WO2004048821A1

WO2004048821A1 - Power transmission unit

Info

Publication number: WO2004048821A1
Application number: PCT/EP2003/013238
Authority: WO
Inventors: Werner Klement; Werner Adams
Original assignee: Voith Turbo Gmbh & Co. Kg
Priority date: 2002-11-25
Filing date: 2003-11-25
Publication date: 2004-06-10
Also published as: EP1565677A1; WO2004048167A1

Abstract

The invention relates to a power transmission unit (1) comprising at least one input (6) and one output (7); a starting element (8) arranged between the input (6) and the output (7); a transmission (45) arranged downstream from said starting element and comprising at least one rotational speed/torque conversion device; a housing (12); and a device which is used to prevent backward roll (2) and comprises at least one positive clutch (11) that can be synchronously actuated. Said positive clutch (11) is arranged between a fixed component or the housing (12) and a rotatable power-transmission element (14) or an element which is coupled to said power transmission element in a rotatably fixed manner, in a region of the power transmission unit (1) which is located between the output of the starting element (8) and the output (7) of the transmission (45).

Description

The power transmission unit

The invention relates to a power transmission unit, in particular with the features from the preamble of claim 1.

Power transmission units, comprising at least one input and one output as well as a starting element arranged therebetween and a transmission connected downstream, are known in a large number of designs. The starting elements can be designed as desired. These can be designed as wear-free starting elements, for example in the form of hydrodynamic components, or as frictionally starting elements. There are also a number of options for the specific structural design of the transmission. This can be designed as a continuously variable transmission or in the form of a manual transmission, comprising at least one switching stage. Power transmission units of this type are used in drive trains for vehicles, the input being connectable at least indirectly, ie directly or indirectly, to a drive machine, while the output is coupled at least indirectly in a rotationally fixed manner to the wheels to be driven. Due to the arrangement in the power flow between the drive machine and the wheels, the introduction of the power is possible both from the input of the power transmission unit, ie from the side of the drive machine and from the side of the output, for example when rolling backwards on the mountain or in overrun with the wheels. This is particularly the case if the vehicle rolls back undesirably during a starting process. This rolling back is generally prevented by the activation of additional braking devices provided for this purpose. These are implemented, for example, in the form of so-called parking brake devices, in the form of hand brake devices in the car as a rule. In order to reliably prevent an unwanted moving back of the vehicle and to ensure a smooth start-up process, a number of measures are known which relate to the release of the braking device with regard to other activities in terms of their time sequence, particularly when starting up on a mountain. For example, the parking brake devices according to DE 44 21 088 A1 are only released after certain conditions have been met. However, this requires a considerable additional Control engineering effort and also an additional element to realize the locking or holding function or the prevention of unwanted rolling back.

The invention is therefore based on the object of preventing rollback for drive trains for use in vehicles of the type mentioned at the outset with an integrated power transmission unit in such a way that these disadvantages are avoided and an undesired rolling back, in particular when starting off on a mountain, is safe is prevented, this possibly no longer having to be dependent on actual variables to be recorded and evaluated in terms of control technology. Furthermore, the device should also reliably preclude unwanted locomotion of the vehicle regardless of the direction of travel, the undesirable locomotion also being able to prevent undesired forward movement on the mountain.

The solution according to the invention is characterized by the features of claim 1. Advantageous refinements are described in the subclaims.

According to the invention, the power transmission unit comprises a starting element and a transmission connected downstream of it, wherein in the power transmission direction, viewed from the input of the power transmission unit to the output of the power transmission unit, a rollback prevention in the form of a synchronously switchable positive clutch is provided between the output of the starting element and the output of the transmission arranged in this area, transmitting power or with an element connected in a rotationally fixed manner to the power-transmitting element and a stationary or stationary component or housing. The clutch, which can be switched synchronously, is arranged spatially in the axial direction from the input to the output of the power transmission unit at any point behind the starting element.

The solution according to the invention thus enables the power-transmitting components to be fixed in a simple manner by only one additional element in the drive train. Depending on the design of the synchronously switchable positive clutch, this function can even take place regardless of the direction of the introduction of the torque into the power transmission unit and thus, when used in drive trains, from the direction of travel or from the overrun mode or traction mode. When the synchronously switchable positive coupling is activated, a blocking effect is always achieved, which enables the power-transmitting element and thus the elements coupled to it - the input of the power transmission unit and / or the output of the power transmission unit - to be braked. The only measure to be taken is that the synchronously switchable clutch is to be activated when the standstill is desired, whereas when the rollback prevention is canceled, this must be deactivated again.

Due to the switchability of the rollback prevention, the vehicle is allowed to rock freely. This is always necessary if the vehicle has got stuck in snow or dirt, for example, and is to be set in motion by alternate starting and rolling back in order to get out of this situation. The direction of travel does not have to be changed in the transmission.

