Vehicle transmission for a vehicle, a vehicle comprising such a transmission, and a method for controlling a transmission

Abstract

Transmission for vehicles comprising a drive motor (4), a main transmission (6), an auxiliary transmission (2) and a clutch device (5) arranged between the drive motor (4) and the main transmission (6), wherein the main transmission (6) comprises a drive shaft (7) connected to the clutch device (5), a countershaft (9) and a main shaft (26), wherein the countershaft (9) is connected to the drive shaft (7) and the main shaft (26) via a splitter gear assembly (11) and a splitter gear assembly (12), respectively.a main gear assembly (13) is connected, and wherein the auxiliary transmission (2) comprises a planetary gear (14) with a ring gear (22), a sun gear (18) and a planet carrier (20) on which at least one planet gear (24) is rotatably mounted, wherein the ring gear (22) and the sun gear (18) engage with the at least one planet gear (24) via teeth (32), wherein the planetary gear (14) is connected to the main shaft (26) of the main transmission (6), and wherein a first braking device (54) is arranged on the countershaft (9) to slow down the countershaft (9) when shifting in the transmission (3), characterized in that: a second braking device (56) is arranged on the drive shaft (7) to slow down the drive shaft (7) when shifting in the transmission (3).

Description

BACKGROUND OF THE INVENTION AND GENERAL STATE OF THE ART The present invention relates to a transmission for vehicles according to the preamble of claim 1. The present invention also relates to a vehicle comprising such a transmission according to the preamble of claim 7. The invention also relates to a method for controlling a transmission according to the preamble of claim 8. In vehicles, and especially heavy-duty transport vehicles such as trucks, an auxiliary gearbox, also called a range gearbox, is often connected to the main gearbox. Its purpose is to double the number of possible gear ratios. Such an auxiliary gearbox usually comprises a planetary gear set with a high and a low gear, allowing the gear range of the main gearbox to be divided into a low-range position and a high-range position. In the low-range position, the planetary gear set provides a reduction in gear ratio, and in the high-range position, the gear ratio in the planetary gear set is 1:1. The range gearbox is located between the main gearbox and a driveshaft connected to the vehicle's drive wheels. The range gearbox is housed in a gearbox casing and comprises an input shaft connected to the main gearbox, an output shaft, and a planetary gear set located between the input and output shafts. The planetary gear set typically includes three components rotatably mounted relative to each other: a sun gear, a planet carrier, and a ring gear. Knowing the number of teeth on the sun gear and the ring gear allows the rotational speeds of these three components to be determined during operation.In a range gearbox, the sun gear can be rotatably mounted to the input shaft, a number of planet gears can mesh with the sun gear, these planet gears being rotatably mounted on the planet carrier, which is rotatably connected to the output shaft, and connected to an axially displaceable ring gear that surrounds and meshes with the planet gears. The teeth of the sun gear, planet gears, and ring gear can be helical, i.e., angled with respect to the axis of rotation common to the sun gear, planet carrier, and ring gear. Alternatively, the sun gear, planet gears, and ring gear can have straight-cut teeth, i.e., teeth that are essentially parallel to the axis of rotation common to the sun gear, planet carrier, and ring gear. The low and high gears of the transmission are achieved by axially displacing the ring gear between the low-range position, in which the ring gear is locked relative to the transmission housing, and the high-range position, in which the ring gear can rotate relative to the transmission housing. Such a prior art range transmission comprises two clutch rings arranged on each side of the ring gear, one high clutch ring and one low clutch ring, and two synchronizer rings arranged on the corresponding sides of the ring gear. The synchronizer rings are designed to effect synchronous gear shifting. The axial movement of the ring gear is limited by the geometric design of the ring gear and the clutch rings. Document WO 01 / 55 620 A1 discloses a synchronizing device on a planetary gear set, the planetary gear set comprising a sun gear, a planet carrier, and a ring gear. The sun gear is rotatably connected to the input shaft, and a number of planet gears mesh with the sun gear, the planet gears being rotatably mounted on a planet carrier which is rotatably connected to the output shaft. An axially displaceable ring gear surrounds and meshes with the planet gears. The low and high gears of the gear set are achieved by axially displacing the ring gear between the low-range and high-range positions. These synchronizing devices are subject to