Abstract:
A clutch assembly for connecting a shaft to a rotary member mounted on said shaft in a rotationally fixed manner comprises: a sliding sleeve which is rotationally fixed to the shaft, is axially slidably mounted on said shaft and is provided with a first gearing. A clutch body is rotationally fixed to the rotary member and provided with a second gearing which can mesh with the first gearing to connect the shaft and the rotary member in a rotationally fixed manner. And, a locking synchronization unit having a synchronizer ring with a friction surface the ring permitting the speeds of the shaft and the rotary member to be synchronized before the meshing of the first and second gearings. The locking synchronization unit further comprises a locking member which is coupled to the sliding sleeve by a detent groove and to the synchronizer ring in the rotational direction (D) by a pair of locking surfaces. The pair of locking surfaces are situated between the locking member and a synchronizer member, the latter being coupled to the locking member in the axial direction (A) and to the synchronizer ring in the rotational direction (D).

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a clutch assembly for connecting a shaft to a rotary member, such as an idle gear, mounted on said shaft in a rotationally fixed manner, wherein the clutch assembly comprises: a sliding sleeve which is rotationally fixed to the shaft, is axially slidably mounted on said shaft and is provided with a first gearing, a clutch body which is rotationally fixed to the rotary member and provided with a second gearing which can mesh with the first gearing to connect the shaft and the rotary member in a rotationally fixed manner, and a locking synchronisation unit having a synchroniser ring with a friction surface, said ring permitting the speeds of the shaft and the rotary member to be synchronised before the meshing of the first and second gearings, wherein the locking synchronisation unit further comprises a locking member which is coupled to the sliding sleeve by means of a detent groove and to the synchroniser ring in the rotational direction by means of a pair of locking surfaces. 
     Such a clutch assembly is known from DE 10 2005 025 569 A1. 
     Clutch assemblies of the generic type are used in countershaft transmissions of motor vehicles. The countershaft transmissions are herein formed as stepped transmissions with a plurality of gear ratios. Each gear ratio is associated with a set of wheels comprising a fixed wheel and an idle gear. The idle gears are respectively supported at one of the shafts of the transmission and can be connected to the shaft by means of a clutch (to shift into gear) and released therefrom (to disengage the gear). 
     Clutches are nowadays usually formed as synchroniser clutches, in which the speeds of shaft and rotary member are synchronised before establishing a positive locking therebetween. Further, synchroniser clutches are nowadays mainly formed as locking synchroniser clutches in which a locking mechanism provides that the engagement of the gearings of sliding sleeve and clutch body is only enabled when the speeds of the shaft and the rotary member are synchronised. 
     The locking mechanism most used today comprises a locking gearing at the outer periphery of the synchroniser ring. The synchroniser ring is supported at the shaft (or a guiding sleeve attached thereto, which is also referred to as a synchroniser body) to be movable in a restricted range. In a release position, the sliding sleeve gearing can be passed through the locking gearing of the synchroniser ring in order to establish the positive locking with the clutch body. In the locked position, the synchroniser ring is twisted such that the sliding sleeve is prevented to be moved in the axial direction toward the clutch body. The locked position of the synchronizer ring is obtained by frictionally engaging the synchroniser ring with the associated clutch body (or any other associated friction surface) due to the applied axial shifting force. Consequently, the synchroniser ring is driven in the rotational direction and thus into the locked position. Only after synchronisation of the speeds, the friction force is reduced so far that a turning back of the synchroniser ring due to the shifting force is possible, such that the sliding sleeve can be pushed through the gearing of the synchroniser ring, which gearing was turned back into the release position. 
     In this kind of synchronisation, the synchroniser ring has to be produced in a comparatively complex manner. 
     The aforementioned DE 10 2005 025 569 A1 proposes a locking mechanism which is realized by using a pressure piece. 
     Such a pressure piece or stone is often used in synchroniser clutch assemblies to lock the sliding sleeve in a neutral position. In DE 10 2005 025 569 A1, it is now proposed to form the synchroniser ring without a locking gearing at its outer periphery. Contrary thereto, a plurality of wedged surfaces is provided at the inner periphery of the synchroniser ring, which are assigned to corresponding wedged surfaces of the pressure pieces. 