The following terms are defined in advance for the following explanation:

Power transmission area - area in the direction of power flow or

Direction of power flow from the input to the output of the power transmission unit viewed between the starting element and the output of the power transmission unit rotating element in

Power transmission area - power transmitting element or element coupled to the power transmitting element

With regard to the arrangement of the synchronously switchable positive coupling between the rotating element in the power transmission area between the Starting element and the output of the power transmission unit and the stationary element or housing in the power transmission unit are a variety of options. The arrangement of the synchronously switchable coupling and thus the intended coupling between the rotating element in the power transmission area and the housing can, as already stated, take place anywhere in the axial direction between the input and the output of the power transmission unit. The following arrangements are conceivable, for example, which are characterized by the design of the power-transmitting elements in accordance with the following options:

Formation of the power-transmitting element as the output of the starting element (in the case of a hydrodynamic coupling, for example, the secondary wheel or the element coupled to it)

Formation of the power-transmitting component in the form of a connecting shaft between the starting element and the transmission or a connecting shaft at any point in the transmission

Design of the power-transmitting element as a transmission input shaft Design of the power-transmitting element as a gear element or an element that is non-rotatably coupled to it, for example a spur gear or planet gear or a shaft or hub that is non-rotatably coupled to it.

The transmission itself can also be designed in a variety of ways. This can be carried out, for example, in countershaft construction, as a planetary gear or a combined planetary spur gear for realizing individual gear stages or as a continuously variable transmission. In the case of a countershaft construction, this comprises at least one first countershaft which connects the output of the starting element to the output of the power transmission unit via a countershaft and via further countershaft which can be coupled and characterizes the switching stages. The individual devices that characterize the individual gear stages are assigned switching elements that, depending on the arrangement, either the gear directly with the output or one coupled to it Connect shaft or a rotating component or a connection of the countershaft implementing the respective gear stage with the countershaft arranged parallel to the starting element. When the switching elements are assigned to the shaft coupled to the output of the power transmission unit, it is possible to arrange the synchronously switchable positive coupling at any point in the axial direction from the input of the power transmission unit to the output of the power transmission unit between the countershaft and the stationary element or housing. The arrangement can then take place, for example, behind the present in the individual gear stages or between the individual present.

A large number of possibilities are conceivable with regard to the design of the starting element. This can be designed as a wear-free starting element or a starting element subject to wear. In the former case, hydrodynamic components are preferably chosen which present as hydrodynamic clutches, comprising at least one primary impeller and one secondary impeller. Designs as hydrodynamic speed / torque converters are also conceivable. In this case, at least one stator is additionally provided. Solutions subject to wear are usually available as wet-running or dry-running multi-plate clutches or simple disc clutches. Other options for designing the starting elements are also conceivable. For example, reference is made to electrical or hydrostatic solutions. In order to use only the advantages of certain operating areas, a device for bridging can also be assigned to the starting element. The input and the output of the starting element are rigidly coupled to one another. The unit consisting of the starting element and the bridging device forms a starting unit, the same applies to the arrangement of the form-fitting, synchronously switchable clutch as to the starting element. To ensure rollback prevention in all operating states of the power transmission unit, however, the connection of the synchronously switchable form-locking clutch is carried out in this area, which is characterized by the output of the starting unit and the output of the power transmission unit. The arrangement at the exit of the Starting element takes place behind the area which is provided for the rotationally fixed coupling between the input and output of the starting element.

An actuating device is assigned to the synchronously switchable positive coupling. This can take many forms. For example, mechanical, electrical, pneumatic, hydraulic and electro-mechanical, electro-pneumatic, electro-hydraulic solutions are conceivable. The specific execution depends on the boundary conditions of the application. However, solutions are preferably chosen in which large forces can be generated with little effort, in particular with small actuating devices, and which can be easily integrated into driving controls.

The synchronously switchable positive coupling comprises at least a first coupling element which has positive driving elements or which carries these, which can be at least indirectly brought into operative connection with activation of the coupling with complementary driving elements on the second coupling element. The first coupling element is formed by the housing or a stationary component, in particular an area provided therefor or an element connected to it, while the second coupling element is formed directly by an element that transmits power or is non-rotatably coupled to it or else is rotatably connected with this. Depending on the design of the power-transmitting element, it can either be brought into operative connection directly with the driving elements on the first coupling element, for example by being displaceable in the axial direction, or indirectly via further intermediate elements. Analogously, this also applies to the first coupling element. In the case of a direct coupling between the first and second coupling elements, at least one of the two elements carrying these can be changed in its position, in particular displaceable in the axial direction. According to a particularly advantageous embodiment, however, the positive connection is generated via a third coupling element in the form of an intermediate element. In this case, the driver elements that characterize the first and second coupling elements are directly on the stationary component and transmit the power Component or an element rotatably coupled to this. The arrangement takes place in designated areas. Means are also provided for, in particular, axially fixing the displaceable coupling element, in particular the intermediate element, ie for fixing its position in the axial direction from the input to the output of the power transmission unit. According to a particularly advantageous embodiment, these are formed by the actuating device, so that no additional measures are necessary. This means that, for example, when using an electro-pneumatic or hydraulic actuating device, the pressure for activating the switchable clutch is also used to hold the clutch element in its position. For this purpose, for example, the intermediate element is designed as a piston or is connected in a rotationally fixed manner to at least one piston, the actuating device acting on the piston. In solutions in which the actuation pressure is generated hydraulically or pneumatically, the piston pressure is guided in the housing or the fixed component or on both, the pressure chambers required for acting on the piston being formed by the housing or the fixed component or both. For this purpose, the actuating device has a pressure supply system, comprising a pressure source which acts on the piston on the end face which is opposite the displacement direction in order to reach the engagement position. This pressure source or a further pressure source can then be used to pressurize the piston on an end face directed towards engagement in the displacement direction. In the former case, the piston or, in the case of solutions with more than one piston, a second piston is acted upon by the pressure source for deactivation on the end face oriented opposite to the displacement device in order to reach the engagement position. The change between activation and deactivation and thus the action on the different piston surfaces is controlled by means for selectively acting on the individual piston faces or pistons, preferably at least one for each direction. The driving elements on the third coupling element, in particular the intermediate element and the further coupling elements, in particular the fixed component or housing and the power-transmitting element or the element coupled to it, are straight in the axial direction or according to one particularly advantageous embodiment aligned obliquely. In other words, the flanks or flank lines that characterize the entrainment elements, viewed in the axial direction, run parallel to the theoretical axis of rotation of the starting element in the first case, and in the second case when the peripheral surfaces carrying the entrainment elements are projected into a plane and the characterize the course of the entrainment elements Flank lines run in a common plane with the axis of rotation at an angle to the axis of rotation. The flank lines describing the course of the individual entrainment elements are then oriented in the axial direction from the entrance to the exit in the circumferential direction against the direction of rotation of the starting element or the drive machine coupled to it. With this solution, it is possible to automatically reset the intermediate element or third coupling element when the actuation and holding force is interrupted or deactivated in the axial direction by the residual torque or the excess torque from the starting element, in particular when using a hydraulic circuit when the Braking process or when starting on a mountain. This solution is characterized by a particularly low manufacturing and control expenditure, since only for activating the switchable clutch, ie in the axial direction for the purpose of engaging the driving elements, an actuating force and for holding the coupling element in its position in the axial direction, a holding force is required, while for deactivation only an interruption or reduction of these forces to zero is required. ,