wear and tear, resulting in high repair costs. When the range transmission transmits high torques, the synchronizing device becomes quite large, leading to increased weight and space requirements. When the high-range position is engaged, the torque is transferred from the sun gear to the planetary gears, which can cause facets to form on the ring teeth of the sun gear. This can generate noise within the transmission and accelerate wear on the planetary gears. There are also range gearboxes in which the synchronizing device is replaced by splined coupling sleeves. By controlling the gearbox to create a synchronous rotational speed between the two components to be engaged, axial movement of the coupling sleeve along the two components is facilitated, with the aim of connecting and engaging them. When the components are to be separated, the gearbox is controlled to create a torque equalization between the two components, meaning that the coupling sleeve does not transmit any torque. It then becomes possible to move the coupling sleeve along the components to separate them. Torque balancing refers to a condition in which a torque acts on an inner ring gear located in the planetary gear set. This torque is the product of the torque acting on the planet carrier of the planetary gear set and the gear ratio of the planetary gear set. Simultaneously, a torque acts on the sun gear of the planetary gear set. This torque is the product of the torque acting on the planet carrier and (1 - the gear ratio of the planetary gear set). If two of the planetary gear set components—that is, the sun gear, the inner ring gear, or the planet carrier—are connected by a coupling device, this coupling device does not transmit any torque between the components of the planetary gear set when torque balancing is present. Consequently, the coupling device can be easily displaced, and the planetary gear set components can be separated. Document US 2009 / 0095101A1 shows a transmission comprising a main transmission and a range transmission. A sliding sleeve is provided for shifting the range transmission into a low-range or high-range position. The main transmission includes an input shaft and a main shaft on which gears can be engaged and disengaged. One or two countershafts may be arranged in the main transmission, one of which may be equipped with a braking device. Document US 2008 / 0113847A1 discloses a shift control method for a multi-stage transmission connected to a drive motor via a clutch. At least one two-stage range group is located downstream of the main transmission. A gear change is achieved by shifting a gear in the main transmission and the range group. The shift sequence is accelerated by reducing engine torque, disengaging and engaging the clutch, and successively disengaging and engaging and synchronizing the previous and new gears, with synchronization occurring via an input shaft of the main transmission. Document US 2012 / 0031230A1 discloses a group transmission with a splitter group transmission and at least one active actuation unit for introducing an actuation torque into the splitter group transmission. An open-loop and / or closed-loop control unit is provided to adapt the actuation torque introduced into the splitter group transmission to at least one synchronized shifting operation performed by the splitter group transmission without a synchronizer ring. SUMMARY OF THE INVENTION Despite existing state-of-the-art solutions, there is a need to further develop a transmission control method that achieves short shift times, high reliability and operational safety, and effective utilization of all transmission components. There is also a need to develop a transmission with small dimensions relative to its potential torque transmission, and a transmission that reduces fuel consumption in a vehicle that incorporates the transmission. The object of the present invention is to provide a gearbox which has small dimensions in relation to the possible torque transmission. Another object of the invention is to provide a transmission that reduces fuel consumption in a vehicle that includes the transmission. Another object of the present invention is to provide a transmission that has low energy consumption during shifting. Another objective of the invention is to provide a gearbox that is low-noise. Another object of the invention is to provide a method for controlling a transmission that results in short shift times. Another object of the invention is to provide a method for controlling a gearbox that results in high reliability and operational safety. Another object of the invention is to provide a method for controlling a transmission that effectively utilizes all component parts in the transmission. These problems are solved using a vehicle transmission of the type described at the beginning, characterized by the features described in claim 1. These problems are further solved using a vehicle comprising such a transmission of the type mentioned above, characterized by the features described in claim 7. These