Abstract:
A method and apparatus for producing clutch bodies, which are suitable for synchronizer systems and provided with teeth or tooth sections, from a blank uses and includes at least one embossing stage, composed of embossing segments and an anvil, for embossing roofs and troughs between root and tip circles into an upper face of the blank, and transfer means for transporting the blanks, First embossing segments form a first section and second embossing segments form a second section for sequential embossing within the at least one embossing stage, wherein the first embossing segments first emboss a first section, then return in relation to the second embossing segments, and thereafter the second embossing segments emboss the second section, wherein the second embossing segments are disposed next to each other in an annular arrangement, and the second embossing segments are designed to be axially movable relative to the first embossing segments of the first section.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a device for producing clutch bodies, which are suitable for synchronizer systems and provided with teeth or tooth sections (both of which my be referred to simply as “teeth”), from a blank using at least one embossing stage, composed of embossing segments and an anvil, for embossing roofs and troughs between the root and tip circles into an upper face of the blank, and transfer means for transporting the blanks. 
     The invention further relates to a method for producing clutch bodies, which are suitable for synchronizer systems, from a blank using an embossing stage, which comprises at least embossing segments and an anvil and in which troughs and roofs in the edge region close to the circumference arranged next to each other in a ring-like manner are introduced into the upper face of the blank by way of embossing along a root circle and tip circle of the future teeth or tooth sections. 
     A method for producing stamped parts, in particular synchronizer rings, clutch bodies or clutch plates, is known from EP 2 263 812 A1 in which, in one method step, the strip stock to be worked is clamped between the hold-down elements of a fine blanking tool, and in a further method step at least the teeth are embossed. In a first process step, an impact pre-embossing step is carried out on the strip stock at least in the region of the teeth that are to be cut out later, and subsequently the fine blanking method step is carried out in conjunction with an impact extrusion step on the strip stock. The teeth are formed by way of a fine blanking operation and subjected to impact extrusion at the same time, during which they are displaced into a free volume created by way of pre-embossing. 
     Impact pre-embossing, which is nothing other than embossing, forces a change in the shape of the strip stock, preserving the cohesion and volume of the material. 
     This is associated with the disadvantage that stresses or compressions are created in the embossing region of the strip stock as a result of the changes in shape and geometry, which can impair the flatness of the strip to be cut and the dimensional accuracy of the future teeth. 
     Moreover, DE 2 222 080 A1 describes a method and a die for producing clutch bodies for synchromesh gears comprising teeth, which have a tooth profile having roof-like axial displacement surfaces on the flank side and stepped head surfaces on the end face side, forming stop lugs, for engaging an associated selector sleeve. The teeth are initially fine blanked, and then the tooth profile is embossed. For this purpose, the stamped teeth are in each case pre-embossed in a die comprising a hollow mold corresponding to the tooth profile and subsequently, with the die closed, finished by way of a displacement punch that is moved into the hollow mold, filling the hollow mold. 
     This known method is very complex since the teeth must be fed consecutively to the die, or each tooth must be assigned a dedicated die. In addition, the teeth must be stamped in an undersized dimension, so that flawless filling of the hollow mold is achieved with the required fine dimension. 
     SUMMARY OF THE INVENTION 
     With this prior art in mind, It is the object of the invention to provide a device and a method for producing clutch bodies that are suitable for synchronizer systems and provided with teeth or tooth sections, which considerably improve the trueness to shape and dimensions and the precision of clutch bodies, while also increasing cost effectiveness and avoiding rework. 
     The solution according to the invention is based on the finding that the change in shape and geometry created by pre-embossing is thereby avoided and a planar blank that is substantially free from stresses for the subsequent production of teeth is achieved. 
     This is made possible in that the embossing segments form a first section and the embossing segments form a second section for sequential embossing within the embossing stage, wherein the embossing segments first emboss the section, then recede in relation to the embossing segments, and thereafter the embossing segments emboss the section, wherein the embossing segments are disposed next to each other in a shared annular arrangement, and the embossing segments are designed so as to be axially movable relative to the embossing segments of the first section, and the device moreover comprises the following: 
     a) a trimming stage for cutting the troughs free to form tooth bodies that project upwardly at the end face side on the blank and have tooth flanks and roofs; and 
     b) an undercutting and shaping stage for creating undercuts in the tooth flanks and shaping the roofs of the tooth body to the net shape by way of embossing punches and a shaping anvil cooperating with the embossing punches. 