     When applying a shifting force, the sliding sleeve tries to move the pressure piece in the radial direction away from the detent groove, and simultaneously pushes the synchroniser ring in the axial direction against a friction surface (starting synchronisation). Hereby, the synchroniser ring is twisted until the pairs of wedged surfaces engage, such that the wedged surfaces counter-effect a radial pushing away of the pressure piece. Accordingly, the sliding sleeve can no longer be displaced axially and is locked in this way. Only after synchronising the speeds of the shaft and the idle gear, the synchroniser ring can be turned back by the shifting force applied to the sliding sleeve, due to the then decreased friction force, such that the pressure piece can be pushed away in the radial inward direction. Consequently, the sliding sleeve can be further displaced in the axial direction in order to engage with the clutch body. 
     A similar locking mechanism for a synchroniser clutch is known from DE 29 15 965 C2. 
     Also in this kind of synchroniser clutch assembly, however, the synchroniser ring has to be produced in a comparatively complex manner. 
     SUMMARY OF THE INVENTION 
     It is therefore an object underlying the invention to provide a clutch assembly in which the synchroniser ring can be produced cost-effectively while providing an optimised function of the locking mechanism. 
     This object is solved by the aforementioned clutch assembly in that the pair of locking surfaces is formed between the locking member and a synchroniser member which is coupled to the locking member in the axial direction and to the synchroniser ring in the rotational direction. 
     In the inventive clutch assembly, the synchroniser ring can be formed without a locking gearing at its outer periphery, as is provided in the state of the art. In addition, it is possible to form the synchroniser ring also without any other wedged surfaces. It is only required to couple the synchroniser ring with the synchroniser member in the rotational direction. The synchroniser member, in turn, meshes with the locking member in the rotational direction by means of the pair of locking surfaces. 
     Consequently, the synchroniser ring may have a particularly simple construction, since it can be produced by simple manufacturing methods (from metal sheet, as a sintered part etc.). 
     Further, the locking member as well as the synchroniser member can be formed comparatively simple, such that they can be manufactured at low costs. 
     The object is therewith completely solved. 
     In a particularly preferred embodiment, the synchroniser member is supported in the rotational direction with respect to a guiding sleeve connected to the shaft to be movable in a restricted manner between a release position and a locked position, such that the synchroniser member, when in the locked position, prevents a movement of the locking member from the detent groove and thus an axial movement of the sliding sleeve. 
     Basically, it is also conceivable to support the synchroniser ring to be movable in a restricted range with respect to the sliding sleeve. The design of the sliding sleeve and the synchroniser member such that the synchroniser member can be moved between the locked position and the release position enables a further simplification of the formation of the synchroniser ring. 
     According to a further preferred embodiment, the synchroniser ring comprises a recess in which a portion of the synchroniser member is arranged to be coupled with the synchroniser ring in the rotational direction. 
     In this embodiment, the connection of the synchroniser ring and the synchroniser member in the rotational direction occurs through recesses in the synchroniser ring. Such recesses can be produced comparatively easily. The portion of the synchroniser member engaging in the recess may be a protrusion, but may also be a portion of a synchroniser member which is formed as a compact body. 
     It is particularly preferred that the recess of the synchroniser ring is formed as an axial recess. This enables a further simplification of the manufacturing method. 
     The recess of the synchroniser ring, however, can also be formed by two radially or axially protruding noses, between which a portion of the synchroniser member engages. 
     Contrary, it is also possible that the synchroniser ring comprises a protrusion which engages with a recess of the synchroniser member in order to be coupled to the synchroniser member in the rotational direction. 
     According to a further preferred embodiment, the locking member is guided at the sliding sleeve in the axial direction. 
     This embodiment is considered to be an independent invention, irrespective of the provision of a synchroniser member. 
     The axial guidance of the locking member is preferably not only performed when the locking member engages with the detent groove, but also when the sliding sleeve pushed away the locking member in the radial direction, such that the locking member no longer engages with the detent groove. 
     Altogether, a clearly stronger guidance of the components of the clutch assembly can be achieved in this way. 
     It is particularly advantageous that the sliding sleeve comprises a radial recess in which the locking member is axially guided. 
     Herein, the radial recess may be formed by recesses at teeth of the first gearing. Such axial guiding grooves at the inside of the sliding sleeve can be manufactured comparatively easily as far as construction is concerned. 
     According to a further preferred embodiment, the locking member comprises at least one guiding nose which engages with a tooth gap of the first gearing for an axial guidance at the sliding sleeve. 
