Patent Application
20250180104
The present invention relates to a differential transmission for a vehicle. Furthermore, the present invention relates to a drive unit having a differential transmission, and to a vehicle having a drive unit.
Differential transmissions are often used in vehicles. Differential transmissions are used to enable drive wheels driven by the same motor to have different rotational speeds. This is required, for example, when cornering. The drive wheel on the inside of the curve covers a shorter path than the drive wheel on the outside of the curve. In this respect, the drive wheel on the inside of the curve has to rotate more slowly than the drive wheel on the outside of the curve.
The present invention is based on the object of providing an improved differential transmission which has an extended service life, may be produced more cost-effectively and has a lower outlay in terms of installation space.
The object is achieved by a differential transmission having the features from claim 1.
A differential transmission for a vehicle comprises a first output shaft, a second output shaft, a first planetary gearset, a second planetary gearset, a sun ring gear and a stationary component. The first output shaft and the second output shaft can extend out of the stationary component in an axial direction. In this case, the axial direction may be determined by the axis of rotation of the first output shaft. The first output shaft and the second output shaft can be coaxial to one another. The vehicle may be, for example, a commercial vehicle, such as a truck, a construction machine or agricultural machine, or a passenger car.
The first planetary gearset comprises a first sun gear, a first planet carrier, a first planet gear and a first ring gear. The first planetary gearset may comprise a plurality of planet gears, preferably three planet gears. The first planetary gearset may be formed as a plus or as a minus planetary gearset. The first sun gear is in engagement with the first planet gear, and the first planet gear is in engagement with the first ring gear. An engagement between two gear wheels is achieved by means of an overlap of the gear wheels in the axial direction and a spacing of the axes of rotation of the gear wheels in a radial direction, so that at least one tooth of the one gear wheel contacts a tooth of the second gear wheel. The first sun gear, the first planet carrier and the first ring gear may be arranged coaxial to one another. The first sun gear may be used to drive the first planetary gearset.
The first planet carrier may be used as an output and is connected with the first output shaft by means of a torque-proof connection. The torque-proof connection may be arranged adjacent to the second output shaft in the region of an end of the first output shaft which is located inside the stationary component. The first output shaft may be arranged coaxially to the first sun gear.
If two elements are connected with one another, they are directly or indirectly coupled with one another such that a movement of one element causes a reaction of the other element. For example, a connection may be provided by a form-fit or friction-fit connection. The connection may correspond to a meshing of corresponding toothings of the two elements. Between the elements, further elements may be provided, for example one or a plurality of spur gear stages. For example, a connection may be toque-proof.
A torque-proof connection of two elements is understood to mean a connection in which the two elements are rigidly coupled with one another in all intended states of the transmission, so that they have substantially the same rotational speed. The elements may be present here as individual components connected torque-proofly with one another or also in one piece. A torque-proof connection may be designed as a splined shaft connection or as a toothed shaft connection. In this case, a securing element, for example a securing ring, snap ring or spiral ring, may be provided for limiting a relative movement in the axial direction. The torque-proof connection may be designed as a press connection or by means of screw connections of flanges of the first planet carrier and the first output shaft.
The first planet carrier is rotatably supported at the stationary component by means of a support. The support of the first planet carrier is arranged opposite the torque-proof connection in the axial direction with respect to the first planet gear. The axial direction may be the axial direction of a planet axis of the first planet carrier, on which the first planet gear is rotatably mounted. The support of the first planet carrier may be designed as a needle sleeve without an inner ring. A bushing may be present inside the needle sleeve. The bushing may be dispensed with if the first planet carrier is produced at least in sections from hardened steel.
As a result, the first planet carrier may be designed to be thinner and the service life of the differential transmission may be extended. In this case, no oil has to be guided between the first output shaft and the second output shaft. As a result, the second output shaft is not weakened and may be designed to be thinner-walled, which leads to a lower weight. In addition, corresponding sealing elements may be dispensed with, which leads to a cost advantage, installation space advantage and weight advantage. No direct oil supply through the stationary component to the support of the second output shaft is necessary, since in total fewer supports require oil.
