Gear synchronizer assembly for power transmission

In a gear synchronizer assembly of the well-known type, a clutch sleeve is formed at its inner periphery with at least one first internal radial projection of large width and a pair of circumferentially spaced second internal radial projections of small width arranged at opposite sides of the first internal radial projection, a synchronizer ring being formed thereon with a pair of raised portions to be engaged with the first internal radial projection and another pair of raised portions to be engaged with the second internal radial projections. A thrust mechanism comprising a radially contractible annular spring is supported in place by engagement with the inner circumference of a cylindrical hub portion of a hub member fixed to a transmission shaft. The annular spring has an axial leg extending therefrom toward the first internal radial projection, and having a radial projection which is arranged to be engaged with the first internal radial projection in shifting operation of the clutch sleeve toward a spline piece integral with a change-speed gear and arranged to abut against and urge the synchronizer ring toward the spline piece upon engagement with the first internal radial projection.

BACKGROUND OF THE INVENTION 
The present invention relates to a gear synchronizer assembly for power 
transmissions, and more particularly to a gear synchronizer mechanism of 
the type which comprises a gear member rotatably mounted on a transmission 
shaft, a spline piece mounted on a hub portion of the gear member for 
rotation therewith and being formed at one side thereof with a conical 
portion and thereon with external spline teeth, a synchronizer ring 
mounted on the conical portion of the spline piece for frictional 
engagement therewith, a hub member fixed to the transmission shaft for 
rotation therewith and being formed thereon with external spline teeth, a 
clutch sleeve encircling the hub member and having internal spline teeth 
in continual engagement with the external spline teeth of the hub member, 
the clutch sleeve being axially shiftable to be engaged at the internal 
spline teeth thereof with the external spline teeth of the spline piece, 
and thrust means for thrusting the synchronizer ring toward the spline 
piece in shifting operation of the clutch sleeve to effect the frictional 
engagement between the synchronizer ring and the spline piece. 
In such a conventional gear synchronizer means as described above, the 
thrust mechanism comprises a plurality of circumferentially spaced strut 
keys each having a raised portion in engagement with the corresponding 
recess in the inner peripheral wall of the clutch sleeve, and an annular 
retainer spring arranged to bias the strut keys radially outwardly for 
engagement with the clutch sleeve. To simplify the thrust means in 
construction, an improved thrust means has been proposed in Japanese Early 
Patent Publications Nos. 55-100428, 58-137627, 58-163829, and 58-174724, 
wherein the strut keys and retainer spring are replaced with a single 
thrust element. It is, however, difficult to enhance productivity of the 
gear synchronizer mechanism because the single thrust element is 
complicated in configuration and construction. 
To overcome the shortcomings of such a conventional thrust means as 
described above, an improved gear synchronizer mechanism has been proposed 
by the inventors in a copending U.S. patent application No. 677,748, filed 
on Dec. 3, 1984, now U.S. Pat. No. 4,625,844, wherein the clutch sleeve is 
formed at its inner periphery with at least one internal radial 
projection, and wherein the thrust means comprises a radially contractible 
annular resilient member supported in place by engagement with the inner 
circumference of a cylindrical hub portion of the hub member, the annular 
resilient member having an axial leg extending therefrom toward the 
internal radial projection of the clutch sleeve and having a radial 
projection arranged to be brought into engagement with the internal radial 
projection of the clutch sleeve and arranged to abut against and urge the 
synchronizer ring toward the spline piece upon engagement with the 
internal radial projection of the clutch sleeve, the axial leg of the 
annular resilient member being arranged to be compressed radially inwardly 
by engagement with the internal radial projection of the clutch sleeve. 
In the above-described synchronizer mechanism, the synchronizer ring is 
integrally formed thereon with a pair of raised portions which are formed 
with a chamfer at each end thereof, and the internal radial projection of 
the clutch sleeve is formed at one side thereof with a pair of chamfers to 
be engaged with the chamfers of the raised portions on the synchronizer 
ring and arranged to pass through an axial groove between the raised 
portions of the synchronizer ring. In operation, the internal radial 
projection of the clutch sleeve is engaged at its chamfers with the 
chamfers of the synchronizer ring to establish a frictional driving 
connection between the parts to be brought into synchronization. For this 
reason, if the number of internal radial projections is reduced, there 
will occur a problem in durability of the radial projections due to 
increase of the pressure acting thereon. If the number of internal radial 
projections is increased, there will occur undesired disengagement between 
the intermeshed spline teeth in deceleration due to reduction of the 
number of internal spline teeth of the clutch sleeve to be meshed with the 
teeth of the gear member. 