     The guiding nose can extend in the radial direction beyond a portion of the locking member, which engages with the detent groove of the sliding sleeve. 
     In this way, an axial guidance at the sliding sleeve can be obtained without providing larger recesses at individual teeth of the gearing of the sliding sleeve. Altogether, the sliding sleeve may be formed substantially without any disadvantages in view of its strength. 
     In total, it is further preferred that the locking member is elastically biased in the radial direction with respect to the shaft or the guiding sleeve and is pushed into the detent groove. 
     The biasing may e.g. be performed by a spring which is arranged between the locking member and the shaft or the guiding sleeve. 
     According to a preferred embodiment, the locking member is biased in the radial direction with respect to the synchroniser member and is pushed into the detent groove. 
     Since the synchroniser member is supported at the guiding sleeve anyway, no further means are required at the guiding sleeve for elastically biasing the locking member. 
     According to a particularly preferred embodiment, the locking member comprises a recess for receiving a spring member for realising the elastic biasing. 
     In this way, a spring member, e.g. a coil spring, can be easily mounted and securely guided during operation. 
     It is particularly advantageous if the locking member and the synchroniser member are formed as a pre-assembled unit. 
     The assembly may therewith be clearly simplified. 
     In this context, it is particularly advantageous if the pre-assembled unit comprises springs for elastically biasing the locking member with respect to the synchroniser member. 
     In this embodiment, the locking member, the synchroniser member and the springs form a pre-assembled unit which can be inserted into the guiding sleeve with a low assembly effort. 
     In total, it is further preferred that the locking member and/or the synchroniser member is/are formed as a sintered part. 
     In this way, a cost-effective production is possible. 
     Also the synchroniser ring may preferably be formed as a sintered part. 
     According to a particularly preferred embodiment, the synchroniser member is formed as a bent metal sheet part. 
     In this embodiment, the synchroniser member may serve as a kind of cage for the locking member and possibly also as spring member. 
     Also the locking member can be formed as a sheet metal part or a bent sheet metal part. Further, it is conceivable to also form the synchroniser ring as a sheet metal part. 
     Further, it is conceivable to form the locking member and/or the synchroniser member as a forging. 
     In total, it is further preferred that the clutch assembly comprises a plurality of locking synchronisation units which respectively comprise a locking member and a synchroniser member and are arranged distributedly about the periphery of the clutch assembly. 
     Dependent on the embodiment, the inventive clutch assembly may achieve the following advantages:
         The synchroniser ring can be manufactured clearly simpler and at lower costs; further, the synchroniser ring can be formed ruggedly. The installation space can be reduced.   Since the synchroniser ring does not require a radially protruding collar for the locking gearing, the length of the gearing of the guiding sleeve (at which the sliding sleeve is axially guided) may be longer in the axial direction, such that the guidance of the sliding sleeve is enhanced (reduced lateral buckling); further, the stopper teeth of the sliding sleeve (which limit the axial shifting path of the sliding sleeve with respect to the clutch body) can extend toward the clutch body without clamping. Therewith, the strength for transmitting a torque through the synchroniser ring can be increased.   The locking member and the synchroniser member can be formed identically for different locking synchronisation units. In particular, they can also be formed identically for both sides of the clutch assembly. In other words: The locking member and the synchroniser member can be formed symmetrically with respect to a cross-sectional plane and/or a longitudinal sectional plane.   Further, the synchroniser ring can be formed identically for single and multi cone synchronisations.   The locking mechanism is separated from the merging mechanism, such that the pointing of the sliding sleeve for merging into the clutch body can be freely selected without consideration of a locking angle. Therewith, the merging behaviour is enhanced, in particular by more acute merging angles.   A lifting of the synchroniser ring (e.g. by a pair of lifting wedged surfaces) can be realised comparatively easily. The drag moment can be reduced.   The merging gearing of the sliding sleeve can be formed in one plane, such that the manufacturing costs of the sliding sleeve are reduced.   When forming chamfers at the detent groove, in particular the process of the unlocking step can be influenced appropriately. The so-called “double engagement” occurring upon a premature merging of the sliding sleeve into the clutch body before equal speeds are obtained may therefore be prevented. With such a stepped detent groove (including a chamfer), an underlocking system can be obtained which is able to decelerate a wheel again accelerating. Cold scraping and vibration scraping can be reduced.   It may be prevented that depositions provided at the first gearing of the sliding sleeve contact the synchroniser ring, as it is the case with synchroniser rings having a locking gearing.   The synchroniser ring can be centered due to the connection with the synchroniser member. A centering diameter at the synchroniser ring and at the guiding sleeve may possibly be omitted.       