     According to a preferred embodiment of the device according to the invention, the roofs together with troughs of the first section and second section form a shared forming region, which is disposed between the root and tip circles of the future teeth close to the edge in the blank. 
     The sequential stepped introduction of roofs and troughs in the region close to the edge of the blank ensures even outflow of the material volume displaced by embossing in the direction of the edge of the blank, and prevents unevenness of the blank. 
     In a further embodiment of the invention, the first section of embossing segments through the 1st, 3rd, 5th and nth embossing segment and the second section of embossing segments through the 2nd, 4th, 6th and n-1 th embossing segment form the annular arrangement, the diameter of which corresponds to the tip circle of the future teeth, wherein the embossing segments of the first section can be filled by at least one filler piece so that clutch bodies having different numbers of teeth and configurations can be created. 
     According to a further embodiment of the invention, the embossing segments of the first and second sections each comprise a shaft having an embossing foot, which includes embossing surfaces having identical shapes and dimensions and a roof ridge, wherein the roof ridge is oriented perpendicularly to the root circle and tip circle. 
     In a further embodiment of the device according to the invention, the shafts of the embossing segments of the first and second sections are provided with hammer head-like trapezoidal heads, which have protrusion-like shoulders with respect to the shafts, wherein the shoulders of the movable embossing segments limit the axial movement on the inner lower holding plate, and the head is laterally guided by cut-outs that are introduced on the outer circumference of the inner upper holding plate and spaced by teeth, and the shoulders of the fixed embossing segments are held on the teeth of the inner upper holding plate in a force-fit manner by a pressure plate, so that the fixed embossing segments are fixed with respect to the movable embossing segments. 
     It is furthermore advantageous that a pressure piece is assigned to each of the movable embossing segments of the section for transmitting the axial movement, the pressure piece being operatively connected to a pressure piece ring on which pressure pins are evenly distributed, multiple pressure pins being combined to form a group under a shared bridge, which in each case maintain the force fit with the embossing segments by way of a pressure piece. 
     In a further preferred embodiment of the device according to the invention, at least one cutting punch, a die plate and an ejector are provided in the trimming stage, the geometries of which are adapted to the tooth flank shape of the future teeth. 
     The trimming stage ensures that the troughs between the root and tip circles are cut free from material to such an extent that in each case two adjoining roofs, together with the respective sheared edges of the 1st section and 2nd section, can form a tooth body on the end face of the blank, without necessitating complex forming/impact extrusion, so that no stresses generated by forming are introduced into the tooth region of the blank. 
     According to a further preferred embodiment of the device according to the invention, a sleeve-like embossing the is provided for undercutting and shaping the cut-free tooth body in the undercutting and shaping stage, the inner wall of the embossing the being provided with recesses between the root and tip circles disposed parallel to the die axis, which are positioned so that they are associated in each case with the cut-free troughs, wherein embossing punches are disposed in the recesses, which comprise shafts having conically increasing cross-sections in the direction of movement for undercutting the tooth flanks of the tooth body and a roof-like head for shaping the roof shape, and a shaping anvil is provided, the shaping surface of which is adapted to the roof shape and geometry of the teeth. 
     In a further preferred embodiment of the invention, the embossing punches are held radially by holding plates and a disk-shaped pressure pad disposed on top of each other in the embossing the perpendicular to the die axis, wherein the embossing punches have a support side that faces the end faces of the pressure pad and holding plates. 
     In a preferred embodiment of the invention, a pressure piece ring is associated with the embossing punches at the foot end and is held in force fit with a the pressure plate by way of pressure pins, so that the desired net shape and geometry can be imparted to the tooth flanks. 
     The embossing punches have a prismatic elongated shape for this purpose, which is adapted to the tooth flank shape, wherein the support side is provided with protrusions for supporting or for holding the holding plates and the pressure pad. 