problems are also solved using a method for controlling a transmission of the type described at the beginning, characterized by the features described in claim 8. Since the second brake device is located on the drive shaft to reduce the speed of the drive shaft when shifting gears, a synchronous speed or torque compensation can be achieved in the auxiliary gearbox with the aim of changing a gear position. Since the first axially displaceable clutch sleeve, in second gear position, transmits torque from the input shaft to the planet carrier and then to the output shaft, and since the second axially switchable clutch sleeve, in first gear position, engages the ring gear with the transmission housing, thus transmitting torque from the input shaft via the ring gear and planet carrier to the output shaft, an effective transmission with high efficiency and low losses is achieved. The transmission components require less lubrication, while bevel damage to the gear teeth is minimized. The axial stroke of each respective clutch sleeve is shorter compared to the stroke of the ring gear in a conventional auxiliary gearbox, which results in faster shifting between different gear positions. The first and second clutch sleeves can each be designed with a limited thickness, meaning that the mass of each clutch sleeve is low. This low mass results in fast shifting between different gear positions. According to one embodiment of the invention, the drive shaft is connected to the sun gear and the planet carrier is connected to the output shaft in the main gearbox. Thus, the auxiliary gearbox has a simple design with few components. According to one embodiment of the invention, the first axially displaceable coupling sleeve is equipped with first wedges on an inner surface, these wedges being arranged such that they interact with the corresponding first wedges located on the drive shaft and the planet carrier. In this way, effective connection and disconnection of the drive shaft and the planet carrier is achieved. According to one embodiment of the invention, the second axially displaceable coupling sleeve is equipped with second wedges on an inner surface, wherein these wedges are arranged in such a way that they interact with the corresponding second wedges that are arranged on the ring gear and the gearbox housing. This ensures effective connection and disconnection of the ring gear and the gearbox housing. According to one embodiment of the invention, the drive motor is disconnected from the drive shaft by the clutch device. In this way, the rotation of the drive shaft is not influenced by the drive motor, which increases the possibility of quickly and effectively changing gear positions in the auxiliary transmission by reducing the speed of the drive shaft with the second braking device. According to one embodiment of the invention, the drive motor is controlled towards a constant motor speed. In this way, an operating condition for the drive motor can be selected during the switching process, resulting in high efficiency and low energy consumption. According to one embodiment of the invention, the rotational speed of the drive shaft is reduced to a speed below that of the drive motor. In this way, the drive motor can be operated at a speed that is favorable with regard to efficiency and energy requirements, while simultaneously the drive shaft with the second braking device can be reduced to a speed below that of the drive motor, thus enabling gear positions to be changed in the auxiliary transmission. Other advantages of the invention are set out in the detailed description below. BRIEF DESCRIPTION OF THE DRAWINGS The following is an exemplary description of preferred embodiments of the invention with reference to the accompanying drawings. These show: Fig. 1 a side view of a vehicle with a transmission according to the present invention, Fig. 2 a schematic sectional view of the transmission according to the invention in a high-range position, Fig. 3 a schematic sectional view of the transmission according to the invention in a low-range position, and Fig. 4 a flowchart of a method for controlling a transmission according to the present invention. DETAILED DESCRIPTION OF PREFERRED FORMATIONS OF THE INVENTION Fig. 1 shows a side view of a vehicle 1, for example a truck, which includes a transmission 3 according to the present invention. The transmission 3 comprises a drive motor 4, a main transmission 6, a clutch device 5 arranged between the drive motor 4 and the main transmission 6, an auxiliary transmission 2, and a driveshaft 10. The drive motor 4 is connected to the main transmission 6, which in turn is connected to the auxiliary transmission 2 according to the present invention. The auxiliary transmission 2 is also connected to the drive wheels 8 of the vehicle 1 via the driveshaft 10. The auxiliary transmission 2 is also referred to as a range transmission, and its purpose is to double the number of possible gear ratios. The auxiliary transmission 2 is enclosed in a transmission housing 12. Fig. 