Synchronizer clutch assembly

Abstract: A synchronizer clutch assembly (10) for a transmission comprising a synchronizer hub (12) carried by a torque delivery shaft (14) and including a clutch member carried by a gear (26,28) forming a part of the transmission gearing and a synchronizer blocker ring (42,44). A C-shaped spring member (60) is positioned in the inner circumference of the rim portion (66) of the clutch hub (12) and has a plurality of lugs (70,72,74) which extend through openings (80) in the hub (12). The shiftable clutch sleeve (22) has ramped ridges (91,92) engageable with the lugs (70,72,74) on the spring member (60) to compress the lugs (70,72,74) radially inwardly. The blocker ring (42,44) has a surface (43,45) to frictionally engage a surface (34,38) of the gear (26,28) upon movement of the clutch sleeve (22) toward an engagement position until the rotary motion of the gear (26,28) is brought into synchronism with the rotary motion of the shaft (14).

Description: The present invention relates to automotive transmissions and more particularly to synchronizer clutches for controlling changes in transmission gearing. Synchronizer clutch assemblies for manual transmissions typically include an intermediate torque transfer shaft situated between a torque input shaft and a torque output shaft. Located in parallel disposition with respect to the intermediate shaft is a cluster gear assembly. Torque delivery gears of different pitch diameters are positioned adjacent the intermediate shaft, and a synchronizer clutch assembly is disposed adjacent one of the gears or between two adjacent gears. The synchronizer clutch assembly functions to drivably connect the torque delivery gears for rotation and unison or to connect one or both of the gears selectively to the intermediate shaft. The synchronizer clutch assembly synchronizes rotary motion of the gears, one with respect to the other, or rotary motion of one or both of the gears selectively with respect to the intermediate shaft prior to the establishment of a driving connection between the rotary members. Synchronizer clutch assemblies for manual transmissions are in US-A-2221900 and US-A-3366208. In the '900 patent, a synchronizer clutch hub is splined to the intermediate shaft at a location between two gears of different pitch diameter. A clutch sleeve with internal clutch teeth is mounted for axially sliding movement on the synchronizer hub. The gear to be synchronized with respect to the shaft carries external clutch teeth as well as an external clutch surface. A synchronizer clutch blocker ring is disposed between the sleeve and external clutch teeth to the gear. The blocker ring is formed with an internal cone surface adapted to engage the external cone surface of the gear. Various spring members are known which are secured to or in cooperative engagement with the blocker ring and engageable by the clutch sleeve as the sleeve is moved toward the gear to be synchronized. As the spring elements are compressed, a blocker ring cone clutch engaging force is created which energizes the friction cone clutch and causes the synchronizer blocker ring to index annularly relative to the synchronizer hub. Spring members which are secured to or operatively interconnerted with the blocker ring are disclosed in US-A-3700083, US-A-4660707, US-A-4828087 and US-A-5531305. DE-A-3225201 discloses a synchroniser clutch assembly according to the preamble of claim 1 for a manual transmission having at least one torque transfer gear and a torque delivery shaft, which clutch assembly comprises a clutch hub which is in use secured to an input shaft; a clutch sleeve secured to said hub and adapted for axial shifting movement relative to said hub, said clutch sleeve having a plurality of clutch teeth; a blocker ring which is in use positioned between the transfer gear and said hub, said blocker ring and said gear having engageable friction clutch surfaces; and a spring extending about the blocker ring and having a plurality of projecting portions engageable by said clutch sleeve teeth as said sleeve is moved toward said blocker ring, whereby a clutch surface engaging force is developed on said blocker ring by said spring member. More particularly, the spring is a wire spring which is carried on the outer periphery of the blocker ring is shaped as a split ring with ends bent to extend in the axial direction, i.e. out of the plane of the ring, and arranged to extend along recesses provided