     It is obvious that the aforementioned features and the features to be explained in the following cannot only be used in the respectively described combination, but also in other combinations or alone, without leaving the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Embodiments of the invention are shown in the drawing and explained in more detail in the following description, wherein 
         FIG. 1  shows a schematic longitudinal sectional view of an embodiment of the inventive clutch assembly; 
         FIG. 2  shows a sectional view along line II-II of  FIG. 1 ; 
         FIG. 3  shows the clutch assembly of  FIG. 1  in a locked position; 
         FIG. 4  shows the clutch assembly of  FIG. 2  in a locked position; 
         FIG. 5  shows the clutch assembly of  FIG. 1  in the moment of unlocking; 
         FIG. 6  shows the clutch assembly of  FIG. 2  in the moment of unlocking; 
         FIG. 7  shows the clutch assembly of  FIG. 1  in the shifted state; 
         FIG. 8  shows the clutch assembly of  FIG. 2  in the shifted state; 
         FIG. 9  shows a perspective sectional view of a further embodiment of the inventive clutch assembly; 
         FIG. 10  shows a perspective sectional view of a further embodiment of the inventive clutch assembly; 
         FIG. 11  shows a perspective sectional view of a further embodiment of the inventive clutch assembly; 
         FIG. 12  shows a schematic illustration of a pre-assembled locking unit in connection with a portion of a synchroniser ring; 
         FIG. 13  shows a sectional view along line XIII-XIII of  FIG. 12 ; 
         FIG. 14  shows an alternative combination of the pre-assembled locking unit including a synchroniser ring; 
         FIG. 15  shows a detailed view XV of  FIG. 14 ; 
         FIG. 16  shows a perspective view of a locking member of an inventive clutch assembly; 
         FIG. 17  shows a perspective view of an alternative embodiment of a locking member of an inventive clutch assembly; 
         FIG. 18  shows a schematic cross-sectional view of a further embodiment of an inventive clutch assembly; 
         FIG. 19  shows a schematic view of a modified detent groove of a sliding sleeve of an inventive clutch assembly; 
         FIG. 20  shows a sectional view corresponding to  FIG. 2  of a further embodiment of an inventive clutch assembly; 
         FIG. 21  shows a sectional view along line XXI-XXI of  FIG. 20 ; 
         FIG. 22  shows a schematic view of a further embodiment of an inventive clutch assembly; 
         FIG. 23  shows a further embodiment of an inventive clutch assembly corresponding to the illustration of  FIG. 2 ; 
         FIG. 24  shows a sectional view along line XXIV-XXIV of  FIG. 23 ; 
         FIG. 25  shows a further embodiment of an inventive clutch assembly corresponding to the illustration of  FIG. 2 ; 
         FIG. 26  shows a schematic view of a synchroniser ring for an inventive clutch assembly; 
         FIG. 27  shows a schematic view of a further embodiment of a synchroniser ring for an inventive clutch assembly; and 
         FIG. 28  shows a schematic view of a further embodiment of a synchroniser ring for an inventive clutch assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIGS. 1 and 2 , a transmission for a vehicle is generally designated with  10 . 
     The transmission  10  comprises an input shaft  12  which is connected to a countershaft  16  through a constant gear set  14  parallel thereto. 
     An output shaft  24  is arranged co-axially with the input shaft  12 . A plurality of shift gear sets  18  is arranged at the countershaft or the output shaft  24 , respectively. In  FIG. 1 , only one shift gear set  18  is shown for a clearer representation, which comprises a fixed wheel  20  connected to the countershaft  16 . The shift gear set  18  further comprises an idle gear  22  which is supported rotatably at the output shaft  24 . 
     A further idle gear  22 ′ is only schematically indicated in  FIG. 1 . 
     It is obvious that the shown transmission assembly adapted for a longitudinal mounting in a vehicle only represents an example. The invention is also applicable for transmissions having different topologies (e.g. for the front-transverse-mounting or as a three shaft transmission). 
     A first embodiment of an inventive clutch assembly is generally designated with  30  in  FIG. 1 . 