The second planetary gearset comprises a second sun gear, a second planet carrier, a second planet gear and a second ring gear. The second planetary gearset may comprise a plurality of planet gears, preferably three planet gears. The second planetary gearset may be formed as a plus or as a minus planetary gearset. The second sun gear is in engagement with the second planet gear, and the second planet gear is in engagement with the second ring gear. The second sun gear, the second planet carrier and the second ring gear may be arranged coaxial to one another and coaxial to the first sun gear, the first planet carrier and the first ring gear. The second ring gear is connected with the second output shaft. The connection of the second ring gear with the second output shaft may be designed as a press connection or by means of screw connections in the axial direction of the second planet carrier to the second ring gear or by means of a shaft-hub connection. The connection of the second ring gear with the second output shaft may be torque-proof.
The sun ring gear forms the first ring gear at an inner circumference and the second sun gear at an outer circumference. The sun ring gear may be designed in one piece. In an alternative embodiment, the sun ring gear may be designed in several parts. In this case, the sun ring gear comprises the first ring gear, the second sun gear and a coupling element. The first ring gear may then be torque-proofly connected at an inner circumference of the coupling element. The second sun gear may then be torque-proofly connected at an outer circumference of the coupling element.
The second planet carrier is supported at the stationary component. The support of the second planet carrier at the stationary component may be designed by means of a press connection, material bond or screw connection of the second planet carrier in the axial direction to the stationary component. Alternatively, the second planet carrier may be fixable to the stationary component via a shifting element. A torque-proof connection between two elements may be selectively established or released via a switching element, for example a clutch. The second planet carrier may comprise a second planet axis, on which the second planet gear is rotatably supported. The second planet axis may be supported at the stationary component. A cylindrical projection of the stationary component may form the second planet axis.
The stationary component may be a transmission housing. The transmission housing may completely surround the first planetary gearset and the second planetary gearset. The transmission housing may comprise a recess to enable a mechanical connection from outside the transmission housing to the first sun gear. In addition, the transmission housing may comprise recesses to enable an extension of the first output shaft and the second output shaft to an outside of the transmission housing.
In one embodiment, the support of the first planet carrier may be supported at a cylindrical outer circumference of a section of the stationary component. For example, the cylindrical outer circumference may be provided at a cylindrical projection, which projects from the stationary component in the axial direction. An intermediate element may also be provided, which provides the cylindrical outer circumference and which is supported at the stationary component. An outer circumference of the support of the first planet carrier is provided at a cylindrical inner circumference of a section of the first planet carrier. An intermediate element may also be provided which provides the cylindrical inner circumference and which is supported at the first planet carrier.
In one embodiment, the support of the first planet carrier may be supported at a cylindrical inner circumference of a section of the stationary component. For example, the cylindrical inner circumference may be provided in a bore or recess in the stationary component in the axial direction. An intermediate component may also be provided, which provides the cylindrical inner circumference and which is supported at the stationary component. An inner circumference of the support of the first planet carrier is provided at a cylindrical outer circumference of a section of the first planet carrier. An intermediate component may also be provided, which provides the cylindrical outer circumference and which is supported at the first planet carrier.
In one embodiment, the differential transmission may comprise an input element. The input element may be torque-proofly connected with the first sun gear. The connection may be designed as a shaft-hub connection, press connection or by means of screw connections of flanges of the sun gear and the input element.
The input element is rotatably supported at the stationary component by means of a support. The first sun gear, the input element and the first output shaft may be arranged coaxially. As a result, a compact design of the differential transmission may be realized.
In one embodiment, the support of the first planet carrier may be arranged outside the support of the input element in the radial direction. The supports may be coaxial to one another.