2 shows a schematic cross-section of a transmission 3 according to the present invention. The main transmission 6 comprises a drive shaft 7 connected to the coupling device 5, a countershaft 9, and a main shaft 26, wherein the countershaft 9 is connected to the drive shaft 7 and the main shaft 26 via a splitter gear assembly 11 and a main gear assembly 13, respectively. The splitter gear assembly 11 comprises a set of gear sets s1 and s2, wherein gear set s1 represents a low split position and gear set s2 a high split position. Gear set s1 can be connected to or disconnected from the drive shaft 7 via a first coupling element 15. Gear set s2 can be connected to or disconnected from the drive shaft 7 via a second coupling element 17. When both coupling elements 15, 17 separate the first and second gear sets s1, s2, the splitter gear group 11 is brought into a neutral position.The main gear group 13 comprises a set of gear sets g1-g3, wherein gear set g1 represents a first gear, gear set g2 represents a second gear, and gear set g3 represents a third gear. The gear sets g1-g3 can be connected or disconnected via a third, fourth, and fifth coupling element 19, 21, 23, respectively. The auxiliary transmission 2 comprises a planetary gear set 14, which has a high and a low gear and with which the transmission options of the main transmission 6 can be divided into a low-range position and a high-range position. In a first gear position, corresponding to the low-range position, downshifting takes place via the planetary gear set 14. In the second gear position, corresponding to the high-range position, the planetary gear set 14 has a gear ratio of 1:1. Fig. 2 shows the auxiliary transmission 2 in a second gear position, corresponding to the high gear or the high-range gear. The auxiliary transmission 2 is housed in the transmission casing 12 and connected to the main shaft 26 of the main transmission 6. The planetary gear set 14 comprises three main components, which are rotatably arranged relative to one another: a sun gear 18, a planet carrier 20, and a ring gear 22. A number of planet gears 24 are mounted on the planet carrier 20. The output shaft 28, which is connected to the driveshaft 10 of the vehicle 1, is also arranged on the planet carrier 20 of the auxiliary transmission 2. Knowing the number of teeth 32 on the sun gear 18 and the ring gear 22, the respective rotational speeds of the three components during operation can be determined. The sun gear 18 is rotatably connected to the main shaft 26, and the planet gears 24 mesh with the sun gear 18. The ring gear 22 surrounds and meshes with the planet gears 24. The teeth 32 of the sun gear 18, the planet gears 24 and the ring gear 22 can be inclined, i.e.The teeth 32 are angled relative to the axis of rotation 30, which is common to the sun gear 18, the planet carrier 20, and the ring gear 22. The helical cutting of the teeth 32 generates a reaction force in the direction of the axis of rotation 30 from the gears 18, 22, and 24 contained in the planetary gear set 14. The direction of the reaction force depends on the direction in which the teeth 32 are helically cut in the planetary gear set 14. In this way, the reaction forces can act forwards or backwards along the extension of the axis of rotation 30. A first axially displaceable coupling sleeve 40 is arranged in the first gear position such that it separates the main shaft 26 from the planet carrier 20, and in the second gear position such that it connects the main shaft 26 to the planet carrier 20. A second axially displaceable coupling sleeve 42 is arranged such that it connects the transmission housing 12, which surrounds the planetary gear 14, to the ring gear 22 in the first gear position, and is arranged such that it separates the transmission housing 12 from the ring gear 22 in the second gear position. The first axially displaceable coupling sleeve 40 is equipped on an inner surface with first keys 44, which are arranged to interact with corresponding first keys 44 located on the main shaft 26 and the planet carrier 20. The corresponding first keys 44 located on the main shaft 26 are machined on the outer edge of a first ring 46, which is rotatably mounted on the main shaft 26. The corresponding first keys located on the planet carrier 20 are machined on the outer edge of a second edge 48, which is rotatably mounted on the planet carrier 20. The second axially displaceable coupling sleeve 42 is equipped on an inner surface with second wedges 50, these wedges being arranged to interact with corresponding second wedges 50 located on the outer edge of the ring gear 22 and on a projection 52 which is rigidly connected to the gearbox housing 12. The high gear of the auxiliary transmission 2 is achieved by means of the first clutch sleeve 40, which is shifted to connect the main shaft 26 to the planet carrier 20. The second clutch sleeve 42 is shifted to disconnect the ring gear 22 from the transmission housing 12. The second clutch sleeve 42 is thus connected only to the transmission