DE102022100802A1 - Differential gear with torque-sensing friction device - Google Patents

Abstract

The invention relates to a differential gear (1) for a motor vehicle drive train, with a planetary carrier (2), several planetary gears (6, 7, 8) rotatably mounted on the planetary carrier (2) and assigned to different planetary gear sets (3, 4, 5), a first sun gear (9) in meshing engagement with the planetary gears (6) of a first planetary gear set (3), a first sun gear (9) in meshing engagement with the planetary gears (7) of a second planetary gear set (4). n, second sun gear (10) and a friction device (12) that inhibits relative rotation between the first sun gear (9) and the second sun gear (10), with an axially displaceably mounted thrust washer (13) of the friction device (12) used to generate a friction force that brakes or blocks the first sun gear (9) and the second sun gear (10) relative to one another or one of the two sun gears (9, 10) relative to the planet carrier (2) on one, also axially displaceably mounted, helical planet gear (8) of a third planetary gear set (5) is supported.

Description

The invention relates to a differential gear for a motor vehicle drive train, preferably a drive train of a purely electrically or hybrid motor vehicle, with a planetary carrier, a plurality of planetary gears rotatably mounted on the planetary carrier and assigned to different planetary gear sets, a first sun gear meshing with the planetary gears of a first planetary gear set , a second sun gear meshing with the planet gears of a second planetary gear set, and a friction device inhibiting relative rotation between the first sun gear and the second sun gear.

Generic differential gears, which are also referred to as spur gear differentials and are constructed according to the principle of a planetary gear, are already well known from the prior art. In this regard, disclosed for example DE 10 2011 085 119 B3 a spur gear differential with at least one friction disk and at least one spring means preloading two sun gears relative to a planet gear carrier. Thus, differential gears with an integrated locking function are already known. Using at least one friction element, the two sun gears, which can be rotated relative to one another, are braked relative to one another during operation.

However, the known friction devices always have a predetermined, fixed limit value, below which the two sun gears are fixed to one another in a rotationally fixed manner/block one another. In the case of motor vehicles, it has been shown that depending on the operating state, it is necessary to select this limit value differently. For example, in wintry weather conditions and in off-road or racing applications, a high limit value / blocking value is usually required. In the case of no-load operation, on the other hand, a lower limit value is desired.

It is therefore the object of the present invention to provide a differential gear whose locking function can be adapted as variably as possible to the different operating states and areas of use of the motor vehicle, while at the same time enabling a compact and simple design.

According to the invention, this is achieved in that an axially displaceably mounted thrust washer of the friction device is used to generate a frictional force that brakes or blocks the first sun gear and the second sun gear relative to one another or one of the two sun gears relative to the planet carrier Planet gear of a third planetary gear set is supported/created.

Due to the arrangement of the thrust washer on the helical planet wheel, this is subjected to axial force directly as a function of a torque to be transmitted through the planet wheel. As a result, the frictional forces acting on the sun gears can be adjusted as a function of the load. This results in the most flexible possible use of the differential gear, in particular also for applications in wintry weather conditions and in off-road or racing applications.

Further advantageous embodiments are claimed with the dependent claims and explained in more detail below.

Accordingly, it is also advantageous if the thrust washer is inserted and axially supported by a spring device in such a way that an increase in a drive torque transmitted (during operation) via the helical planetary gear increases the frictional force that brakes the two sun gears relative to one another or one of the sun gears to the planet carrier (against a biasing force of the spring device) causes. This keeps the structure as simple as possible. The spring device preferably serves as a restoring spring, so that in the load-free state (state in which no sufficiently high axial force acts on the helical planet wheel), the usual differential function is ensured.

If the thrust washer is mechanically or hydraulically (alternatively also pneumatically) coupled to a friction lining that is or can be placed on at least one sun gear, the friction device can be integrated in a space-saving manner.

In this regard, it is also advantageous if the thrust washer is equipped or connected directly to a (first) friction lining, this (first) friction lining being in contact with one of the two sun gears. This also keeps the structure as simple as possible.

As an alternative to this, however, it is advantageous if the thrust washer is coupled by means of a hydraulic unit (or alternatively mechanically) to a (second) friction lining that is in contact with one of the two sun gears.

If the thrust washer is supported on an axial end face of the helical planet gear, its arrangement is realized in an even more space-saving manner.

Furthermore, it is expedient if the helical planet wheel is designed as a double gear wheel/stepped gear wheel. The helical planet wheel is then in meshing engagement with at least one helical gear section with a further (second) planet wheel.

The invention is now presented below by way of example using figures, which also explain various exemplary embodiments.