In one embodiment, the support of the first planet carrier may overlap the support of the input element in the axial direction. In particular, this embodiment may be used in combination with the arrangement of the support of a section of the first planet carrier in the radial direction outside the support of the input element. Furthermore, this embodiment may be used in particular in combination with the backing of the support of the first planet carrier at the cylindrical outer circumference of a section of the stationary component. For example, the support of the input element may be arranged completely inside the support of the first planet carrier in the axial direction. In this case, a very compact design of the differential transmission in the axial direction is possible.
In one embodiment, the support of the first planet carrier may be arranged next to the support of the input element in the axial direction. In particular, this embodiment may be used in combination with the backing of the support of the first planet carrier at the cylindrical inner circumference of a section of the stationary component. This enables a simpler oil supply to the support of the first planet carrier. In this embodiment, the diameter of the cylindrical inner circumference of a section of the stationary component may be selected to be small. It is advantageous here that small bearing diameters lead to low friction losses. In this respect, the efficiency of the differential transmission may be increased.
Furthermore, a bushing made of hardened steel may be provided at the cylindrical outer circumference of a section of the first planet carrier. The first planet carrier may then be produced, for example, from aluminum. Alternatively, a section of the first planet carrier may serve as a running surface for the support of the first planet carrier. The planet carrier may be produced, for example, at least in sections from hardened steel. A separate bushing, which serves as a running surface for rolling bodies of the support of the first planet carrier, made of hardened steel at a cylindrical outer circumference of a section of the first planet carrier may then be dispensed with. This reduces the number of components of the differential transmission and enables a simple construction.
A cylindrical recess in the stationary component for a bearing seat, at which an outer ring of the support of the input element is mounted, may be used to form a bearing seat, at which an outer ring of the support of the first planet carrier is mounted. In other words, two bearing seats in the stationary component may be produced with one machining step. This reduces the production costs.
In one embodiment, the first sun gear may be hollow. For example, the first sun gear may be ring-shaped. In this case, the first output shaft may extend through the first sun gear and coaxially to the first sun gear. As a result, a compact design of the differential transmission is possible.
In one embodiment, the input element may be designed as a hollow shaft, wherein the first output shaft may extend through the input element. As a result, a compact design of the differential transmission may be realized.
In one embodiment, the input element and the first sun gear may be formed in one piece. In other words, the input element may form the first sun gear. As a result, the number of components of the differential transmission may be reduced and a compact design of the differential transmission may be realized.
In one embodiment, the sun ring gear may be ring-shaped. The first ring gear may be arranged radially inside the second sun gear, and the first ring gear may overlap the second sun gear in the axial direction. The first ring gear and the second sun gear may overlap such that the gear having the smaller extension in the axial direction is arranged inside the other gear. For example, the second sun gear may be wider than the first ring gear in the axial direction. Then, the first ring gear may be arranged inside the second sun gear in the axial direction, such that the first ring gear does not protrude from the second sun gear in the axial direction.
In one embodiment, the second output shaft may be arranged coaxially to the first output shaft and opposite the first output shaft in the axial direction with respect to the stationary component. The first output shaft and the second output shaft may each extend as far as a drive wheel, a wheel hub or a cardan shaft of the vehicle. As a result, a compact design of the differential transmission is possible and the number of components of the differential transmission may be reduced.
In one embodiment, a torque introduced into the first sun gear may be transmittable to the first output shaft and to the second output shaft.
In a further embodiment, the first output shaft and the second output shaft may each be rotatably supported at the stationary component by means of a support. The supports of the first output shaft and the second output shaft may be arranged coaxially to one another.
The second output shaft may comprise a first support and a second support. The first support may be a floating bearing. The second support may be a fixed bearing. The first support of the second output shaft may be arranged outside the support of the first planet carrier in the radial direction. The first support of the second output shaft may overlap the support of the first planet carrier in the radial direction. The first support of the second output shaft and the support of the first planet carrier may be designed in the same way. The second support of the second output shaft may be arranged inside the support of the first planet carrier in the radial direction.