     The object is further achieved by a method comprising the following steps: 
     a) introducing roofs and troughs by way of a first embossing step, in which the roofs together with the troughs are positioned at equal distances from each other in an annular arrangement, and by way of a second roofs and troughs embossing step following the first embossing step, in which the distances in the annular arrangement are filled with roofs and troughs, wherein the first embossing step and the second embossing step are carried out in a single embossing stage; 
     b) trimming the troughs to remove a material region at the respective lowest points thereof, so that tooth bodies are created at the end face of the blank along the root circle having tooth flanks and roofs without embossing; and 
     c) undercutting the tooth flanks by way of embossing using embossing punches and shaping the roof shape of the roofs by way of a shaping anvil that is adapted to the roof shape. 
     Further advantages, features and details of the invention will be apparent from the following description with reference to the accompanying drawings. 
     The invention will be described in more detail hereafter based on the example of producing a clutch body having outer teeth. It goes without saying that the invention also covers synchronizer parts, parts having roof-shaped teeth, or clutch parts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIGS. 1 a  and  b    show views of a conventional clutch body; 
         FIGS. 2 a  to 2 f    show schematic illustrations of the sequence of the production of the clutch body using the method according to the invention; 
         FIG. 3  shows a perspective view of the embossing stage of the device according to the invention; 
         FIG. 4 a    shows a perspective illustration of a bottom view of the embossing stage comprising a guide plate, without the upper block; 
         FIG. 4 b    shows a perspective illustration of a top view of the embossing stage comprising a guide plate, without the upper block; 
         FIG. 4 c    shows an exploded view according to  FIG. 4   b;    
         FIGS. 5 and 6  show annular arrangements of the fixed and movable embossing segments of the embossing stage; 
         FIG. 7  shows a perspective illustration of an exploded view of the outer guide of the embossing segments; 
         FIG. 8  shows a section along line VIII-VIII from  FIG. 7 ; 
         FIG. 9  shows a perspective illustration of the inner guide of the movable embossing segments; 
         FIGS. 10 a  and 10 b    show perspective views of a fixed and a movable embossing segment; 
         FIG. 11  shows a perspective illustration of one example of even pressure application of the movable embossing segments comprising filler pieces; 
         FIG. 12  shows a perspective illustration of the assembly of the embossing anvil of the embossing stage on the lower block of the device according to the invention; 
         FIG. 13  shows a perspective view of the undercutting and shaping stage of the device according to the invention; 
         FIG. 14  shows a perspective view of the cavity side of the undercutting and shaping stage on the lower block of the device according to the invention; 
         FIG. 15  shows a perspective illustration of the embossing die of the undercutting and shaping stage, without the upper block; 
         FIG. 16  shows a view of an embossing punch; 
         FIG. 17  shows a section according to line B-B from  FIG. 14 ; and 
         FIG. 18  shows a detailed view of the inner guide of the embossing punches. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 a  and 1 b    show one example of a clutch body  1  for a synchromesh gear. This clutch body includes cogging having teeth  2 , which comprise recessed tooth flanks  3 , roof surfaces  4  converging in a ridge  5 , and a flattened head surface  6  (see  FIG. 1 b   ). In  FIG. 1 a   , the tip circle KK and the root circle FK of the teeth are identified. 
       FIGS. 2 a  to 2 f    show the essential sequence of the method according to the invention for producing such a clutch body. 
     In a first step (see  FIG. 2 a   ), a blank  8  is cut out of a flat strip  7 , wherein the diameter D of the blank  8  has an undersized dimension that is adjusted to the change in shape resulting from embossing. Cutting out takes place by way of a known fine blanking tool, which essentially comprises an upper part having a guide or knife-edge ring plate, a cutting punch and an ejector, and a lower part having a the plate and an ejector. Further representation may thus be dispensed with. 
     By a transfer means, which is not shown in more detail, the blank  8  is fed to the next process step, the embossing stage P, in which in a first embossing step roofs  11  that are spaced apart from each other by distances  10  are impressed in the region of the upper face  9  of the bank  8  dose to the edge between the tip circle KK and the root circle FK. The roofs  11  disposed next to each other in each case converge in troughs  12 , wherein the distances  10  are dimensioned so that the lengths  1  and widths b correspond to two converging roofs  11 . 
