangement (25) which is in the form of a crown gear differential for the drive train of a motor vehicle. The crown gear (2) comprises an annular disk shaped toothing section (3), which forms a crown toothing (6), and a hub (4) which axially projects over the crown toothing (6). Transition areas (12), which connect to head lines (8) of the crown toothing (6), are formed between the crown toothing (6) and the hub (4), and merge into the hub (4).

Description

Crown wheel and differential assembly with a crown wheel

description

The invention relates to a crown wheel, in particular for a differential assembly for the drive train of a motor vehicle, as well as a differential assembly in the form of a Kronenraddifferentials.

From EP 1 203 900 A2, a crown gear differential with a differential carrier and two side-wave wheels arranged here on a rotation axis in the form of crown wheels and a plurality of countershafts in the form of spur gears meshing therewith in meshing engagement are known. The differential gears are rotatably mounted on pins of a star-shaped support member which rotates with the differential carrier. The crown wheels have a toothed portion and a relative to this axially recessed hub into which a side shaft can be inserted for torque transmission.

DE 103 54 998 A1 shows a similar crown gear differential, in which the side gear wheels are designed as crown wheels and comprise an annular disk-shaped toothed section and a hub formed integrally therewith. The hub has a greater axial extent relative to the toothed section and projects partially into a central bore of the pin star. The transition between the base of the gearing and the hub is rounded.

From PCT / EP2004 / 009607 a locking differential in the form of a Kronenraddifferentials is known, in which the side shaft gears are designed as crown wheels. The crown wheels each have an approximately cylindrical hub, to which - with respect to the axial extent of the hub - an annular disk-shaped toothed portion approximately connected in the middle. Between the teeth and the cylindrical outer surface of the hub, an annular undercut is provided.

From EP 787 055 B1 a crown wheel for a crown gear and a method for producing the crown wheel is known. The crown wheel is designed essentially annular disk-shaped and has a relation to the annular disc axially projecting teeth. The toothing is produced by means of a Wälzfräsverfahrens, the hob is moved radially with respect to the Kronenradachse and axially delivered. EP 227 152 B1 shows a similar crown wheel, which is also produced by hobbing.

US 6 129 793 shows a method for forging crown wheels, wherein the forging tools are manufactured by means of EDM. The forged crown wheels are disc-shaped.

CH 448 629 discloses a gear, in particular made of plastic. This has a face gear and a circumferential ring gear in a side surface whose teeth are set back relative to the side surface of the gear.

DE 102 35 677 A1 discloses a toothed pairing with a crown wheel and a pinion. The crown wheel is formed as a ring and has a collar whose axial height corresponds to the top surface of the crown teeth.

DE 43 09 559 A1 discloses a bevel gear with a housing in which a pinion and a gear in the form of a front-toothed face gear are mounted.

The present invention has for its object to provide a crown gear for a differential assembly, which allows a lightweight and compact design; Furthermore, it is an object of the present invention to propose a light and kurzbau- end differential assembly.

A first solution of the problem consists in a crown gear according to the invention, which can be brought into tooth engagement with a spur gear, in particular for use in a differential arrangement in the drive train of a motor vehicle, comprising an annular disc-shaped toothed portion which forms a crown toothing with head lines, and a hub which projects axially beyond the head lines of the crown toothing, wherein transition areas are formed between the crown toothing and the hub, which are at the Kopflipien connect the crown teeth and go over to the hub.

The solution according to the invention has the advantage that a stiffening of the crown wheel is effected by the transition regions between the crown toothing and the hub. This has the consequence that the toothed section can be made narrower without loss of strength. The crown wheel thus has a low weight and a short axial length.

