Transmission, especially for a single-wheel drive unit

Abstract

A transmission, which is provided in particular within a single-wheel drive unit and which comprises a transmission carrier (8), an input shaft (14) rotatably driven about an axis, at least one planetary gear stage (10) with a first externally toothed sun gear (18, 18') which can be driven via the input shaft (14), with an internally toothed ring gear (28) which is rotatably mounted on the transmission carrier (8), and with a rotatably mounted planet carrier (27) on which at least one externally toothed planet gear (25) which engages with both the sun gear (18, 18') and the ring gear (28) is rotatably mounted and which has internal teeth (35), a further transmission stage (11) which comprises at least one spur gear (43) which is rotatably mounted on a bearing journal (41) which is fixed in position with respect to the transmission carrier (8) and whose axis is arranged at a distance from the axis of the input shaft (14), and with which The ring gear (28) is in tooth engagement,and a second externally toothed sun gear (37, 37'), characterized in that the two components second externally toothed sun gear (37, 37') and input shaft (14) are axially displaceable relative to each other between two end positions, that in a first end position of the two components second externally toothed sun gear (37, 37') and input shaft (14) the second externally toothed sun gear (37, 37') and the input shaft (14) are rotationally fixed to each other and rotate at the same speed and the power flow from the input shaft (14) via the planetary gear stage (10) to the second externally toothed sun gear (37, 37') is interrupted, and that in the second end position the second externally toothed sun gear (37, 37') meshes with the internal teeth (35) of the planet carrier (27) without direct coupling to the input shaft (14) and can be driven via the planetary gear stage (10) from the input shaft (14).

Description

The invention relates to a transmission, which is provided in particular within a single-wheel drive unit, and which comprises a transmission carrier, an input shaft rotatably driven about an axis, at least one planetary gear stage with a first externally toothed sun gear, which is driveable via the input shaft, with an internally toothed ring gear rotatably mounted on the transmission carrier, and with a rotatably mounted planet carrier on which at least one externally toothed planet gear, which engages with both the sun gear and the ring gear, is rotatably mounted and which has internal teeth. A further transmission stage comprises at least one spur gear, which is rotatably mounted on a bearing journal that is fixed relative to the transmission carrier and whose axis is arranged at a distance from the axis of the input shaft, and which engages with the ring gear. A second externally toothed sun gear is also provided. Such transmissions are primarily used within the individual wheel drives of mobile machinery, especially construction or agricultural machinery, or transport units. In practice, these machines first travel along a road or access track to their work site, for example, a field, and then perform the work there. During the journey to the work site, the required torque is low, while high speed is desired. In the field, the machine typically operates with high torque and low speed. This necessitates a multi-start, or at least two-start, transmission of the aforementioned type. A transmission with the aforementioned features is already known from DE 10 2004 031 009 B4. In this transmission, a further planetary gear stage with a sun gear, a ring gear, and a planet carrier with planet gears meshing with the sun gear and the ring gear is arranged upstream of the planetary gear stage and the transmission stage, which share a common ring gear representing the transmission output. The planet carrier is rotationally fixed to the sun gear of the downstream planetary gear stage. Depending on the state of two multi-plate clutches, the ring gear of the further planetary gear stage is either fixed to the housing or rotationally fixed to the sun gear of the further planetary gear stage, so that the planet carrier rotates either slower than the sun gear or at the same speed as the sun gear of the further planetary gear stage. This provides two gears for the transmission. Document DE 10 2018 205 562 A1 is also known from the prior art. The object of the present invention is a transmission, which is provided in particular within a single-wheel drive unit and which comprises, firstly, a transmission carrier, secondly, an input shaft rotatably driven about an axis, thirdly, at least one planetary gear stage with a first externally toothed sun gear which can be driven via the input shaft, with an internally toothed ring gear which is rotatably mounted on the transmission carrier, and with a rotatably mounted planet carrier on which at least one externally toothed planet gear, which engages with both the sun gear and the ring gear, is rotatably mounted and which has internal teeth, and fourthly, a further transmission stage comprising at least one spur gear which is rotatably mounted on a bearing journal which is fixed in position with respect to the transmission carrier and whose