     The clutch assembly  30  serves to couple the idle gear  22  or the idle gear  22 ′ to the output shaft  24 . Consequently, the clutch assembly  30  is formed as a clutch pack including two individual clutches. For reasons of simple illustration, the following description only refers to the function of the clutch assembly  30  with respect to the idle gear  22 . It is, however, obvious that the following description is also applicable for the idle gear  22 ′. 
     The clutch assembly  30  comprises a guiding sleeve (also referred to as synchroniser body)  32  which is attached to the output shaft  24  (e.g. by means of an appropriate gearing). The guiding sleeve  32  further comprises an outer gearing which is not shown in detail in  FIG. 1 . 
     A sliding sleeve  34  is supported at the guiding sleeve  32  in a manner to be slidable in an axial direction A. The sliding sleeve  34  comprises—in a manner known per se—an outer radial groove  36  to be engaged with a shift fork or the like. Further, the sliding sleeve  34  comprises an inner gearing  38  at its inner periphery, which in engaged with the outer gearing of the guiding sleeve  32 . 
     The clutch assembly  30  further comprises a clutch body  40  which is fixedly connected to the associated idle gear  22 . The clutch body  40  comprises an outer gearing  42  onto which the inner gearing  38  of the sliding sleeve  34  can be slid on in order to establish a form-fit connection between the shaft  24  and the idle gear  22  in the rotational direction D. Although the guiding sleeve  32  and the shaft  24  on the one hand and the idle gear  22  and the clutch body  40  on the other hand are respectively shown as individual components, the invention also provides that same may be formed integrally. 
     The clutch assembly  30  further comprises a synchroniser ring  44 . The synchroniser ring  44  comprises—in a manner known per se—a friction surface  46  which co-effects with a counter friction surface  48  of the idle gear  22  (or of the clutch body  40  or of an intermediate cone ring). 
     The clutch assembly  30  further comprises a locking member  50  which is supported to be movable in the radial direction R. In the neutral position shown in  FIGS. 1 and 2 , the locking member  50  engages with a detent groove  52  at the inner periphery of the sliding sleeve  34 . As is shown in  FIG. 2 , the locking member  50  is axially guided at the inner periphery of the sliding sleeve  34 . For this purpose, the sliding sleeve  34  comprises an axial guiding groove  53  at its inner periphery. The axial guiding groove  53  is formed between two teeth Z 2 , Z 3  of the inner gearing  38 . An intermediately arranged tooth Z 1  is somewhat retreated in the radial direction, in order to guarantee an axial guidance of the locking member  50  even if the locking member  50  is pushed out of the detent groove  52  (to be described in the following). 
     The clutch assembly  30  further comprises a synchroniser member  54  which is formed as a component separately from the locking member  50  and separately from the synchroniser ring  44 . 
     The clutch assembly  30  further comprises springs  56  which serve to push the locking member  50  outwardly in the radial direction and into the detent groove  52  in the shown neutral position. 
     The synchroniser member  54  is supported at the guiding sleeve  32  and is movable within a restricted range in the axial direction A as well as in the rotational direction D, as is shown in particular in  FIG. 2 . 
     Further, the synchroniser member  54  comprises a reception  58  for the locking member  50 . By means of the locking member reception  58 , the synchroniser member  54  and the locking member  50  are coupled in the axial direction A in a manner substantially free of play. Further, the synchroniser member  54  comprises engaging means  60  which co-effect with engaging means  62  of the synchroniser ring  44 . Due to the engaging means  60 ,  62 , the synchroniser member  54  and the synchroniser ring  44  are coupled in the rotational direction in a manner substantially free of play. 
     Further, the synchroniser member  54  comprises a pushing surface  64  with which the synchroniser ring  44  can be pressed on in the axial direction A in order to establish a friction contact between the friction surfaces  46 ,  48 . In the shown embodiment, the engaging means  60  of the synchroniser member  54  are formed as an axial recess, the axial front face of which forms the pushing surface  64 . The synchroniser ring  44  comprises a conical ring body and portions radially protruding therefrom, which are formed as engaging means  62  and engage with the recess  60  of the synchroniser member  54 . Further, the synchroniser ring  44  is pressed on by these protrusions in the axial direction A. 