According to a preferred embodiment, the transition areas in cross-section of the teeth of the crown teeth, with two mutually adjacent transition areas converge in the direction of the hub. Thus, a rib-like structure results radially between the teeth and the hub, which causes an increase in the rigidity of the crown wheel. The surfaces of the transition regions extend - as viewed in longitudinal section - preferably exclusively continuously in order to minimize stresses. The term 'continuous' is understood here in the mathematical sense, that is, the transition areas are - viewed in longitudinal section through a tooth tip - free of cracks or kinking. In concrete terms, the transition areas - when viewed in longitudinal section - are rounded and connect tangentially to the hub. This embodiment results in a particularly rigid structure with low voltages. The hub is preferably designed sleeve-shaped following the transition regions. In opposite direction to the crown toothing, the hub can also protrude axially beyond the toothed portion. It is favorable for a low-voltage transition, if this projecting portion has a conical outer surface. But it is also conceivable that this projecting portion is designed sleeve-shaped and has a rounded transition to the contact surface. According to a preferred development, an annular region of the toothed section lying axially between a radial abutment surface and a plane spanned by the root lines of the teeth has an axial thickness L3 which corresponds to one to two times the modulus m of the teeth, that is m < L3 ≤ 2m. In particular, it is favorable if the axial thickness L3 of the annular region corresponds approximately to 1.0 times the modulus m of the teeth, that is to say L3 = 1.0 μm. This results in a particularly short-building crown wheel, which also has low stresses in the area of the tooth roots. The teeth preferably have a variable cross-section in their longitudinal extent and a height that is variable with respect to the tooth root lines. This preferably corresponds to about 2.25 times the module m, that is, L2 - L3 = 2.25m. In this case, the teeth widen radially outward, so that a uniform gear engagement can be done with a spur gear. The crown toothing can be designed as a straight toothing or helical toothing.

According to a preferred embodiment, the crown gear is produced by forming, with particular forging or extrusion molding are suitable as a manufacturing process. Alternatively, the crown wheel also primitive, in particular by sintering can be produced.

A second solution to the above object consists in a differential assembly in the form of a crown gear differential, in particular for use in the drive train of a motor vehicle, comprising a differential carrier, which is rotatably driven about a rotation axis A; two in the differential carrier about the rotation axis A rotatably mounted side shaft gears; as well as a plurality of differential wheels revolving together with the differential carrier about the axis of rotation A, which are in meshing engagement with the side-shaft gears; wherein the side gear wheels are designed as crown wheels according to one of the embodiments of the invention described above and the differential gears are designed as spur gears.

The differential assembly according to the invention has the advantage of a particularly short axial length, since the crown gears used have a high rigidity due to the transition regions between the crown toothing and the hub and can be made very narrow. The axially compact design of Kronenraddifferentials also has a reduction in weight result.

According to a preferred embodiment of the differential carrier is designed in one piece and has two opposing openings for mounting the side shaft and the differential gears. This has the advantage of a small number of parts, whereby manufacturing and assembly costs are reduced. The differential gears are preferably supported with their inner end faces on the hubs of the Seitenwellenrä- in the direction of the axis of rotation. In concrete terms, the compensating wheels are mounted on a journal which has two bearing sections and an intermediate central section with a cross-section that is tapered relative to the bearing sections. In the central section inserted side waves can dip into the crown wheels, so that there is a further reduced length.

A preferred embodiment will be explained below with reference to the drawing. Herein shows

1 shows a crown wheel according to the invention in a perspective view;

Figure 2 shows the crown wheel of Figure 1 in side view;

Figure 3 shows the crown wheel of Figure 1 in longitudinal section;

Figure 4 shows a differential gear set with two crown wheels according to the invention in side view;

Figure 5 shows a differential assembly with mounted differential gear set of Figure 4 in side view;

Figure 6 shows the differential assembly of Figure 5 in longitudinal section;

FIGS. 1 to 3, which will be described jointly below, show a crown wheel 2 according to the invention. The crown wheel 2 is essentially ring-shaped. designed disc-shaped and comprises a toothed portion 3 and a radially inner hub 4, which protrudes axially with a sleeve-shaped projection on the toothed portion 3. The hub 4 has a longitudinal toothing 5, in which a drive shaft, not shown here for torque transmission can be inserted non-rotatably. The crown wheel 2 is produced by a forming process, for example by means of forging or cold extrusion.