SUMMARY OF THE INVENTION 
It is, therefore, a primary object of the present invention to provide an 
improved gear synchronizer mechanism, wherein the thrust means is 
constructed to enhance the durability of the clutch sleeve without causing 
disengagement of the intermeshed spline teeth in a shifted condition of 
the synchronizer mechanism. 
According to the present invention, there is provided a gear synchronizer 
mechanism wherein the clutch sleeve is formed at its inner periphery with 
a first internal radial projection of large width arranged to be engaged 
with the axial leg of the annular resilient member and a pair of 
circumferentially spaced second internal radial projections of small width 
arranged at opposite sides of the first internal radial projection, the 
first and second internal radial projections each being formed at one side 
thereof with a pair of chamfers, and wherein the synchronizer ring is 
formed thereon with a pair of raised portions which are respectively 
chamfered at one end thereof to be engaged with the chamfers of the first 
internal radial projection, the synchronizer ring being further formed 
thereon with another pair of raised portions which are respectively 
chamfered at one end thereof to be engaged with the chamfers of the second 
internal radial projections.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, where like reference numerals represent the 
same or corresponding parts throughout the figures, there is illustrated 
in FIG. 1 a transmission shaft 21, on which are rotatably supported a pair 
of change-speed gears 22 and 22. Disposed between the change-speed gears 
22 and 22 is a pair of synchronizer assemblies which are operable to cause 
selective speed synchronization between the shaft 21 and the gears 22 and 
22, respectively. As is illustrated in FIGS. 1 and 2, the synchronizer 
assemblies have a commcn hub assembly which includes a hub member 11, and 
a pair of radially contractible annular resilient member 14, 14. The 
synchronizer assemblies are arranged to be operated through a clutch 
sleeve 12 which is connected by a yoke groove to a conventional manually 
operated shift mechanism (not shown). The hub member 11 is fixed at its 
inner hub portion to the transmission shaft 21 by means of a spline 
connection for rotation therewith. As can be well seen in FIGS. 2 and 5, 
the hub member 11 is integrally formed with an outer cylndrical hub 
portion 11b which is formed thereon with external spline teeth 11a. The 
clutch sleeve 12 is arranged in surrounding relationship with the outer 
cylindrical hub portion 11b of hub member 11 and has internal spline teeth 
12a in continual engagement with the external spline teeth 11a of hub 
member 11. The clutch sleeve 12 is axially shiftable to be engaged at the 
internal spline teeth thereof with external spline teeth 23b of a spline 
piece 23. 
The left-hand synchronizer assembly is substantially the same as the 
right-hand synchronizer assembly such that a detailed description of the 
right-hand synchronizer assembly only is believed necessary. The 
right-hand synchronizer assembly includes the spline piece 23 and a 
synchronizer ring 13. The spline piece 23 is fixedly mounted on a hub 
portion of change-speed gear 22 by means of a spline connection for 
rotation therewith. The spline piece 23 is formed at its left end with a 
conical portion 23a and thereon with the external spline teeth 23b which 
are chamfered at each end thereof. The synchronizer ring 13 is rotatably 
and axially slidably mounted on the conical portion 23a of spline piece 23 
and has an internal conical surface 13a for frictional engagement with the 
surface of the conical portion 23a of spline piece 23. Thus, the 
synchronizer ring 13 cooperates with the spline piece 23 to provide a 
friction clutch in a well-known manner. 
In this embodiment, the outer cylindrical hub portion 11b of hub member 11 
is axially recessed in its circumferentially equi-spaced three portions. 
As can be well seen in Figs, 2, 3 and 4, the axially recessed portions 
each are formed as an axial groove 11c. The clutch sleeve 12 is formed at 
its inner periphery with circumferentially equi-spaced three internal 
radial projections 12b of large width which are axially shiftable in the 
axial grooves 11c of hub member 11. The clutch sleeve 12 is further formed 
at its inner periphery with a pair of internal radial projections 12c of 
small width which are arranged at opposite sides of the respective large 
width radial projections 12b. 
