Steering device for a tracked vehicle drive train

Abstract

The invention relates to a steering device (19) comprising a steering gear (35) and an electric machine (39) which can be operated both as an electric motor and as a generator, the steering gear (35) having a first input shaft (36), a second input shaft (37) which is connected (39) to the electric machine, a neutral shaft (18), and a superposition stage (40) which has a first element (45), a second element (46), and a third element (47). At the superposition stage (40), a rotational movement of the first element (45) can be converted into a rotational movement of the third element (47) by superimposing a rotational movement of the second element (46), and by means of the superimposition in the steering gear (35), at least one steering ratio can be expanded to a continuously adjustable steering ratio range.In this case, the at least one steering ratio lies in terms of value between respective ends of the respective steering ratio range, wherein, during the superposition, starting from the at least one steering ratio, the widening takes place in the direction of one end of the respective steering ratio range in the generator operation of the electric machine (39) and in the direction of the other end of the respective steering ratio range in the electromotor operation of the electric machine (39).

Description

[0001] The invention relates to a steering device for a tracked vehicle drive train, comprising a steering gear and an electric machine which can be operated as an electric motor and as a generator, the steering gear having a first input shaft which is provided for coupling to a drive machine, a second input shaft which is connected to the electric machine, a neutral shaft and a superposition stage which has a first element, a second element and a third element, the first element of the superposition stage being coupled or couplable to the first input shaft, the second element of the superposition stage being coupled to the second input shaft and the third element of the superposition stage being couplable or couplable to the neutral shaft,and wherein, at the superposition stage, a rotational movement of the first element can be converted into a rotational movement of the third element by superimposing a rotational movement of the second element, and at least one steering ratio can be expanded to a continuously adjustable steering ratio range by the superimposition in the steering gear. Furthermore, the invention relates to a tracked vehicle drive train, a tracked vehicle, and a method for operating a steering device.

[0002] Tracked vehicles have tracked or crawler undercarriages, whereby a tracked or crawler undercarriage usually consists of at least one left and at least one right tracked or crawler undercarriage. With each track, the drive movement of the respective drive chain is usually realized via a track drive wheel. If at least one left track is operated at the same speed as at least one right track, then straight-ahead travel of the respective tracked vehicle is realized under the same ground conditions on both tracks. If, on the other hand, the tracks are operated at different speeds, cornering of the respective tracked vehicle can be achieved by driving the track on the inside of the curve more slowly than the track on the outside. If the tracks rotate in opposite directions at the same speed, the tracked vehicle can also pivot on the spot.

[0003] Steering systems for tracked vehicle drive trains are often designed as superimposed steering systems, in which a drive movement is superimposed on a steering movement at summing stages. Typically, there is a mechanical coupling between at least one left and at least one right drive unit via a so-called neutral shaft, which is essentially stationary when the respective tracked vehicle is traveling straight ahead and under the same ground conditions on both drives. However, to represent cornering, a rotary movement of the neutral shaft is induced, which causes the drive movement to be superimposed on opposing steering movements at the summing stages.

[0004] Typically, a zero-shaft superimposed steering system is integrated into the respective tracked vehicle drivetrain in a steering system, where different steering ratios can often be implemented via a steering gear. However, since these fixed steering ratios would result in choppy steering behavior of the respective tracked vehicle, the steering ratios are sometimes switched via force-locking switching elements in the steering gear. The individual steering ratio can then be continuously expanded to a steering ratio range by slipping the switching elements. However, this can potentially generate considerable heat at the switching elements.For this reason, a hydrostatic or electric variator is often combined with a superposition stage in a steering device in order to superimpose a rotary movement initiated in the steering device by a drive motor with a rotary movement of the variator and thus to realize the respective steering ratio range continuously.

[0005] The generic document DE 10 2021 107 419 A1 discloses a steering device in which a steering gear in a tracked vehicle drive train is coupled to a drive motor at a first input shaft, wherein a rotationally fixed connection to a first electric motor is also established at the first input shaft. The steering gear also has a superposition stage composed of two planetary gear sets, wherein a sun gear of one planetary gear set is rotationally fixedly connected to the first input shaft, while a sun gear of the other planetary gear set is rotationally fixedly connected to a second input shaft of the steering gear, to which a second electric motor is rotationally fixedly connected.Furthermore, the planet carriers of the two planetary gear sets are connected to one another in a rotationally fixed manner, with the ring gear of the other planetary gear set being permanently fixed, whereas a coupling can be established between the ring gear of one planetary gear set and a neutral shaft of the steering device. Different gear ratios can be switched as steering ratios between the ring gear of one planetary gear set and the neutral shaft by selectively actuating switching elements. The two electric machines can each be operated either as an electric motor or as a generator, with the electric machine operating as a generator supplying the electric machine operating as an electric motor with the necessary electrical power.At the superposition stage, rotational movements of the first input shaft and the second input shaft can be superimposed in order to continuously expand the respective steering ratio to a steering ratio range depending on the respective superposition.

[0006] Furthermore, DE 10 2022 108 892 A1 discloses a drive device for a tracked vehicle with a drive shaft for driving the vehicle and a neutral shaft for steering the tracked vehicle. The drive shaft and the neutral shaft can be coupled together to at least one drive sprocket of a tracked chassis via a summation gear. A main drive unit is provided for driving the drive shaft. The main drive unit is also coupled to the neutral shaft via a steering gear unit to drive the neutral shaft.

[0007] Based on the prior art described above, it is the object of the present invention to provide a steering device in which at least one steering ratio range can be designed to be continuously variable, wherein this steering device should also be characterized by the lowest possible manufacturing costs.

[0008] This problem is solved from a device-related perspective based on the preamble of the independent claim 1 in conjunction with its characterizing features. The dependent claims that follow thereon each represent advantageous developments of the invention. A tracked vehicle drive train having a steering device according to the invention is the subject of claim 11, while claim 12 relates to a tracked vehicle with the aforementioned tracked vehicle drive train. Furthermore, the problem is solved from a process-related perspective by the technical teaching of the independent claim 13, with claims 14 to 16 representing advantageous developments.