     In a second embossing step following the first embossing step, the distances  10  are provided with further roofs  11  connected to troughs  12  (see  FIG. 2 b   ). Along the region dose to the edge, this creates a self-contained, tooth ring-like forming region that is oriented vertically in the direction of the upper face of the blank  8 , wherein the tooth tips  13  are formed of a roof  11  generated in the first embossing step and a roof  11  embossed in the second embossing step as the distances  10  are closed, and the ridges  14  of the roofs  11  are located in the plane of the upper face of the blank  8  and delimited by the root circle FK. The special feature of sequential embossing of the first and second sections is that the two embossing steps are carried out in a single forming stage P. 
     The position and shape of the toothed ring-like forming region U is shown in  FIG. 2 c   . It is clearly apparent that the ridge  14  is created by the roof  11  that is generated in the first embossing section abutting a roof  11  that is generated in the second embossing section. The troughs  12  in each case represent the lowest region of the adjoining roofs  11  which is formed by a surface F disposed parallel with respect to the upper face of the blank  8 . 
     In the trimming stage B (see  FIG. 2 d   ), which is the subsequent process step, the material of the forming region U beneath the surface F is cut free, so that tooth bodies  15  are created along the root circle FK at the end face S of the blank  8  without embossing. The tooth bodies  15  are formed by the tooth flanks  16 . 1  and  16 . 2  and roof surfaces  17 . 1  and  17 . 2  each converging at the ridge  14 . 
     In the process step of the undercutting and shaping stage HK (see  FIGS. 2 e  and 2 f   ), the tooth flanks  16 . 1  and  16 . 2  of adjoining tooth bodies  15  are formed in a first sub-step by way of an embossing or undercutting punch  63  (see  FIG. 17 ), which creates undercuts in the tooth flanks  16 . 1  and  16 . 2  at an angle α of 5°, for example. The roof surfaces  17 . 1  and  17 . 2  are then shaped in a second sub-step by a shaping anvil  74  (see  FIG. 18 ) that is adapted to the future roof shape, so that the final tooth shape on the tooth body  1  is created. 
     Reference is now made to  FIGS. 3 to 12 .  FIG. 3  shows a perspective view of the embossing stage P of the device according to the invention, The embossing stage P comprises an upper part  18  and a lower part  19 . The upper part  18  includes an upper block  20  and a guide plate  21 , on the lower face of which a guide  22  having a guide insert  23  is provided for guiding and holding active action elements (see  FIGS. 4 a  to 4 c    and  FIG. 7 ). An annular arrangement of individual embossing segments  24  and  25  is located in the guide insert  23 , which will be addressed in more detail in  FIG. 5 . The assembly of embossing segments  24  and  25  is held on the guide plate  21  by a guide holding plate  26 , a pressure plate  27 , a spacer ring  32 , a lower pressure plate  28 , and an intermediate plate  29 . 
       FIGS. 5 and 6  show the annular arrangement of the embossing segments  24  and  25 . The embossing segments  24  are fixed with respect to the embossing segments  25  and disposed offset from each other by gaps  30 . As is shown in  FIG. 6 , the embossing segments  25 , which are designed to be axially displaceable with respect to the embossing segments  24 , are inserted into the gaps  30 . The dimensions of the gaps  30  are matched to the widths b and lengths l of the roofs of the forming region U. The number of embossing segments  24  and  25  in the annular arrangement is dependent on the number of teeth  2  desired on the clutch body  1 . If only tooth sections are required on the periphery of the clutch body  1 , the annular arrangement is filled with filler pieces  31 , as is illustrated in  FIG. 6 . 
       FIG. 7  shows an exploded view of the outer lower guide of the annular arrangement of the embossing segments  24  and  25 , which is formed from the guide insert  23 , spacer rings  32 ,  33 , an outer central holding plate  34 , and an outer upper holding plate  35 . At the wall sections thereof facing the embossing segments  24  and  25 , the guide insert  23  and the upper holding plate  35  are provided with axially extending groove-shaped regions for the embossing segments  24  and  25 . 