housing 12, meaning that the second clutch sleeve 42 comes to a standstill and does not influence the inertial forces during the rotation of the ring gear 22. The torque transmission from the main shaft 26 to the output shaft 28 therefore occurs via the main shaft 26 and the planet carrier 20, and then to the output shaft 28, resulting in a gear ratio of 1:1 via the planetary gear set 14. The axial displacement of the first and second coupling sleeves 40, 42 is achieved by a first and second shift fork 58, 60, which is arranged in a groove 62 on the outer circumference of the first and second sleeves 40, 42. A first power element 64 acts on the first shift fork 58, and a second power element 66 acts on the second shift fork 60. The first and second power elements 64, 66 can consist of a pneumatic or a hydraulic cylinder. The first and second shift forks 58, 60 and the first and second power elements 64, 66 are shown schematically in Fig. 2. Preferably, the corresponding clutch sleeves 40, 42 have a low mass, which results in low energy and power consumption when moving the clutch sleeves 40, 42 during gear changes. In this way, rapid shifting between the different gear positions in the auxiliary transmission 2 can be carried out within a short time. Fig. 3 shows a cross-section of the auxiliary transmission 2 according to the invention in the first gear position or the low-range position. The low gear of the auxiliary transmission 2 is achieved by axially displacing the first clutch sleeve 40 to disconnect the planet carrier 20 from the main shaft 26, while simultaneously, or closely related thereto, the second clutch sleeve 42 is displaced so that the ring gear 22 is connected to the transmission housing 12. By moving the first clutch sleeve to a position where it engages only the main shaft or the planet carrier, while simultaneously moving the second clutch sleeve to a position where it engages only the gearbox housing, the auxiliary gearbox is switched to a neutral state in which no torque transmission takes place via the auxiliary gearbox. A first braking device 54 is arranged on the countershaft 9 to reduce the rotational speed of the countershaft 9 during gear changes in the transmission 3, and a second braking device 56 is arranged on the input shaft 7 to reduce the rotational speed of the input shaft 7 during gear changes in the transmission 3. Since the second braking device 56 is arranged on the input shaft 7 to reduce its rotational speed during gear changes in the transmission 3, synchronous speed or torque compensation can be achieved in the auxiliary transmission 2 for the purpose of changing gear positions. The first and second braking devices 54 and 56 can each consist of friction brakes that are hydraulically, pneumatically, and / or electrically controlled. The transmission 3 according to the invention operates in conjunction with shifting from the second to the first gear position, i.e., from the high-range position to the low-range position, as follows, and is described in connection with Fig. 2-3. In Fig. 2, the drive motor 4 was controlled to a constant engine speed and an operating condition that is advantageous from an energy point of view. If the drive motor 4 is an internal combustion engine, fuel consumption is minimal at the constant engine speed. The clutch device 5 was controlled to a disengaged state, meaning that the drive motor 4 and the drive shaft 7 are no longer connected and no torque is transmitted. The splitter gear assembly 11 was brought into the neutral state, as the first and second clutch elements 15, 17 were disengaged from their respective gear sets s1, s2. This is facilitated because the drive shaft 7 is in torque compensation with the corresponding gear sets s1, s2 located on the drive shaft 7. In this way, no torque is transmitted from the drive shaft 7 to the respective gear sets s1, s2.By reducing the rotational speed of the drive shaft using the second braking device 56, the engagement of the previously unengaged gear sets s1 and s2 is facilitated. Once the drive shaft 7 has been slowed to a rotational speed corresponding to that of the previously unengaged gear set s1 or s2, the first or second clutch element 15 or 17 engages the gear set s1 or s2 with the drive shaft. In this way, a new gear position is engaged in the splitter gear group 11. The gear sets g1-g3 of the main gear group 13 were moved into a neutral position by disengaging them from the main shaft 26 using the third, fourth, and fifth clutch elements 16, 21, 23. This is possible because the main shaft 26 is in torque compensation with the corresponding gear sets g1-g3 located on it. In this way, no torque is transmitted from the main shaft to the respective gear sets g1-g3. To engage a gear in the main gear group 13, the countershaft 9 is slowed down using the first brake device 54, after which a suitable gear set g1-g3 is connected to the main shaft 26 via one of the third, fourth, or fifth clutch elements 16, 21, 23. This is facilitated when a synchronous rotational speed