axis is arranged at a distance from the axis of the input shaft, and which engages with the ring gear.and fifthly, which has a second externally toothed sun gear, to further develop it in such a way that two different gears are obtained with a small number of components and thus with low complexity and cost, as well as largely without component wear. The problem is solved by a device according to claim 1. Further developments of the device are the subject of the dependent claims. The problem is solved in particular by the fact that, in a transmission of the type specified, the two components, the second externally toothed sun gear and the input shaft, are axially displaceable relative to each other between two end positions; that in a first end position of the two components, the second externally toothed sun gear and the input shaft, the second externally toothed sun gear and the input shaft are rotationally fixed to each other and rotate at the same speed, and the power flow from the input shaft via the planetary gear stage to the second externally toothed sun gear is interrupted; and that in the second end position, the second externally toothed sun gear meshes with the internal teeth of the planetary ridge without direct coupling to the input shaft and can be driven by the input shaft via the planetary gear stage. According to the invention, the two gears are not achieved using multi-plate clutches, but rather by changing the relative position between the input shaft and the second externally toothed sun gear. Only a few components of low complexity are required. The transmissible torque is independent of the force with which the plates of a multi-plate clutch are pressed together. A transmission according to the invention can be advantageously further developed. In a particularly advantageous embodiment, in an intermediate position between the two end positions of the two components, the second externally toothed sun gear and the input shaft, the second externally toothed sun gear is, on the one hand, rotationally fixed to the input shaft and, on the other hand, is subject to a power transmission from the input shaft via the planetary gear stage. The input shaft is engaged with the planet gears via the first sun gear and, in parallel, with the second sun gear. The transmission is thus locked. Rotation of the ring gear and the input shaft is not possible. In the first end position of the two components, the second externally toothed sun gear and the input shaft, relative to each other, one of the two components is decoupled from the planetary gear stage to interrupt the power flow from the input shaft via the planetary gear stage to the second externally toothed sun gear. In a transmission according to the invention with only one planetary gear stage, the sun gear of the planetary gear stage is driven by the input shaft at the same speed, and the second externally toothed sun gear is driven by the planet carrier of the planetary gear stage at the same speed. Thus, when coupled to the input shaft, the sun gear of the planetary gear stage rotates at the same speed as the input shaft, and when coupled to the planet carrier, the second sun gear rotates at the same speed as the planet carrier. Advantageously, only one of the two components, the second externally toothed sun gear and the input shaft, is axially displaceable relative to the gearbox carrier. In a special further development, the input shaft is arranged in a fixed position relative to the gearbox carrier in the axial direction, and the second externally toothed sun gear is axially displaceable relative to the input shaft. In another specific embodiment, the second externally toothed sun gear is fixed axially to the gear carrier, and the input shaft is axially displaceable relative to the second externally toothed sun gear. This solution is particularly advantageous when at least two planetary gear stages are present, with the second planetary gear stage, located downstream of the first in the power flow, being closer to a drive motor than the first planetary gear stage. With such a gear design, it is easier to displace the input shaft than the second sun gear. The latter is instead rotationally fixed to the planetary rib of the first planetary gear stage and meshes with the planet gears of the second planetary gear stage. It is also conceivable, however, that in a transmission with two planetary gear stages, the third sun gear is movable and, in one position, is rotationally fixed to the planetary carrier of the second planetary gear stage and meshes with the spur gears of the next gear stage. In a second position, it is decoupled from the planetary carrier of the second planetary gear stage and directly and rotationally fixed to the input shaft. With such a solution, the difference in the gear ratios of the two gear stages would be very large. The second externally toothed sun gear and the input shaft can be coupled together in a rotationally fixed manner by means of a splined shaft or a toothed shaft connection. Preferably, one of the two components, the second externally toothed sun gear and the input shaft, is axially displaceable with a fluid piston, in particular with a hydraulic fluid piston. The fluid piston is preferably designed as a