• 1 eine schematische Längsschnittdarstellung eines erfindungsgemäßen Differenzialgetriebes nach einem ersten Ausführungsbeispiel, wobei ein Gesamtaufbau des Differenzialgetriebes gut zu erkennen ist, sowie
• 2 eine schematische Längsschnittdarstellung eines erfindungsgemäßen Differenzialgetriebes nach einem zweiten Ausführungsbeispiel, wobei eine alternative Koppelung der Anlaufscheibe mit einem weiteren Reibbelag zu erkennen ist.

Show it:

• 1 a schematic longitudinal sectional view of a differential gear according to the invention according to a first embodiment, wherein an overall structure of the differential gear is clearly visible, and
• 2 a schematic longitudinal sectional view of a differential gear according to the invention according to a second embodiment, wherein an alternative coupling of the thrust washer can be seen with a further friction lining.

The figures are only of a schematic nature and serve exclusively for understanding the invention. The same elements are provided with the same reference numbers.

With the 1 a differential gear 1 according to the invention according to a first exemplary embodiment can be seen clearly with regard to its overall structure. The differential gear 1 is implemented as a spur gear differential. In its preferred area of use, the differential gear 1 is used in a conventional manner in a motor vehicle drive train. A first sun gear 9 and a second sun gear 10 of the differential gear 1 constructed in the manner of a planetary gear each form a torque output/power output of the differential gear 1 and are rotationally coupled during operation with tires on the motor vehicle wheels. Another, third sun wheel 11 forms a torque input/power input of the differential gear 1.

The differential gear 1 has a common planet carrier 2 . In this planet carrier 2 are several planetary gear sets 3, 4, 5, each having several planetary gears 6, 7, 8, rotatably mounted. The first sun gear 9 meshes with first planet gears 6 (of a first planetary gear set 3). The second sun gear 10 is in meshing engagement with the second planetary gears 7 (of a second planetary gear set 4), the second planetary gears 7 only being indicated with regard to their position for the sake of simplicity. The third sun gear 11 meshes with a plurality of third planetary gears 8 (a third planetary gear set 5).

It can also be seen that the respective third planet wheel 8 is designed as a double gear wheel 19 and thus has two axially spaced toothed sections 20a, 20b that differ in terms of their diameter. A first toothed section 20a is (diameter) larger than a second toothed section 20b. The first toothed portion 20a is in meshing engagement with the third sun gear 11. The second toothed portion 20b is preferably in meshing engagement with the second planet gears 7.

Every third planet wheel 8 is designed as a helical planet wheel 8 . In particular, in this embodiment both toothed sections 20a and 20b of the third planet wheel 8 are designed with helical teeth. Every third planet wheel 8 is also accommodated in the planet carrier 2 in a targeted, axially displaceable manner within a limited displacement range.

For the sake of completeness, it should be mentioned that the directional information used in the present case is to be seen as axial, radial and circumferential in relation to a central axis of rotation 21 of the planetary carrier 2 . The axial/axial direction is therefore a direction along/parallel to the axis of rotation 21, the radial/radial direction is a direction perpendicular to the axis of rotation 21 and the circumferential direction is a direction along a circular line coaxial with the axis of rotation 21.

According to the invention, a friction device 12 is present, which has a blocking/braking/inhibiting effect on a relative rotation of the two first and second sun gears 9, 10. That friction device 12 has a thrust washer 13 which is supported/applied in an axially fixed manner on an end face 18 of the helically toothed (third) planet wheel 8 . Furthermore, a thrust washer 13 is preferably associated with each third planet wheel 8, these thrust washers 13 being constructed and used in an identical manner in the manner described below.

The respective thrust washer 13 is in this first embodiment 1 further coupled for movement with at least one (first) friction lining 15, which (first) friction lining 15 serves to align the relative movement between the two sun gears 9, 10 during operation/to brake/block the two sun gears 9, 10 to one another. In this embodiment, the first friction lining 15 is attached directly to the thrust washer 13 .

The thrust washer 13 generates an axial force/contact force on the first friction lining 15 through a torque-dependent displacement of the third planet wheel 8 during operation, as a result of which the first friction lining 15 is applied to at least one of the sun wheels 9, 10 with a specific axial contact force.

Matched to this, the thrust washer 13 is elastically prestressed by means of a spring device 14 on a side facing away axially from the third planet wheel 8 . The spring device 14 serves to press the thrust washer 13 against the end face 18 . The spring device 14 consequently serves as a restoring spring in order to return the thrust washer 13 to an initial state in which it does not produce any braking effect on the sun gears 9, 10.

It is thus clear again that the thrust washer 13 is inserted and axially preloaded by the spring device 14 in such a way that an increase in the torque transmitted during operation via the third planet gear 8 causes an increase in the frictional force that brakes the two first and second sun gears 9, 10 relative to one another . The spring device 14 preferably has at least one compression spring, such as a helical compression spring or a plurality of plate springs or leaf springs or corrugated springs. The thrust washer 13 is used in 1 for pressing / for generating a braking torque on the first sun gear 9. The first sun gear 9 is preferably braked relative to the second sun gear 10, alternatively also directly to the planet carrier 2.

