Multiratio power transmission

A step ratio power transmission provides a plurality of drive ratios between the input and output shafts. The power transmission, in addition to the input and output shafts, has a countershaft on which a plurality of ratio gears are rotatably mounted. The input shaft has at least one ratio gear rotatably mounted thereon while the output shaft has at least one gear secured thereto. A cluster gear is secured to either the input shaft or the output shaft while the other of these shafts has roatably mounted thereon one or more ratio gears. At least one of the ratio gears on the input shaft serves as an idler gear for one or more of the ratio gears on the countershaft.

BACKGROUND OF THE INVENTION 
This invention relates to power transmissions and more particularly to 
countershaft type power transmissions having a plurality of step ratios. 
SUMMARY OF THE INVENTION 
With an increase in the number of transverse front wheel drive vehicles 
having a reduced dimension between the front wheels, it is necessary to 
maintain or reduce the axial length of the transmission mechanism. It is 
also desirable to increase the number of speed ratios which are available 
during operation of the transmission. 
The present invention provides for a gearing arrangement within a 
countershaft type transmission wherein the same axial length of prior art 
transmissions is maintained or slightly decreased while an increase in the 
number of forward speed ratios from four to five is obtained. 
It is therefore an object of this invention to provide an improved step 
ratio power transmission having an input shaft, an output shaft and a 
countershaft with intermeshing gears disposed coaxially with the 
respective shaft members and wherein at least one ratio gear rotatably 
disposed on the input shaft acts as an idler gear between a ratio gear on 
the countershaft and an output gear secured for rotation with the output 
shaft. 
It is another object of this invention to provide an improved step ratio 
power transmission having an input shaft, an output shaft and a 
countershaft with intermeshing gear members disposed coaxially with the 
shafts wherein a cluster gear is secured for rotation with either the 
input shaft or the output shaft, and ratio gears meshing with the cluster 
gear are rotatably mounted on the other of the input or output shaft, and 
also wherein at least one ratio gear is rotatably mounted on the input 
shaft to provide idler gear operation between a ratio gear on the 
countershaft and a gear member secured for rotation with the output shaft. 
It is a further object of this invention to provide an improved step ratio 
countershaft type power transmission having an input shaft, an output 
shaft and a countershaft and wherein at least one gear member is secured 
for rotation with the output shaft, and intermeshing ratio gear members 
are rotatably mounted on the input shaft and the countershaft with the 
ratio gear member on the input shaft operating as an idler gear between 
the ratio gear member on the countershaft and the gear member secured to 
the output shaft and also wherein a pair of selectively engageable clutch 
members are operable to connect the ratio gears to their respective shaft 
members. 
These and other objects and advantages of the present invention will be 
more apparent from the following specification and drawings.

DESCRIPTION OF THE EMBODIMENTS 
Referring to the drawings, wherein like characters represent the same or 
corresponding parts throughout the several views, there is seen in FIG. 1 
a power transmission, generally designated 10, having a transmission 
housing or case 12 in which is rotatably disposed an input shaft 14. The 
input shaft 14 is mounted on a needle or roller bearing 16 and a ball 
bearing 18. The input shaft 14 has a transfer or head gear 20 secured for 
rotation therewith, and a plurality of ratio gears 22, 24 and 26 rotatably 
mounted thereon. The ratio gears 22 and 24 can be selectively connected 
for rotation with the input shaft 14 by a conventional synchronizer clutch 
28, while the ratio gear 26 is selectively connectible for rotation with 
the input shaft 14 by a synchronizer clutch 30. The synchronizer clutches 
28 and 30 and other synchronizer clutches, which will be referred to 
during the subsequent description of the embodiments are conventional 
well-known mechanisms which are generally operated by shift lever and 
shifter fork mechanisms, also which are well-known. Those familiar with 
the operation of countershaft type transmissions are aware that manual 
shift controls including the shifter lever and forks, prevents the 
simultaneous engagement of more than one synchronizer clutch at any given 
time. 
The transfer gear 20 meshes with a transfer or head gear 32 which is 
secured for rotation with a countershaft 34 which is rotatably supported 
in the transmission housing 12 on a roller bearing 36 and a ball bearing 
38. Since the gears 20 and 32 are secured to their respective shaft 
members 14 and 34, the countershaft 34 will rotate whenever the input 
shaft 14 is rotated. 
The countershaft 34 has rotatably disposed thereon a plurality of ratio 
gears 40, 42 and 44. The ratio gears 40 and 42 are selectively connectible 
for rotation with the countershaft 34 through a synchronizer clutch 
assembly 46, while ratio gear 44 is selectively connectible with the 
countershaft 34 through a synchronizer clutch assembly 48. The ratio gear 
40 is in continuous mesh with the ratio gear 22 and the ratio gear 42 is 
in continuous mesh with the ratio gear 24. The ratio gear 44 meshes with a 
reverse idler gear 50, shown in phantom, which in turn meshes with ratio 
gear 26. 