has been achieved between the main shaft 26 and the gear set g1-g3, which is to be connected to the main shaft 26.In this way, a new gear position was engaged in the main gear group 13. The auxiliary transmission is then moved into a neutral state by axially displacing the first clutch sleeve 40 to disconnect the planet carrier 20 from the main shaft 26. To shift the gear positions in the auxiliary transmission 2 to low gear, the clutch device 5 is activated, connecting the drive motor 4 to the main transmission 6. The drive motor is then accelerated to engine speed, causing the ring gear 22 in the auxiliary transmission 2 to stop. Finally, the gear position in the auxiliary transmission 2 is shifted to low gear by moving the second clutch sleeve 42, connecting the ring gear 22 to the transmission housing 12. This engages a new gear position in the auxiliary transmission 2. The new gear positions in the main transmission 6 and the auxiliary transmission 2 are shown schematically in Fig. 3. In this context, it should be noted that the drive shaft 7 and the main shaft 26 can be connected to each other to create a direct drive via the main gearbox 6. In such a direct drive position, the gear ratio via the main gearbox 6 is 1:1, and the torque between the drive shaft 7 and the main shaft 26 is transmitted via the direct connection between the drive shaft 7 and the main shaft 26. In this direct drive position, no torque is transmitted via the countershaft 9. The direct connection between the drive shaft 7 and the main shaft 26 is implemented via the second clutch element 17 or the third clutch element 19. When the second clutch element 17 is disengaged from the gear set s2, it can be axially displaced and engage with the main shaft 26 to transmit torque between the drive shaft 7 and the main shaft 26.Alternatively, if the third clutch element 19 is disengaged from the gear set g1, it can be axially displaced and engage with the drive shaft 7 to transmit torque between the drive shaft 7 and the main shaft 26. When the main gearbox 6 is moved into such a direct drive position, either the splitter gear set 11 or the main gear set 13 is brought into a neutral position, so that the engaged gear set 11 or 13 causes the countershaft 9 to rotate, but without the countershaft transmitting torque between the drive shaft 7 and the main shaft 26. Alternatively, both the splitter gear set 11 and the main gear set 13 can be brought into the neutral position, so that the countershaft 9 comes to a standstill. Fig. 4 shows a flowchart of a method for controlling a transmission 3 according to the present invention. The method comprises the following steps: a) slowing down the drive shaft 7 by means of a second braking device 56 arranged on the drive shaft 7, b) slowing down the countershaft 9 by means of the first braking device 54, and c) changing the gear positions in the auxiliary transmission 2. Preferably, in step c) the gear position is changed to a first gear in which a gear housing 12 surrounding the planetary gear 14 is connected to the ring gear 22. Before step a), the drive motor 4 is preferably separated from the drive shaft 7 in a step d) via a coupling device 5. After step a) and before step b), the gear position in the splitter gear group 11 is preferably changed in a step e). After step d) and before step a), the drive motor 4 is preferably controlled in a step f) in the direction of a constant motor speed. After step b) and before step c), the gear position in the main gearbox 13 is preferably changed in a step g). After step g) and before step c), preferably in a step h) the drive motor 4 is connected to the drive shaft 7 via the coupling device 5, and the motor speed of the drive motor 4 is increased. An electronic control device 70 is connected to the auxiliary transmission 2, the main transmission 6, the drive motor 4, and the clutch 68 to execute the shifting steps described above. Preferably, a number of speed sensors (not shown) in the auxiliary transmission 2, the main transmission 6, and the drive motor 4 can be connected to the control device 70. A further computer 72 can also be connected to the control device 70. The control device 70 can be a computer with suitable software for this purpose. The control device 70 and / or the computer 72 comprise a computer program P, which may include methods for controlling the auxiliary transmission 2 according to the present invention. The program P can be stored in an executable form or in compressed form in a memory M and / or a read / write memory R.Preferably, a computer program product is provided that includes program code stored on a computer-readable medium to perform the switching steps mentioned above when the program code is executed in the control device 70 or on another computer 72 connected to the control device 70. The program code may be stored on the computer-readable medium in a non-volatile manner. The components and features described above can be combined between different described embodiments within the scope of the invention.