in the inner periphery of the clutch sleeve over substantially the full length of the sleeve. The purpose of these axially directed ends is to prevent the ring from expanding radially outwards, e.g. under the influence of centrifugal forces, and possibly moving into a locking position in which engagement of the associated gear would no longer be possible. The need to shape the spring by bending wire and to orientate and assemble the spring relative to the sleeve and blocker ring have the disadvantage of complicating manufacture. Additionally, the positioning of the spring around the blocker ring limits the diameter of wire which may be used to manufacture the spring, since the portions of the spring which are between the radial projections and abut against the outer periphery of the blocker ring must not interfere with the teeth on the inner periphery of the clutch sleeve as the sleeve moves towards the gear. This limitation on the diameter of the wire in the spring limits the stiffness of the spring and therefore the range of shift characteristics that can be achieved with the assembly. The bent wire spring is also fragile and susceptible to being bent out of shape during assembly of the synchroniser system. In accordance with the present invention as claimed, there is provided a synchronizer clutch assembly for a manual transmission having at least one torque transfer gear and a torque delivery shaft, said clutch assembly comprising a clutch hub which, in use, is secured to said shaft; a clutch sleeve secured to said hub and adapted for axial shifting movement relative to said hub, said clutch sleeve having a plurality of clutch teeth; a blocker ring which, in use, is positioned between said gear and said hub, said blocker ring and said gear having engageable friction clutch surfaces; and a spring having a plurality of projecting portions engageable with at least one of said clutch sleeve teeth as said sleeve is moved toward said blocker ring, whereby a clutch surface engaging force is developed on said blocker ring by said spring member; characterized in that the spring is a flat C-shaped member with projecting lugs and is positioned between said blocker ring and said hub. A synchroniser clutch assembly in accordance with the invention has the advantage that the spring member is flat and may therefore be manufactured easily and cheaply by, for example, a stamping operation. This permits a broad range of materials to be used to produce the spring enabling a spring with much better wear characteristics to be produced, and desired shift characteristics to be obtained over a wide range. By positioning the spring between the blocker ring and the hub, the thickness of the spring, as well as its inner and outer diameters, can be varied within greater limits, enabling the shift characteristics to be tailored to an even greater degree. Also, due to the fact that the spring merely abuts against the end of the blocker ring, existing systems can at minimal expense be upgraded to incorporate the synchroniser clutch assembly of the present invention without requiring replacement of the blocker rings. The system is therefore much simpler and more flexible. Preferably, the spring is housed within a recessed area of the clutch hub. In this way, it is retained from radially outward movement in a very simple manner. This also enables the spring to be preloaded with the assembly, providing even greater flexibility in the shift characteristics obtainable from the assembly. The spring member preferably has at least three outwardly projecting lugs which are positioned in corresponding spaces or gaps between the external teeth on the hub. The blocker ring also has corresponding openings or spaces between the blocker teeth and the spaces are aligned with the lugs on the spring member. When the lugs are compressed radially during operation of the clutch assembly, the arms flex towards each other. The C-shaped spring member is preferably formed by a stamping procedure or other similar method and has a flat cross-sectional shape in order to lie flat in the annular recess in the hub and lie flush against the inner surface of the blocker ring. The arms of the spring member are preferably initially biased outwardly to aid in the assembly of the clutch mechanism. The projecting lugs on the spring member are engageable by certain of the teeth of the clutch sleeve as the sleeve is moved toward the gear to be synchronized. As the lugs are depressed, a