An output shaft 52 is rotatably supported in the housing 12 by a pair of 
tapered roller bearings 54 and 56 and a needle roller bearing 58. The 
output shaft 52 has fixed thereon gear members 60, 62 and 64. This gear 
arrangement 60, 62 and 64 is quite often referred to as a cluster gear 
since, in general practice, the three gears are made integral and then the 
cluster is assembled for rotation with the shaft member. 
The gear 60 meshes with the ratio gear 22, the gear 62 meshes with the 
ratio gear 24 and the gear 64 meshes with the ratio gear 26. The output 
shaft 52 also has secured thereto an output gear member 66 which meshes 
with a ring gear 68, shown in phantom, which is a component of a 
conventional differential gear set, not shown. 
By judicious selection and engagement of the synchronizer clutch mechanisms 
28, 30, 46 and 48, the transmission 10 can be operated to provide five 
forward speed ratios and one reverse speed ratio. The first and lowest 
speed ratio is provided when synchronizer mechanism 46 engages ratio gear 
40. When this occurs, power flows from the input shaft 14 through the 
transfer gears 20 and 32 to the countershaft 34 and therefore ratio gear 
40. Ratio gear 40 rotates ratio gear 22, which acts as an idler, which in 
turn rotates gear 60 and therefore output shaft 52. 
Second gear or speed ratio is established by engaging synchronizer clutch 
46 with ratio gear 42. The rotation of input shaft 14 is transmitted 
through transfer gears 20 and 32 to ratio gear 42 which in turn rotates 
ratio gear 24. Ratio gear 24, acting as an idler, rotates gear 62 which in 
turn rotates output shaft 52. 
The third gear or speed ratio is established by the selective engagement of 
synchronizer clutch 28 with ratio gear 22. During third gear operation, 
input shaft 14 rotates ratio gear 22 through synchronizer clutch 28. Ratio 
gear 22 rotates gear 60 which in turn rotates the output shaft 52. 
Fourth gear or speed ratio is established by selective engagement of 
synchronizer clutch 28 with ratio gear 24 such that rotation of the input 
shaft 14 is transmitted to the output shaft 52 through gears 24 and 62. 
The fifth gear or speed ratio is established by selective engagement of 
synchronizer clutch 30 with the ratio gear 26. In fifth gear operation, 
the rotation of input shaft 14 is transmitted to the output shaft 52 
through the operation of gears 26 and 64. 
The reverse gear ratio is established by selective engagement of the 
synchronizer clutch 48 with the ratio gear 44. During reverse operation, 
rotation of the input shaft 14 is reversed and transmitted to the output 
shaft 52 through the action of ratio gear 44, reverse idler gear 50, ratio 
gear 26 and gear member 64. During reverse drive ratio there are two idler 
gears provided; namely, 50 and 26. 
During first and second gear operation, the ratio gears 22 and 24 
respectively provide idler gear operation. Without the use of the ratio 
gears 22, 24 and 26 as idler gear members, the length of the transmission 
10 would have to be increased to accommodate an increased number of ratio 
gears on the input shaft 14 and a corresponding increase in the length of 
the cluster gear disposed on the output shaft 52. 
There is seen in FIG. 2 a power transmission 100 which has an input shaft 
102, a countershaft 104 and an output shaft 106. The input shaft 102 has 
rotatably secured thereto a cluster gear, generally designated 108, and 
comprised of gear members 110, 112, 114, 116 and 118. If desired, one or 
more of these gears 110-118 can be individually secured to the input shaft 
102. There is also rotatably mounted on the input shaft 102 a ratio gear 
120 which is selectively connectible therewith through a synchronizer 
clutch 122. The countershaft 104 has rotatably secured thereto a transfer 
gear member 124 which meshes with the ratio gear 120. Rotatably mounted on 
the countershaft 104 is a pair of ratio gears 126 and 128 which mesh with 
gears 110 and 116, respectively. The ratio gears 126 and 128 are 
selectively connectible for rotation with the countershaft 104 by a 
synchronizer clutch assembly 130. The output shaft 106 has rotatably 
secured thereto an output gear 132 and a transfer gear 134. Rotatably 
mounted on the output shaft 106 is a pair of ratio gears 136 and 138 which 
mesh with gears 112 and 118, respectively. The gears 136 and 138 are 
selectively connectible with the output shaft 106 by a synchronizer clutch 
assembly 140. The synchronizer clutch assembly 140 has formed integrally 
therewith a gear member 142 which is adapted to mesh with a reverse idler 
gear 144, shown in phantom, which meshes with gear 114. When a reverse 
drive ratio in transmission 100 is desired, gear 144 is shifted into mesh 
with gear 142 so that rotation of input shaft 102 is transmitted through 
gears 114, 144 and 142 to the output shaft 106. 
