WO2015127914A1

WO2015127914A1 - Spur gear differential transmission with a bridging torque which varies depending on the load

Info

Publication number: WO2015127914A1
Application number: PCT/DE2014/200725
Authority: WO
Inventors: Harald Martini; Thorsten Biermann
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2014-02-27
Filing date: 2014-12-18
Publication date: 2015-09-03
Also published as: DE102014203522A1

Abstract

The invention relates to a spur gear differential transmission with an epicyclic housing (H), a first sun gear (S1) which is designed as a spur gear and is received in the epicyclic housing (H), a second sun gear (S2) which is likewise designed as a spur gear, is received in the epicyclic housing (H), and is arranged on the same axis as the axis (X1) of rotation of the first sun gear (S1), a planet arrangement (P) which rotates with the epicyclic housing (H) for coupling the two sun gears (S1, S2) such that the two sun gears can be rotated in opposite directions relative to each other, a clutch device (K) for generating a clutch torque which loads the differential action of the differential on frictionally engaging paths, and an actuating mechanism (M) for actuating the clutch device (K) such that the clutch torque is increased on the basis of a drive torque applied to the epicyclic housing (H), wherein the first sun gear (S1) forms a part of the actuating mechanism (M), is provided with a helical toothing (Z1), and can be moved axially relative to the epicyclic housing (H), and the axial movement of the first sun gear (S1) is accomplished on the basis of the gear reaction forces acting on the helical toothing (Z1) of the first sun gear (S1).

Description

Name of the invention

Spur gear differential gear with load-dependent varying bridging torque

FIELD OF THE INVENTION The invention is directed to a spur gear differential with a circulation housing, a first and a second sun gear which is accommodated in the circulation housing, a planetary arrangement revolving around the circulation housing for coupling the two sun gears in such a way that they rotate in opposite directions to each other, a clutch device for generating a bridging torque which loads the compensating effect of the differential by frictional engagement, and an actuating mechanism for actuating the clutch device such that the bridging torque changes in accordance with a drive torque applied to the circulation housing.

Such Stirnraddifferentiale find particular as axle or center differentials in motor vehicles application and generally improve the driving stability of the vehicle by at higher load moments in the drive train is a certain frictional coupling of the two outputs of the differential. In the case of an axle differential results in an improved straight-ahead, in the case of a center differential results in a load-dependent coupling of the two vehicle axles, whereby excessive wheel slip on the axis with the wheel with the lowest traction is counteracted.

From DE 10 2008 050 059 A1, which is based on the applicant, a spur gear differential of the type mentioned in the introduction is known. In this spur gear differential, the actuating mechanism comprises a thrust ring assembly with two pressure rings supported on each other via inclined surfaces for generating an axial force acting on a multi-disc clutch pack. The multi-plate clutch pack is integrated into the spur gear differential in such a way that it can be frictionally coupled to the circulating housing via this one of the sun gears. Due to the frictional coupling of one of the sun gears with the circulation housing results due to the further kinematic coupling of the two sun gears on the planetary arrangement, the effect that the relative rotation of the two sun gears braked by a friction torque and thus a certain frictional coupling of the two sun gears, ie the outputs of the differential.

OBJECT OF THE INVENTION The invention is based on the object of providing a spur gear differential of the type mentioned above, which is distinguished by a robust and cost-effective construction and in which the axial force required to actuate the coupling device can be advantageously generated.

Inventive solution

The above object is achieved by a Stirnraddifferentialgetriebe with:

a circulation housing,

a first sun gear, designed as a spur gear, which is received in the circulation housing,

a second sun gear, likewise designed as a spur gear, which is accommodated in the circulation housing and arranged coaxially to the axis of rotation of the first sun gear,

a planetary arrangement revolving around the circulation housing for coupling the two sun gears such that they are rotatable in opposite directions to one another, a coupling device for generating a compensation effect of the differential loading coupling moment by friction, and

an actuating mechanism for actuating the coupling device such that the coupling moment increases in accordance with a torque applied to the rotary housing,

wherein the first sun gear forms part of the actuating mechanism and in this case provided with a helical toothing and axially displaceable relative to the rotary housing and the axial displacement of the first sun gear in accordance with the acted on the helical teeth of the first sun gear gear reaction forces is accomplished.