[0009] According to the independent claim 1, a steering device comprises a steering gear and an electric machine operable both as an electric motor and as a generator. The steering gear has a first input shaft, which is provided for coupling to a drive motor, a second input shaft, which is connected to the electric machine, a neutral shaft, and a superposition stage, which has a first element, a second element, and a third element. The first element of the superposition stage is coupled to the first input shaft or can be coupled thereto, whereas the second element of the superposition stage is coupled to the second input shaft, and the third element of the superposition stage is or can be coupled to the neutral shaft.At the superposition stage, a rotational movement of the first element can be converted into a rotational movement of the third element by superimposing a rotational movement of the second element, and at least one steering ratio can be expanded to a continuously adjustable steering ratio range by the superimposition in the steering gear.

[0010] The steering device according to the invention thus allows a drive motor and an electric motor to be connected to input shafts of a steering gear in order to generate a rotary movement of a zero-axis shaft of the steering device. The zero-axis shaft is particularly intended to be coupled to summing stages on both sides in a tracked vehicle drive train in the manner of a superimposed steering system, at each of which a drive movement can be superimposed with a respective steering movement. In a manner known in principle to those skilled in the art, the coupling of the zero-axis shaft to one summing stage is implemented with one tooth mesh more than the coupling of the zero-axis shaft to the other summing stage in order to represent the superpositions with opposing steering movements.

[0011] The steering gear has a superposition stage equipped with a first element, a second element, and a third element. The first element of the superposition stage is either permanently coupled to the first input shaft or can be coupled to the first input shaft, which is then coupled to the prime mover when the steering device is used in a tracked vehicle drive train. In contrast, the second element is permanently coupled to the second input shaft of the steering gear, with the second input shaft being connected to the electric motor within the steering device. At the superposition stage, rotational movements of the first element and the second element can be superimposed and converted into rotational movements of the third element, which in the steering device can either be coupled to the neutral shaft or is permanently coupled to the neutral shaft.The rotational movements of the first element and the second element are caused by respective rotational movements of the respective input shaft.

[0012] The superpositions at the superposition stage are carried out in order to expand at least one steering ratio to a respective steering ratio range. This expansion is stepless, which in the sense of the invention means that, starting from the at least one steering ratio of the steering gear within the respective ratio range to be represented, further ratios can be represented without steps. This is achieved in each case by superimposing the rotary movement generated at the first element of the superposition stage with a rotary movement generated at the second element of the superposition stage in such a way that a rotary movement realizing the respective steering ratio to be represented results at the third element.

[0013] Preferably, in the steering gear of the steering device according to the invention, several steering ratios can be switched, for which purpose the steering gear is in particular equipped with several switching elements, the selective actuation of which can be used to represent the different steering ratios. By appropriately superimposing the rotational movements at the superimposition stage, each of these switchable steering ratios can then be expanded to a respective associated steering ratio range. Most preferably, the first element of the superimposition stage is permanently coupled to the first input shaft, while the third element of the superimposition stage is coupled to the zero shaft by switching one of the steering ratios. In this case, switching of the different steering ratios therefore takes place between the third element of the superimposition stage and the zero shaft.Alternatively, a permanent coupling could exist between the third element of the superposition stage and the neutral shaft, whereas the first element of the superposition stage and the first input shaft are coupled by switching one of the available steering ratios. Thus, in this case, the different steering ratios are switched between the first input shaft and the first element of the superposition stage.

[0014] Within the scope of the invention, however, the steering gear of the steering device according to the invention could also be configured to switch to exactly one steering ratio, in which case the first element of the superposition stage would be permanently coupled to the input shaft, and the third element of the superposition stage would be permanently coupled to the neutral shaft. By superimposing the rotational movements at the superposition stage, this single steering ratio can then be continuously expanded to exactly one steering ratio range.

[0015] The drive motor to be coupled to the first input shaft of the steering gear is preferably a main drive motor, which, in addition to inducing a rotational movement into the first input shaft of the steering gear, also serves to generate a drive movement in the tracked vehicle drive train. For this purpose, the drive motor is then preferably coupled or can be coupled to a drive transmission in the tracked vehicle drive train in addition to the steering gear. In particular, the drive motor is an internal combustion engine.

[0016] The electric machine provided in the steering device according to the invention can be operated both as an electric motor and as a generator, so that this electric machine can operate both as an electric motor and as a generator. This electric machine is connected in a rotationally fixed manner to the second input shaft, which in turn is permanently coupled to the second element of the superposition stage. In this respect, there is also a permanent coupling between the electric machine and the second element of the superposition stage, whereby an acceleration realized in the electric motor operation of the electric machine also results in an acceleration of the second element, and a deceleration realized in the generator operation of the electric machine also results in a deceleration of the second element.

[0017] For the purposes of the invention, a "coupling" is understood to mean a connection established between components, due to which these components perform rotational movements not independently of one another, but rather in a specific relationship. A "rotationally fixed connection," on the other hand, means a rigid connection between components, whereupon the rotational movements of the rotationally fixedly connected components correspond to one another.

[0018] The invention now encompasses the technical teaching that the at least one steering ratio lies in value between the respective ends of each steering ratio range. Furthermore, during the superposition, starting from the at least one steering ratio, the widening occurs toward one end of each steering ratio range during generator operation of the electric machine and toward the other end of each steering ratio range during electromotive operation of the electric machine.

[0019] In other words, the value of the at least one steering ratio lies in an intermediate range between an upper end and a lower end of each steering ratio range. In order to be able to represent the expansion to the entire steering ratio range, the expansion takes place, starting from the at least one steering ratio, on the one hand, towards the lower end of each steering ratio range by the superposition taking place at the superposition stage during generator operation of the electric machine. On the other hand, the at least one steering ratio expands towards the upper end of each steering ratio range by superposition at the superposition stage during electromotor operation of the electric machine.