In connection with the second embodiment of the 2 it should be pointed out that the thrust washer 13 can also alternatively be coupled to a (second) friction lining 16 arranged at a radial distance from the thrust washer 13 . In 2 In principle, an alternative mechanical coupling of the thrust washer 13 to the second friction lining 16 is indicated, but in principle a hydraulic coupling can also be provided instead, as indicated by reference number 17 . In this case, for example, the thrust washer 13 could be coupled to a hydraulic master chamber and the second friction lining 16 to a hydraulic slave chamber of a common hydraulic unit 17 .

With 2 A connecting web 22 is present for the mechanical coupling of the thrust washer 13 to the second friction lining 16 lying radially outside of the thrust washer 13 . The thrust washer 13 has a direct braking effect on the second sun gear 10 via the second friction lining 16 . Also on the second friction lining 16 are axially remote sides of the first and second sun gears 9, 10 friction disks 23 which are also used to brake the first and second sun gears 9, 10 relative to one another.

In other words, according to the invention a stepped planet (third planet gear 8) is used to lock the spur gear differential (differential gear 1) or to change the locking value with an axial force generated by it during operation.

The surfaces of the planetary carrier 2, on which the thrust washers 13 transmit the axial force to the carrier, are slidably (spring-mounted) in the carrier so that the thrust surface and thus the thrust washer 13 can be displaced in the event of an axial force in traction operation.

This displacement of the contact surface can be used mechanically and hydraulically to achieve an axial movement of a friction surface in the differential. If the friction surface in the differential is axially displaced, additional friction occurs when the suns rotate at different speeds and the locking torque of the differential is increased.

In the first exemplary embodiment, the right contact surface (front side 18) of the planet (third planet wheel 8) is mounted in the planet carrier 2 so that it can move axially via a spring (spring device 14).

A friction lining 15 is attached through a ridge on the thrust washer 13, which has a braking effect on the differential sun (first sun gear 9) during axial movement and the associated tensioning of the spring. The resulting friction increases the locking value of the differential.

Reference List

1

differential gear

2

planet carrier

3

first planetary gear set

4

second planetary gear set

5

third planetary gear set

6

first planet wheel

7

second planet gear

8th

third planet gear

9

first sun wheel

10

second sun wheel

11

third sun wheel

12

friction device

13

thrust washer

14

spring device

15

first friction lining

16

second friction lining

17

hydraulic unit

18

face

19

double gear

20a

first gear section

20b

second gear section

21

axis of rotation

22

connecting bar

23

friction disc

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102011085119 B3 [0002]

Claims (7)

Differential gear (1) for a motor vehicle drive train, with a planetary carrier (2), several planetary gears (6, 7, 8) rotatably mounted on the planetary carrier (2) and assigned to different planetary gear sets (3, 4, 5), one, with the planetary gears ( 6) a first planetary gear set (3) in meshing, a first sun gear (9), with the planetary gears (7) of a second planetary gear set (4) in meshing, second sun gear (10) and a relative rotation between the first sun gear ( 9) and the second sun gear (10), characterized in that a friction device (12) is mounted so as to be axially displaceable and for generating a the first sun gear (9) and the second sun gear (10) relative to one another or one of the two sun gears (9, 10) the thrust washer (13) of the friction device (12) used to brake or block the frictional force relative to the planetary carrier (2) is supported axially on a helical-toothed planet wheel (8) of a third planetary wheel set (5), also mounted so that it can be moved axially. Differential gear (1) after claim 1 , characterized in that the thrust washer (13) is inserted and axially supported by a spring device (14) in such a way that an increase in the drive torque transmitted via the helical planet wheel (8) results in an increase in the frictional force braking the two sun wheels (9, 10) relative to one another causes. Differential gear (1) after claim 1 or 2 , characterized in that the thrust washer (13) is coupled mechanically or hydraulically to a friction lining (15, 16) which rests or can be placed on at least one sun wheel (9). Differential gear (1) according to one of Claims 1 until 3 , characterized in that the thrust washer (13) is equipped or connected directly to a friction lining (15), the friction lining (15) resting on one of the two sun gears (9, 10). Differential gear (1) according to one of Claims 1 until 4 , characterized in that the thrust washer (13) is coupled by means of a hydraulic unit (17) to a friction lining (16) resting on one of the two sun gears (9, 10). Differential gear (1) according to one of Claims 1 until 5 , characterized in that the thrust washer (13) is supported on an axial end face (18) of the helical planet wheel (8). Differential gear (1) according to one of Claims 1 until 6 , characterized in that the helical planet gear (8) is designed as a double gear (19).

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