single-acting piston and borders a pressure chamber, wherein the axially displaceable component can be moved by the fluid piston towards the second end position when pressure medium is supplied into the pressure chamber and by a spring means by displacing pressure medium from the pressure chamber towards the first end position. Two embodiments of a transmission according to the invention are shown in the drawings. The invention will now be explained in more detail with reference to the figures in these drawings. Figure 1 shows an axial section through the first embodiment, which has exactly one planetary gear stage and in which the second sun gear is axially displaceable and is in an end position corresponding to the first gear; Figure 2 shows an axial section through the first embodiment, wherein the second sun gear is in an intermediate position and the transmission is locked; Figure 3 shows an axial section through the first embodiment, wherein the second sun gear is in a second end position corresponding to the second gear; Figure 4 shows an axial section through the second embodiment, which has exactly two planetary gear stages and in which the input shaft is axially displaceable and is in an end position corresponding to the first gear; Figure 5 shows an axial section through the second embodiment, wherein the input shaft is in an intermediate position and the transmission is locked; and Figure 6 shows...6 an axial section through the second embodiment, wherein the input shaft is in a second end position corresponding to the second gear. The transmission according to Figs. 1, 2 to 3 comprises a transmission carrier 8 with a mounting flange 9, with which the transmission carrier can be attached to the chassis of a vehicle. The transmission carrier 8 is a hollow body having outer and inner wall sections that differ in their diameters. The transmission further comprises a planetary gear stage 10 and another gear stage 11. The gear stages are driven by a motor, in this case a hydraulic motor 12 in a swashplate configuration, which is only shown in a highly schematic way in the figures, via a drive sleeve 13 and an input shaft 14. At the end furthest from the motor, the input shaft 14 is integrally fitted with external teeth, which form the sun gear 18 of the planetary gear stage 10. Beyond the sun gear 18, the input shaft 14 is rotatably mounted by a roller bearing 19. The sun gear 18 meshes with several externally toothed planet gears 25, which are rotatably mounted at equal intervals on double-row roller bearings on bearing journals 26 of a planet carrier 27. In addition to the sun gear 18, the planet gears 25 also mesh with an internally toothed ring gear 28, which has a mounting flange 29 for attaching it to the rim of a wheel. The ring gear 28 thus forms the wheel-side output of the transmission. It is rotatably mounted on the outside of the transmission carrier 8, which projects into the ring gear 28 from one end face, by means of two tapered roller bearings 30 arranged in an O-arrangement. A cover 31, which carries the roller bearing 19 for the input shaft 14, is inserted into the ring gear 28 at the other end face. The planetary gear 27 is provided with an internal toothing 35 into which a sleeve-shaped second sun gear 37, provided with an external toothing 36, can be inserted for a rotationally fixed connection. The second sun gear 37 is axially guided by flanged bolts 38, which are inserted into bores 34 of the gear carrier 5 and bear against it, and by flanged bolts 39, which bear against the cover 31. The sun gear 37 is arranged coaxially with the input shaft 14. On the gear carrier 8, several axially aligned bearing journals 41 are formed around the input shaft 14 at equal angular intervals. Each of these journals supports an externally toothed spur gear 43 via a double-row rolling bearing arrangement 42. This spur gear meshes with both the sun gear 37 and the ring gear 28. The bores 34 for the collar bolts 38, which serve to axially guide the planet carrier 27, are located in the bearing journals 41. The bores 34 are offset inwards towards the axis of the input shaft 14 and are arranged eccentrically to the axes of the bearing journals. Since the bearing journals 41 are fixed in position relative to the gear carrier, the second gear stage 11 does not have rotating planetary gears. However, because of the similar arrangement of the gears compared to the planetary gear stage 10, the second gear stage is also often referred to as a planetary gear stage. The second sun gear 37, which projects beyond the spur gears 43 and overlaps the drive sleeve 13 over a certain distance, and the input shaft 14 are arranged axially overlapping in the embodiments according to Fig. 1, Fig. 2 to Fig. 3, with the input shaft 14 dipping into the sun gear 37. The sun gear 37 is axially displaceable between a first end position and a second end position. Regardless of its position, it always meshes with the spur gears 43. In the first end position, shown in Fig. 1, its external teeth 36 engage with the internal teeth 35 of the planet carrier 27, and it rotates at the same speed as the planet carrier. In the second end position, shown in Fig. 3, it is disengaged from the planet carrier 27 and its internal teeth 44 engage with