In one aspect, a drive unit comprises a motor and a differential transmission according to the previously described embodiments. The motor is coupled to the differential transmission in order to drive the first sun gear.
In one aspect, a vehicle comprises a drive unit according to the previously described embodiment and drive wheels. The drive unit is mounted in the vehicle in order to drive the drive wheels.
The first output shaft 5 and the second output shaft 6 extend from the differential transmission 3 in opposite directions parallel to that of the first axle 71 towards the drive wheels 70. The first output shaft 5 extends through the transmission 3 and the motor 73. The first axle 71 is a driven rear axle of the vehicle 1 in the present case. In an alternative embodiment, the first axle 71 may be a driven front axle of the vehicle 1. The first output shaft 5 and the second output shaft 6 are connected with the drive wheels 70 of the vehicle 1 in such a way that the first output shaft 5 and the second output shaft 6 may each drive one of the drive wheels 70.
One of the drive wheels 70 transmits a driving power of the motor 73 to a ground on which the drive wheels 70 rest and generates a travelling motion of the vehicle 1. Steerable wheels 74 of the vehicle 1 are rotatably arranged on a second axle 72, in the present case a front axle. In an alternative embodiment, the second axle 72 may be a rear axle of the vehicle 1.
In a further embodiment, joints and wheel hubs may be arranged between the respective drive wheels 70 and the first output shaft 5 and the second output shaft 6 in order to compensate for possible misalignments of the first output shaft 5 and the second output shaft 6, respectively.
The support 40 of the first planet carrier 12 is described in more detail below.
The support 40 of the first planet carrier 12 is arranged in the axial direction opposite a torque-proof connection 30 of the first planet carrier 12 with the first output shaft 5 with respect to the first planet gears 13 of the first planetary gearset 10. The first planet carrier 12 is thus supported on both sides in the axial direction with respect to the first planet gears 13. A radial force from one of the first planet gears 13 can thus be distributed to the support 40 of the first planet carrier 12 and the torque-proof connection 30. This leads to a more uniform force distribution in the first planet carrier 12.
The support 40 of the first planet carrier 12 is designed here as a needle sleeve without an inner ring. The support 40 of the first planet carrier 12 further comprises a bushing 44, here a hardened steel sleeve. The bushing 44 is arranged radially inside the needle sleeve. Needles of the needle sleeve can thus roll on the bushing 44. In this case, the bushing 44 is positioned such that it projects beyond the needle sleeve in the axial direction. The width of the bushing 44 in the axial direction is greater than the width of the needle sleeve.
The differential transmission 3 further comprises an input element 4. The input element 4 is rotatably supported at the stationary component 31 by means of a support 43.
The support 40 of the first planet carrier 12 overlaps the support 43 of the input element 4 in the axial direction. In this case, the support 40 of the first planet carrier 12 is arranged outside the support 43 of the input element 4 in the radial direction. In other words, the support 40 of the first planet carrier 12 is arranged above the support 43 of the input element 4 in the sectional view in
Further details of the embodiment are described below.
The input element 4 is formed as a hollow shaft. The input element 4 can rotate about its central axis. The input element 4 is torque-proofly connected with a rotor shaft of the motor 73 and is driven therewith. The rotor shaft of the motor is not shown in
The differential transmission 6 comprises a sun ring gear 32. The sun ring gear 32 is hollow and ring-shaped. The sun ring gear 32 forms the first ring gear 14 at an inner circumference and the second sun gear 21 at an outer circumference. The sun ring gear 32 is arranged radially outside the first planet gears 13. The sun ring gear 32 is simultaneously in engagement with the first planet gears 13 and the second planet gears 23.