       FIG. 8  illustrates the inner guide of the embossing segments  24  and  25  in a section along line A-A of  FIG. 7 . The embossing segments  24  and  25  are guided along the shafts  36  thereof, on the inside, by the ejector  37 . 
     As is apparent from  FIG. 9 , the shoulder  39  of the axially displaceable embossing segment  25  formed with respect to the shaft  36 , at the head  38 , is seated on a ring  40  associated with the ejector  37  in the lower end position. The shoulder  39  thus limits the axial movement in the manner of a stop, The head  38  of the embossing segment  25  is seated in the toothed ring-like cut-outs  41  of the inner holding plate  42 , so that the embossing segment  25  is radially secured during the axial movement thereof. On one side, the embossing segments  24  are seated, by way of an inner shoulder  44 . 1  formed at the respective head  43 , on the teeth  45  of the inner holding plate  42  and, on the other side, they are secured on the outer shoulder  44 . 2  of the head  43  by the outer holding plate  35 , wherein the head surfaces of the embossing segments  24  are supported on the pressure plate  27 , so that the embossing segments  24  are fixed and can only carry out the embossing movement thereof during a downward movement of the upper block  20 . The heads  43  of the embossing segment  24  protrude a certain degree in relation to the heads  38  of the embossing segments  25 , this degree being matched to the axial travel of the embossing segments  25 , so that, initially all movable embossing segments  25  of section B, and subsequently all fixed embossing segments  24  of section A, engage the blank  8  supported on an embossing anvil  57 . 
     In other words, in the annular arrangement, the movable embossing segments  25  form a shared section B made of the 2nd, 4th, 6th and nth embossing segments of the embossing segments  25 , and the fixed embossing segments  24  form a shared embossing segment A made of the 1st, 3rd, 5th to n-1 th embossing segments of the embossing segments  24 . The fixed and movable embossing segments  24  and  25  can form a completely closed annular arrangement, as well as one that is supplemented by filler pieces  31 , so that clutch bodies  1  having different numbers of teeth and configurations can be created. 
     All embossing segments  25  operate simultaneously in the first embossing section A and impress the roofs  11  into the surface region of the blank  8  close to the edge between the tip circle FK and the roof circle KK, the roofs converging in the troughs  12 , and in each case, two roofs  11  together with the trough  12  thereof are spaced from neighboring roofs by a gap  10 . Likewise, in the second embossing section B, the fixed embossing segments  24  emboss the roofs  11  together with troughs  12  into the gaps  10 , so that a closed forming region U close to the edge is formed on the blank  8 , which is formed of roofs  11  and troughs  12  disposed next to each other in a toothed ring-like manner and oriented in the direction of the upper face of the blank  8 . 
       FIGS. 10 a  and 10 b    show the designs and shapes of the embossing segments  24  and  25 , according to which the shaft  36  and the embossing foot  46  of the two embossing segments  24  and  25  have the same shapes and dimensions. The embossing foot  46  has roof-like embossing surfaces  47 , which converge in a ridge  48 . The ridge  48  of the embossing foot  46  is disposed so as to end up seated vertically between the root circle FK and the tip circle KK and corresponds to the position of the trough  12 . 
     The shoulder  39  of the embossing segment  25  is considerably deeper than the inner shoulder  44 . 1  of the embossing segment  24 , so that the head  38  of the embossing segment  25  is held securely in the cut-out  41  of the inner holding plate  42 . The two heads  38  and  43  have a slightly tapered shape toward the center of the root circle FK or tip circle KK, so that the embossing segments  24  and  25 , when disposed next to each other, can form a closed annular arrangement. 
       FIG. 11  shows pressure application of the movable embossing segments  25 , which are acted upon in accordance with the annular arrangement of the embossing segments by pressure pieces  49  that are in force fit with a pressure piece ring  50 , on which pressure pins  51  are evenly distributed. Three pressure pins are combined respectively under a bridge  52  and are subjected to pressure by a hydraulic system, which is not shown in greater detail, by way of a pressure piece  53  so as to carry out a axial movement preceding that of the fixed embossing segments  24  in order to sequentially emboss the roofs  11  and troughs  12  in the region of the blank  8  close to the edge. 