external teeth 45 of the input shaft 14. In the second end position, the second sun gear 37 is thus decoupled from the planet carrier 27 and rotationally fixed to the input shaft 14, rotating at the same speed as the input shaft. In an intermediate position, shown in Fig. 2, the second sun gear 37 engages both with its external teeth 36 with the internal teeth 35 of the planet carrier 27 and with its internal teeth 44 with the external teeth 45 of the input shaft. In this intermediate position of the sun gear 37, the transmission is locked. A hydraulic fluid piston designed as an annular piston 50, guided in the gear carrier 8, serves to axially displace the second sun gear 37 in one direction. A sealing ring 51 seals the radial gap between the annular piston and the gear carrier 8. The annular piston 50 is single-acting. The sun gear is therefore only displaced in one direction by the annular piston 50. In the opposite direction, the sun gear 37 is displaced by spring force. Specifically, the annular piston 50 exerts a force on the second sun gear 37 in the direction of the second end position, and the spring force exerts a force on it in the direction of the first end position. For this purpose, a pressure chamber 54 is first formed between the ring piston 50 and a base 53 inserted into the gear carrier 8 and secured by a snap ring 52. This is fluidically connected to a hydraulic pressure source and a pressure sink via a connecting bore 55, an angled bore 56, and a round milled slot 57. The annular piston 50 is externally unstepped and has a base 58 with the same outer diameter as the actual annular piston 50. A ball bearing 59 is axially fixed in this base and in the sun gear 37, forming a rotary bearing between the annular piston 50 and the sun gear 37. The annular piston 50 and the sun gear 37 are axially fixed to each other via the inner and outer rings of the ball bearing. These bearings rest axially against a shoulder of the annular piston and the sun gear 37, respectively, and against snap rings inserted into the annular piston and the sun gear 37, respectively. On the outer side of the base 58, the annular piston 50 is acted upon by helical compression springs 62. Each helical compression spring 62 extends into a blind bore 63, which reaches into a bearing journal 41, and is supported at the bottom of the blind bore. The number of blind bores 63, and thus the number of helical compression springs 62, is equal to the number of bearing journals 41. The axis of each blind bore 63 is aligned with a bore 34, which has a smaller diameter than the blind bore 63 and is open to the corresponding blind bore 63. In this way, the two bores 34 and 63 can be easily manufactured. Fig. 1 shows the first embodiment in a state where the second sun gear 37 and the planet carrier 27 with their teeth 35 and 36 are engaged, while the teeth 44 and 45 of sun gear 37 and input shaft 14 are disengaged. The pressure chamber 54 is pressurized, and the annular piston 50 is displaced against the force of the helical compression springs 62 until it reaches a stop on the gear carrier 8. The second sun gear 37 rotates at the same speed as the planet carrier 27 and meshes with the spur gears 43, which are engaged with the ring gear 28. The gear ratio is thus at its maximum. First gear is engaged. A pressure exceeding the spring forces is maintained in the pressure chamber 54 as long as the transmission is operated in first gear. To engage second gear, the pressure chamber 54 is connected to a volume, for example a tank, where only low pressure or atmospheric pressure prevails. The helical compression springs 62 can then move the annular piston 50 and the sun gear 37 towards a second end position. If the pressure chamber 54 is then closed when the second sun gear 37 has not yet fully emerged from the planet carrier 27 and its teeth 44 have already partially engaged the teeth 45 of the input shaft 14, thus assuming an intermediate position between its two end positions, the transmission is locked. If, however, the pressure chamber 54 is not sealed, the helical compression springs 62 push the annular piston 50 and the sun gear 37 into the first end position shown in Fig. 3. In this position, the sun gear 37 is decoupled from the planet carrier 27 and non-rotatably connected to the input shaft 14. In the now engaged second gear, the gear ratio is determined solely by the number of teeth on the sun gear 37 and the ring gear 28 and is significantly lower than in first gear. The transmission according to Figs. 4, 5 to 6, like the transmission according to Figs. 1, 2 to 3, comprises a transmission carrier 8 with a mounting flange 9, with which the transmission carrier can be attached to the chassis of a vehicle. The transmission carrier 8 is a hollow body having outer and inner wall sections that differ in their diameters. The transmission according to Figs. 4, 5 to 6, like the transmission according to Figs. 1, 2 to 3, comprises a planetary gear stage 10 with planet gears 25 rotatably mounted on a planet carrier 27 and a further gear stage 11 with a sun gear 67 that meshes with spur gears 43 of the further gear stage 11. A further planetary gear stage 70 with planet gears 72 rotatably mounted on a planet carrier 71 is also present; these planet