[0020] Such a design of a steering device for a tracked vehicle drive train has the advantage that, during generator operation of the electric motor, no supply of electrical power is required to the electric motor for part of the continuously variable representation of each steering ratio range, whereby only a single electric motor needs to be provided in the steering device according to the invention. This allows the steering device to be implemented with low manufacturing costs. The power density of a mechanical steering gear can still be maintained, while the electric motor enables continuously variable steering with high efficiency compared to systems with slipping switching elements or hydrodynamic or hydrostatic variators.Furthermore, due to its integration, the electric motor can easily handle additional hybrid functions such as boosting, recuperation, or high generator output. If either the first element of the superposition stage can be coupled to the first input shaft or the third element of the superposition stage can be coupled to the zero shaft, starting the drive motor, particularly designed as an internal combustion engine, without coupling results in the electric motor not being dragged along. This allows for trouble-free starting of the internal combustion engine. Furthermore, the electric motor can be used to achieve more agile steering behavior, thereby reducing the dynamic demands of the drive motor, particularly designed as an internal combustion engine.

[0021] The value of at least one steering ratio can be located between the respective ends of each steering ratio range such that the widening toward both ends is essentially the same. Alternatively, the widening may also require predominantly generator operation of the electric motor or predominantly electric motor operation.

[0022] Preferably, the electric machine is assigned an electrical energy storage device, which is implemented in particular in the form of an electrical accumulator. The electric machine can then store electrical energy in this electrical energy storage device during its generator operation and draw electrical energy from this electrical energy storage device during its electromotor operation. If the accumulator is missing or empty, steering via the steering device according to the invention then functions, at least temporarily, only with the at least one steering ratio. On the other hand, if the accumulator is sufficiently full, assistance in carrying out steering movements can be provided via the electric machine, wherein a spontaneous torque build-up of the drive machine, which is designed in particular as an internal combustion engine, is no longer so important in this case, so that an internal combustion engine with a less favorable torque curve can subsequently also be used.

[0023] According to one embodiment of the invention, the first input shaft is connected in a rotationally fixed manner to the first element of the superposition stage. Furthermore, an intermediate gear ratio can be provided between the first input shaft and the drive motor, whereby a suitable gear ratio can be achieved on the first input shaft. This intermediate gear ratio is particularly preferably formed by a first spur gear stage and a second spur gear stage, with the first spur gear stage coupling the first input shaft to an intermediate shaft, which is further coupled to the drive motor via the second spur gear stage.The two spur gear stages each consist of two spur gears that are constantly meshing with each other, whereby in the first spur gear stage, one spur gear is arranged in a rotationally fixed manner on the first input shaft and the other spur gear is arranged in a rotationally fixed manner on the intermediate shaft, while in the second spur gear stage, one spur gear is arranged in a rotationally fixed manner on the intermediate shaft and the other spur gear is coupled to the drive machine.

[0024] According to an alternative or additional embodiment of the invention, the second input shaft is coupled to the second element of the superposition stage via an intermediate gear ratio. In this case, the coupling between the second input shaft and the second element of the superposition stage is therefore also carried out with an additional gear ratio, whereby a suitable gear ratio can also be realized between the electric machine and the second element of the superposition stage. In particular, this intermediate gear ratio is formed by a spur gear stage which couples the second input shaft to the second element. This spur gear stage is preferably composed of two permanently meshing spur gears, one of which is arranged on the second input shaft in a rotationally fixed manner and the other is connected to the second element of the superposition stage in a rotationally fixed manner.However, the second element of the superposition stage could additionally be equipped with a toothing at which the tooth engagement with the spur gear mounted on the second input shaft in a rotationally fixed manner is established.

[0025] One embodiment of the invention provides a switching element by which the second input shaft can be fixed. This can specifically prevent free rotation of the second input shaft, particularly when the battery is empty. Otherwise, the drive motor could not transmit any rotational movement to the neutral shaft due to the effect of the superposition stage, which would subsequently make the tracked vehicle impossible to steer. Alternatively, the electric motor can also be designed such that it can still apply a counter-torque even when the battery is empty, thus preventing free rotation of the second input shaft.

[0026] In particular, in the aforementioned embodiment, the switching element locks the second input shaft in a non-actuated state, whereas in an actuated state the switching element enables rotation of the second input shaft. Consequently, the switching element is designed to be closed in the non-actuated state (normally closed), so that in the absence of power supply, the second input shaft locks.

[0027] According to an advantageous embodiment of the invention, several steering ratios can be switched in the steering gear, each of which lies between the respective ends of a steering ratio range and can be continuously expanded to the respective steering ratio range by superimposing them, on the one hand in generator mode and on the other hand in electromotive mode of the electric machine. This allows different steering ratio ranges to be continuously represented via the steering device according to the invention.

[0028] In particular, the steering gear has a first planetary stage, a second planetary stage, a reversing stage, a first shifting element, a second shifting element, a third shifting element, a fourth shifting element, and a fifth shifting element. The first planetary stage and the second planetary stage each have a first element, a second element, and a third element in the form of a sun gear, a planet carrier, and a ring gear, respectively. The first element of the first planetary stage and the first element of the second planetary stage are connected to one another in a rotationally fixed manner and are connected to the third element of the superposition stage in a rotationally fixed manner. Furthermore, the third element of the first planetary stage and the second element of the second planetary stage are connected to one another in a rotationally fixed manner and are coupled to a permanently fixed component via a first freewheel.When actuated, the first shifting element connects the first element of the first planetary stage, the first element of the second planetary stage, and the third element of the superposition stage in a rotationally fixed manner to an intermediate shaft, which, when the second shifting element is actuated, is rotationally fixedly connected to the neutral shaft. When actuated, the third shifting element couples the intermediate shaft to the neutral shaft via the reversing stage, whereas the fourth shifting element couples the second element of the first planetary stage to the intermediate shaft via a second freewheel, when actuated. Finally, the fifth shifting element locks the third element of the second planetary stage in an actuated state.In this way, a suitable construction of a steering gear can be realized, whereby three different steering ratios can be realized in the steering device according to the invention, which can each be expanded to the respective associated steering ratio ranges.