The gearing arrangement of transmission 100 provides the first or lowest 
gear ratio through the engagement of synchronizer clutch 130 with gear 
ratio 126. During first gear operation, the input shaft 102 rotation is 
transmitted through gear 110, ratio gear 126, countershaft 104, transfer 
gear 124, ratio gear 120 and transfer gear 134 to the output shaft 106. 
The second gear ratio is provided in transmission 100 by engagement of 
synchronizer clutch 130 with ratio gear 128. During second gear, the 
rotation of input shaft 102 is transmitted to the output shaft 106 through 
gear 116, ratio gear 128, countershaft 104, transfer gear 124, ratio gear 
120 and transfer gear 134. 
During both first and second ratios, the ratio gear 120, rotatably disposed 
on the input shaft 102, operates as an idler gear between the countershaft 
104 and the output shaft 106. The third and fourth gear ratios are 
established through the engagement of synchronizer clutch 140 with ratio 
gears 136 and 138, respectively. The fifth and highest gear ratio of the 
transmission is established by the engagement of the synchronizer clutch 
122 with the ratio gear 120. The paths of the ratios three through five 
are conventional and should be apparent without a detailed description. 
In FIG. 3, there is seen a power transmission, generally designated 200, 
having an input shaft 202, a countershaft 204 and an output shaft 206. The 
input shaft 202 has rotatably secured therewith three transfer gears 208, 
210 and 212. Also, rotatably mounted on the input shaft 202 is a pair of 
ratio gears 214 and 216. The ratio gears 214 and 216 can be selectively 
connected with the input shaft 202 by a synchronizer clutch assembly 218. 
The countershaft 204 has secured thereto a transfer gear 220 which meshes 
with the transfer gear 210. Rotatably disposed on the countershaft 204 are 
a pair of ratio gear members 222 and 224. Gear 222 is selectively 
connectible with the countershaft 204 by a synchronizer clutch assembly 
226 while gear 224 is selectively connectible with gear 222 through the 
assembly 226. The ratio gears 222 and 224 mesh with ratio gear 214 and 
transfer gear 208, respectively. Also rotatably disposed on the 
countershaft 204 is a ratio gear 228 which is selectively connectible with 
the countershaft 204 by a synchronizer 230. The ratio gear 228 is in mesh 
with a reverse idler gear, shown in phantom at 232, which in turn meshes 
with the ratio gear 216. 
The output shaft 206 has secured thereto an output gear 234 and a cluster 
gear, designated 236, and comprised of gears 238 and 240. Rotatably 
disposed on the output shaft 206 is a ratio gear 242 which is selectively 
connectible with the output shaft 206 by a synchronizer clutch 244. 
To establish the first and lowest ratio, the synchronizer clutch 226 is 
manipulated to selectively connect ratio gear 222 to the countershaft 204. 
During first gear operation, the rotation of input shaft 202 is 
transmitted to output shaft 206 via transfer gears 210 and 220, 
countershaft 204, ratio gears 222, 214 and gear 240. 
It should be appreciated that ratio gear 214 is an idler gear during 
operation of this drive ratio. To establish the second gear ratio in the 
transmission 200, the synchronizer clutch 226 is manipulated to connect 
ratio gear 224 to ratio gear 222. During second gear operation, the 
rotation of input shaft 202 is transmitted to the output shaft 206 via 
transfer gear 208, ratio gear 224, ratio gear 222, ratio gear 214 and gear 
240. It will be appreciated that the ratio gear 214 also serves as an 
idler gear during second gear operation. 
Third, fourth and fifth gear operations are accomplished through the 
selective engagement of synchronizer 218 with ratio gears 214 and 216 and 
synchronizer clutch 244 with ratio gear 242, respectively. These ratios 
and the gear meshes which accomplish them are straightforward such that a 
more detailed description of the drive path is not believed necessary. 
The reverse drive ratio is established by manipulating synchronizer clutch 
230 to connect ratio gear 228 with the countershaft 204. During reverse 
drive operation, the rotation of input shaft 202 to output shaft 206 is 
accomplished via transfer gear 210, transfer gear 220, ratio gear 228, 
reverse idler gear 232, ratio gear 216 and gear 238. It will be noted that 
ratio gear 216 is operative as an idler gear during reverse operation. 
In each of the above described embodiments, it should be appreciated that 
in at least one forward gear ratio that a ratio gear rotatably disposed on 
the input shaft provides an idler gear action between gears on the 
countershaft and on the output shaft. It is the use of this idler gear 
operation which permits the transmission mechanism to be maintained at the 
same or shorter axial length while also permitting the addition of one 
more gear ratios in the transmission mchanism. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teaching. It is therefore to be understood, 
that within the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described.