     As is shown in  FIG. 1 , the sliding sleeve  34  and the locking member  50  are coupled in the axial direction A through a pair of wedged surfaces  66  which form a part of the detent groove  52 . Further, it is discernible from  FIG. 2  that the locking member  50  and the synchroniser member  54  are coupled in the rotational direction D through a second pair of wedged surfaces  70 . The angle of the first pair of wedged surfaces  66  is in the following referred to as the detent angle  68  and may range e.g. between 30° and 70°, in particular between 40° and 60° and preferably between 50° and 55°. Further, the second pair of wedges surfaces  70  forms an angle between the locking member  50  and the synchroniser member  54 , which angle is referred to as locking angle in the following and may range between 30° and 70°, in particular between 40° and 60°. 
     As is shown in  FIG. 2 , the synchroniser member  54  is supported at the guiding sleeve  32  in a synchroniser member reception  74  to be movable in a limited range in the rotational direction D. In detail, the synchroniser member  54  is movable between a neutral or release position F shown in  FIG. 2  and a locked position S (see  FIG. 4 ). The transition path required for this movement is designated with  76  in  FIG. 2 . Stopper surfaces of the guiding sleeve  32 , against which the synchroniser member  54  abuts in the rotational direction, are designated with  78  in  FIG. 2 . 
     The abutment may also occur between the locking surfaces  70 . 
     The operation of the clutch assembly shown in  FIGS. 1 and 2  is explained in detail in the following with reference to  FIGS. 3 to 8 , wherein  FIGS. 3 and 4  show how the locking means lock the sliding sleeve  34  and prevent a shifting as long as no equality of speeds between the shaft  24  and the idle gear  22  is achieved, wherein  FIGS. 5 and 6  show the process of unlocking (releasing) which is enabled when the friction moment is decreased due to the synchronicity of the speeds, and wherein  FIGS. 7 and 8  show the shifted state of the clutch assembly, in which the idle gear  22  and the output shaft  24  are connected in a form-fit manner in the rotational direction D through gearings  38 ,  42 . 
     When the clutch assembly  30  is actuated based on the neutral or release position shown in  FIGS. 1 and 2  in order to connect the idle gear  22  and the output shaft  24 , an axial force  82  (shifting force) is applied to the sliding sleeve  34  through the shift fork, which pushes the sliding sleeve  34  toward the idle gear  22 . 
     In this context, it has to be assumed that the output shaft  24  and therewith the guiding sleeve  32  and the components synchroniser member  54  and synchroniser ring  44  being connected thereto in the rotational direction in a form-fit manner feature a first speed ω 1 , and that the idle gear  22  has a second, different speed ω 2 . 
     As soon as the sliding sleeve  34  is pushed to the right in  FIG. 3  (which results in a sliding sleeve path  80 ), the locking member  50  is driven in the axial direction by the first pair of wedged surfaces  66 , and also the synchroniser member  54  by the axial coupling therewith, such that the pushing surface  64  presses the synchroniser ring  44  axially on the idle gear  22 . Consequently, the conical friction surfaces  46 ,  48  are frictionally engaged. Due to this, the synchroniser member  54  is driven by the synchroniser ring  44  in the rotational direction D, until it abuts at the stopper surface  78  (see  FIG. 4 ). In this state, the second pair of wedged surfaces  70  is engaged, such that a pressing down of the locking member  50  in the radial direction R is not possible. The shifting force applied through the sliding sleeve  34  is designated with  82  in  FIG. 3 . The radial force applied on the locking member  50  through the first pair of wedges surfaces  66  is designated with  84  in  FIGS. 3 and 4 , the axial force applied to the locking member  50  is designated with  86 . The friction force generated at the pair of friction surfaces  46 ,  48  is schematically shown as  88 , and the friction force generated at the second pair of wedged surfaces  70  is schematically shown as  90 . 
     In  FIGS. 3 and 4 , a so-called locking condition is fulfilled, which prevents a pressing down of the locking member  50 . In the shown clutch assembly, the locking condition is a function of the detent angle  68 , the locking angle  70  and the tribologic properties. Further, the locking condition of course also depends on the friction force  88  applied through the pair of friction surfaces  46 ,  38 . 
     If the speeds have been adjusted to one another (ω 2  approximately equal to ω 1 ), the friction force  88  transmitted through the pair of friction surfaces  46 ,  48  is relatively small, such that the locking member  50  can be pushed downward by the pair of wedged surfaces  66  ( FIG. 5 ). Herein, the synchroniser member  54  is in addition pushed back into the release position F through the second pair of wedged surfaces  70 . The return force required for this process is schematically designated with  92  in  FIG. 6 . 