In order to implement an intervention based on a starting position and the automatic return to it, the orientation of the individual driving element is characterized by a very large slope. Viewed over the length in the axial direction, there is no complete wrap in the circumferential direction, preferably only a partial wrap. The size of the flank angle of the driver elements is preferably in a range from 20 to 45 degrees inclusive. In order to overcome the static friction of a coupling element, a return spring unit is arranged between the latter and the housing or the stationary component. Depending on the design of the individual coupling elements or their assignment to the individual elements of the power transmission unit, the form-fitting entrainment elements are arranged on these directly or on elements that are coupled to them in a rotationally fixed manner. In doing so, versions with

a) driving elements arranged on the outer and inner circumference of the third coupling element, or b) driving elements arranged on the outer or inner circumference of the third coupling element, the driving elements required for the individual positive connections being arranged on a common diameter or a different diameter

distinguished. The possibility mentioned under a) offers the advantage of the possibility of different configurations of the form-fitting connections of the third coupling element and the stationary element and the third coupling element and power-transmitting element. One of the connections can be characterized by the straight alignment of the driving elements and the other by the oblique alignment of the driving elements. In the case of oblique alignment, this is preferably carried out with an incline counter to the direction of rotation of the drive machine. This ensures an automatic reset. This embodiment is only possible to a limited extent in an embodiment according to b). If the third coupling element is at least partially designed as a sleeve with a larger inner diameter than the outer diameter of the second coupling element, that is to say the region or a region that is non-rotatably coupled to the power-transmitting element, driving elements are implemented in the simplest case on the inner circumference and on the outer circumference of the third coupling element designed as an intermediate element each arranged a positive connection with the power-transmitting element and the stationary component. The driving elements on the power-transmitting element or an element that is non-rotatably connected to the driving elements that are complementary to the driving elements on the third coupling element are then arranged on its outer circumference. The driver elements on the stationary component or the housing, which are complementary to the driver elements on the intermediate element, are arranged on the inner circumference thereof. The reverse assignment is also conceivable.

The stationary component can be a stationary component or a component that can be braked to zero speed via a braking device.

The synchronously switchable clutch can be designed as a dog clutch or toothed clutch. The driving elements are then designed as claws or spur teeth or with another toothing.

The solution according to the invention is explained below with reference to figures. The following is shown in detail:

Figure 1 illustrates the schematically highly simplified representation

Basic structure of a designed according to the invention

Power transmission unit with integrated rollback prevention; Figure 2 illustrates a possible embodiment of the synchronously switchable positive coupling; Figure 3 illustrates an embodiment according to Figure 2 with connection of the first

Coupling element via a braking device to a stationary or circumferential component, in particular housing; FIG. 4 illustrates, by way of example, arrangement options according to the invention of a synchronously switchable positive coupling in one

Gearbox in countershaft design; Figures 5a to 5c illustrate possible configurations of the synchronously switchable

Clutch; Figure 6 illustrates a particularly advantageous embodiment of the synchronously switchable clutch with automatic reset; FIG. 7 illustrates a further development according to FIG. 6. FIG. 1 illustrates the basic structure and the basic principle of a design according to the invention in a schematically simplified representation

Power transmission unit 1 with rollback prevention 2 in a vehicle 3. The power transmission unit 1 is arranged between a drive machine 4 and the wheels 5.1 and 5.2 to be driven. The