blocker ring cone clutch engaging force is created which energizes the friction cone clutch. This causes a radial force to be generated which in turn causes the synchronizer blocker ring to index annularly relative to the synchronizer hub. The teeth of the synchronizer ring and blocker ring travel with the sleeve. Movement of the sleeve toward the gear causes engagement of the cone surfaces on the inside of the blocker ring with the gear cone surface, thereby creating a radial force component on the cone clutch which changes the relative angular velocity of the gear to be synchronized until synchronism is established between the gear and the shaft. After synchronization is established between the hub, synchronizer ring and gear, the radial force component falls to zero. The thrust force of the sleeve causes the synchronizer ring to move radially due to the contact between the teeth of the ring and the teeth of the sleeve. This radial movement causes alignment of the ring and sleeve teeth and allows the sleeve to move axially through the teeth of the synchronizer ring and to engage the dog teeth of the gear cone assembly. In order that the invention may be well understood, there will now be described an embodiment thereof, given by way of example reference being made to the accompanying drawings, in which : FIGURE 1 is a cross-sectional view of a double-acting synchronizer assembly for a manual transmission incorporating the present invention; FIGURE 2 is an exploded view of a portion of the cross-sectional view of Figure 1 depicting a synchronizer clutch hub, a C-shaped energizing spring member, and a blocker ring; FIGURE 3 is an elevational view of a flat C-shaped spring member in accordance with the present invention; FIGURE 4 is a partial cross-sectional view of the.double-acting synchronizer assembly shown in Figure 1, but showing the sleeve engaging the teeth of the blocker ring; FIGURE 5 is a cross-sectional view of the synchronizer assembly shown in Figure 1, the view taken along lines 5-5 in Figure 1 and in the direction of the arrows; FIGURE 6 is a cross-sectional view of the synchronizer assembly shown in Figure 4, the view taken along lines 6-6 in Figure 4 and in the direction of the arrows; and FIGURE 7 illustrates an alternate embodiment of the spring member. A double-acting synchronizer assembly for a manual transmission is designated by the numeral 10 in Figure 1. The assembly includes a synchronizer clutch hub 12 which is splined or otherwise secured to a shaft member 14 shown in phantom in Figure 1. For this purpose, the central opening of the clutch hub 12 includes a series of teeth 16. The teeth 16 assure that the clutch hub is secured to and rotates with shaft 14. The periphery of the synchronizing clutch hub 12 is provided with external splined teeth 18 that register with internal teeth 20 of an axially movable synchronizer clutch sleeve 22. A groove 24 is formed on the external periphery of the sleeve 22 to receive shifter fork fingers that are carried by a shift fork rail (not shown) for the manual transmission. The synchronizer clutch hub 12 and clutch sleeve 22 are positioned between a pair of gears 26 and 28. In the assembly 10 shown in Figure 1, gear 26 is a small pitch diameter gear while gear 28 is a large pitch diameter gear. Each of gears 26 and 28 include gear teeth 30 and 32, respectively, that mesh with gear teeth formed on a cluster gear assembly (not shown) for the transmission. Gear 26 is formed with a gear cone surface 34 and gear teeth 36. The gear teeth 36 are also called "dog teeth" and are provided on the gear 26 between the teeth 30 and the gear cone surface 34. The teeth 36 are provided with lead-in chamfer surfaces as is well known in the art. Similarly, gear 28 is provided with a gear cone surface 38 and an annular ring of gear teeth (or dog teeth) 40. The teeth 40 also have lead-in chamfer surfaces (not shown). Blocker rings 42 and 44 are positioned on opposite sides of the synchronizer clutch hub 12. (Blocker ring 42 is also shown in Figure 2.) The blocker rings are also known as "synchronizer rings". Each of the blocker rings 42 and 44 are provided with a ring of teeth 46 and 48, respectively, surrounding the periphery of the blocker rings. These teeth are also provided with lead-in chamfer surfaces, such as surfaces 50 shown on blocker ring 44 in Figure 2. Three spaces 52 are provided in the ring of gear teeth 48 and 46 on the blocker rings 42 and 44. Raised bosses or