Eco 4x4 Front-Axle Transmission Having an Integrated Shut-Off Unit for All Wheel Drives

Abstract

An axle drive mechanism includes a driving toothed wheel, a drive mechanism housing, a differential cage, a differential gear, a first and a second output shaft, and at least one shiftable torque transmission device. The at least one shiftable torque transmission is disposed between the driving toothed wheel and the first output shaft and includes a torque transmission region. The torque transmission region is at least partially disposed between said differential cage bearings in the axial direction.

Claims

1. An axle drive mechanism, comprising: a driving toothed wheel; a drive mechanism housing; a differential cage, which is mounted rotatably in the drive mechanism housing by way of a first and a second differential cage bearing, with said bearings being spaced apart from one another in an axial direction; a differential gear; a first and a second output shaft; and at least one shiftable torque transmission device, which is disposed between the driving toothed wheel and the first output shaft and comprises a torque transmission region, wherein the torque transmission region is at least partially disposed between said differential cage bearings in the axial direction.

2. The axle drive mechanism according to claim 1, wherein the torque transmission region is disposed inside at least one of the differential cage bearings in the radial direction, in particular radially inside the differential cage bearing neighboring the torque transmission region.

3. The axle drive mechanism according to claim 2, wherein the torque transmission device comprises a radially inner output part and a radially outer driving part, and the driving part can make contact with the output part in said torque transmission region, and the output part can be connected to the driving part in a form-locked manner.

4. The axle drive mechanism according to claim 3, wherein the driving part and the output part, for the form-locked connection to one another, each comprise one first and at least one further, in particular several further, rows of form-locking elements, in particular teeth distributed in a row across the circumference, and two consecutive rows are spaced apart from one another in the axial direction by a gap, and said gap is larger than the axial extension of at least one of the rows of form-locking elements.

5. The axle drive mechanism according to claim 4, wherein the driving part is mounted displaceably in axial direction.

6. The axle drive mechanism according to claim 5, wherein the torque transmission device is transferable from the first into the second operating mode thereof by way of an actuator, the actuator comprises a rotatably mounted actuator shaft, and the actuator shaft and a rotational axis of the torque transmission device form an angle of 80 to 100, the actuator shaft preferably being disposed perpendicularly to said rotational axis.

7. The axle drive mechanism according to claim 6, further comprising one further shiftable torque transmission device, which is disposed between the driving toothed wheel and the second output shaft; and a torque transmission region, wherein the torque transmission region is at least partially disposed between said differential cage bearings in the axial direction.

8. The axle drive mechanism according to claim 7, wherein at least one of the output shafts is mounted rotatably with respect to the differential cage by way of an output shaft mounting system, and the output shaft mounting system comprises at least one rolling bearing.

9. The axle drive mechanism according to claim 8, wherein the output part is mounted rotatably with respect to the driving part by way of a clutch mounting system, and the clutch mounting system comprises at least one rolling bearing.

10. A method for operating an axle drive mechanism for transferring the torque transmission device from a first operating state, in which no torque can be transmitted, into a second operating state, in which torque can be transmitted, comprising the acts of: ascertaining a rotational speed of the output part; ascertaining a rotational speed of the driving part; determining an equalizing speed from said rotational speeds (n.sub.8c, n.sub.8d); driving the driving toothed wheel until the equalizing speed reaches or drops below a predefinable threshold value; transferring at least one of the torque transmission device into the second operating state.

11. The method for operating an axle drive mechanism according to claim 10, wherein the threshold value is selected from a range in which the threshold is smaller than 500 rpm applies, especially smaller than 300 rpm, preferably smaller than 200 rpm, and particularly preferably smaller than 100 rpm, and furthermore the threshold is greater than or equal to 0 rpm applies, especially greater than 10 rpm, preferably greater than 30 rpm, and particularly preferably greater than or equal to 50 rpm.

12. The method for operating an axle drive mechanism according to claim 11, wherein the time for axially displacing the driving part from a first axial end position into a second axial end position is selected from a certain range, said range being smaller than 1 second, especially smaller than 500 milliseconds, preferably smaller than 300 milliseconds, and particularly preferably smaller than 100 milliseconds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a full section view of the axle drive mechanism; and

[0039] FIG. 2 is a flow chart for the inventive operating method disclosed herein.