Power transmission unit 1 comprises at least one input 6 and at least one output 7. Between them there is an actuating element 8 and at least one gear 45, comprising, for example, a switching stage 9. According to the invention, a positive coupling 11 is provided in the power flow direction from the input 6 to the output 7, in a power transmission area 13, which characterizes the area between the starting element 8 and the output 7 of the power transmission unit 1 and is thus arranged downstream of the starting element 8, which enables the realization of a positive connection between a housing 12, for example the housing of the power transmission unit 1 or another stationary component and a power-carrying or transmitting element 14 or an element rotatably coupled thereto. The positive coupling is a releasable, synchronously switchable, positive coupling. The positive connection takes place in the circumferential direction, so that a relative movement of the power-carrying or transmitting element 14 with respect to the housing 12 or the stationary component in the circumferential direction is excluded or is only possible within the scope of the coupling play. The synchronously switchable, form-fitting clutch 11 thus functions as a brake or locking or roll-back prevention 2 for the power-carrying or power-transmitting element 14. Under power-carrying or power-transmitting element, gear elements, in particular spur gear or planetary gear elements, or with them, are rotationally fixed connected shafts, hubs or other rotatably mounted elements understood. The arrangement takes place spatially between the input 6 and the output 7, viewed at any position in the area 13. When the synchronously switchable form-fitting clutch 11 is designed with obliquely oriented entrainment elements, the arrangement for ensuring rollback prevention in all operating states is preferably carried out in an area 13 ′ through which the output of the starting element 8 and a device for reversing the direction of travel 12 is characterized. The invention The solution thus enables the construction of very simple means to prevent undesired movement of the vehicle regardless of the direction of travel.

According to FIG. 2, the synchronously switchable positive coupling 11 comprises at least two coupling elements which can be at least indirectly connected to one another - a first and a second coupling element - for realizing a rotationally fixed coupling between the power-carrying or transmitting element 14 or a component connected to it in a rotationally fixed manner and the Housing 12 or another stationary component. The first coupling element 16 is mounted or guided on the housing 12 or another stationary or stationary component 15 or is formed directly by the latter. The second coupling element 17 is connected to the power-carrying or transmitting element 14 or a component that is coupled to it in a rotationally fixed manner or is formed by the latter. According to a particularly simple embodiment, in which the axial position of the first and second coupling elements 16, 17 remains unchanged, the positive connection between the housing 12 and the power-transmitting element 16 is ensured via a third coupling element 18. This can be moved relative to the other two coupling elements 16, 17 or its position can be changed relative to the latter. For this purpose, the individual coupling elements 16, 17, 18 each have driving elements 19, 20, 21, 22, which are designed to be complementary to one another and are aligned and designed such that they are suitable for interaction, a relative movement of the individual coupling elements 16, 17, 18 or to prevent the elements connected to each other in the circumferential direction. The connection to the housing 12 or another stationary component 15 can also take place according to FIG. 3 via a braking device, only indicated here and designated by 23. The remaining basic structure corresponds to that described in FIG. 2. If the synchronously switchable positive coupling 11 is then actuated, the power-carrying element 14 is supported on the housing 12 or another fixed component via the braking device 23.

1 generally illustrates the arrangement according to the invention of a positive-locking synchronously switchable clutch 11, which in the operating state, i. H. When actuating a fixing of at least one power-carrying element 14 in the power flow in the power transmission unit 1 and thus the elements coupled to it, FIG. 4 illustrates with the aid of a power transmission unit 1 according to FIG. 1 possibilities of arranging such a synchronously switchable positive coupling 11. This is on arranged anywhere between the starting element 8 and the output 7. The starting element 8 can be designed in various ways, preferably this is designed as a wear-free starting element. Formations not shown here are conceivable as a hydrodynamic clutch or hydrodynamic converter or as a wear-prone starting element in the form of a friction clutch, for example a disk clutch 10. The individual switching stages 9 are arranged downstream of the starting element 8. The power transmission unit 1 according to FIG. 4 is designed as a countershaft construction. The starting element 8 can be seen, which is coupled to subordinate gear stages or gear stages 9 in a countershaft design. The part of the power transmission unit 1 which forms the switching stages 9 is drawn as a gearbox in a countershaft design. This comprises an input 24 and an output 25, which corresponds to the output 7. The gearbox in countershaft construction comprises a first countershaft 26, which connects the output 28 of the starting element 8 with a countershaft 29. This is arranged, for example, parallel to the input 6 and also parallel to the output 7. Different further ratios 27.1 to 27.5 are used to implement different ratios and thus the gear stages 9. The reduction gear 27.5 is used to implement the reverse gear stage. The individual countershafts are designed as a spur gear set. The positions 11 'to 11 ^ιx illustrate possible arrangements of the synchronously switchable positive clutch 11 in the power ^{flow of} the transmission, the ^{rollback prevention} 2 being effective in all forward ^driving stages and in reverse gear. These arrangement options are suitable without restriction for driving elements with a straight alignment of the flank lines describing them. In contrast, the positions 11 'to 11 ^ιx only illustrate the arrangement ^options , which are characterized by an operation of the ^{rollback prevention} 2 with inclined driving ^elements , in all forward driving ^stages . This is the synchronously switchable Coupling 11 can be coupled to the output 28 of the starting unit or the input 24 of the transmission 45 in a countershaft design or between the first countershaft 26 and the counters 27.1 to 27.5. The countershaft 29 is fixed at any point relative to the housing 12 or another stationary component 15. It is crucial in the case of an inclined alignment of the entrainment elements on one of the clutch elements and the complementary entrainment elements that the arrangement of the synchronously switchable clutch 11 takes place before the reverse gear stage 27.5. Only in this case is it always guaranteed that even when reverse gear is engaged, there is protection against rolling back when the driving elements are inclined.

