Variable-speed V-belt drive for vehicle

Details Variable-speed V-belt drive for vehicle Variable-speed V-belt drive for vehicle

2002-02-21

2004-05-11

Charles, Marcus (Department: 3682)

Endless belt power transmission systems or components

Pulley with belt-receiving groove formed by drive faces on...

Speed responsive

C474S019000, C474S014000

Reexamination Certificate

active

06733406

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a variable-speed V-belt drive for a vehicle with an engine.
2. Description of Related Art
Referring to
FIG. 13
showing a related art of a variable-speed V-belt drive for a vehicle with an engine disclosed in JP-A 173392/1999, a driven pulley
200
has a fixed sheave
201
and a movable sheave
202
, and a cylindrical cam shaft
203
having helical cam grooves
211
. The cylindrical cam shaft
203
is formed integrally with the fixed sheave
201
of the driven pulley
200
and is fixedly mounted on a driven shaft
207
. A sleeve
205
formed integrally with the movable sheave
202
is mounted on the cylindrical cam shaft
203
so that the sleeve
205
can axially move and rotate.
A pressure adjusting mechanism for the driven pulley
200
includes the cylindrical cam shaft
203
, the sleeve
205
, rollers
214
retained on the sleeve
205
and engaged in the cam grooves
211
of the cylindrical cam shaft
203
, and pressure springs
206
biasing the movable sheave
202
toward the fixed sheave
201
.
Referring to
FIG. 14
showing the cylindrical cam shaft
203
and the sleeve
205
in an exploded perspective view, each cam groove
211
has a first working surface
211
a
and a second working surface
211
b
opposite and parallel to the first working surface
211
a
. The first working surface
211
a
, which is on the front side with respect to a rotating direction F, of each cam groove
211
engages with the roller
214
when the engine is operating in a driving mode. The second working surface
211
b
, which is on the rear side with respect to the rotating direction F, of each cam groove
211
engages with the roller
214
when the engine is operating in an engine-braking mode. The working surfaces
211
a
and
211
b
are smooth, continuous surfaces from one end of the cam groove
211
for a high reduction ratio to the other end of the same for a low reduction ratio to enable the rollers to move smoothly along the cam groove
211
.
When the vehicle travels down a hill in an engine-braking mode, the movable sheave
202
of the driven pulley
200
is shifted to a position for a high reduction ratio by the pressure springs
206
and the each roller
214
is at a position near the position for a maximum reduction ratio in the cam groove
211
(
FIG. 14
) to set the variable V-belt drive at a high reduction ratio.
As shown in
FIG. 14
, the second working surface
211
b
of the cam groove
211
, with which the roller
214
engages while the vehicle is traveling in the engine-braking mode, is parallel to the first working surface
211
a
and is a smooth, continuous surface. Therefore, it is possible that the roller
214
is forced to move from a position near the position for the maximum reduction ratio along the second working surface
211
b
toward a position for a low reduction ratio when the vehicle travels down a hill of a steep slop in the range of about 20° to about 30° and the rotative driving force of the rear wheels of the vehicle is very high. Consequently, the effective pitch diameter of the driven pulley
200
is decreased and the effect of engine brake is reduced.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a variable-speed V-belt drive for a vehicle with an engine, capable of maintaining a high engine-braking effect even while the vehicle is traveling down a hill, of enabling moderate shift from a normal engine-driving mode to an engine-braking mode without causing the vehicle to generate shocks when the vehicle starts traveling down a hill, and of enabling smooth shift from the engine-braking mode to the normal engine-driving mode.
According to a first aspect of the present invention, a variable-speed V-belt drive for a vehicle with an engine, comprises: a drive pulley mounted on a drive shaft; a thrusting mechanism mounted on the drive shaft and capable of exerting thrust to the drive pulley to vary effective pitch diameter of the drive pulley; a driven pulley mounted on a driven shaft, the driven pulley including a fixed sheave fixedly mounted on the driven shaft and a movable sheave, the fixed sheave being integrally provided with a cylindrical shaft, the movable sheave being mounted on the cylindrical shaft so that the movable sheave can rotate and axially move on the cylindrical shaft; a V belt extended between the drive pulley and the driven pulley; and a pressure mechanism of applying pressure to the movable sheave of the driven pulley, the pressure mechanism including a helical cam groove formed in one of the cylindrical shaft and the movable sheave of the driven pulley, and a roller mounted on other of the cylindrical shaft and the movable sheave of the driven pulley so that the roller engages with the cam groove, the cam groove having opposite side surfaces respectively serving as a first working surface with which the roller engages when the vehicle travels in an engine-driving mode and a second working surface with which the roller engages when the vehicle travels in an engine-braking mode, the second working surface of the cam groove having a retaining surface of retaining the roller thereon when the vehicle travels in the engine-braking mode.
Even when the vehicle travels down a hill in the engine-braking mode and the rotative driving force of the rear wheels of the vehicle increases, the roller is retained on the retaining surface of the second working surface of the cam groove to maintain the variable-speed V-belt drive at a fixed reduction ratio. Consequently, the high effect of engine brake can be maintained.
Preferably, the retaining surface is formed so that the roller is retained at a position displaced from a position for a maximum reduction ratio toward a position for a low reduction ratio.
Thus, the engine-driving mode is changed moderately to the engine-braking mode when the vehicle starts traveling down a hill.
Preferably, the second working surface is provided with a recess involving the retaining surface and having a depth equal to about half a diameter of the roller.
Thus, the recess involving the retaining surface retains the roller therein to maintain the effect of engine-braking, and enables the roller to move out of the recess smoothly when the traveling mode of the vehicle changes from the engine-braking mode to the engine-driving mode to ensure smooth change from the engine-braking mode to the engine-driving mode.
Preferably, the recess involves the retaining surface and a guide surface, the guide surface extending from the retaining surface and smoothly merging into an end surface of the cam groove on a side of the position for the maximum reduction ratio.
Thus, the traveling mode of the vehicle can be smoothly changed from the engine-driving mode to the engine-braking mode when the vehicle starts traveling down a hill.
According to a second aspect of the present invention, a variable-speed V-belt drive for a vehicle with an engine, comprises: a drive pulley mounted on a drive shaft; a thrusting mechanism mounted on the drive shaft and capable of exerting thrust to the drive pulley to vary effective pitch diameter of the drive pulley; a driven pulley mounted on a driven shaft, the driven pulley including a fixed sheave fixedly mounted on the driven shaft and a movable sheave, the fixed sheave being integrally provided with a cylindrical shaft, the movable sheave being mounted on the cylindrical shaft so that the movable sheave can rotate and axially move on the cylindrical shaft; a V belt extended between the drive pulley and the driven pulley; and a pressure mechanism of applying pressure to the movable sheave of the driven pulley, the pressure mechanism including a helical cam groove formed in one of the cylindrical shaft and the movable sheave of the driven pulley, and a roller mounted on other of the cylindrical shaft and the movable sheave of the driven pulley so that the roller engages with the cam groove, the cam groove having opposite side surfaces respectively serving as a first working sur

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