     In  FIG. 6 , it is further discernible that an axial guidance of the locking member in the axial direction between the teeth Z 2 , Z 3  is still secured, even if the locking member  50  is completely pushed out of the detent groove  52 . The depth of the remaining recess between these two teeth Z 2 , Z 3  of the radial groove used for the axial guidance is schematically designated with  94  in  FIG. 6 . 
     After the locking member  50  was completely pushed out of the detent groove  52 , no axial force is transmitted to the synchroniser ring  44 . The sliding sleeve  34  is in a so-called “free flight phase”, during which it may be possible that the speeds of the output shaft  24  and the idle gear  22  diverge again. This free flight phase, however, can be configured to be relatively short, since it can be designed such that the guidance of the sliding sleeve  34  at the (not shown) outer gearing of the guiding sleeve  32  is positioned near to the clutch body  40 . Based on the inventive embodiment of the clutch assembly  30 , it is further possible to form the pointing of the gearing  38  relatively acute, such that a fast merging into the outer gearing  42  of the clutch body  40  is possible. The shifted state achieved therewith is shown in  FIGS. 7 and 8 . 
     In the clutch assembly  30  described in  FIGS. 1 to 8 , the synchroniser ring  44  does not have a locking gearing. It is also not required to form wedged surfaces at the synchroniser ring for realising the locked condition (except for the optionally provided third pair of wedged surfaces  96 ). The required pairs of wedges surfaces  66 ,  70  are exclusively established between the relatively compact components sliding sleeve  34 , locking member  50  and synchroniser member  54 . Consequently, the synchroniser ring  44  does not have to transmit large locking forces and may therefore be manufactured cost-effectively, e.g. as a sintered part. 
     Also the components synchroniser member  54  and locking member  50  can be manufactured as simple components, e.g. as sintered parts, as metal sheet parts or as forgings. 
     Also the axial guiding groove  53  or the detent groove  52 , which have to be inserted into the sliding sleeve  34 , can be realized with commonly used tools. 
     In the following, modified or alternative embodiments of clutch assemblies are explained on the basis of  FIGS. 9 to 28 . All these embodiments basically correspond to the clutch assembly  30  of  FIGS. 1 to 8  as far as structure and operation are concerned. In the following, only the differences will be explained. 
     In  FIG. 9 , a modified embodiment is shown, in which the engaging means  60 ′ of the synchroniser member are formed as a recess (as in the embodiment of  FIGS. 1 to 8 ), wherein the engaging means  62 ′ of the synchroniser ring  44 ′ are formed as radial protrusions meshing with the recesses  60 ′. In this embodiment, the radial protrusions  62 ′ are produced separately from the cone ring of the synchroniser ring  44 ′ and are subsequently connected thereto. 
       FIG. 10  shows a further alternative embodiment, in which the synchroniser ring  44 ′ comprises a synchroniser ring carrier  110  in which recesses  62 ″ (engaging means) are formed, which engage with axial protrusions  60 ″ of the synchroniser member  54 ″. 
       FIG. 11  shows an embodiment in which the locking member  50 ″′, the synchroniser member  54 ″′ and the springs  56 ″′ are formed as a pre-assembled unit  112 . 
     In detail, the locking member  50 ″′ is supported in the synchroniser member  54 ″′ to be never lost, and the springs  56 ″′ are disposed within the synchroniser member  54 ″′. In addition, protrusions  60 ″′ are formed at the synchroniser member  54 ″′, which engage with recesses  62 ″′ of the synchroniser ring  44 ″′, just like the protrusions  60 ″ of  FIG. 10 . 
     In the embodiment  30 ″′ of  FIG. 12 , the synchroniser member  54 ″′ can be formed as a sintered part or as a bent metal sheet part. 
       FIG. 12  schematically shows the pre-assembled unit  112  of  FIG. 11 , wherein it is also shown that protrusions are formed at the synchroniser member  56 ″′, which prevent that the locking member  50 ″′ detaches from the synchroniser member  56 ″′. 
       FIG. 13  shows a sectional view along the line XIII-XIII of  FIG. 12 . As shown, the synchroniser member  54 ″′ can be formed as a metal sheet part, whereas the locking member  50 ″′ can be formed as a compact component, e.g. as a sintered part. 
