Continuously variable speed transmission for motor vehicles

A continuously-variable speed transmission for motor vehicles, which transmission comprises an input variable pitch pulley arranged on the input shaft of the transmission, an output variable pitch pulley arranged on the output shaft of the transmission, an endless belt interconnecting the input and the output variable pitch pulleys, a forward-drive planetary gear mechanism disposed on one axial side of the variable pitch pulley arranged either on said input shaft or on said output shaft, and a reverse-drive planetary gear mechanism disposed on the other axial side of said variable pitch pulley.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a continuously-variable speed 
transmission for motor vehicles and more particularly to a transmission 
for motor vehicles employing a belt type continuously-variable change 
ratio device, designated as "a belt device" hereinafter. The belt drive 
device includes a first variable pitch pulley and a second variable pitch 
pulley being associated with an input shaft and an output shaft, 
respectively and rotatively connected. 
Each of the variable pitch pulleys of the belt drive device comprises a 
fixed flange secured to the associated input or output shaft, a movable 
flange axially and slidably mounted on the other shaft, an endless belt 
interconnecting said variable pitch pulleys and means capable of 
regulating the distance between the movable flange and the fixed flange in 
order to change the radial position of the endless belt which is held 
between the fixed flange and the movable flange so that the ratio of the 
revolving speed of the output shaft to that of the input shaft, that is, 
the speed change ratio, is changed. Belt drive devices of this type are 
well-known. Incorporation of a belt drive device of this type into a 
transmission for motor vehicles allows continuously-variable change of the 
revolving ratio between the input shaft and the output shaft, namely, the 
speed change ratio, automatically but not necessarily in response to the 
driver's demands or road conditions. 
However, in applying such a belt drive device as described hereinbefore to 
a transmission for motor vehicles, additional provision of a reversing 
changeover gear mechanism and a reduction gear is required since the speed 
change ratio of the belt drive device, in general, is variable within a 
range of 2.0 to 0.5. The input shaft of the belt drive device and the 
output shaft of a prime mover are interconnected with a coupling device 
which transmits rotation without converting the torque, such as a fluid 
coupling or a clutch, and the output shaft of the belt drive device is 
connected to the driving axle of a motor vehicle through a conventional 
final reduction gear mechanism of the hypoid gear type. 
Employment of a planetary gear mechanism in the reversing changeover 
mechanism is desirable in order to provide a compact transmission for 
motor vehicles. A simple planetary gear mechanism of the single planetary 
pinion type is unsuitable to the reversing changeover mechanism for the 
transmission for motor vehicles, owing to a great difference between the 
gear ratio for normal rotation and that for reverse rotation, which is 
inherent to the planetary gear mechanism of a single planetary pinion 
type. 
A planetary gear mechanism of the double planetary pinion type is quite 
favorable, since the gear ratio is 1.0 both for normal rotation and for 
reverse rotation. However, when the planetary gear mechanism of the double 
planetary pinion type is coupled directly to the belt drive device as 
described hereinbefore, a reduction gear ratio of approximately 8 is 
required of the final reduction gear mechanism. A final reduction gear 
mechanism of the hypoid gear type with such a great reduction gear ratio 
has never been available and is not suitable for motor vehicles. 
Accordingly, machine designers having ordinary skill will incorporate a 
reduction gear of the necessary reduction gear ratio into a reversing 
changeover planetary gear mechanism of the double planetary pinion type in 
order to attain a combination of the belt drive device and a conventional 
final reduction gear of the hypoid gear type. In this case, it is usual to 
arrange and interlock the mechanisms in a sequence of a fluid coupling or 
a clutch, a belt drive device, reversing changeover planetary gear 
mechanism of the double planetary pinion type, a reduction gear and a 
conventional final reduction gear mechanism. In a transmission system for 
motor vehicles thus constructed, torque transmission efficiency is likely 
to be reduced since the torque of the prime mover is transmitted to the 
conventional final reduction gear mechanism through two sets of gear 
trains of a planetary gear mechanism and a reduction gear. At the same 
time, the high-speed operation of a planetary gear mechanism of the double 
planetary pinion type affects the durability of the planetary gear 
mechanism disadvantageously. 
