Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
2002-01-15
2003-10-28
Charles, Marcus (Department: 3682)
Machine element or mechanism
Gearing
Interchangeably locked
C474S128000, C474S011000
Reexamination Certificate
active
06637283
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns transmission mechanisms for automotive vehicles, and more particularly relates to a control apparatus for a continuously variable speed ratio transmission.
2. Description of the Prior Art
Continuously variable transmission (CVT) devices employing movable-sheave pulleys with variable pitch diameters are in widespread use in recreational vehicles, golf carts, go-carts, mini-bikes and snowmobiles.
The CVT with variable pitch pulleys is described below, and this description will be best understood when read in conjunction with the following drawings in which:
FIG. 11A
is a top view of a speed-sensitive CVT at low speed.
FIG. 11B
is a top view of a speed-sensitive CVT at high speed.
FIG. 11C
is a top view of a torque-sensitive type CVT at low speed.
FIG. 11D
is a top view of a torque-sensitive type CVT at high speed.
FIG. 11E
is a top view of a torque-sensitive type CVT at medium output speed.
FIG. 11F
is a sectional view along line
11
F—
11
F of FIG.
11
A.
FIG. 11G
is a sectional view along line
11
G—
11
G of FIG.
11
.
FIG. 11H
is a sectional view along line Z-Z′ of FIG.
11
E.
Referring now to the above drawings wherein similar letters refer to similar parts, there is shown a driver pulley F and a driven pulley G interconnected by a “V” type belt H. Driver pulley F is fixedly mounted on the engine output shaft I, and is comprised of stationary sheave J and axially movable sheave K. Associated with sheave K is a bowl-shaped ramp plate L which houses centrifugally actuated roller weights M. When the engine speed increases, the roller weights M follow the contour of ramp plate L and force movable sheave K toward stationary sheave J. Such action moves V-belt H toward the outer circumference of drive pulley F, further causing the belt to pull against driven pulley G.
Driven pulley G is fixedly mounted on output shaft N, and has a stationary sheave P and axially movable sheave Q. The movable sheave Q is normally constantly pressed against the stationary sheave P by the action of a spring R and/or a cam actuator S. When equipped with spring R, pulley G is speed sensitive. When equipped with cam actuator S, pulley G is torque sensitive.
When the engine is at “idle”, or running below a preset “engagement speed”, the movable sheave K of driver pulley F rests at its farthest point from stationary sheave J, and does not apply pressure on the belt. In such condition, no power is transmitted to driven pulley G, and the system remains disengaged, namely at “neutral”. As the engine speed increases beyond the “engagement speed”, the centrifugally actuated roller weights M follow the inner contour of bowl-shaped ramp plate L, forcing movable sheave K towards stationary sheave J, thereby exerting axial displacement force against the belt. Initially, as the belt is engaged, it rides close to the center of driver pulley F and it also rides at the outer edge of driven pulley G, as shown in FIG.
11
A. The driver pulley F, therefore, carries the belt at a smaller pitch diameter while the driven pulley G carries the belt at a correspondingly larger pitch diameter by virtue of the action of the driven pulley spring R and/or cam actuator S. This creates a “low gear” ratio condition.
As the rotational speed of output shaft I increases, roller weights M move further centrifugally on ramp plate L, forcing movable sheave K against belt H which is then forced farther toward the outer edge of driver pulley F. This causes the belt to force itself deeper into the inner portion of drive pulley G as it forces driven pulley movable sheave Q farther from driven pulley stationary sheave P and compresses spring R. This creates a “high gear” ratio condition, as shown in
FIG. 11B
If the driven pulley G is equipped with a cam actuator S, when increased load occurs (such as on climbing a hill) after the vehicle is up to speed, the cam actuator takes over and automatically “downshift” without loss of engine speed, as shown in FIG.
11
E.
It is accordingly seen that the CVT mechanism is infinitely variable between the low gear position shown in
FIGS. 11A and 11C
and high gear positions shown in
FIGS. 11B and 11D
. Furthermore, the torque-sensitive type system automatically and continuously adjusts for variations in load as well.
The CVT automatic transmission is relatively inexpensive, and has found wide application in recreational vehicles, snowmobiles, lawn mowers, go-karts, golf carts, and similar vehicles. However, its use in automotive vehicles has been limited by its relatively narrow range of speed reduction ratios generally no greater than from 3:1 for “low” through 1:0.81 for “high”. This has not been adequate for cars and trucks, which require not only greater low speed torque for satisfactory acceleration, but also much higher top speeds for highway travel. Furthermore, the CVT mechanism does not readily accommodate reverse motion and parking brake functionality.
Efforts to extend the operational range of the CVT have been varied, most being through the addition of complex and expensive machinery which tends to nullify any cost advantage over conventional automatic transmissions which use hydraulic torque converters. Typical prior efforts are described in the following patent references.
U.S. Pat. No. 5,971,887 discloses infinitely variable ratio pulleys similar to the CVT described above and adds a planetary gear system associated with the output shaft, complete with the necessary hydraulic pumps, valves, pump and valve control means, brakes and clutches required for the proper functioning of a planetary gear system, to increase the range of operational speed ratios. Furthermore, instead of having a centrifugally actuated driver pulley and spring or cam actuated driven pulley, this invention uses a hydraulic system with associated sensors and control means to actuate the movable sheaves of both pulleys. These features make this transmission too complex and expensive for use in inexpensive light weight vehicles.
U.S. Pat. No. 5,931,760 describes a dual mode CVT having two sets of hydraulically controlled planetary reduction gears to extend the operating range of the system. Additionally, it places a bladed hydrokinetic torque converter unit between the engine and the planetary gearing to provide further torque multiplication for accelerating the vehicle from rest. It also provides means for bypassing the CVT altogether when large starting torque is needed. Again, this system is too complex and expensive for light inexpensive vehicles.
U.S. Pat. No. 5,961,414 describes a dual mode CVT with multiple torque input paths and at least two planetary gearsets, one for reverse and the other(s) for forward drive. Two fixed ratio drive mechanisms provide additional torque pathways with the necessary actuating and control mechanism for coordinating the functioning of the multiple torque input paths.
U.S. Pat. No. 4,990,127 describes a dual range CVT having an added fixed ratio speed mechanism to provide a second power path from the input to output shafts. Two planetary gearsets are employed to extend the torque reduction range of transmission. Multiple plate clutches and a hydraulic system are employed to operate the planetary gear system and move the flanges of the pulleys, with the help of sensors and associated control mechanisms.
U.S. Pat. No. 6,146,308 discloses a transmission having a CVT plus a planetary gear mechanism to extend the operational speed range of the system. Such transmission, as previously stated is expensive because of the necessary system of hydraulic pumps, valves, oil pressure chambers, and associated sensing and control features. Furthermore, the means for applying axial forces to the movable sheaves of the driver and driven pulleys is in the form of oil pressure chambers operated and regulated by hydraulic pumps and valves. This adds even more complexity and cost to the transmission.
U.S. Pat. No. 6,189,412 discloses a CVT wherein the movable sheaves of both the primary and secondary pulleys are hyd
Charles Marcus
Rainer Norman
LandOfFree
Control apparatus for a continuously variable transmission does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control apparatus for a continuously variable transmission, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control apparatus for a continuously variable transmission will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3145148