[0029] The first planetary stage and the second planetary stage are each composed of a first element, a second element and a third element, wherein the elements of the first and second planetary stages are each formed by a sun gear, a planet carrier and a ring gear. Particularly preferably, the first planetary stage and the second planetary stage are each in the form of a minus planetary set, in which the respective planet carrier rotatably guides at least one planetary gear, wherein the at least one planetary gear meshes with both the respective sun gear and the respective ring gear. If the first planetary stage or the second planetary stage is designed as a minus planetary set, the first element of the first or second planetary stage is the respective sun gear, and the second element of the first or second planetary stage is the respective sun gear.second planetary stage around the respective planet carrier and in the third element of the first or second planetary stage around the respective ring gear.

[0030] Alternatively, the first planetary stage and / or the second planetary stage could in principle also be designed as a plus planetary gear set. In this case, at least one pair of planetary gears is rotatably mounted in the respective planet carrier, of which one planetary gear meshes with the respective sun gear and one planetary gear meshes with the respective ring gear. In addition, the planetary gears of the at least one pair of planetary gears mesh with one another. In contrast to a design as a minus planetary gear set, the first element of the first or second planetary stage is preferably the sun gear, the second element of the first or second planetary stage is the ring gear, and the third element of the first or second planetary stage is the planet carrier. In comparison to a design as a minus planetary gear set, the stationary gear ratio of the respective planetary stage must also be increased by one.As already described above, in the sense of the invention, the first planetary stage and the second planetary stage are preferably designed as minus planetary sets.

[0031] In a further development of the invention, the superposition stage is formed by a planetary gear, wherein of the first element, the second element and the third element of the superposition stage, one element is present as a sun gear of the planetary gear, one element is present as a planet carrier of the planetary gear and one element is present as a ring gear of the planetary gear. The planetary gear is particularly preferably designed as a minus planetary gear set, wherein the first element is the ring gear, the second element is the sun gear and the third element is the planet carrier of the planetary gear. Alternatively, the planetary gear forming the superposition stage could also be designed as a plus planetary gear set, wherein the second element is then present as a sun gear, the first element as the planet carrier and the third element as a ring gear.

[0032] The invention also relates to a tracked vehicle drive train in which a steering device according to one or more of the aforementioned variants is provided. Preferably, the first input shaft of the steering gear in the tracked vehicle drive train can be connected to a drive machine, via which a corresponding rotary movement of the first input shaft of the steering gear can then be represented. This takes place in particular with an intermediate gear ratio. The drive machine is also in particular part of a drive device in the tracked vehicle drive train, for which purpose the drive machine can be coupled via an intermediate drive gear to a drive shaft that is permanently coupled to summing stages. At these summing stages, a drive movement of the drive shaft is then superimposed on a steering movement of the neutral shaft of the steering device.Most preferably, the drive engine is an internal combustion engine.

[0033] The aforementioned tracked vehicle drive train is preferably provided for a tracked vehicle, which is in particular a military tracked vehicle, such as a tank. Alternatively, the tracked vehicle can also be a construction machine.

[0034] The invention further relates to a method for operating a steering device. According to the independent claim 13, a steering ratio range is continuously provided in a steering gear of the steering device by superimposing a rotational movement, which is initiated at a first input shaft of the steering gear provided for coupling to a drive motor, at a superposition stage of the steering gear with a rotational movement, which is initiated at a second input shaft connected to an electric motor.To represent each steering ratio range, at least one steering ratio, which in the steering gear lies between the respective ends of the respective steering ratio range, is expanded by superimposing the electric motor in the direction of one end by generator operation and the electric motor in the direction of the other end by electromotive operation. This advantageously allows for the continuous representation of different steering ratios with the single electric motor.

[0035] As already described above, within the scope of the invention, one or more steering ratio ranges can be realized by correspondingly widening one or more steering ratios. The at least one steering ratio can be located between the respective ends of each steering ratio range in such a way that the widening toward both ends of the respective steering ratio range is essentially the same size, that the electric machine is predominantly operated as a generator for the widening, or that the electric motor is predominantly operated as an electric motor for the widening.

[0036] In a further development of the method according to the invention and when operating a steering device described above, in which a steering gear has a first planetary stage, a second planetary stage, a reversing stage and five switching elements, the second switching element and the third switching element are actuated simultaneously to achieve straight-ahead travel. As a result, the neutral shaft is fixed via the intermediate shaft, so that straight-ahead travel can take place reliably. In addition, the first switching element could also be closed, whereby the third element of the superposition stage is also fixed, thereby coupling the electric motor to the drive motor. As a result, the electric motor can then be used for boosting in boost mode or for recuperation in charging mode.

[0037] Alternatively or in addition to the aforementioned development, to represent a first steering ratio, only the fourth switching element of the first switching element, the fourth switching element, and the fifth switching element is actuated. Furthermore, to represent a second steering ratio, only the fourth switching element and the fifth switching element of the first switching element, the fourth switching element, and the fifth switching element are actuated simultaneously, wherein to represent a third steering ratio, the first switching element, the fourth switching element, and the fifth switching element are actuated simultaneously. Advantageously, this thus makes it possible to represent three different, fixed steering ratios, which can then each be expanded to three different steering ratio ranges in the manner according to the invention.For a left turn, the third switching element must also be closed, while for a right turn, the second switching element must also be closed.