gears, like the planet gears 25, mesh with the ring gear 28. The planet carrier 71 is provided with internal teeth 73 into which the sun gear 67 engages axially with its external teeth 74, so that the sun gear 67 and the planet carrier 71 rotate at the same speed. The sun gear 67 is permanently coupled to the planetary bridge 71 and the spur gears 43 of the further gear stage 11. The planetary gear stage 10, as in the embodiment shown in Figs. 1, 2 to 3, has an internal toothing 35 into which a sun gear 37' engages with its external toothing 36, which also meshes with the planet gears 72 of the planetary gear stage 70 via this external toothing 36. Unlike the embodiment shown in Figs. 1, 2 to 3, the axial position of the sun gear 37' in the embodiment shown in Figs. 4, 5 to 6 is not adjustable. The transmission according to Figs. 4, 5 to 6 has an input shaft 80 which, with a cup-shaped and internally toothed end, engages an externally toothed stub shaft 81 of the hydraulic motor 12 and is rotationally fixed to the stub shaft 81. At the other end, the input shaft 80 has external teeth or knurling by means of which it is rotationally fixed to a correspondingly toothed or knurled sun gear 18' of the planetary gear stage 10. The same teeth or knurling as the sun gear 18' have internal teeth on the sun gear 37'. The teeth or knurling on the input shaft 80, as well as on the sun gear 18' and the sun gear 37', are such that axial displacement of the input shaft 80 relative to the sun gears 18' and 37' is possible. This is the same as in the embodiment according to Figs. 1, 2 to 3.3. In the embodiment shown in Figures 4, 5 to 6, a change in the relative axial position between the input shaft 80 and the sun gear 37 allows a change between two gears. However, in the embodiment shown in Figures 4, 5 to 6, the input shaft is axially displaced relative to the other transmission parts, not the sun gear. As in the embodiment shown in Figures 1, 2 to 3, a hydraulic fluid piston designed as an annular piston 50 serves to axially displace the input shaft 80 in one direction. This piston is guided in the gear carrier 8, acts against helical compression springs 62, and is axially fixed but rotatably coupled to the input shaft 80 via a ball bearing 59. The arrangement and shape of the displacement mechanism for the input shaft 80, comprising the annular piston 50, is identical to the displacement mechanism for the sun gear 37 shown in Figures 1, 2 to 3, except for minor details. Therefore, it will not be discussed in more detail here, but rather the corresponding description above is provided. Figure 4 shows the second embodiment in a state where the input shaft is inserted into the sun gear 18' and there is no direct coupling between the input shaft 80 and the sun gear 37'. The pressure chamber 54 is pressurized, and the annular piston 50 is displaced against the force of the helical compression springs 62 until it reaches a stop on the gear carrier 8. The sun gear 18' is driven via the input shaft 80 and meshes with the planet gears 25, which are also engaged with the ring gear 28. This causes the planet carrier 27 to rotate and engage the sun gear 37'. This engages with the planet gears 72, which are also engaged with the ring gear 28. This causes the planet carrier 71 to rotate and engage the sun gear 67. This engages with the spur gears 43. With the power flow described, the gear ratio of the transmission is at its maximum. First gear is engaged.In pressure chamber 54, a pressure force that generates a pressure force predominating over the spring forces is maintained as long as driving is to be done in this first gear. To engage second gear, the pressure chamber 54 is connected to a volume, for example a tank, in which only a low pressure or atmospheric pressure prevails. The helical compression springs 62 can then move the annular piston 50 and the input shaft 80 from the second end position, as shown in Fig. 4, towards a first end position. If the pressure chamber 54 is closed when the input shaft 80 has not yet fully emerged from the sun gear 18' and its external teeth or serrations have already partially engaged the sun gear 37', and it assumes an intermediate position between its two end positions, as shown in Fig. 5, then the transmission is locked. If, however, the pressure chamber 54 is not sealed, the helical compression springs 62 push the annular piston 50 and the input shaft 80 into the first end position shown in Fig. 6. In this position, the input shaft 80 is decoupled from the sun gear 18' and rotationally fixed to the sun gear 37'. In the now engaged second gear, the planetary stage 10 no longer contributes to the gear ratio. This ratio is now lower than when the input shaft 80 is coupled to the sun gear 18'. Second gear is engaged. Reference symbol list 8 Gear carrier 9 Mounting flange on 8 10 Planetary gear stage 11 Further gear stage 12 Hydraulic motor 13 Drive sleeve 14 Input shaft 18 Sun gear 18' Sun gear 19 Roller bearing 25 Planet gear 26 Bearing journal 27 Planetary web 28 Ring gear 29 Mounting flange on 28 30 Tapered roller bearing 31 Cover 34 Bore 35 Internal teeth of 27 36 External teeth of 37 37 Second sun gear 37' Second sun gear 38 Flange bolt 39 Flange bolt 41 Bearing journal on 8 42 Roller bearing arrangement 43 Spur gear 44 Internal teeth of 37 45 External teeth of 14 50 Hydraulic ring piston 51 Sealing ring 52 Snap ring 53 Base 54 Pressure chamber 55 Connection bore 56 Angled bore 57 Milling slot 58 Base of 50 59 Ball bearing 62 Helical compression spring 63 Blind bore 70 Planetary gear stage 71 Planetary web of 70 72 Planet gears of 70 73 Internal toothing on 71 74 External toothing of 67 80 Input shaft 81 Stub shaft of 12