projections 54 are provided on the blocker rings in axial alignment with the spaces 52. When the synchronizer assembly 10 is assembled, the teeth 20 of the sleeve 22, the teeth 46 and 48 of the blocker rings 42 and 44, respectively, and the teeth 36 and 40 on the gears 26 and 28 respectively, are all in axial alignment. Teeth 18 on hub 12 are also in axial alignment with the other teeth. This allows the clutch sleeve 22 to be able to move into engagement with the gears 26 and 28 as desired during shifting of the transmission. A generally C-shaped spring member 60 is positioned in the synchronizer assembly 10 between the hub 12 and each of the blocker rings 42 and 44. One of the spring members is shown in Figure 3. An exploded view of a subassembly including the hub, spring member and blocker ring is shown in Figure 2. The clutch hub 12 has annular recessed portions 62 positioned on both sides thereof, the recesses 62 being positioned between internal cylindrical shoulder 64 and external cylindrical shoulder 66. The spring member 60 is preferably made from a flat piece of stamped metal material such as steel, and has two or more and preferably three protruding tabs or lugs 70, 72 and 74. Small fillets or radii 71 are provided on each side of the lugs 70, 72 and 74 where they extend from the central body of the spring member 60, creating small clearance spaces. These spaces are provided to provide clearance between the spring member 60 and tabs 70, 72 and 74 if any burrs or rough edges remain on the edges of the openings in the clutch hub 12. The clutch hub 12 has three openings or spaces 80 in the cylindrical surfaces 66 and the plurality of teeth 18 positioned on the periphery of the clutch hub. The openings 80 all have uniform width and are provided in order to mate with the lugs 70, 72 and 74 of the spring member 60. When the spring members 60 are assembled with the hub 12, the spring members are positioned in the recessed area 62 with the lugs 70, 72 and 74 protruding through the openings 80. In order to aid assembly and interconnection between the spring members 60 and hub 12, the spring member 60 is formed such that the arm members 81 and 82 provide an outward spring force against the cylindrical surface 66. Also, the width W1 of lug members 72 and 74 is less than the width W2 of lug members 70. This allows the lug members 72 and 74 to have some freedom of movement or "play" in the circumferential direction in their respective openings 80 in the clutch hub 12. The spring member 60 is generally C-shaped with an opening 84 between the ends of the arm members 81 and 82. Angle A is more than 5° and less than 90°. Although the actual angle A as shown in Figure 3 is not critical, it is important that there be at least some clearance between the ends of the arm members 81 and 82 in order to allow movement relative to each other during operation of the clutch assembly. The inner surfaces 43 and 45 of the blocker rings are angled corresponding to the angle of the cone surfaces 34 and 38 on the gears 26 and 28. The surfaces 43 and 45 also are covered with friction members (not shown) which are conventional in the art. The friction members help apply torque to the gears when the blocker ring is moved onto and secured to the gear cone surfaces. When the clutch hub, C-shaped spring member 60 and blocker ring 44 are assembled, the spaces 80 on the hub, the lugs 70, 72 and 74 on the spring member, and the spaces 52 and raised ridges 54 on the blocker rings are all positioned in axial alignment. Thereafter, when that subassembly is mated with the other parts of the synchronizer and gear assembly 10, the clutch sleeve 10 is positioned on the other periphery of the hub 12 and the gears 26 and 28 are positioned on the opposite sides as shown. As indicated above, the clutch sleeve 22 has a plurality of teeth 20 around the inner circumference or surface. Raised ridges 90 are formed on three of the teeth spaced 120° apart. Each of the ridges 90 have angled surfaces 91 and 92 in axial alignment with the shaft and gear teeth. The surfaces 91 and 92 act as ramps or cam surfaces. In the assembly 10 shown in Figure 1, the clutch sleeve 22 is in the neutral position. In this position, the ridge 90 is axially positioned between the two spring members 60 and the teeth 20 are not engaged with the teeth on the blocker ring or the gear teeth 36 and 40. When the clutch sleeve is assembled with the other parts discussed above, the three teeth with the