[0038] Advantageous embodiments of the invention, which are explained below, are illustrated in the drawings. It shows: Fig. 1 a schematic view of a tracked vehicle; Fig. 2 is a schematic representation of a tracked vehicle drive train according to a first embodiment of the invention; Fig. 3 a tabular representation of different switching states of a steering gear of a steering device of the tracked vehicle drive train from Fig. 2; and Fig. 4 a schematic view of a tracked vehicle drive train according to a second embodiment of the invention.

[0039] Fig. 1 shows a schematic view of a tracked vehicle 1, which may be a work vehicle, such as a construction machine, or even a military vehicle. The tracked vehicle 1 comprises a vehicle body 2 and two tracked units 3 and 4, of which the tracked unit 3 is provided in the front direction of the tracked vehicle 1 on a right side of the vehicle body 2 and the tracked unit 4 is provided on a left side of the vehicle body 2. The two tracked units 3 and 4 each comprise a drive chain 5 and 6, respectively - only indicated here. The drive chains 5 and 6 can each be driven via an associated drive sprocket 7 and 8, respectively, wherein the drive sprockets 7 and 8 are part of a tracked vehicle drive train 9, which in Fig. 1 is merely indicated.

[0040] Out of Fig. 2 shows a schematic view of the tracked vehicle drive train 9, which is designed according to a first embodiment of the invention. The tracked vehicle drive train 9 comprises a drive motor 10 in the form of an internal combustion engine, which is connected to a spur gear 11 on the output side. This connection to the spur gear 11 is preferably made via intermediate gear ratios (not shown here). The spur gear 11 is, on the one hand, connected in a rotationally fixed manner to a hydrodynamic torque converter 12, which is Fig. 2 is not shown in detail and has a structure known in principle to those skilled in the art. The hydrodynamic torque converter 12 can be used to couple the spur gear 11, and thus also the drive motor 10, to a transmission input shaft 13 of a transmission 14.

[0041] The transmission gear 14 is also in Fig. 2 is not shown in detail, wherein the transmission gear 14 is preferably designed as a planetary automatic transmission in which different transmission ratios can be switched as gears between the transmission input shaft 13 and a drive shaft 15.

[0042] Apart from a transmission output of the transmission gear 14, the drive shaft 15 is also connected to two summing stages 16 and 17, wherein the drive shaft 15 is coupled at the summing stage 16 to the drive sprocket 7 and a neutral shaft 18 of a steering device 19, and at the summing stage 17 to the drive sprocket 8 and the neutral shaft 18. At the individual summing stage 16 or 17, a rotational movement of the drive shaft 15 can be superimposed on a rotational movement of the neutral shaft 18. The individual summing stage 16 or 17 is designed as a respective planetary gear set, which is composed of a first element 20 or 21, a second element 22 or 23, and a third element 24 or 25.

[0043] In this case, the respective first element 20 or 21 of the respective summing stage 16 or 17 is a respective sun gear, while the respective second element 22 or 23 of the respective summing stage 16 or 17 is designed as a respective planetary carrier, and the respective third element 24 or 25 of the respective summing stage 16 or 17 is designed as a respective ring gear. The respective planetary carrier carries several planetary gears, which mesh individually with both the respective sun gear and the respective ring gear. In this respect, the planetary gear sets forming the summing stages 16 and 17 are designed as minus planetary gear sets.

[0044] As in Fig. 2, the drive shaft 15 is connected in a rotationally fixed manner to the third element 24 of the summing stage 16, as well as in a rotationally fixed manner to the third element 25 of the summing stage 17, for which purpose the drive shaft 15 runs axially between the two summing stages 16 and 17 and, as a solid shaft, is guided axially and radially on the inside through the transmission gear 14, the transmission input shaft 13 and the hydrodynamic torque converter 12. In the summing stage 16, the second element 22 is connected in a rotationally fixed manner to the drive sprocket 7 via an output shaft 26, while in the summing stage 17 the second element 23 is connected in a rotationally fixed manner to the drive sprocket 8 via an output shaft 27. Furthermore, the remaining first element 20 or 21 of the respective summing stage 16 or 17 is permanently coupled to the zero wave 18.

[0045] In the summing stage 16, the first element 20 is non-rotatably connected to a spur gear 28, which meshes with an intermediate gear 29. The intermediate gear 29 is mounted in a fixed position for rotation and, in addition to meshing with the spur gear 28, permanently meshes with a spur gear 30, which is mounted in a rotationally fixed manner on the neutral shaft 18. In the summing stage 17, the first element 21 is also permanently connected in a rotationally fixed manner to a spur gear 31, whereby this spur gear 31 meshes with an intermediate gear 32, which is mounted in a fixed position for rotation. At the same time, the intermediate gear 32 is permanently meshed with another intermediate gear 33, which is also mounted in a fixed position for rotation and additionally meshes with a spur gear 34. The spur gear 34 is mounted in a rotationally fixed manner on the neutral shaft 18.

[0046] A coupling of the zero shaft 18 to the summing stage 17 is thus realized with one more tooth mesh than is the case with the coupling of the zero shaft 18 to the summing stage 16. This results in a rotational movement of the zero shaft 18 being converted into a co-directional rotational movement of the first element 20 in the summing stage 16, while in the summing stage 17 this results in an opposite rotational movement of the first element 21 of the summing stage 17. The rotational movement of the zero shaft 18 is transmitted to the elements 20 and 21 of the summing stages 16 and 17 with corresponding gear ratios.

[0047] Overall, a rotary movement of the neutral shaft 18 accordingly causes rotary movements of the first elements 20 and 21, whereby the rotary movements of the first elements 20 and 21 are oriented opposite to one another. Depending on the direction of rotation of the neutral shaft 18 and in the course of a superposition with a rotary movement of the drive shaft 15, this results in an increase in the rotary movement of the drive shaft 15 at one summing stage 16 or 17 and a reduction in the rotary movement of the drive shaft 15 at the other summing stage 17 or 16. Overall, this results in different rotary movements of the drive sprockets 7 and 8 and thus also in different speeds of the drive chains 5 and 6. Thus, by rotating the neutral shaft 18 in the sense of superposition steering, corresponding cornering of the tracked vehicle 1 or, with the drive shaft 15 stationary, even a turn on the spot (pivot) can be realized.The latter is achieved by a blocking transmission gear 14.

