Continuously variable transmission

Details Continuously variable transmission Continuously variable transmission

2000-09-08

2002-10-08

Bucci, David A. (Department: 3682)

Planetary gear transmission systems or components

Nonplanetary variable speed or direction transmission...

Nonplanetary transmission is belt or chain gearing

C477S046000, C474S018000

Reexamination Certificate

active

06461269

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a continuously variable transmission equipped with a forward-speed/reverse-speed changeover mechanism.
2. Description of the Related Art
As a technique associated with this type of continuously variable transmission, a belt-type continuously variable transmission disclosed in JP-A-10-274319 can be given as an example. The transmission mechanism of this continuously variable transmission is constructed in such a way that a primary shaft and a secondary shaft are disposed in parallel with each other within a casing, and an endless belt is suspended between a primary pulley provided on the primary shaft and a secondary pulley provided on the secondary shaft. The primary pulley and the secondary pulley are each constructed of a fixed sheave and a movable sheave. The movable sheave is made movable by an actuator in the axial direction. By the oil-pressure, etc. supplied to the actuator, the spacing between corresponding ones of the sheaves is adjusted such that the speed-change ratio can be varied continuously.
The drive force of an engine is transmitted to a drive-wheel side sequentially through a torque converter, an input shaft that is a rotating shaft, a forward-speed/reverse-speed changeover mechanism comprised of a planetary-gear mechanism, connected to an output side of the input shaft, the above-described speed-change mechanism, differential gears, etc.
The rotation of a turbine runner, output from the torque converter, is output to the primary shaft by being selectively changed over, through the forward-speed/reverse-speed changeover mechanism, to either one of a normal rotating direction (the forward direction of the vehicle) or a reverse rotating direction (the reverse direction of the vehicle).
Incidentally, the concrete construction is as follows. First, the input shaft is connected to the turbine runner, and the input shaft has a sun gear on the outer-periphery of its output side. Also, the planetary-gear mechanism includes pinion gears, a carrier, and a ring gear. The pinion gears mesh with the sun gear and the carrier is connected to an input side of the primary shaft. Among these members, the carrier and the input shaft are mutually connectable or disconnectable by a clutch. Also, the rotation of the ring gear can be regulated by a brake. By controlling operations of the clutch and brake independently, it is possible to change the rotating direction of the carrier, i.e. the rotating direction of the primary shaft to the normal or reverse rotating direction with respect to the input shaft.
As illustrated in
FIG. 5
, the continuously variable transmission disclosed in the Japanese Patent Publication is constructed in such a form wherein a casing
101
is formed by connecting a main casing
101
a
and a sub-casing
101
b.
The above-described forward-speed/reverse-speed changeover mechanism
102
is incorporated into a brake support
104
shaped like a cup flared from and about the primary shaft
103
. The brake support
104
is disposed within the main casing
101
a
in a state of being supported by the sub-casing
101
b
by means of bolts
105
. An input end of the primary shaft
103
is connected to the carrier of the forward-speed/reverse-speed changeover mechanism
102
. Also, the input end of the primary shaft
103
is rotatably supported by the brake support
104
through a bearing
106
.
In the belt-type continuously variable transmission, a strong clamping force is imparted to the pulley for the purpose of preventing the slip of the belt. For this reason, the tension of the belt is necessarily increased with the result that a force causing the primary shaft and the secondary shaft to move toward each other acts upon these shafts. As a result, a high magnitude of load acts upon the bearings as well that support the primary and secondary shafts.
On the other hand, as apparent from the figure (FIG.
5
), the bearing
106
for supporting one end (the rightward end in the figure) of the primary shaft
103
is supported, as if it were a cantilever, by the sub-casing
101
b
through the brake support
104
. However, there was the problem that, due to the above-described tension of the belt, the brake support
104
was flexed and resultantly the bearing
106
shifted out of its regular position. As a result of this, the belt became mis-aligned and partial (uneven) contacts thereof occurred, with the result that the cone surface of the belt or pulley (the surface or surfaces over which the belt makes its contact with the pulley) became deteriorated in a short period of time.
Also, this belt-type continuously variable transmission has a structure that two members share the function of the input shaft. The detailed construction is as follows. First, as illustrated in
FIG. 5
, a reaction shaft support
101
c,
connected to the sub-casing
101
b
, is extended to the not-illustrated torque converter side (the rightward side in the figure) along an outer surface of the input shaft
107
, and supports a stator of the torque converter. Further, one end (the rightward end in the figure) of the input shaft
107
is supported by the sub-casing
101
b
via the reaction shaft support
101
c
and a not-illustrated bearing provided between the reaction shaft support
101
c
and the input shaft
107
. Also, the other end (the leftward end in the figure) of the input shaft
107
is supported by the brake support
104
via the bearing
106
, the primary shaft
103
, and the bearing
27
provided between the primary shaft
103
and the input shaft
107
.
Here, the reaction shaft support
101
c
and the brake support
104
are positioned with respect to the sub-casing
101
b
. However, each of the bearing for supporting the one end (the rightward end in the figure) of the input shaft
107
, the bearing
106
for supporting the one end (the rightward end in the figure) of the primary shaft
103
, and the bearing
27
provided between the primary shaft
103
and the input shaft
107
contains the part-precision error and assembling error within a prescribed permissible range. For this reason, the center axes of these bearings are not in coincidence with one another, with the result that there was the problem of the input shaft
107
becoming deteriorated in terms of the centering precision. It is to be noted that it is difficult, with an ordinary attaching operation, to cause the center axes of these bearings to coincide with one another with high precision. So, there was conventionally a certain limit to enhance the centering precision of the input shaft
107
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a continuously variable transmission that can maintain the bearing members of the primary and secondary shafts at their regular positions despite the tension or tensile force of the belt, and maintains the belt alignment as it is being apt, thereby enhancing the durability, especially a bearing structure of the belt-type continuously variable transmission.
Another object of the present invention is to provide a continuously variable transmission that can obtain the centering precision of each rotating shaft at very high accuracy.
To attain the above object, according to the first aspect of the present invention, there is provided a continuously variable transmission including, within a casing, a continuously variable transmission mechanism that includes a primary pulley provided on a primary shaft, a secondary pulley provided on a secondary shaft, and a belt suspended between both pulleys and enabling the transmission of a motive force between the pulleys, and that, by changing-the groove width of one of the primary pulley and secondary pulley relative to the groove width of the other, enables continuous adjustment of the speed-change ratio, and a motive-force connection/disconnection mechanism that, by being connected to either one of the primary shaft and the secondary shaft, enables connection/disconnection between an input side element for the motive force and an out

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