raised ridges 90 are positioned in axial alignment with the openings 80 in the hub 12 and the spaces 52 in the teeth on the blocker rings 42 and 44. In this manner, the raised ridges 90 are positioned to come in contact with the lugs or tabs 70, 72 and 74 on the spring member 60. The ends of the teeth on the inner surface of the clutch sleeve also have lead-in chamfer surfaces. This effectuates lead-in of the teeth with the teeth 48 on the blocker rings, as well as the dog teeth 36 and 40 on the gears. In operation of the clutch mechanism, the clutch sleeve 22 is moved axially by the shift fork rail toward engagement of one of the gears 26 or 28. The situation in which the sleeve 22 is moved toward engagement with gear 26 is shown in Figure 4. The procedure for engagement with gear 28 is similar, but in the opposite direction. As shown in Figure 4, when the clutch sleeve 22 is moved in the direction of arrow 100, the ramp surface 91 and raised projection 90 cause the corresponding tab or lug on the spring member 60 to be depressed in a downward radial direction. Since there are three raised ridges 90 and three tangs 70, 72 and 74, each of the lugs 70, 72 and 74 are compressed in a radial downward direction when the clutch sleeve is moved toward either of the gears 26 and 28. As shown in Figure 6, compression of the lugs 70, 72 and 74 cause arms 81 and 82 of the C-shaped spring member 60 to move in an inward and downward direction. This is shown by arrows 102 and 104. In this regard, Figure 6 can be compared with Figure 5 wherein the C-shaped spring member is in its neutral and uncompressed condition. The shifting or movement of the lugs 72 and 74 in a circumferential direction (shown by arrows 104) in the spaces 80 in the clutch hub 12 is also shown by comparison of Figures 5 and 6. When the lugs of the spring member are compressed as the clutch sleeve passes over them, the spring is caused to move axially against the blocker ring. This forces the blocker ring into engagement with the gear cone. As indicated above, the spring member 60 has the raised portions 70, 72 and 74. The raised portions are compressed by the ramp portions 91 and 92 as the sleeve 22 moves relative to the hub. When the ramp portions pass over the lugs 70, 72 and 74, the leading edges of the teeth on the clutch sleeve begin to engage the chamfered lead-in edges 50 of the blocker ring teeth 48. The axial force on the sleeve 22, upon engagement of the blocker ring teeth, establishes a clutching force on the blocker ring, thereby imparting a synchronizing torque on the gear 26. When the gear and synchronizer clutch hub 12 are in synchronism, the teeth of the clutch sleeve can then move through the blocker ring teeth onto engagement with the dog teeth 36 on the gear 26, thereby locking the shaft 10 to the gear 26. The initial force caused by the engagement of the sleeve teeth with the spring member 60 will cause the blocker ring to index to the angular extent permitted. Since spring member 60 is positioned adjacent the blocker ring, ramp 91 causes the spring member to be forced against the inner surface 55 of the blocker ring in an axial direction. As indicated, the synchronizer and gear assembly 10 has a synchronizer blocker ring on each side of the hub 12. The operation of the synchronizer clutch elements associated with gear 28 is the same as that described above relative to gear 26, merely with movement of the clutch sleeve 22 in the opposite direction. Thus, the synchronizer elements associated with the synchronizer and gear assembly 10 function in the same manner regardless of in which axial direction the clutch sleeve 22 is moved. Due to the shape and configuration of the spring members 60, they do not bend or twist in the axial direction during operation of the assembly. The flat shape of the spring member allows the ends 81 and 82 to flex in the manner described above, and for the lugs 70, 72 and 74 to be radially compressed when the clutch sleeve is moved toward the gears 26 and 28. The fact that the arms 81 and 82 of the spring member are initially biased outwardly and have to be compressed in order to position the spring member in the annular recess 62 in the clutch hub, allows for easier assembly of the synchronizer and gear assembly 10. When the assembly 10 is assembled, the lugs 70, 72 and 74 are positioned in the spaces 80 in the hub, and one of the flat sides of the spring member is positioned in contact with the bottom of the recess 