[0048] The zero shaft 18 is part of the steering device 19, which is designed according to a first embodiment of the invention and comprises a steering gear 35. The steering gear 35 has a first input shaft 36 and a second input shaft 37, wherein the steering gear 35 is coupled to the drive motor 10 at the first input shaft 36. A rotationally fixed connection to an electric machine 39 of the steering device 19 is also established at the second input shaft 37, wherein this electric machine 39 is Fig. 2 is shown only schematically and can be operated as an electric motor or as a generator.

[0049] In addition, the steering gear 35 also comprises a superposition stage 40, two planetary stages 41 and 42, a reversing stage 43, and five shift elements KL, K1, K2, KR, and B1. The shift elements KL, K1, K2, KR, and B1 are each designed as force-locking shift elements and are specifically in the form of multi-disk shift elements. The superposition stage 40 is designed as a planetary gear 44 and consists of a first element 45, a second element 46, and a third element 47. The third element 47 is a planet carrier in which several planetary gears are each rotatably mounted, with each individual planetary gear meshing with the first element 45, designed as a ring gear, and with the second element 46, designed as a sun gear. Accordingly, the planetary gear 44 is designed as a minus planetary gear set.

[0050] The first element 45 of the superposition stage 40 is non-rotatably connected to the input shaft 36, which is coupled to the spur gear 11 and thus also to the drive motor 10 via a spur gear stage 48 and a spur gear 38. The spur gear stage 48 consists of a spur gear 49 and a spur gear 50, with the spur gear 50 being non-rotatably mounted on the input shaft 36 and permanently meshing with the spur gear 49, which is non-rotatably connected to the spur gear 38. The spur gear 38 is also permanently meshing with the spur gear 11.

[0051] Furthermore, there is a permanent coupling between the second element 46 of the superposition stage 40 and the input shaft 37, and thus also the electric motor 39, which is realized here via a spur gear stage 51. This spur gear stage 51 consists of a spur gear 52 and a spur gear 53 permanently meshing therewith, wherein the spur gear 52 is arranged in a rotationally fixed manner on the input shaft 37, while the spur gear 53 is permanently connected in a rotationally fixed manner to the second element 46 of the superposition stage 40.

[0052] As in Fig. 2, the two planetary stages 41 and 42 are each composed of a first element 54 or 55, a second element 56 or 57, and a third element 58 or 59. The respective first element 54 or 55 of the respective planetary stage 41 or 42 is a respective sun gear, whereas the respective second element 56 or 57 of the respective planetary stage 41 or 42 is a respective planet carrier and the respective third element 58 or 59 of the respective planetary stage 41 or 42 is a respective ring gear. In each case, a plurality of planet gears are rotatably mounted in the respective planet carrier, each of which is in meshing engagement with both the respective sun gear and the respective ring gear. In this respect, the two planetary stages 41 and 42 are designed as minus planetary sets.

[0053] In the present case, the third element 58 of the planetary stage 41 and the second element 57 of the planetary stage 42 are permanently connected to one another in a rotationally fixed manner and are coupled via a freewheel 60 to a permanently fixed component 61, which is in particular a gear housing of the steering gear 35. Furthermore, the third element 59 of the planetary stage 42 can also be connected to one another in a rotationally fixed manner by actuating the switching element B1 and thereby fixed, so that the switching element B1 in the present case is a brake. In addition, the first element 54 of the planetary stage 41 and the first element 55 of the planetary stage 42 are permanently connected to one another in a rotationally fixed manner and are jointly connected to the third element 47 of the superposition stage 40 in a rotationally fixed manner, so that the first element 54, the first element 55, and the third element 47 always rotate together.

[0054] The first element 54 of the planetary stage 41, the first element 55 of the planetary stage 42, and the third element 47 of the superposition stage 40 can be connected in a rotationally fixed manner to an intermediate shaft 62 by actuating the switching element K2. The intermediate shaft 62 runs as a hollow shaft coaxial with the neutral shaft 18 and can also be coupled to the second element 56 of the planetary stage 41 via a freewheel 63 by actuating the switching element K1. Furthermore, this intermediate shaft 62 can also be connected in a rotationally fixed manner to the neutral shaft 18 by actuating the switching element KR and coupled to the neutral shaft 18 via the reversing stage 43 by actuating the switching element KL. In the latter case, the reversing stage 43 ensures equal speeds of the intermediate shaft 62 and the neutral shaft 18 with opposite directions of rotation.

[0055] In the steering gear 35, different switching states can be realized by selectively operating the switching elements KL, KR, K1, K2 and B1, which in Fig. 3 are shown in tabular form. On the one hand, a straight-ahead travel function GA can be realized by simultaneously actuating the switching elements KL and KR, whereby the zero shaft 18 is blocked and thus no superposition of the drive movement with longitudinal movements takes place at the summing stages 16 and 17. If the switching element K2 is also closed in this switching state, the third element 47 of the superposition stage 40 is also fixed and thus a coupling of the electric machine 39 to the drive machine 10 is brought about via the superposition stage 40. As a result, the electric machine 39 can, on the one hand, support the drive machine 10 in driving the tracked vehicle 1 (boosting) or, in its generator mode, ensure that the tracked vehicle 1 is braked by recuperation or, if the electric machine 39 is driven alone, generate power via the drive machine 10.