The toothing section 3 has an end-face crown toothing 6 with a multiplicity of teeth 7 distributed over the circumference. The tooth head lines 8 and the tooth roots 9 of the teeth run essentially radially with respect to the axis of rotation A of the crown wheel 2. That is, the crown wheel 2 has a spur toothing, which can mesh with a corresponding spur toothing of a cylindrical spur gear, not shown here. It can be seen that the teeth 7 of the crown gear 6 have a variable cross-section and a variable height over their radial extent. The teeth 7 widen radially outward, the tooth flanks 10 flattening with respect to a cross-sectional plane. Radially between the teeth 7 and the hub 4 transition areas 12 are formed, which connect seamlessly to the teeth 7 and pass into the hub 4. In this case, the transition regions 12 are designed as rounded ribs whose outer surfaces 14 on the one hand connect to the tooth head lines 8 of the teeth and on the other pass tangentially into the hub 4. Two mutually adjacent ribs 12 converge in the direction of the hub 4, so that a trough 15 formed between the ribs 12 terminates at the hub 4. In this case, lateral flanks of the trough 15 close to the tooth flanks 10 seamlessly. The seamless, continuous transitions minimize stresses.

In opposite direction to the crown gear 6 of the toothed portion 3 has a perpendicular to the axis of rotation A contact surface 16, via which the crown gear 2 axially supported in the installed state against a support surface. Radially inside, a conical surface 17 connects, which is an outer surface of the axially projecting hub 4. The length L1 of the hub 4 is calculated from the torque to be transmitted and the diameter of the toothing 5. As has already been stated above, the hub 4 stands axially in both directions with respect to the gear tooth. cut 3 ago. That is, the length L1 of the hub 4 is greater than the axial Erstrek- tion L2 between the abutment surface 16 and a plane spanned by the maxima of the tooth head lines 8 level. Between the contact surface 16 and a plane spanned by the foot lines of the teeth, a ring region 18 having an axial thickness L3 is formed, which corresponds approximately to the tooth height of the teeth 7. Mathematically, the thickness L3 of the annular region can be between one and two times the modulus m of the teeth 7, that is to say m ≦ L3 ≦ 2m. An axially particularly short-building crown wheel 2 results when the axial thickness L3 corresponds to the simple modulus m of the teeth 7, namely L3 = m.

Hereinafter, FIGS. 4 to 6 will be described together. In Figure 4, a Differentialrädersatz 19 is first seen as a detail, the two crown gears according to the invention 2, 2 'and two meshing with these differential gears 20, 20', which are rotatably mounted on a common pin 22. In this case, the differential gears 20, 20 'in the form of cylindrical spur gears with Geradverzahnungen 23 which are with the crown gears 6 of the crown gears 2, 2' in engagement. In Figures 5 and 6, the differential gear set 19 in the installed state in a differential carrier 24 is shown. The differential assembly 25 formed in this way is to be designed in a stationary housing of a differential gear (not shown here). For this purpose, the differential carrier 24 has two sleeve-shaped bearing lugs 26, 27 facing in the opposite direction, onto which rolling bearings can be mounted. Differential gear of the type mentioned are used in particular in the drive train of a motor vehicle and are used for torque distribution from an input shaft to two output shafts. For torque introduction into the differential basket 24, a flange 28 is integrally formed thereon, on which a ring gear can be fastened.

The introduced into the differential carrier 24 torque is transmitted to the crown gears 2, 2 'via the mounted on the pin 22 and together with the differential carrier 24 about the axis of rotation A differential gears 20, 20'. In this case, the spreading forces acting in the axially opposite direction are introduced into the differential carrier 24 via the abutment surfaces 16 of the crown wheels 2, 2 ', which are supported against support surfaces 21. The pin 22 is in radial bores 29 in Inserted differential cage 24 and fixed axially by means of a locking ring 13, wherein other securing means are conceivable. The pin 22 has a central portion 30 with respect to the bearing portions reduced diameter D. Thus, in the crown wheels 2 rotatably inserted side waves can dip into the central portion 30, whereby space is saved. Upon rotation of the differential assembly 25, the differential gears 20, 20 'acted upon radially outwardly due to centrifugal forces and lie down with their spherical contact surfaces 31 against a corresponding hollow spherical counter-surfaces 32 in the differential carrier 24 at. In order to prevent at low speeds that the differential gears 20, 20 'wander radially inward to the axis of rotation A, the differential gears 20, 20' run with their end faces 33 against outer contact surfaces of the hubs 4 of the crown wheels 2. This results in a simple structure with few components. The differential cage 24 is designed in one piece and has two opposing openings 34 for mounting the crown gears 2 and the differential gears 20. The inventive differential assembly 25 has the advantage of a particularly short axial length, since the crown gears 2 used have a minimum thickness. This is particularly advantageous when using the differential assembly 25 in a front-wheel drive motor vehicle, where little space is available.