Claims

A transmission, which is provided in particular within a single-wheel drive unit and which comprises a transmission carrier (8), an input shaft (14) rotatably driven about an axis, at least one planetary gear stage (10) with a first externally toothed sun gear (18, 18') which can be driven via the input shaft (14), with an internally toothed ring gear (28) which is rotatably mounted on the transmission carrier (8), and with a rotatably mounted planet carrier (27) on which at least one externally toothed planet gear (25) which engages with both the sun gear (18, 18') and the ring gear (28) is rotatably mounted and which has internal teeth (35), a further transmission stage (11) which comprises at least one spur gear (43) which is rotatably mounted on a bearing journal (41) which is fixed in position with respect to the transmission carrier (8) and whose axis is arranged at a distance from the axis of the input shaft (14), and with which The ring gear (28) is in tooth engagement.and a second externally toothed sun gear (37, 37'), characterized in that the two components second externally toothed sun gear (37, 37') and input shaft (14) are axially displaceable relative to each other between two end positions, that in a first end position of the two components second externally toothed sun gear (37, 37') and input shaft (14) the second externally toothed sun gear (37, 37') and the input shaft (14) are rotationally fixed to each other and rotate at the same speed and the power flow from the input shaft (14) via the planetary gear stage (10) to the second externally toothed sun gear (37, 37') is interrupted, and that in the second end position the second externally toothed sun gear (37, 37') meshes with the internal teeth (35) of the planet carrier (27) without direct coupling to the input shaft (14) and can be driven via the planetary gear stage (10) from the input shaft (14). Gearbox according to claim 1, wherein in an intermediate position of the two components, the second externally toothed sun gear (37, 37') and the input shaft (14), is located between the two end positions and is both rotationally fixed to the input shaft (14) and is also in a power flow from the input shaft (14) via the planetary gear stage (10). Gearbox according to claim 1, wherein in the first end position of the two components, the second externally toothed sun gear (37, 37') and the input shaft (14) are decoupled relative to each other, one of the two components (14; 37) is decoupled from the planetary gear stage (10). Gearbox according to a preceding claim, wherein the sun gear (18, 18') of the planetary gear stage (10) can be driven at the same speed as the input shaft (14) and wherein the second externally toothed sun gear (37, 37') can be driven at the same speed by the planet carrier (27) of the planetary gear stage (10). Gearbox according to a preceding patent claim, wherein only one of the two components, second externally toothed sun gear (37, 37') and input shaft (14), is axially displaceable relative to the gearbox carrier (8). Gearbox according to claim 5, wherein the input shaft (14) is arranged in an axially fixed position relative to the gearbox carrier (8) and the second externally toothed sun gear (37) is axially displaceable relative to the input shaft (14). Gearbox according to claim 5, wherein the second externally toothed sun gear (37') is arranged in an axially fixed position relative to the gearbox carrier (8) and the input shaft (14) is axially displaceable relative to the second externally toothed sun gear (37'). Gearbox according to claim 7, wherein at least two planetary gear stages (10, 70) are provided and wherein the second externally toothed sun gear (37') is rotationally fixed to the planet carrier (27) of the first planetary gear stage (10) and meshes with the planet gears (72) of the second planetary gear stage (70). Gearbox according to a preceding claim, wherein the second externally toothed sun gear (37, 37') and the input shaft (14) can be coupled together in a rotationally fixed manner by a splined shaft or a toothed shaft connection. Gearbox according to a preceding claim, wherein a fluid piston (50), in particular a hydraulic fluid piston, is provided with which one of the two components second externally toothed sun gear (37) and input shaft (14) is axially displaceable. Gearbox according to claim 10, wherein the fluid piston (50) is single-acting and adjoins a pressure chamber (54) and wherein the axially displaceable component (14; 37) is movable by the fluid piston (50) in the direction of the second end position when pressure medium is supplied to the pressure chamber (54) and by means of springs (62) in the direction of the first end position by displacing pressure medium from the pressure chamber (54).

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