[0056] Furthermore, different steering ratios R1, R2, and R3 can be implemented via the steering gear 35, in each of which a rotary movement introduced into the steering gear 35 via the drive motor 10 is translated to the neutral shaft 18, which, through superposition at the summing stages 16 and 17, ensures corresponding steering movements of the tracked vehicle 1 or, with a fixed drive shaft 15, causes a turning around the vertical axis of the tracked vehicle (pivot). If, in addition, the switching element KL is actuated simultaneously when the respective steering ratio R1, R2, or R3 is displayed, this results in the tracked vehicle 1 being steered to the left, whereas the simultaneous actuation of the switching element KR when the respective steering ratio R1, R2, or R3 is displayed causes the tracked vehicle 1 to steer to the right.

[0057] The steering ratio R1 is realized in the steering gear 35 by actuating the switching element K1, whereas the switching element K2 and the switching element B1 are not actuated. Starting with the steering ratio R1, if the switching element K2 is also actuated in addition to the switching element K1, this results in the representation of the steering ratio R2. However, if the switching elements K1, K2, and B1 are actuated simultaneously, the steering ratio R3 is realized.

[0058] The individual steering ratios R1, R2, or R3 can each be expanded to a continuously adjustable steering ratio range in the steering gear 35 of the steering device 19 by superimposing the rotary movement induced by the drive motor 10 on the input shaft 36 at the superposition stage 40 with a rotary movement induced by the electric motor 39 on the input shaft 37. This induced rotary movement is then transmitted via the spur gear stage 51 to the second element 46 of the superposition stage 40.

[0059] As a special feature, each individual steering ratio R1, R2, or R3 lies between respective ends of the respective steering ratio range with regard to the respective associated steering ratio range, to which it can be continuously expanded by the superposition at the superposition stage 40. Accordingly, when the respective steering ratio R1, R2, or R3 is engaged and the input shaft 37 is at a standstill, no end of the respective steering ratio range is established; rather, a ratio lying between the respective ends is realized in the respective associated steering ratio range. Based on this, the continuous expansion can now be achieved towards one end of the respective steering ratio range by the generator operation of the electric machine 39 and towards the other end of the respective steering ratio range by the electromotive operation of the electric machine 39.Accordingly, the electric machine 39 operates first as a generator and then as an electric motor when the respective steering ratio range is fully represented.

[0060] Finally, Fig. 4 shows a schematic representation of a tracked vehicle drive train 64, which alternatively to the tracked vehicle drive train 9 of Fig. 2 on the tracked vehicle 1 in Fig. 1 and is realized according to a further embodiment of the invention. The tracked vehicle drive train 64 largely corresponds to the preceding variant according to Fig. 2, whereby, in contrast, in a steering gear 65 of a steering device 66, a switching element B is additionally arranged on the input shaft 37, which can lock the input shaft 37 and subsequently prevent it from rotating. In this respect, the switching element B is designed as a brake, which locks the input shaft 37, particularly in an unactuated state, whereas in an actuated state of the switching element B, the input shaft 37 is freely rotatable. In this respect, the switching element B is therefore closed in the actuated state (normally closed). Otherwise, the tracked vehicle drive train 64 corresponds to the tracked vehicle drive train 9 from Fig. 2, so that reference is made to the description in this regard. In this case, the steering gear 65 of the steering device 66 can also be Fig.3 shown and described switching states are shown, and the stepless expansion to the steering ratio ranges is realized.

[0061] By means of the embodiments according to the invention, at least one continuously variable steering ratio range can be realized with low manufacturing costs. Reference symbol 1 tracked vehicle 2 Vehicle body 3 crawler tracks 4 crawler tracks 5 drive chain 6 drive chain 7 Drive sprocket 8 Drive sprocket 9 Tracked vehicle drive train 10 drive machine 11 Spur gear 12 hydrodynamic torque converter 13 Gearbox input shaft 14 drive gear 15 Drive shaft 16 summing stage 17 summing stage 18 zero wave 19 Steering device 20 first element 21 first element 22 second element 23 second element 24 third element 25 third element 26 Output shaft 27 Output shaft 28 Spur gear 29 Intermediate gear 30 spur gear 31 Spur gear 32 intermediate gear 33 intermediate gear 34 Spur gear 35 steering gear 36 Input shaft 37 Input shaft 38 Spur gear 39 Electric machine 40 overlay level 41 planetary stage 42 planetary stage 43 turning step 44 planetary gears 45 first element 46 second element 47 third element 48 spur gear stage 49 Spur gear 50 spur gear 51 Spur gear stage 52 spur gear 53 Spur gear 54 first element 55 first element 56 second element 57 second element 58 third element 59 third element 60 freewheel 61 permanently fixed component 62 intermediate shaft 63 Freewheel 64 Tracked vehicle drive train 65 steering gear 66 Steering device KL switching element KR switching element K1 switching element K2 switching element B1 switching element B switching element R1 steering ratio R2 steering ratio R3 steering ratio