FIGS. 5 or 6 illustrate, in a schematically simplified representation, possible basic designs of the synchronously switchable, form-fitting coupling 11 used. The synchronously switchable, form-fitting coupling 11 is assigned an actuating device 28. The synchronously switchable, form-fitting clutch 11 comprises a third clutch element 18 which carries driver elements 21 and 22. This can come into operative connection with the complementary driving elements 19 on the housing 12 and 20 on the power element 14. The first coupling element 16 is mounted on the housing 12 or another stationary component 15 or is formed by this. The second coupling element 17 is formed by a power-carrying element 14 or is connected to it in a rotationally fixed manner. The position of the first and second coupling elements 16, 17 is unchangeable. The third coupling element 18 is arranged to be displaceable in the axial direction relative to the other two coupling elements 16, 17 and is preferably guided on one of the two elements. In the initial position, that is to say in the non-actuated state, there is no engagement of the driving elements 21 with the driving elements 20 on the power-carrying element 14, but preferably with the driving elements 19 on the housing or stationary component 15. To achieve the rollback prevention 2, the form-fitting, synchronously switchable clutch is used 11 operated. For this purpose, the third coupling element 18 is displaced in the axial direction, so that the driving elements 21 and the driving elements 18 while maintaining a positive fit with the driving elements 19 in Be brought into operative connection and enable a positive connection between the power-carrying element 14 and the housing 12 in the circumferential direction. Due to the mounting of the first coupling element 16 on the housing 12 or another stationary or stationary component 15, the forces introduced via the output 7 into the first coupling element 16 are supported on the housing 12 or the stationary component 15. The force required for displacement of the third coupling element 18 is realized via an actuating device 30, which can be configured differently. In the simplest case, the third clutch element 18 is preferably designed as a piston, which is actuated via a pressure supply unit 31. However, connection to a piston is also conceivable. The pressure supply unit 31 is effective on the third coupling element 18, preferably on its end face 32 lying in the direction of displacement when actuated. In the embodiment shown in FIG. 5, the positive driving elements 9 on the coupling element 16 and 20 on the power-carrying element 14 and 21 or 22 on the third coupling element 18 are straight, ie the alignment of the driving elements or their extension takes place in the axial direction parallel to the axis of rotation of the power-carrying component 14. In this embodiment, it is necessary to actively engage and disengage the third clutch element 18 when the synchronously switchable, form-fitting clutch 11 is actuated. This means that the actuating device 30 must be designed accordingly. A displacement of the first coupling element 16 in both directions is preferably made possible via the pressure supply unit 31.

In the embodiment according to FIG. 5 a, the third coupling element 18 is also designed, for example, as a sleeve 33, which carries the driving elements 21 on the outer circumference 34 for coupling with the driving elements 19 on the housing 12 and 35 driving elements 22 on its inner circumference for coupling with the power-carrying element 14. The driving elements 19 on the housing 12 are arranged on a partial area forming an inner circumference 36, while the driving elements 20 on the power-carrying or transmitting element 14 are arranged on a partial area 37 forming an outer circumference. This opportunity is a possibility that is relatively easy and simple to design with regard to the arrangement of the pressure supply device 31, the loading of the third coupling element 18 and the guidance thereof. Also conceivable are, according to the configuration of the geometric shape of the coupling elements 16, 17 or the sub-areas forming the housing 12 and the power-carrying element 14, in which, for example, according to FIG. 5b, the positive connection with the power-carrying component 14 via positive driving elements 21 on one an outer periphery forming portion 37 of the third coupling element 18 and an inner periphery forming portion 38. The complementary driving elements 20 and 19 are then arranged on a partial region 39 of the second coupling element 17 forming an inner circumference and a partial region 40 of the first coupling element 16 forming an outer circumference. The third coupling element 18 is thus quasi as a stepped sleeve.

In contrast, FIG. 5c illustrates an embodiment with arrangement of the driving elements 21, 22 on a partial area of the third coupling element 18 that forms an inner circumference. These interact with driving elements 19 and 20 on the housing 12 and the power-transmitting element 14 that are complementary thereto.

The possible embodiments shown in FIGS. 5a to 5c represent examples. These are not necessarily suitable for every installation situation. The specific selection depends on the requirements of the individual case and is at the discretion of the responsible specialist. The designs described here are also conceivable with inclined driving elements.

The driving elements of the form-fitting, synchronously switchable clutch 11 are preferably designed in the form of claws. Certain types of toothing are also conceivable.