What is needed is a continuously variable transmission for motor vehicles 
which has high torque transmission efficiency, simple construction and 
high durability. 
SUMMARY OF THE INVENTION 
Generally speaking, in accordance with the invention, there is provided a 
continuously-variable transmission for motor vehicles employing the belt 
drive device described hereinbefore, more particularly, a continuously 
variable speed transmission for motor vehicles employing a belt drive 
device, with a reversing change-over gear mechanism and a forward-drive 
reduction gear mechanism both of simplified construction. The present 
invention relates to a continuously-variable speed transmission for motor 
vehicles, having a belt drive device comprising an input shaft, an output 
shaft, a first variable pitch pulley arranged on the input shaft, a second 
variable pitch pulley arranged on the output shaft and an endless belt 
interconnecting the first and second pulleys, an individual forward-drive 
planetary gear mechanism and an individual reverse-drive planetary gear 
mechanism. 
An intermediate shaft is mounted coaxially either on the input shaft or on 
the output shaft for relative rotation thereon, while a variable pitch 
pulley, which is arranged on a shaft which is coaxial with the 
intermediate shaft, is disposed on the intermediate shaft. A forward-drive 
planetary gear mechanism and a reverse-drive planetary gear mechanism are 
disposed on one side of said variable pitch pulley and the other side of 
said variable pitch pulley, respectively. Either one of the shafts coaxial 
with the intermediate shaft or the intermediate shaft is rotatively 
connected to the respective input gears of the forward-drive planetary 
gear mechanism and the reverse-drive planetary gear mechanism, while the 
other shaft is rotatively connected to the respective output gears of the 
forward-drive planetary gear mechanism and the reverse-drive planetary 
gear mechanism. Each of the forward-drive planetary gear mechanism and the 
reverse-drive planetary gear mechanism includes a control means capable of 
controlling the interruption of the rotational transmitting operation of 
the corresponding planetary gear mechanism. 
More particularly, either one of the shafts coaxial with the intermediate 
shaft or the intermediate shaft is connected to the ring gear of the 
forward-drive planetary gear mechanism and the sun gear of the 
reverse-drive planetary gear mechanism, while the other shaft is connected 
to the planetary carrier of the forward-drive planetary gear mechanism and 
the ring gear of the reverse-drive planetary gear mechanism so that the 
rotation of the former shaft, that is, either one of the shafts coaxial 
with the intermediate shaft or the intermediate shaft, is changed to a 
rotation of a lower rate. Then the rotation of the lower revolving rate is 
transmitted to the latter shaft, that is, the other shaft. 
The control means for controlling the interruption of the rotational 
transmitting operation of the forward-drive planetary gear mechanism is a 
clutch provided between the ring gear or the planetary carrier and the 
corresponding rotatable shaft, or a brake provided between the sun gear of 
the forward-drive planetary gear mechanism and the casing of the 
transmission. The control means for controlling the interruption of the 
rotational transmitting operation of the reverse-drive planetary gear 
mechanism is a clutch provided between the ring gear or the sun gear and 
the corresponding rotatable shaft, or a brake provided between the 
planetary carrier and the casing of the transmission. Accordingly, each of 
the forward-drive and the reverse-drive planetary gear mechanisms reduces 
the rate of rotation transmitted to the input gear to a lower revolving 
rate and transmits rotation at the lower revolving rate to the 
corresponding rotatable shaft through the output gear. 