LIST OF REFERENCE NUMBERS

2 crown wheel

3 toothing section

4 hub

5 spline

6 crown toothing

7 tooth

8 head line

9 foot line

10 tooth flank

12 transition area

13 circlip

14 outer surface

15 trough

16 contact surface

17 cone surface

18 ring area

19 differential gear set

20 balancing wheel

21 support surface

22 cones

23 spur toothing

24 differential carrier

25 differential arrangement

26 bearing approach

27 bearing approach

28 flange

29 bore 30 central section

31 contact area

32 mating surface

33 face

34 opening

A axis

B journal axis

D diameter

L length m module

Claims

claims

1 crown gear (2) which can be brought into toothed engagement with a spur gear, in particular for use in a differential assembly in the drive train of a motor vehicle comprising an annular disc-shaped toothed portion (3) which forms a crown toothing (6) with head lines (8), and a hub (4) which projects axially beyond the head lines (8) of the crown toothing (6), wherein transition areas (12) are formed between the crown toothing (6) and the hub (4), which are adjacent to the head lines (8) of the crown toothing (6) connect and go into the hub (4).

2. crown wheel according to claim 1,

characterized,

that the transition regions (12) in cross section of the teeth (7), wherein each two adjacent transition regions (12) converge in the direction of the hub (4).

3. crown wheel according to claim 1 or 2,

characterized, that the transition regions (12) - viewed in longitudinal section - run exclusively steadily.

4. crown wheel according to one of claims 1 to 3,

characterized,

that the transition regions (12) - viewed in longitudinal section - are rounded and tangentially to the hub (4).

5. crown wheel according to one of claims 1 to 4,

characterized,

in that an annular region (18) formed between an end bearing surface (16) and foot lines (9) of the toothed section (3) has an axial thickness (L3) which corresponds to one to two times the modulus (m) of the teeth (7) ( m <L3 <2m).

6. crown wheel according to claim 5,

characterized,

that the axial thickness (L3) of the annular region (18) corresponds approximately to the simple module (m) of the teeth (7) (L3 = 1, 0m).

7. crown wheel according to one of claims 1 to 6,

characterized,

in that the teeth (7) have, in their longitudinal extension, a height which is variable with respect to the tooth root lines (9).

8. crown wheel according to one of claims 1 to 7,

characterized,

in that the hub (4) is sleeve-shaped following the transition regions (12) to the teeth (7).

9. crown wheel according to one of claims 1 to 8,

characterized,

in that the hub (4) projects axially beyond the toothed section (3) in the direction opposite to the crown toothing (6) and has a conical outer surface (17).

10. crown wheel according to one of claims 1 to 9,

characterized,

that it is forming, in particular by forging or extrusion.

11. crown wheel according to one of claims 1 to 9,

characterized,

that it is original, in particular as a sintered part, made.

12. differential assembly in the form of a Kronenraddifferentials, in particular for use in the drive train of a motor vehicle, comprising a differential carrier (24) which is rotatably driven about a rotational axis (A); two in the differential carrier (24) about the axis of rotation (A) rotatably mounted side shaft wheels (2); such as a plurality of differential gears (20) revolving together with the differential carrier (24) about the axis of rotation (A), which are in meshing engagement with the side-shaft gears (2); wherein the side shaft gears (2) are designed as crown wheels according to one of claims 1 to 11 and the differential gears (20) are designed as spur gears.

13. differential assembly according to claim 12,

characterized,

that the differential carrier (24) is designed in one piece and has two mutually opposite openings (34) for mounting the side shaft gears (Z) and the differential gears (20).

14. Differential arrangement according to claim 12 or 13,

characterized,

that the differential gears (20) are radially supported with their inner end faces (33) on the hubs (4) of the side shaft gears (2) with respect to the axis of rotation (A).

15. Differential arrangement according to one of claims 12 to 14,

characterized,

that the differential gears (20) are mounted on a pin (22) having two bearing portions and an intermediate central portion (30) with respect to the bearing portions tapered cross-section.