FIG. 6 illustrates a particularly advantageous further development for an embodiment according to FIG. 5a and, for example, of FIG. 2. This Further development can also be used for the designs shown in FIGS. 5b and 5c. The prerequisite is that the complementary driving elements 22 on the coupling element 18 and 20 on the power-carrying element 14 and 21 and 19 on the housing 12 are aligned obliquely. The alignment both on the housing 12 and in the coupling element 18 must take place in the same way. In this embodiment, the third coupling element 18 can be automatically reset in its initial position, this being achievable solely on the basis of design measures. For this purpose, the positive driving elements 20 arranged on the power-carrying component 14 are aligned in an oblique direction, the alignment, viewed in the axial direction, taking place against the direction of rotation of the power-carrying element 14 during power transmission from the input 6 to the output 7 in traction mode. In analogy, this also applies to the driving elements 21 arranged on the third coupling element 18 and the driving elements 19 arranged on the housing 12 or the stationary component 15. The driving elements 19, 20 and 21, 22 are designed as claws or preferably toothing. The individual claws or toothings, in particular the flank lines that characterize them, are characterized by a course with a large incline against the direction of rotation of the input shaft, which is indicated by the arrow, ie that the third coupling element 18 can be pushed back or screwed back in this direction of rotation, which counteracts a displacement the direction of engagement. Furthermore, a spring device 41 is provided. This functions as a return spring and is dimensioned in terms of its design such that the spring force applied by it is sufficient only to overcome the friction caused by the third clutch element 18 and to ensure secure positioning in the starting position. An activation device, not shown here, is provided for activation. In the simplest case, this comprises a pressure supply device which acts on the third coupling element 18 at least indirectly, ie directly or via further elements, for example a piston. The mode of operation is as follows: the third clutch element 18 is moved into the engagement position via the pressure preparation unit and, if the driving elements 19, 20, 21 and 22 are configured appropriately, are retracted immediately relative to one another. According to the choice of Pressure supply unit, the third coupling element is acted upon with the required pressure either pneumatically or hydraulically or by another energy source. The means for providing the force applied to the third coupling element 18 are designed such that this corresponds to the maximum axial forces to be supported and the third coupling element 18. When the pressurization via the pressure supply unit is deactivated or interrupted, the residual torque which is still present is used to bring the third coupling element 18 back to its starting position. The return spring 41 supports the third coupling element 18 in the starting position. The system is based on the fact that the excess torque is used for the automatic release of the clutch. This occurs as soon as the propulsion torque, which is introduced into the power transmission unit 1 via the input 6, is greater than the torque on the output side, ie as the torque introduced via the output 7. This excess torque is thus greater than the holding torque for the third coupling element 18. Both are dependent on the design of the form-fitting driving elements, in particular their pitch. Preferably, a very large slope of the driving elements is always chosen.

A further design option of a power transmission unit designed according to the invention, in particular the form-fitting, synchronously switchable clutch 11, is shown in FIG. The basic structure corresponds to that shown in FIG. 6. The synchronously switchable, form-fitting coupling 11 comprises a third coupling element 18, which carries the driving elements 21 and 22, which can be positively brought into operative connection with driving elements 20 of complementary design on the power-carrying element and 19 on the housing 12 or another stationary component 15. The coupling element 18 is designed as a sleeve 33, which has the entrainment elements 22 on its inner circumference 35, which can be positively brought into operative connection with the entrainment elements 20 arranged on an outer circumference 37 on the power-carrying component 14. The second positive connection for supporting the third coupling element 18 on the housing 12 or a stationary component 15 is carried out between the coupling element 18 and the housing 12 or the stationary component 15. For this purpose, the coupling element 18 on its outer circumference 34 comprises entrainment elements 21, which can be brought into operative connection with the entrainment elements 19 on a partial region 36 forming an inner circumference on the housing 12 or the stationary component 15. The outer and inner circumferences are always at least partial areas on these components. According to the invention, the mitna meelemente of the two form-fitting connections are carried out with different orientations, one of the form-fitting connections being designed with straight entrainment elements, while the second is designed with an oblique orientation. In the case shown, the positive connection between the third coupling element 18 and the power-carrying element 14 is designed with helical teeth, ie the flank lines describing the course of these run at an angle to the axis of rotation. In addition, however, the second positive connection between the third coupling element 18 and the housing 12 is formed with straight teeth, ie the flank lines describing their course run parallel to the axis of rotation R. The driving elements 21 arranged on the outer circumference 34 of the coupling element 18 are straight. The entrainment elements 22 arranged on the inner circumference 35, in particular their flank lines, run at an angle to the axis of rotation, ie are designed, for example, with an incline to the right, so that the torque acting on the housing 12 causes the axial force. The torque introduced into the power transmission unit 1 when the drive motor rotates to the right pushes the driving elements, which describe a shifting claw, out of engagement, ie during normal traction operation when power is transmitted from input 6 to output 7. When stationary on the mountain or in overrun mode, this causes the drive train from the output , ie the torque introduced by the output 7, which is opposite to that in the case of power transmission from the direction of the drive machine, the engagement of the third coupling element 18 on the housing 12 or, owing to the structural coupling, also on the power-carrying component 14. Analogously, the slope would have to be aligned in a different direction, if the direction of rotation of the drive machine were different. Furthermore, it is possible by analogy to assign diagonal and straight alignment of the driving elements between the positive connections between coupling element 18 and power-carrying component 14 and coupling element 18 and housing 12 to be exchanged. This means that the oblique orientation, ie inclined orientation, of the flank lines which determine the course of the entrainment elements is also possible for the connection between coupling element 16 and housing. It is also conceivable here, according to further embodiments, not shown, to design the positive connection between the coupling element 18 and the power-carrying component 14 in such a way that the driving elements 22 on the coupling element 18 are arranged on an outer circumference or a partial area thereof and the driving elements 20 on the power-carrying element Component 14 on an inner circumference, in which case the third coupling element 18 would have to be designed as a stepped sleeve, while the corresponding area on the power-carrying component is designed as a hollow shaft. With regard to the implementation of the form-fitting connection between coupling element 16 and housing 12, it is conceivable to design this with respect to the arrangement of the driving elements on the outer and inner circumferences of the housing and coupling element, as shown in FIGS. 5a and 5b, or an embodiment here to choose, which is characterized by an arrangement of the driving elements on the coupling element 18 on an inner circumference, while the configuration or arrangement of the driving elements 19 is provided on an outer circumference on the housing 12. In order to realize the form-fitting connections between the housing 12 and the coupling element 18 as well as the coupling element 18 and the power-carrying component 14, the possible assignments or arrangements of the driving elements on the elements to be brought into operative connection can be combined with one another as desired. This only has an effect on the design of the third coupling element 18, which would then have to be designed with different diameter sections. The specific design depends on the requirements of the application, in particular the available axial installation space and is at the discretion of the responsible specialist. The designs made for the third coupling element with regard to the displaceability can also be transferred to the other coupling elements.