The second planet carrier 22 is supported at the stationary component 31 in a torque-proof manner in that the second planet carrier 22 is fastened to the stationary component 31 in the axial direction. The second ring gear 24 is torque-proofly connected with the second output shaft 6. The first output shaft 5 and the second output shaft 6 are coaxial to one another and rotatably supported in the stationary component 31.
In a further embodiment, which comprises all the features of the preceding embodiment, the stationary component 31 is a two-part transmission housing. A section of a first part of the two-part transmission housing is shown in
The support 40 of the first planet carrier 12 forms a floating bearing. The support 43 of the input element 4 is in the present case a grooved ball bearing and forms a fixed bearing.
The first output shaft 5 is rotatably supported in the stationary component 31 by means of a support, which is not shown. The support of the first output shaft 5, here a grooved ball bearing, is designed as a fixed bearing.
The second output shaft 6 is rotatably supported at the stationary component 31 by means of a first support 41 and a second support 42. The first support 41 of the second output shaft 6, here a needle bearing, is a floating bearing. The second support 42 of the second output shaft 6, here a grooved ball bearing, is a fixed bearing. In an alternative embodiment, the first support 41 is designed as a fixed bearing and the second support 42 is designed as a floating bearing.
In a further embodiment, which comprises all the features of the preceding embodiment, the width of the first sun gear 11 in the axial direction is greater than the width of the first planet gears 13. Furthermore, the width of the sun ring gear 32 in the axial direction is greater than the width of the first planet gears 13 and the second planet gears 23, respectively. Furthermore, for positioning the sun ring gear 32 relative to the first planet gears 13 in the axial direction, securing elements 56, 57, here snap rings, and thrust washers are provided at an inner circumference of the sun ring gear 32 on both sides of the first planet gears 13.
An outer ring of the needle sleeve of the support 40 of the first planet carrier 12 is positioned in the axial direction by means of a shoulder of the first planet carrier 12 and a securing element 50, here a snap ring. The bushing 44 is positioned in the axial direction by means of a shoulder of the stationary component 31 and a securing element 51, here a securing ring.
An outer ring of the first support 41 of the second output shaft is positioned in the axial direction by means of a shoulder in the stationary component 31 and by means of a securing element 53, here a snap ring. An outer ring of the second support 42 is positioned in the axial direction by means of a shoulder in the stationary component 31 and by means of a securing element 58, here a snap ring. An inner ring of the second support 42 is positioned in the axial direction by means of a shoulder in the second output shaft 6 and by means of a securing element 54, here a snap ring.
The width of the second ring gear 24 is greater than the width of the second planet gears 23. For the torque-proof connection of the second ring gear 24 to the second output shaft 6, the second ring gear 24 and the second output shaft 6 each comprise a toothing of a shaft-hub connection. Furthermore, the torque-proof connection comprises a securing element 55, here a snap ring, for relative positioning in the axial direction.
The torque-proof connection 30 of the first planet carrier 12 with the first output shaft 5 comprises a securing element 52, here a snap ring, for axial relative positioning. In the present embodiment, the input element 4 is formed in one piece with the rotor shaft and is rotatably supported in the stationary component 31 via a rotor support. In an alternative embodiment, the input element 4 comprises a toothing for a shaft-hub connection for a torque-proof connection of the input element 4 to the rotor shaft.
The support 40 of the first planet carrier 12 is arranged next to the support 43 of the input element 4 in the axial direction. The support 40 of the first planet carrier 12 is arranged inside the support 43 of the input element in the radial direction. The bushing 44 of the support 40 of the first planet carrier 12 may be dispensed with here, since the first planet carrier 12 is produced at least in regions from hardened steel. In an alternative embodiment, the first planet carrier 12 is produced from aluminum. The bushing 44 is then provided at an outer circumference of a section of the first planet carrier 12.
In a further embodiment, the outer ring of the support 40 of the first planet carrier 12 is positioned in the axial direction by means of a shoulder of the stationary component 31 and a securing ring 50, here a snap ring.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102023212119.0 | Dec 2023 | DE | national |