This advantageously makes it possible to provide a differential gear in which the axial force required to actuate the clutch device can be generated via the first sun gear and transmitted to the clutch device through the first sun gear, wherein the first sun gear is not only an output member, but at the same time also acts as an actuator of the actuating mechanism.

According to a particularly preferred embodiment of the invention, the coupling device is designed as a multi-plate clutch. The coupling device may in this case have a plurality of clutch plates, which are alternately rotatably coupled via a corresponding toothing with a hub portion of the first sun gear or an inner wall of a pot portion of the circulation housing. The coupling device is preferably designed as a so-called. Wet clutch, so that the clutch plates are initially wetted in the unloaded state of the sheer medium of the differential gear. The lubricating film is reduced under axial load of the clutch plates and built up a corresponding friction torque between the slats. The clutch plates are preferably made of high-strength and flat in the region of its inner bore or its outer periphery with a tooth profile Sheet steel rings which are preferably provided with a Reibmaterialbelag.

The differential gear according to the invention is advantageously constructed such that the coupling device between the first sun gear and the circulation housing is effective. In this variant, the first sun gear is then preferably provided with a hub portion which has an axial toothing, on which the corresponding, internally toothed clutch disks are axially displaceable, rotatably guided. The circulation housing can then be designed such that it forms in an axially adjacent to the first sun gear and the hub portion of the sun gear encompassing a pot portion in which the externally toothed fins of the multi-plate clutch pack is received and guided accordingly and rotationally secured. In this multi-plate clutch packing, the internally and externally toothed multi-disc clutch disks are alternately secured against rotation on the hub portion of the first sun gear, or the inner wall of the pot portion.

As an alternative to the above-mentioned embodiment or possibly also in combination herewith, it is also possible to design and arrange the coupling device in such a way that it acts directly between the two sun gears. In this variant, either the first sun gear is urged axially against the second sun gear and thereby the coupling device loaded, or possibly both sun gears are urged axially against each other and thereby loaded the coupling device. In particular, in this variant, the coupling device can also be realized by a single friction lining, which is located axially between the two sun gears and generated at a corresponding axial load effective between the two sun gears frictional torque.

It is also possible to apply an axial force to the other sun gear via one of the two sun gears and then load the clutch device through this other sun gear and thereby actuate it. Also, both sun gears can be provided with a helical toothing in such a way that both wheels each generate an axial force acting in the same direction, which then summarily activates the coupling device. The spur gear according to the invention is preferably designed so that this causes a symmetrical power split. This is accomplished by tuning the numbers of teeth of the sun gears and the numbers of teeth of the planetary gears of the planetary gear meshing with these sun gears so as to provide a stand ratio of -1 between the sun gears. However, especially in the case of a center differential, it is also possible to provide a deviating stand ratio which, for example, takes into account the axle load ratio or otherwise provides asymmetrical torque distribution. If, in the case of a center differential, no coupling of the two sun gears in opposite directions is required, since a corresponding reversal of rotation is effected, for example, via the angle gear of a subsequent axle differential, the two sun gears can directly contact one another with a pair of sun gears toothed planet be coupled and then generate together used for actuating the clutch device axial force.

The aforementioned level ratio of -1 can be achieved in particular by both sun gears have the same number of teeth regardless of the number of teeth of the planet. The number of teeth on the suns can be designed differently, but then this must be compensated again on a stepped planet with different numbers of teeth. The planetary arrangement can then be designed such that on the one hand it has first planets which engage in the first sun gear and on the other hand has second planets which engage in the second sun gear. The first and the second planets are then coupled together via a coupling planet. The coupling planet is arranged coaxially with one of the first or second planets and coupled with this torsionally rigid and is then corresponding to a second or first planet engaged.

According to a particular aspect of the present invention, it is possible to arrange the two sun gears in the immediate vicinity of each other and make the engagement of the coupling planet in the associated second planet in that toothing plane in which engages the second planet in the second sun gear associated therewith. In this concept, a negative profile shift is then preferably realized on the second sun gear, and a positive profile shift is realized on the second planet engaging in this second sun gear. At the coupling planet a negative profile shift is realized. The profile shifts are adjusted so that the tip circle of the second sun gear does not engage in the tip circle of the coupling planet.

The inventive concept can be implemented so that only at the first sun gear, a helical toothing is provided and the second sun gear is designed as a straight toothed spur gear. It is also possible to carry out both sun gears as helical spur gears, or only to perform a helical gearing on the second sun gear and then to use this second sun gear for generating axial force.