Reference numerals list

1 power transmission unit

2 Rollback prevention

3 vehicle

4 prime mover

5.1, 5.2 wheels

6 entrance

7 exit

8 starting element

9 switching stage

10 disc clutch

11 synchronously switchable, form-fitting coupling

12 housing

13 Area of power flow

14 Performance leading or performance transmitting element

15 stationary component

16 first coupling element

17 second coupling element

18 third coupling element

19 Driving elements on the housing

20 driving elements on the second coupling element

21 Driving elements on the service leading or transferring

element

22 Driving elements on the service leading or transferring

element

23 braking device

24 Input of the transmission

25 Output of the transmission

26 first gear

27.1 - 27.4 additional stages

27.5 reverse gear

28 Output of the starting element Countershaft

actuator

Pressure supply device

face

shell

Partial area forming the outer circumference

Partial area forming the inner circumference

Partial area forming the outer circumference

Partial area forming the inner circumference

Partial area forming the outer circumference

spring unit

transmission

Claims

claims

1. Power transmission unit

1.1 with at least one input and one output;

1.2 with a starting element arranged between the input and the output and a transmission connected downstream thereof, comprising at least one speed / torque conversion device;

1.3 with a housing; characterized by the following features:

1.4 with a rollback prevention device, comprising at least one synchronously switchable positive clutch;

1.5 the synchronously switchable positive coupling is arranged between a stationary component or the housing and a rotatable power-transmitting element or an element rotatably coupled to it in the power transmission unit in a region lying in the power flow between the output of the starting element and the output.

2. Power transmission unit according to claim 1, characterized by the following features:

2.1 the synchronously switchable positive coupling comprises a first coupling element which is at least indirectly connected to the stationary component or the housing or is formed by the latter;

2.2 the synchronously switchable positive coupling comprises a second coupling element which is at least indirectly connected to or is formed by the power-transmitting element or an element connected to it in a rotationally fixed manner;

2.3 first and second coupling elements can be brought into operative connection directly or via a third coupling element;

2.4 the individual coupling elements have positive driving elements which extend over at least a partial area of the respective coupling element.

3. Power transmission unit according to claim 2, characterized in that at least one of the coupling elements for activating or deactivating the synchronously switchable positive coupling is displaceable relative to the one or the other.

4. Power transmission unit according to claim 3, characterized in that the displaceable coupling element is displaceable in the axial direction.

5. Power transmission unit according to one of claims 2 to 4, characterized in that the driving elements on the third coupling element for positive coupling with the other two coupling elements - the first coupling element and the second coupling element - are each arranged on an outer circumferential area of the third coupling element.

6. Power transmission unit according to claim 5, characterized in that the entrainment elements on the other coupling elements - first coupling element and second coupling element - are each arranged on a region of these coupling elements forming an inner circumference.

7. Power transmission unit according to one of claims 2 to 4, characterized in that the entrainment elements on the third coupling element for positive coupling with the other two coupling elements - first coupling element and second coupling element - are each arranged on an inner circumference area of the third coupling element.

8. Power transmission unit according to claim 7, characterized in that the entrainment elements on the other coupling elements - first coupling element and second coupling element - are each arranged on a region of these coupling elements forming an outer circumference.

9. Power transmission unit according to one of claims 4 to 8, characterized in that in each case the areas of the third coupling element carrying a driving elements and forming an inner circumference or outer circumference and the driving elements carrying areas forming an outer circumference or inner circumference of the two coupling elements - first coupling element and second coupling element - are characterized by different diameters.

10. Power transmission unit according to one of claims 4 to 8, characterized in that in each case the driving elements carrying, an inner circumference or outer circumferential areas of the third coupling element and the driving elements bearing, an outer circumference or inner circumference forming areas of the two coupling elements - first coupling element and second coupling element - are characterized by the same diameter.

11. Power transmission unit according to claim 10, characterized in that the driving elements for realizing the connection between the third coupling element and stationary component are formed by the driving elements of the third coupling element for realizing the connection with the power-transmitting component.

12. Power transmission unit according to one of claims 2 to 4, characterized in that the driving elements on the third coupling element for positive coupling with the other two coupling elements - first coupling element and second coupling element - each arranged on an inner circumference and an outer circumference area of the third coupling element are.

13. Power transmission unit according to claim 12, characterized in that the driving elements on the first or second coupling element for positive coupling with the third coupling element an area of the first or second coupling element forming an inner circumference or an outer circumference.

14. Power transmission unit according to one of claims 2 to 13, characterized in that the driving elements on the first and second coupling element and / or the third coupling element viewed in the axial direction from the entrance to the exit are directed straight ahead.