As can be well seen in FIGS. 3 and 6, the large width radial projections 
12b each are formed at their inner end corners with tapered surfaces 12d 
and at their side corners with chamfers 12e. The large width radial 
projections 12b are respectively arranged between a pair of raised 
portions 13b which are integrally formed on the synchronizer ring 13 and 
circumferentially equi-spaced. The raised portions 13b each are formed at 
their inner ends with a pair of chamfers 13c which are engageable with the 
chamfers 12e of large width radial projections 12b, respectively. As can 
be well seen in FIGS. 4 and 6, the small width radial projections 12c each 
are formed at their opposite ends with chamfers 12f and are arranged 
between the raised portion 13b and another raised portion 13d formed on 
the synchronizer ring 13 adjacent the respective raised portions 13b. The 
raised portions 13d each are formed at their inner ends with a chamfer 
13e which is engageable with the chamfer 12f of small width radial 
projection 12c. 
As can be well seen in FIGS. 2 and 3, the radially contractible annular 
resilient member 14 includes a C-letter shaped ring portion 14a which is 
formed at opposite ends thereof with a pair of axial legs 14b and at an 
intermediate portion thereof with an axial leg 14b. The ring portion 14a 
of resilient member 14 is formed larger in diameter than the inner 
circumference of outer cylindrical hub portion 11b of hub member 11 and 
supported in place by engagement with the inner circumference of hub 
portion 11b in the presence of a radial force imposed thereto. The axial 
legs 14b of resilient member 14 each extend from the ring portion 14a 
toward the internal radial projection 12b of clutch sleeve 12 through an 
axial groove between the raised portions 13b and 13b of synchronizer ring 
13. The axial legs 14b of spring 14 each are formed with a radial 
projection which is arranged between the inner end surface of synchronizer 
ring 13 and the tapered surface 12d of the internal radial projection 12b 
of clutch sleeve 12. 
In shifting operation of the clutch sleeve 12 toward the spline piece 23, 
the axial legs 14b of spring 14 are slightly moved in an axial direction 
by engagement with the tapered surfaces 12d of large width radial 
projections 12b at their inner shoulders such that each radial projection 
of axial legs 14b abuts against and urges the synchronizer ring 13 toward 
the spline piece 23 which will effect frictional engagement of the 
internal conical surface 13a of synchronizer ring 13 and the surface of 
the conical portion 23a of spline piece 23. Simultaneously, the axial 
movement of clutch sleeve 12 will be resisted by the balk action or 
engagement between the chamfers 12e, 12f of large and small width radial 
projections 12b and 12c and the chamfers 13c, 13e of raised portions 13b 
and 13d. When the thrust pressure acting on resilient member 14 exceeds a 
predetermined value, synchronization between the relative rotating parts 
is established, and the large width radial projections 12b of clutch 
sleeve 12 ride over the axial legs 14b of resilient member 14 thereby 
compressing them radially inwardly. This permits the radial projections 
12b, 12c of clutch sleeve 12 to pass through axial grooves respectively 
formed between the raised portions 13b and 13d of synchronizer ring 13. 
Thus, the internal splines 12a of clutch sleeve 12 will be brought into 
engagement with the external spline teeth 23b of spline piece 23 to 
accomplish the synchronization. 
From the above description, it will be understood that the gear 
synchronizer mechanism is characterized by provision of the clutch sleeve 
12 which is integrally formed at its inner periphery with the 
circumferentially equi-spaced large and small width radial projections 12b 
and 12c to be engaged at their chamfered ends 12e, 12f with the chamfers 
13c, 13e of raised portions 13b and 13d on synchronizer ring 13. With this 
arrangement, it is advantagous that even if the number of large width 
radial projections 12b is reduced to form a sufficient number of internal 
spline teeth on the clutch sleeve 12 for reliable torque transmission, the 
small width radial projections 12c can be formed to increase the number of 
intermeshed portions between the clutch sleeve 12 and the synchronizer 
ring 13 thereby to decrease the pressure acting on the respective chamfers 
12e, 12f of radial projections 12b and 12c. This serves to enhance the 
durability of clutch sleeve 12. 
Having now fully set forth both structure and operation of a preferred 
embodiment of the concept underlying the present invention, various other 
embodiments as well as certain variations and modifications of the 
embodiment herein shown and described will obviously occur to those 
skilled in the art upon becoming familiar with the underlying concept. It 
is to be understood, therefore, that within the scope of the appended 
claims, the invention may be practiced otherwise than as specifically set 
forth herein.