Brief description of the figures

Further details and features of the invention will become apparent from the following description taken in conjunction with the drawings. It shows:

1 is a simplified axial sectional view for illustrating the structure of a Stirnraddifferentialgetriebes invention with a clutch plate pack, which is loaded via one of the two sun gears in accordance with the torque acting on the circulation housing and this case a coupling moment generated.

DETAILED DESCRIPTION OF THE FIGURES The illustration according to FIG. 1 shows a differential gear according to the invention with a circulation housing H, a first sun wheel S1 designed as a spur gear, which is received in the circulation housing H, a second sun gear S2, which is also embodied as a spur gear, and which is also accommodated in the circulation housing H. and is arranged coaxially to the axis of rotation X1 of the first sun S1, one of the planetary gear H rotating planetary arrangement P for coupling the two sun gears S1, S2 such that they are mutually oppositely rotatable, a coupling device K for generating a balancing effect of the differential loading coupling moment Reibschlüssigem ways, and a Betätigungsme- mechanism M for actuating the coupling device K such that increases the coupling torque in accordance with a voltage applied to the circulation housing H drive torque.

The Stirnraddifferentialgetriebe invention is designed such that the first sun gear S1 forms part of the actuating mechanism M and in this case provided with a helical tooth Z1 and axially displaceable, wherein the axial displacement of the first sun gear S1 is caused by the engaging on the helical tooth Z1 gear reaction forces. The coupling device K is designed in this embodiment as a multi-plate clutch and has first clutch plates K1 and second clutch plates K2. The coupling device K is effective in itself between the first sun gear S1 and the circulation housing H. Due to the kinematic coupling of the two sun gears S1, S2 via the planetary arrangement P, however, a frictionally engaged coupling of the two sun gears S1, S2 results for the outside observer. Depending on how high the coupling device K is loaded axially results in a correspondingly high frictional coupling of the sun gears S1, S2 possibly one Achieve value that corresponds to a total blocking of the differential. In this state, then both sun gears S1, S2 are coupled to the rotary housing H with high torque transmission capability and run with this. It is possible to structurally limit the maximum blocking torque of the coupling device K, so that no inadmissibly high locking torques can occur. The coupling characteristic may be substantially linear or preferably flat asymptotically designed, so that the clutch bridging torque increases relatively strongly with the load torque in the lower load range, varies substantially proportionally to the load torque in the central region and asymptotically approaches a maximum value in the upper load range. The differential gear can also be designed so that the coupling device K is active only from reaching a structurally predetermined minimum load torque. This approach is especially when driving on roads with low grip, for example, on snowy roads of particular advantage, since then the vehicle is not under-controlled because of a too early locked differential.

In the embodiment shown here, the planetary arrangement P is designed such that it has first planets P1 which engage in the first sun gear S1 and have second planets P2 which engage in the second sun gear S2, the first and the second planets P1, P2 are coupled together via a coupling planet PK. The coupling planet PK are arranged here coaxially to the first planet P1 and coupled torsionally rigid. The coupling planet PK are then in engagement with the second planet P2, which is only recognizably recognizable here.

The second sun gear S2 has the same number of teeth in this embodiment as the first sun gear S1, but has a negative profile shift. The first sun gear S1 can have a positive profile shift, and profile displacements can also be made on the first planet P1 and on the coupling planet PK. The aim of these tooth modifications is that, while maintaining a required ratio of -1 ultimately the coupling planet PK from the top circle of the second sun gear S2 is released. This makes it possible in an advantageous manner that the coupling planet PK can be arranged in the toothing plane of the second sun gear S2 while still engaging in this toothing plane in the second planet P2.

In the embodiment shown here, the second sun gear S2 is designed as a straight-toothed spur gear. The tooth engagement between the second planet P2 and the second sun gear S2 thus generates no axial forces acting on the second sun gear S2. However, it is also possible to carry out the second sun gear S2 as a helical spur gear, wherein the orientation of the skew is then preferably chosen so that either the axial forces of the two sun gears S1, S2 add, or the axial forces of the first planet P1 and rigid with this Compensate coupled coupling planet PK.