       FIG. 14  shows a modification of the embodiment  30 ″′ of  FIGS. 11 to 13 , wherein an axial protrusion having a recess  60   IV  is formed at the synchroniser member  54   IV  of the pre-assembled unit  112   IV , into which a protrusion  62   IV  of the synchroniser ring  44   IV  engages (similar to the embodiment of  FIGS. 1 to 8 ). 
       FIG. 15  shows a detailed view XV of  FIG. 13  and shows e.g. a relatively large coverage between the engaging means  60   IV ,  62   IV . 
       FIG. 16  shows an embodiment of a locking member  50   V . It is discernible in the illustration of  FIG. 16  that a locking member  50   V  comprises wedged surfaces  114  arranged oppositely in the axial direction A, which form part of a first pair of wedged surfaces  66 . It is further discernible that the locking member  50   V  comprises second wedged surfaces  116  arranged oppositely in the rotational direction D, which respectively form a part of the second pair of wedged surfaces  70 . 
     In  FIG. 17 , a variation of a locking member  50   VI  is shown, which comprises guiding noses  118  respectively extending in the axial direction A at its ends opposing in the rotational direction D, which guiding noses protrude in the radial direction R with respect to an upper side of the locking member. 
     The guiding noses  118  are configured to engage with tooth gaps in the inner gearing  38 , as is shown as an example in  FIG. 18 . 
     With this embodiment, the stability of the axial guidance can be enhanced considerably, since a guidance depth increase  119  results in the radial direction, which is schematically indicated in  FIG. 18 . 
     In this embodiment, all teeth Z of the sliding sleeve  34  may have the same height, i.e. be arranged without any retreated teeth, such that the inner diameter of the sliding sleeve  34  can be substantially constant (as it is schematically indicated in  FIG. 18  by a dashed inner diameter). 
       FIG. 19  shows a modified embodiment of a detent groove  52   VII . The detent groove  52   VII  comprises wedged surfaces  122  which form a part of the first pair of wedged surfaces  66 . At the transitional area from the wedges surfaces  122  to the axially extending gearing  38 , chamfers  124  are provided which have a chamfer angle  120  which is considerably smaller than the detent angle  68 . The chamfer angle may e.g. range between 5° and 40°, in particular between 10° and 30°. 
     With these chamfers  124 , an underlocking system can be generated during unlocking. In other words, this means that the synchroniser ring  44  is still pushed against the idle gear  22  to a certain extent, whereas the edge of the locking member is pushed along the chamfer. The anew acceleration of the idle gear  22  may thus be prevented more easily. In other words, the free flight phase can be shortened. However, the chamfer angle  120  will preferably be selected such that no locking condition can be actuated by same. 
       FIG. 20  shows an illustration corresponding to  FIG. 2  of a further embodiment of an inventive clutch assembly  30   V . The synchroniser member  54   V  is formed as a bent metal sheet part. The locking member  50   V  comprises a recess  130  at its radial inside for receiving and guiding the springs  56   V  (in particular in the shown embodiment as a coil spring). 
       FIG. 21  shows a sectional view along the line XXI-XXI of  FIG. 20  and shows how engaging means  62   V  can be formed at the synchroniser ring  44   V , which engage with a recess of the synchroniser member  54   V . 
       FIG. 22  shows a further embodiment of an inventive clutch assembly  30   VI , wherein the springs  56   VI  are formed as a kind of plate spring or the like. 
       FIGS. 23 and 24  show a further alternative embodiment of an inventive clutch assembly  30   VII , wherein the basic structure and operation are similar to that of the clutch assembly  30   V  of  FIGS. 20 and 21 . In the clutch assembly  30   VII , the synchroniser member  54   VII  is, however, not formed as a sheet metal part, but as a compact component (e.g. a sintered component or a forging). 
       FIG. 25  shows a further embodiment of an inventive clutch assembly  30   VIII  wherein, similar to the embodiment of  FIG. 22 , a plate spring is used as spring  56   VIII . It is obvious that no recess has to be provided at the radial inside of the locking member  50  when using a plate spring. 
       FIGS. 26 to 28  show different embodiments of synchroniser rings which are suited to be used in the inventive clutch assembly. In particular, the synchroniser rings differ from those of the state of the art in that they do not comprise a locking gearing. The engaging means are partly formed as radial protrusions  62   IX , alternatively as axial recesses  62   X  or as axial protrusions  62   XI . It is obvious that preferably a plurality of the shown engaging means are distributed about the periphery of the respective synchroniser ring; preferred is a number of three engaging means per periphery.