DETAILED DESCRIPTION OF THE DRAWINGS

[0040] The axle drive mechanism 1 comprises a driving toothed wheel 2, which is accommodated in an axle drive mechanism housing 3 and mounted rotatably about the rotational axis 9. The driving toothed wheel 2 is non-rotatably connected to the differential cage 4. The differential gear 6 is accommodated in the differential cage 4, and said differential gear 6 can likewise be rotated about the rotational axis 9, together with the differential cage 4. The output of power to the driving wheels (not shown) takes place via the two output shafts 7a, 7b. The output shafts 7a, 7b are likewise mounted rotatably about the rotational axis 9. The output shafts 7a, 7b each comprise a needle bearing 10, 11 for axial mounting with respect to the differential cage 4.

[0041] The first output shaft 7a comprises a shiftable torque transmission device 8. The shiftable torque transmission device 8 comprises a torque transmission region 8a. The torque transmission region 8a is configured to transmit torque between the driving part 8c and the output part 8d. The driving part 8c is mounted be axially displaceable in the axial direction, which is to say in the direction of the rotational axis 9, for the transmission of torque from the driving part 8c to the output part 8d. For axial displacement, a force is applied to the driving part 8c by the actuator 13 in the direction of the rotational axis 9. The actuator 13 comprises an eccentric 13c for generating said force. This eccentric 13c is non-rotatably connected to the output shaft 13a of the actuator 13 and thus is mounted rotatably about the rotational axis 13b of the output shaft 13a. For transmitting the driving torque, the driving part 8c comprises multiple rows 8c.1 (4 rows) of teeth (form-locking elements) for torque transmission. The teeth 8c.1 are disposed at least substantially in a straight line in the circumferential direction (same axial position). The output part 8d furthermore comprises the same number of rows of teeth 8d.1 (4 rows) for torque transmission.

[0042] In the shift position shown in FIG. 1, the driving part 8c is in the first axial end position thereof, which is to say the different rows of teeth 8c.1 and 8d.1 are positioned in such a way with respect to one another that these rows of teeth slide past one another about the rotational axis 9 in the circumferential direction, and consequently no torque can be transmitted from the driving part 8c to the output part 8d.

[0043] In particular to improve the efficiency, the output part 8d is mounted rotatably with respect to the driving part 8c by a rolling mounting system 12. The output part 8d comprises an additional rolling mounting system 12a with respect to the axle drive mechanism housing 3.

[0044] The region A shows the axial distance between the rolling bearings 5a, 5b for the differential cage 4 in relation to the housing 3. The region B indicates the axial extension of the torque transmission region 8a of the torque transmission device 8. It is clearly apparent that the torque transmission region 8a (region B) at least partially overlaps the axial distance of the rolling bearings 5a, 5b (region A), and thus the torque transmission region 8a is at least partially disposed between the differential cage bearings 5a/b in the axial direction along the rotational axis 9.

[0045] FIG. 2 shows a flow chart for an operating method for an axle drive mechanism according to the invention. This operating method in particular relates to the engagement, which is to say to the transfer of the torque transmission device from the first operating state thereof into the second operating state thereof.

[0046] As is shown, no torque can be transmitted from the driving side to the output side of the torque transmission device in the first operating state, and torque can be transmitted in the second operating state.

[0047] Within the scope of the method, initially the rotational speed of the driving part of the torque transmission device is ascertained. Furthermore, the rotational speed of the output part is ascertained. Ascertaining the rotational speed in particular relates to the measurement of said rotational speed by way of a direct or indirect method. Indirect measuring of the rotational speed shall be understood to mean that the rotational speed of the component (driving/output part) is not directly determined, but rather the rotational speed of another component, which rotates at a particular speed ratio to the driving or output part.

[0048] An equalizing speed is then determined from the rotational speeds of the driving and output parts. In particular, the equalizing speed represents a rotational speed difference (magnitude) between the driving part and the output part. Said equalizing speed A is compared to a predefined threshold value. If the equalizing speed is smaller than said threshold value or corresponds to said threshold value, a control command is outputted to the torque transmission device, so that the same is transferred from the first into the second operating state thereof.

[0049] Examinations have shown that a rotational speed difference of <500 rpm is particularly advantageous for an operating the inventive method.

[0050] Further examinations have shown that a displacement of the driving part for transferring the torque transmission device into the second operating state thereof should take place within a time period that is less than one second. In particular at larger rotational speed differences A and shifting times longer than one second, shifting errors may occur, which is to say the torque transmission device cannot be transferred from the first into the second operating state thereof when the rotational speed difference A is too large and/or shifting is too slow, and such events in particular result in poorer comfort.

[0051] The foregoing disclosure has been set forth merely to illustrate the embodiments of the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the embodiments of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.