The introduction of a drive torque, or at least the initiation of the required circumferential force for generating this drive torque in the circulation housing H via an externally toothed ring gear ZK. This is manufactured as a solid part and carries a helical toothing made as external teeth ZK1. In the present variant, the ring gear ZK is driven by a not-shown spur gear and the circulation housing H is accommodated in a transmission housing which is integrally formed with the housing of a transmission in transverse arrangement. Alternatively, the ring gear ZK can also be designed as a crown wheel and thus form part of an angular gear, for example. Here then the drive train would be arranged in the longitudinal direction. The sprocket ZK forms two opposing seats ZK2, ZK3. The cover elements H1, H2 of the circulating housing H are seated on these seats. The cover elements H1, H2 are firmly connected to the sprocket ZK. The two cover elements H1, H2 each form bearing bushes H1a, H2a in which the sun gears S1, S2 are radially mounted. The cover element H1 forms a pot portion H1 b in which the coupling device K is received. This pot portion H1 b is provided with an internal toothing in which the second Clutch plates K are axially displaceable, rotatably guided. The first clutch plates K1 are guided on an external toothing S1Z. This external toothing S1 Z1 is formed on an outer surface of a hub portion S1 N which forms an integral part of the first sun gear S1. This hub portion S1 N of the first sun gear S1 is provided with an inner toothing S1 Z2, via which a complementary toothed end portion of a drive shaft rotatably coupled to the first sun gear S1. The second sun gear S2 is provided with a boss portion S2N which is supported in the bushing portion H2a of the second cover member H2. This hub section S2N is provided with an internal toothing S2Z2 which, analogous to the toothing S1 Z2, serves for the rotationally fixed reception of a complementarily toothed section of a drive shaft.

The first planet P1 and the coupling planet PK are torsionally coupled together. These two planets can either be integrally formed or otherwise connected or positively coupled. This is achieved here by an indicated only rotatable connection point between the two components. The two gears P1, PK are rotatably mounted on a planetary bearing bolt B which in turn is rotatably anchored in the circulation housing H. It is also possible, the two gears P1, PK rotatably coupled via the bolt B and to store the bolt B in the circulation housing H rotatable.

Since the second planet P2, which radially engages in the second sun gear S2 from the outside, is only partially recognizable in this illustration, it is once again pointed out that the latter is in mesh with the coupling planet PK in the toothing plane of the second sun gear S2 and nem not further recognizable further planetary bearing pin is rotatably mounted. In the present illustration of Figure 1, only one planetary arrangement P is shown. Preferably, at least two, in particular three or four such planetary arrangements in the same pitch in the following sequence Circulating housing H arranged.

The number of teeth of the sun gears S1, S2 and the planets P1, P2, PK of the planetary arrangement are tuned so that a coupling results with the state ratio of "-1".

(-Zpi / Z _S i) x (-Z _P2 / Z _PI ) x (-Z _S2 / Z _PK ) = -1

Where: Z _P1 = number of teeth planet P1, Z _S i = number of teeth sun gear S1, Z _P2 = number of teeth planet P2, and Z _PK = number of teeth of the coupling planet PK.

Optionally: Z _S i = Z _S2 and Z _P1 = Z _P2

In essence, the invention relates to a spur gear differential with a torque sensing barrier. In this case, an axial force is generated via the helical toothing of at least one sun gear, which is used to actuate a friction clutch. If a torque is transmitted via the differential, the axial force of the helical sun is transmitted to the clutch. This clutch then brakes the relative rotation of the sun gear relative to the circulation housing.

In the embodiment according to FIG. 1, only the left-hand sun gear S1 in the representation has helical toothing. It is also possible to provide a helical toothing on the right-hand sun gear S2, which is oriented in such a way that an axial force builds up on the second sun gear S2, which as such is likewise directed "to the left" and thus under slight axial displacement of the second Sun gear for actuating the coupling device K contributes. It is also possible to associate with the second sun gear S2 a second clutch corresponding in its construction to the first sun gear S1, which is then actuated by the second sun gear S2. Both sun gears S1, S2 then migrate axially with increasing load torque on the outside and brakes on the circulation housing H increasingly frictional firmly.

The coupling device can also be arranged axially floating between the two sun gears S1, S2 and thereby activated by axial Gegeneinanderrücken the two sun gears S1, S2. In this case, then the coupling device K brakes the two sun gears S1, S2 together. If necessary, this variant can be realized with a single, possibly axially profiled friction ring, which sits between the sun gears S1, S2 and is axially loaded in the load case.