62. Thereafter, the blocker ring is assembled in that same recess 62 such that the surface 55 is positioned flush against the opposite side of the flat spring member 60. When the blocker ring is assembled with the hub, the projections 54 are positioned such that they are axially aligned with lugs 70, 72 and 74 and spaces 80. Due to the positioning and functioning of the spring members 60, it is not necessary with the present invention to affix the spring member 60 to the blocker ring. Thus, it is not necessary to weld, clamp or otherwise interlock the spring member to the blocker ring. An alternate embodiment of a C-shaped spring member 60' is shown in Figure 7. The use and operation of the spring member 60' are the same as those described above with reference to spring member 60. The various portions of the synchronizer and gear assembly 10 can be made of materials that are conventional in the art, and can be made by any well known conventional methods or machining. For example, it is common practice to manufacture synchronizer clutch assemblies with blocker rings which are formed of brass or that are formed by powdered metal casting techniques. The synchronizer blocker ring may also be formed by an orbital forging process that comprises cold working flat carbon steel stock. The geometry and structure of the present inventive system allows significant flexibility for optimization of the system and its operation for any particular application. For example, the C-shaped spring can have many variations in stiffness, deflection rates and materials in order to increase the operation and benefits of the system. Also, the number of parameters which can be varied to allow optimization of the system is greatly increased. The design of the synchronization ring is also simplified in accordance with the present invention. Special recesses or pockets for the location of the spring are unnecessary. The spring further is simple and cheap to manufacture in comparison to many other synchronizer springs.

Claims: A synchronizer clutch assembly (10) for a manual transmission having at least one torque transfer gear and a torque delivery shaft (14), said clutch assembly (10) comprising: a clutch hub (12) which, in use, is secured to said shaft (14); a clutch sleeve (22) secured to said hub (12) and adapted for axial shifting movement relative to said hub (12), said clutch sleeve (22) having a plurality of clutch teeth (20); a blocker ring (42, 44) which, in use, is positioned between said gear (26, 28) and said hub (12), said blocker ring (42, 44) and said gear (26, 28) having engageable friction clutch surfaces (34, 43; 38, 45); and a spring (60; 60') having a plurality of projecting portions (70, 72, 74; 70', 72', 74') engageable with at least one (90) of said clutch sleeve teeth (20) as said sleeve (22) is moved toward said blocker ring (42, 44), whereby a clutch surface engaging force is developed on said blocker ring (42, 44) by said spring member (60; 60'); characterized in that the spring is a flat C-shaped member (60; 60') with projecting lugs (70,72,74;70'72'74) and is positioned between said blocker ring (42, 44) and said hub (12). An assembly as claimed in claim 1, wherein said spring member (60; 60') has three lugs (70, 72, 74; 70', 72', 74') which are compressible radially inwardly upon engagement with said clutch sleeve teeth (90). An assembly as claimed in claim 1 or claim 2, wherein said clutch teeth (20) on said sleeve (22) are internal clutch teeth, and include ramped projection means (90) on a plurality of clutch teeth (20) which are positioned to engage said projecting lugs (70, 72, 74; 70', 72', 74'). An assembly as claimed in any of the preceding claims, wherein blocker ring (42, 44) and the hub (12) each have a plurality of axially aligned circumferential openings (52, 80) corresponding to the plurality of lugs (70, 72, 74; 70', 72', 74') on the spring member (60; 60'). An assembly as claimed in claim 4, wherein the spring member (60; 60') is positioned in a recessed area (62) of the hub (12) with the lugs (70, 72, 74; 70', 72', 74') protruding through the openings (80). A synchromesh transmission including a synchroniser clutch assembly as claimed in any of the preceding claims.

Inventors: LARSEN JONATHAN G, ROBERTS KEITH, SKIPPER GARY I, LARSEN, JONATHAN G., ROBERTS, KEITH, SKIPPER, GARY I.
Applicants: BORG WARNER AUTOMOTIVE, BORG-WARNER AUTOMOTIVE, INC.
Application year: 1996
Main classification: F16D23
IPC codes: F16D23