During forward running of the motor vehicle, the reverse-drive planetary 
gear mechanism is made idle by the control means so that the revolving 
rate of the input shaft of the forward-drive planetary gear mechanism is 
reduced to the revolving rate of the output shaft produced by multiplying 
the revolving rate of the input shaft by a ratio equivalent to the product 
of the speed change ratio of the belt drive means and the reduction gear 
ratio of the forward-drive planetary gear mechanism. During reverse 
running of the motor vehicle, the forward-drive planetary gear mechanism 
is made idle by the control means so that the revolving rate of the input 
shaft is reduced to the revolving rate of the output shaft produced by 
multiplying the revolving rate of the input shaft by a ratio equivalent to 
the product of the speed change ratio of the belt drive means and the 
reduction gear ratio of the reverse-drive planetary gear mechanism. 
Accordingly, it is an object of this invention to provide an improved 
continuously-variable speed transmission for motor vehicles, including 
individual planetary gear mechanisms for forward running and for reverse 
running, respectively, and being capable of allowing optional selection of 
the reduction gear ratios of the forward-drive and the reverse-drive 
planetary gear mechanisms. 
A further object of this invention is to provide a compact and improved 
continuously-variable speed transmission for motor vehicles, including a 
forward-drive planetary gear mechanism and a reverse-drive planetary gear 
mechanism each of a simple planetary gear system. 
A still further object of this invention is to provide a compact and 
improved continuously-variable speed transmission for motor vehicles, 
which transmission has an increased torque transmitting capacity and 
requires no additional provision of a reduction gear owing to the 
appropriate design of the reduction ratios of the forward-drive and the 
reverse-drive planetary gear mechanisms. 
Still other objects and advantages of the invention will in part be obvious 
and will in part be apparent from the specification. 
The invention accordingly comprises the features of construction, 
combination of elements, and arrangement of parts which will be 
exemplified in the construction hereinafter set forth, and the scope of 
the invention will be indicated in the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An exemplary continuously-variable speed transmission for motor vehicles in 
accordance with the invention is described referring to FIGS. 1 and 2. 
Reference numerals 1, 2 and 3 designate a starting clutch connected to an 
internal combustion engine (not shown), an input shaft of a transmission 
rotatably supported on a casing 10 of the transmission, and a well-known 
belt drive device, respectively. The belt drive device 3 comprises an 
input variable pitch pulley 31 mounted on the input shaft 2 and including 
a fixed flange fixed to the input shaft 2 and a movable flange capable of 
being moved toward or away from the fixed flange by means of a hydraulic 
servomechanism (not shown) in order to regulate the distance between the 
fixed flange and the movable flange. The belt drive device 3 also 
comprises an output variable pitch pulley 32 mounted on an intermediate 
shaft 4 disposed in parallel to the input shaft 2 and rotatably supported 
on the transmission casing 10. The output variable pitch pulley 32 has a 
construction the same as that of the input variable pitch pulley 31, and a 
V-belt 33 interconnects the variable pitch pulleys 31, 32. 
A forward-drive planetary gear mechanism 5 and a reverse-drive planetary 
gear mechanism 6 are interposed between the intermediate shaft 4 and an 
output shaft 7 of the transmission which shaft is rotatably supported on 
the transmission casing 10 coaxially with the intermediate shaft 4. The 
gear mechanisms 5, 6 are disposed independently and separately on the 
opposite sides of the output variable pitch pulley 32. The forward-drive 
planetary gear mechanism 5 comprises a ring gear 51 connected to the 
intermediate shaft 4 through a multiple disk clutch 8, a sun gear 52 
connected to the transmission casing 10, planetary pinions 53 engaging 
both with the ring gear 51 and with the sun gear 52, and a planetary 
carrier 54 rotatably supporting the planetary pinions 53 and connected to 
the output shaft 7. The forward-drive planetary gear mechanism 5 serves 
also as a reduction gear. 
The reverse-drive planetary gear mechanism 6 comprises a ring gear 61 
connected to the output shaft 7, a sun gear 62 connected to the 
intermediate shaft 4, planetary pinions 63 engaged both with the ring gear 
61 and with the sun gear 62, and a planetary carrier 64 rotatably 
supporting the planetary pinions 63 and engaged with the transmission 
casing 10 through a multiple disk brake 9. The reverse-drive planetary 
gear mechanism 6 serves also as a reduction gear. The output shaft 7 is 
connected to the driving axle of the motor vehicle through a conventional 
final reduction gear mechanism (not shown) of the hypoid gear type. 