The operation of the differential gear according to the invention is as follows: About the ring gear ZK a drive torque is introduced into the circulation housing H. In this circulation housing H, the planetary arrangement P is stored. The planetary arrangement P couples the two sun gears S1, S2 to the transmission ratio "-1." As soon as, for example, a load torque is applied to the two sun gears S1, S2 as part of an acceleration process, the first planetary gear P1 is coupled via the helical toothing Z1 The first sun gear S1 accordingly moves to the left and loads the multi-disc clutch pack K. As a result, a braking torque builds up between the cover element H1 and the first sun gear S1. Since the two sun gears S1, S2 are rotatably coupled to each other in opposite directions via the planetary arrangement P as a result of frictional torque between the first sun gear S1 and the circulation housing H also results in a frictional coupling of the second Sonnerads S2 with the circulation housing H. As a result, the two Sonnenräd he S1, S2 and the circulation housing H with each other according to the transmitted by the coupling device K friction torque coupled together. If the torque applied to the toothed ring ZK is further increased, the first sun gear is subjected to further axial load via the first planet P1 and the torque transmitted via the coupling device K is increased even further. As soon as the Wreath ZK applied load decreases the first sun gear S1 is axially relieved and lowered the transmitted via the coupling device K friction torque. The characteristic of the differential according to the invention can be tuned via the torque transmission behavior of the coupling device, the angle of inclination of the toothing of the first sun gear S1 and, in particular, also via restoring elements not shown here. The circulation housing H and the sun gears S1, S2 are designed coordinated with one another such that a sufficient axial displacement of the sun gear S1, possibly also of the sun gear S2, is made possible for actuating the clutch device K. The possible displacement can be designed so large that this is sufficient to total wear of the coupling device. Alternatively, an adjusting mechanism can be provided in the coupling device, which causes a slight axial adjustment of the same when removing the clutch plates.

Claims

Claims with differential gears with:

a circulation housing (H),

a first sun gear (S1) designed as a spur gear, which is accommodated in the circulation housing (H),

a second sun gear (S2), also embodied as a spur gear, which is accommodated in the circulation housing (H) and arranged coaxially with the axis of revolution (X1) of the first sun gear (S1),

- One with the circulation housing (H) rotating planetary arrangement (P) for coupling the two sun gears (S1, S2) such that they are mutually rotatable in opposite directions,

a clutch device (K) for generating a coupling moment loading the differential action of the differential in a frictional manner, and

- An actuating mechanism (M) for actuating the coupling device (K) such that the coupling torque increases in accordance with a torque applied to the circulation housing (H) drive torque,

- Wherein the first sun gear (S1) forms part of the actuating mechanism (M) and in this case provided with a helical toothing (Z1) and axially displaceable, and the axial displacement of the first Sonnenra- (S1) on the at the helical gearing (Z1) attacking Gear reaction forces is caused.

2. Stirnraddifferentialgetriebe according to claim 1, characterized in that the coupling device (K) is designed as a multi-plate clutch.

3. Stirnraddifferentialgetriebe according to claim 2, characterized in that the coupling device (K) between the first sun gear (S1) and the circulation housing (H) is effective.

4. Stirnraddifferentialgetriebe according to claim 1 or 2, characterized in that the coupling device (K) between the two sun wheels (S1, S2) is arranged.

5. Stirnraddifferentialgetriebe according to at least one of claims 1 to 4, characterized in that the planetary arrangement (P) first Planten- th (P1), which engage in the first sun gear (S1) and second planetary (P2), which in the engage second sun gear (S2), and that the first and the second planet (P1, P2) via a coupling planet (PK) are coupled together.

6. Stirnraddifferentialgetriebe according to claim 5, characterized in that the coupling planet (K) to one of the first or second planet (P1, P2) are arranged coaxially coupled and torsionally rigid with this and then corresponding to a second or first planet (P2, P1) engage.

7. Stirnraddifferentialgetriebe according to claim 5 or 6, characterized in that the second sun gear (S2) has a negative profile shift.

8. Stirnraddifferentialgetriebe according to claim 7, characterized in that the first sun gear (S1) has a positive profile shift.

9. Stirnraddifferentialgetriebe according to claim 7 or 8, characterized in that the coupling planet (PK) engages in the toothing plane of the second sun sun gear (S2) in the second planet (P2).

10. Stirnraddifferentialgetriebe according to at least one of claims 1 to 9, characterized in that the second sun gear (S2) is designed as a spur gear spur gear.