       FIG. 12  shows the lower part  19  of the embossing stage P comprising the lower block  54 , which at the upper face thereof facing the upper block  18  carries a cavity frame  55 . A cavity insert  56  is inserted into the cavity frame  55 , in which pressure can be applied to an embossing anvil  57  of the embossing stage P via a pressure plate, which is not shown in greater detail, to absorb the embossing forces. The embossing anvil  57  has a planar circular shape, the diameter of which is matched to the diameter D of the blank  8 . 
     Reference is now made to the trimming stage BS of the device according to the invention. The trimming stage BS is essentially composed of a cutting punch accommodated in an upper part, a guide plate or knife-edge ring plate, an ejector and corresponding pressure pins, and a die plate disposed in a lower part, an ejector, and pressure pins. Such a system corresponds to the prior art and therefore the design need not be illustrated in more detail. It goes without saying that the geometries and shapes of the cutting punch and of the die plate are matched appropriately for cutting the troughs  12  free. 
       FIGS. 13 to 18  now describe the undercutting and shaping stage HK device according to the invention in more detail. 
       FIG. 13  shows a perspective view of the undercutting and shaping stage HK, which similarly to the embossing stage P is composed of an upper part  18  and a lower part  19 . The lower block  54  of the lower part  19  carries a cavity frame  58 , in which a cavity insert  59  is inserted, which accommodates an embossing die  60  (see  FIG. 14 ). 
     As is shown in  FIG. 15 , the embossing die  60  has a sleeve-like design. Prismatic cut-outs  62 , in which embossing punches  63  can be axially guided, are introduced into the inner wall  61  of the embossing die  60  in the direction of the die axis LA. The cut-outs  62  are disposed so that they correspond to the respective cut-free troughs  12  on the blank  8 , so that the embossing punches  63  can each work the tooth flanks  16 . 1  and  16 . 2  of two adjoining tooth bodies  15 . 
       FIG. 16  shows an embossing punch  63 , which has an elongated prismatic shaft  64  having a head  65  and a foot  66 . The head  65  has a head surface KF, the shape and geometry of which correspond to the troughs  12  formed from the roofs  11 . The shaft  64  has a cross-section Q that decreases slightly from the foot  66  to the head  65 , so that a conicity is created across the length of the shaft. The conicity is matched to the desired undercutting angle α of the tooth flanks  16 . 1  and  16 . 2 , so that the tooth flanks  16 . 1  and  16 . 2  of the tooth body can be deformed in the desired range by facing lateral faces  75   a ,  75   b  of the shaft  64 . 
       FIG. 17  shows a section along line B-B of  FIG. 15 , which illustrates the inner support of the embossing punches  63  in the embossing die  60 . The feet  66  of the embossing punches  63  are seated on a pressure piece ring  68 , which is in turn attached to a cavity pressure plate (not shown in detail). A pressure pad  69 , holding plates  70  and  71 , and a pressure plate  72  for the pressure pad  69  are part of the inner radial support and guidance. 
     With reference to  FIG. 17  in conjunction with  FIG. 16 , the side of the shaft  64  facing the pressure pad  69  and the holding plate  71  has protrusions  73 , on which the pressure pad  69  and the holding plate  71  are seated. 
       FIG. 18  shows a sectional illustration through the embossing die  60  forming part of the lower block  19  and the annular shaping anvil  74 , which forms part of the upper block  18  and has a shape that is adapted to the future roof shape of the teeth  2 , on the side thereof facing the embossing die  60 . 
     The blank  8 , which is cut free in the troughs  12  and provided with tooth flanks  16 . 1  and  16 . 2 , is located between the embossing die  60  and the shaping anvil  74  so that, during the feed motion, the embossing punches  63  enter the cut-free region of the tooth bodies  15  with the lower block  54  and thereby undercuts the tooth flanks  16 . 1  and  16 . 2  in the desired angular position, while the shaping surface of the shaping anvil  74  at the same time creates a shaped roof shape on the tooth.