In the forward running mode of this continuously-variable speed 
transmission for motor vehicles, the multiple disk clutch 8 is engaged and 
the multiple disk brake 9 is released by operation of a hydraulic control 
circuit, so that power is transmitted from the input shaft 2 through the 
intermediate shaft 4 and the planetary carrier 54 to the output shaft 7. 
When the gear ratio between the ring gear 51 and the sun gear 52 is 
.lambda., the forward-drive planetary gear mechanism operates as a 
reduction gear having a reduction gear ratio of 1+.lambda.. 
During the reverse running mode of the continuously-variable speed 
transmission, the multiple disk clutch 8 is released while the multiple 
disk brake 9 is engaged, so that the power is transmitted from the input 
shaft 2 through the intermediate shaft 4, planetary pinions 63 and the 
ring gear 61 to the output shaft 7. When the gear ratio between the ring 
gear 61 and the sun gear 62 is .lambda., the reduction gear ratio of the 
reverse-drive planetary gear mechanism is 1/.lambda.. 
In an alternative embodiment of the forward-drive planetary gear mechanism 
5 in accordance with the invention shown in FIG. 2, the forward-drive 
planetary gear mechanism 5' comprises a ring gear 51 connected directly to 
the intermediate shaft 4, a sun gear 52 connected to the transmission 
casing 10 through a brake 8', planetary pinions 53 and a planetary carrier 
54 connected to the output shaft 7. This embodiment provides a reduction 
gear ratio the same as that of the embodiment of FIG. 1. Similar parts 
have the same reference numerals in the Figures. 
FIG. 3 shows an alternative embodiment of the reverse-drive planetary gear 
mechanism 6. This reverse-drive planetary gear mechanism 6' comprises a 
ring gear 61 connected to the output shaft 7 through a clutch 9', a sun 
gear 62 connected to the intermediate shaft 4, planetary pinions 63 and a 
planetary carrier 64. 
FIG. 4 shows an alternative embodiment of the continuously-variable speed 
transmission for motor vehicles in accordance with the invention, wherein 
a forward-drive planetary gear mechanism 5" and a reverse-drive planetary 
gear mechanism 6" are disposed separately on opposite sides of an input 
variable pitch pulley 31 and are interposed between the input shaft 2 and 
an intermediate shaft 4' which is disposed coaxially with the input shaft 
2. The input variable pitch pulley 31 and the output variable pitch pulley 
32 of a belt drive device 3 are mounted on the intermediate shaft 4' and 
the output shaft 7, respectively. Performance results are the same as 
described above. 
It will be apparent from what has been described hereinbefore that, since a 
forward-drive planetary gear mechanism and a reverse-drive planetary gear 
mechanism are disposed separately on opposite sides of either input 
variable-pitch pulley or the output variable pitch pulley of a belt type 
continuously-variable change ratio device, and are employed as reduction 
gears, the continuously-variable speed transmission for motor vehicles in 
accordance with the invention eliminates need for the additional provision 
of a reduction gear. The continuously variable speed transmission can be 
compactly constructed and is capable of using planetary gear mechanisms of 
a single planetary pinion type since the transmission is exempt from 
constructional restrictions. Therefore, the continuously-variable speed 
transmission in accordance with the invention is compactly constructed, is 
excellent in durability, and has greater torque transmitting capacity. 
Furthermore, the respective reduction gear ratios of the forward-drive 
planetary gear mechanism and the reverse-drive planetary gear mechanism 
are subject to individual and optional selection. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are efficiently attained and, 
since certain changes may be made in the above constructions without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense. 
It is also to be understood that the following claims are intended to cover 
all of the generic and specific features of the invention herein described 
and all statements of the scope of the invention which, as a matter of 
language, might be said to fall therebetween.