Claims

Transmission for vehicles comprising a drive motor (4), a main transmission (6), an auxiliary transmission (2) and a clutch device (5) arranged between the drive motor (4) and the main transmission (6), wherein the main transmission (6) comprises a drive shaft (7) connected to the clutch device (5), a countershaft (9) and a main shaft (26), wherein the countershaft (9) is connected to the drive shaft (7) and the main shaft (26) via a splitter gear assembly (11) and a splitter gear assembly (11), respectively.a main gear group (13) is connected, and wherein the auxiliary transmission (2) comprises a planetary gear (14) with a ring gear (22), a sun gear (18) and a planet carrier (20) on which at least one planet gear (24) is rotatably mounted, wherein the ring gear (22) and the sun gear (18) engage with the at least one planet gear (24) via teeth (32), wherein the planetary gear (14) is connected to the main shaft (26) of the main transmission (6), and wherein a first braking device (54) is arranged on the countershaft (9) to slow down the countershaft (9) when shifting in the transmission (3), characterized in that: a second braking device (56) is arranged on the drive shaft (7) to slow down the drive shaft (7) when shifting in the transmission (3). Transmission according to claim 1, characterized by a first axially displaceable coupling sleeve (40) which in the first gear position is arranged such that it separates the main shaft (26) to the auxiliary transmission (2) from the planet carrier (20), and in the second gear position is arranged such that it connects the main shaft (26) to the planet carrier (20); and a second axially displaceable coupling sleeve (42) which is arranged such that in the first gear position it connects a transmission housing (12) surrounding the planetary gear (14) to the ring gear (22), and in the second gear position separates the transmission housing (12) from the ring gear (22). Transmission according to one of claims 1 - 2, characterized in that the main shaft (26) of the main transmission (6) is connected to the sun gear (18) of the planetary transmission and in that the planet carrier (20) is connected to an output shaft (28) of the auxiliary transmission (2). Transmission according to one of the preceding claims, characterized in that the first axially displaceable coupling sleeve (40) is equipped on an inner surface with first wedges (44) which are arranged such that they interact with corresponding first wedges (44) which are arranged on the main shaft (26) and the planet carrier (20). Transmission according to one of the preceding claims, characterized in that the second axially displaceable coupling sleeve (42) is equipped on an inner surface with second wedges (50) which are arranged such that they interact with corresponding second wedges (50) which are arranged on the ring gear (22) and the transmission housing (12). Transmission according to one of the preceding claims, characterized in that the auxiliary transmission (2) is a range transmission. Vehicle (1), characterized in that it comprises a transmission (3) according to one of claims 1 - 6. Method for changing gears in a transmission (3) for vehicles, comprising a drive motor (4), a main transmission (6), an auxiliary transmission (2) and a clutch device (5) arranged between the drive motor (4) and the main transmission (6), wherein the main transmission (6) comprises a drive shaft (7) connected to the clutch device (5), a countershaft (9) and a main shaft (26), wherein the countershaft (9) is connected to the drive shaft (7) and the main shaft (26) via a splitter gear assembly (11) and a splitter gear assembly (11), respectively.a main gear assembly (13) is connected, and wherein the auxiliary transmission (2) comprises a planetary gear (14) with a ring gear (22), a sun gear (18) and a planet carrier (20) on which at least one planet gear (24) is rotatably mounted, wherein the ring gear (22) and the sun gear (18) mesh with the at least one planet gear (24) via teeth (32), wherein the planetary gear (14) is connected to the main shaft (26) of the main transmission (6), and wherein a first braking device (54) is arranged on the countershaft (9) to slow down the countershaft (9) when shifting in the transmission (3), characterized in that the method comprises the following steps: a) slowing down the drive shaft (7) by means of a second braking device (56) arranged on the drive shaft (7), b) slowing down the countershaft (9) by means of the first braking device (54), and c) changing the gear positions in the Auxiliary gearbox (2). Method according to claim 8, characterized in that the gear position in step c) is changed to a first gear in which a gear housing (12) surrounding the planetary gear (14) is connected to the ring gear (22). Method according to one of claims 8 - 9, characterized in that before step a):d) the drive motor (4) is separated from the drive shaft (7) via a coupling device (5). Method according to one of claims 8 - 10, characterized in that after step a) and before step b):e) gear positions in the splitter gear group (11) are changed. Method according to claim 10, characterized in that after step d) and before step a):f) the drive motor (4) is controlled in the direction of a constant motor speed. Method according to one of claims 8 - 12 , characterized in that after step b) and before step c): g) gear positions in the main transmission (13) are changed. Method according to claim 13, characterized in that after step g) and before step c): h) the drive motor (4) is connected to the drive shaft (7) via the coupling device (5) and the motor speed of the drive motor (4) is increased. Computer program product comprising program code stored in a computer-readable medium for carrying out the method steps according to any one of claims 8-14, wherein the program code is executed in an electronic control device (48) or in another computer (53) connected to the electronic control device (48).

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