15. Power transmission unit according to one of claims 2 to 13, characterized by the following features:

15.1 the driving elements of two interlocking coupling elements are oriented obliquely in the axial direction from the entrance to the exit;

15.2 the flank lines describing the course of the individual entrainment elements are, viewed in the axial direction from the entrance to the exit in the circumferential direction, oriented in the opposite direction to the direction of rotation of the power-transmitting element in traction operation when transmitting power from the entrance to the exit of the power transmission unit.

16. Power transmission unit according to claim 15, characterized in that the arrangement and alignment of two mutually adjacent driving elements is characterized by an incline.

17. Power transmission unit according to one of claims 15 or 16, characterized in that the flank angle of the driving elements is carried out in a range from 15 ° to 45 ° inclusive.

18. Power transmission unit according to one of claims 14 to 17, characterized by the following features:

18.1 the complementary driving elements of the connection between the first coupling element and the third coupling element and the connection between the second and third Coupling elements are designed differently with regard to their alignment, one of the connections being made via straight driving elements and the other via obliquely aligned driving elements; 18.2 the inclined carrier elements run in the axial direction from the input to the output of the power transmission unit, viewed against the direction of rotation of the drive machine coupled to the input.

19. Power transmission unit according to one of claims 2 to 18, characterized in that for activating the synchronously switchable positive coupling at least one of the coupling elements is displaceable relative to the other.

20. Power transmission unit according to claim 19, characterized in that the third coupling element is displaceable in the axial and / or radial direction relative to the other coupling elements.

21. Power transmission unit according to claim 20, characterized in that the third coupling element is guided on one of the other two coupling elements.

22. Power transmission unit according to one of claims 2 to 21, characterized in that the third coupling element is at least partially designed as a sleeve.

23. Power transmission unit according to one of claims 19 to 22, characterized in that means for fixing are assigned to the displaceable coupling element.

24. Power transmission unit according to claim 23, characterized in that the means for fixing the coupling element are formed by an actuating device assigned to it.

25. Power transmission unit according to one of claims 23 or 24, characterized in that the respective coupling element is designed as a piston or is connected to at least one piston.

26. Power transmission unit according to claim 25, characterized in that the piston is pressure-tight in the housing or the stationary component or on both, the pressure chambers required for acting on the piston being formed by the housing or the stationary component or both.

27. Power transmission unit according to one of claims 23 to 26, characterized in that the actuating device has a pressure supply system, comprising a pressure source which acts on the piston or a first piston on the end face oriented opposite to the displacement direction to reach the engagement position.

28. Power transmission unit according to claim 27, characterized in that a further pressure source acts on the pistons or a second piston on an end face directed towards engagement in the displacement direction.

29. Power transmission unit according to claim 28, characterized in that the further pressure source is formed by the pressure source, which acts on the piston or a first piston on the end face oriented opposite the displacement direction to reach the engagement position, and means for selectively loading the individual piston faces or pistons are provided.

30. Power transmission unit according to one of claims 1 to 29, characterized in that an actuating device is assigned to the synchronously switchable positive coupling.

31. Power transmission unit according to claim 30, characterized in that the actuating device is designed as one of the actuating devices mentioned below: mechanically electrically pneumatically hydraulically electropneumatically electrohydraulically by means of memory metals.

32. Power transmission unit according to one of claims 1 to 31, characterized in that the start-up element is assigned a lock-up clutch or lock-up circuit, forming a start-up unit, which rotatably couples the input to the output of the start-up element, the synchronously switchable positive coupling between the output of the start-up unit and the output of the power transmission unit is arranged.

33. Power transmission unit according to one of claims 1 to 32, characterized by the following features:

33.1 the transmission is designed as a countershaft transmission;

33.2 the countershaft transmission comprises a first countershaft, the input of which is connected to the output of the starting element and the output of which is connected via a first countershaft to at least one further countershaft, which characterizes a switching stage, and which can be connected to the output of the power transmission unit.

34. Power transmission unit according to claim 33, characterized in that the gear train characterizing a gear stage is assigned a switchable clutch for realizing a rotationally fixed connection of the respective gear train with the output of the power transmission unit.

35. Power transmission unit according to one of claims 33 to 34, characterized in that the synchronously switchable positive clutch viewed in the axial direction between the input and the output of the power transmission unit is arranged in front of the first countershaft.

36. Power transmission unit according to one of claims 33 to 35, characterized in that the synchronously switchable positive coupling viewed spatially between the input and the output of the power transmission unit in the installed position, is arranged between the first countershaft and a stationary component or the housing.

37. Power transmission unit according to one of claims 33 to 36, characterized in that the synchronously switchable positive clutch is arranged in the power transmission direction in front of a transmission gear which characterizes the individual switching stages.

38. Power transmission unit according to one of claims 33 to 37, characterized in that the synchronously switchable positive clutch is arranged in the power transmission direction from the input to the output of the power transmission unit in the axial direction behind the individual, characterizing the switching stages.

39. Power transmission unit according to one of claims 1 to 38, characterized in that the transmission comprises a device for reversing the direction of travel and the synchronously switchable positive clutch is arranged in the direction of power transmission from the input to the output of the power transmission unit before the device for reversing the direction of travel.

0. Power transmission unit according to one of claims 1 to 39, characterized in that the synchronously switchable positive clutch is designed as a claw clutch.