Claims

[1] Steering device (19; 66) for a tracked vehicle drive train (9; 64), comprising a steering gear (35; 65) and an electric machine (39) which can be operated on the one hand as an electric motor and on the other hand as a generator, wherein the steering gear (35;65) a first input shaft (36) which is provided for coupling to a drive machine (10), a second input shaft (37) which is connected to the electric machine (39), a neutral shaft (18) and a superposition stage (40) which has a first element (45), a second element (46) and a third element (47), wherein the first element (45) of the superposition stage (40) is coupled or can be coupled to the first input shaft (36), the second element (46) of the superposition stage (40) is coupled or can be coupled to the second input shaft (37) and the third element (47) of the superposition stage (40) is coupled or can be coupled to the neutral shaft (18), and wherein at the superposition stage (40) a rotary movement of the first element (45) is converted into a rotary movement of the third element (47) by superimposing a rotary movement of the second element (46). implementable and by the superposition in the steering gear (35;65) at least one steering ratio (R1, R2, R3) can be expanded to a continuously adjustable steering ratio range; characterized by that the at least one steering ratio (R1, R2, R3) lies in terms of value between respective ends of the respective steering ratio range, and that during the superposition, starting from the at least one steering ratio (R1, R2, R3), the widening takes place in the direction of one end of the respective steering ratio range in the generator operation of the electric machine (39) and in the direction of the other end of the respective steering ratio range in the electromotor operation of the electric machine (39). [2] Steering device (19; 66) according to claim 1, characterized by that the first input shaft (36) is connected in a rotationally fixed manner to the first element (45) of the superposition stage (40). [3] Steering device (19; 66) according to claim 1 or 2, characterized bythat the second input shaft (37) is coupled to the second element (46) of the superposition stage (40) via an intermediate transmission. [4] Steering device (19; 66) according to claim 3, characterized by that the intermediate transmission is formed by a spur gear stage (51), wherein the spur gear stage (41) has a spur gear (52) arranged in a rotationally fixed manner on the second input shaft (37), which spur gear (52) meshes with a spur gear (53) connected in a rotationally fixed manner to the second element (46) of the superposition stage (40). [5] Steering device (66) according to one of the preceding claims, characterized by that a switching element (B) is provided, via which the second input shaft (37) can be fixed. [6] Steering device (66) according to claim 5, characterized by that the switching element (B) fixes the second input shaft (37) in an unactuated state and enables the second input shaft (37) to rotate in an actuated state. [7] Steering device (19; 66) according to one of the preceding claims, characterized by in that a plurality of steering ratios (R1, R2, R3) can be switched in the steering gear (35; 65), which are each located between respective ends of a steering ratio range and can each be continuously expanded to the respective steering ratio range by superimposing them on the one hand in generator operation and on the other hand in electromotor operation of the electric machine (39). [8] Steering device (19; 66) according to one of the preceding claims, characterized by that the first element (45) of the superposition stage (40) is coupled to the first input shaft (36), wherein the third element (47) of the superposition stage (40) can be coupled to the zero shaft (18) by representing the respective steering ratio range (R1, R2, R3). [9] Steering device (19; 66) according to claims 7 and 8, characterized bythat the steering gear (35; 65) has a first planetary stage (41), a second planetary stage (42), a reversing stage (43), a first switching element (K2), a second switching element (KR), a third switching element (KL), a fourth switching element (K1) and a fifth switching element (B1), - wherein the first planetary stage (41) and the second planetary stage (42) each have a first element (54, 55), a second element (56, 57) and a third element (58, 59) in the form of a sun gear, a planetary carrier and a ring gear, - wherein the first element (54) of the first planetary stage (41) and the first element (55) of the second planetary stage (42) are connected to one another in a rotationally fixed manner and are connected to the third element (47) of the superposition stage (40) in a rotationally fixed manner, - wherein the third element (58) of the first planetary stage (41) and the second element (57) of the second planetary stage (42) are connected to one another in a rotationally fixed manner and are coupled to a permanently fixed component (61) via a first freewheel (60), - wherein the first switching element (K2) in an actuated state connects the first element (54) of the first planetary stage (41), the first element (55) of the second planetary stage (42) and the third element (47) of the superposition stage (40) in a rotationally fixed manner to an intermediate shaft (62), - wherein the second switching element (KR) in an actuated state connects the intermediate shaft (62) in a rotationally fixed manner to the zero shaft (18), - wherein the third switching element (KL) in an actuated state couples the intermediate shaft (62) to the zero shaft (18) via the reversing stage (43), - wherein the fourth switching element (K1) in an actuated state couples the second element (56) of the first planetary stage (41) to the intermediate shaft (62) via a second freewheel (63), - and wherein the fifth switching element (B1) in an actuated state fixes the third element (59) of the second planetary stage (42). [10] Steering device (19; 66) according to one of the preceding claims, characterized by that the superposition stage (40) is formed by a planetary gear (44), wherein of the first element (45), the second element (46) and the third element (47) of the superposition stage (40), one element (46) is present as a sun gear of the planetary gear (44), one element (47) is present as a planet carrier of the planetary gear (40) and one element (45) is present as a ring gear of the planetary gear (40). [11] Tracked vehicle drive train (9; 64) comprising a steering device (19; 66) according to one or more of claims 1 to 10. [12] Tracked vehicle (1) comprising a tracked vehicle drive train (9; 64) according to claim 11. [13] Method for operating a steering device (19; 66) of a tracked vehicle drive train (9; 64), wherein in a steering gear (35; 65) of the steering device (19; 66) a steering ratio range is represented continuously by a rotational movement which is initiated at a first input shaft (36) of the steering gear (35; 65) provided for coupling to a drive machine (10), being superimposed at a superposition stage (40) of the steering gear (35; 65) with a rotational movement which is initiated at a second input shaft (37) connected to an electric machine (39), and wherein to represent the respective steering ratio range at least one steering ratio (R1, R2, R3) which is provided in the steering gear (35;65) lies in value between respective ends of each of the steering ratio ranges, by the superposition is expanded on the one hand in the direction of one end by a generator operation of the electric machine (39) and on the other hand in the direction of the other end by an electromotive operation of the electric machine (39); [14] Method according to claim 13 and for operating a steering device (19; 66) designed according to claim 9, wherein the second switching element (KR) and the third switching element (KL) are actuated simultaneously to represent straight-ahead travel. [15] Method according to claim 14, characterized by that a charging or boosting operation is carried out via the electric machine (39) by additionally closing the first switching element (K2) and operating the electric machine (39) as a generator or electric motor. [16] Method according to one of claims 13 to 15 and for operating a steering device (19; 66) designed according to claim 9, - wherein, to represent a first steering ratio (R1), only the fourth switching element (K1) of the first switching element (K2), the fourth switching element (K1) and the fifth switching element (B1) is actuated, - wherein, to represent a second steering ratio (R2), only the fourth switching element (K1) and the fifth switching element (B1) are actuated simultaneously from the first switching element (K2), the fourth switching element (K1) and the fifth switching element (B1), - and wherein to represent a third steering ratio (R3) the first switching element (K2), the fourth switching element (K1) and the fifth switching element (B1) are actuated simultaneously.

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