Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Load responsive
Patent
1998-01-20
2000-04-18
Bucci, David A.
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Load responsive
474 28, 474 70, F16H 5900, F16H 6100, F16H 6300
Patent
active
060509120
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to improvements in a continuously variable transmission of the type wherein a belt is passed on drive and driven pulleys to accomplish power transmission from the drive pulley to the driven pulley, more particularly to the improvements to prevent the belt from slipping relative to the pulleys.
BACKGROUND ART
Continuously variable transmissions of the type wherein a belt is passed on drive and driven pulleys have been proposed and put into practical use. The belt includes an endless (loop-shaped) steel belt or cylindrical ring which is formed by laminating a plurality of endless steel sheets. A plurality of steel elements are supported on the ring in a manner to be aligned along the periphery of the ring so that the adjacent ones are contactable with each other. Each pulley includes axially movable and fixed wheel counterparts which are coaxial with and face each other to define therebetween a pulley groove. The axially movable wheel counterpart is axially movable under an axial thrust of a controlled hydraulic pressure so as to change the width of the pulley groove. A clearance is formed between the adjacent elements of the belt owing to an initial clearance and extension of the steel band. This clearance causes the belt to slip relative to the belt. Such a slip is remarkable particularly at a low gear (large transmission ratio) and reaches to several % to several tens %. This slip of the belt cannot be suppressed under changing transmission ratio even if a predetermined axial thrust is applied to the movable wheel counterpart to put the belt between the movable and fixed wheel counterparts of the pulley under a pressure. As a result, the continuously variable transmissions of this type are degraded in durability and power transmission efficiency.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide an improved continuously variable transmission which can overcome drawbacks encountered in conventional continuously variable transmissions of the type similar to that of the present invention.
Another object of the present invention is to provide an improved continuously variable transmission of the type wherein a belt is passed on drive and driven pulleys, which transmission can be effectively prevented from being lowered in durability and power transmission efficiency of the transmission.
A further object of the present invention is to provide an improved continuously variable transmission of the type wherein a belt is passed on drive and driven pulleys, which transmission can effectively and securely suppress the belt from making its slip relative to the pulley regardless of variation of a transmission ratio.
A continuously variable transmission of the present invention is for a vehicle and comprises, as shown in FIG. 14, a drive pulley 16 including axially first and second wheel counterparts which define therebetween a pulley groove. The first wheel counterpart of the drive pulley is axially movable under an axial thrust to decrease the width of the pulley groove. A driven pulley 26 is provided including first and second wheel counterparts which define therebetween a pulley groove. The first wheel counterpart of the driven pulley is axially movable under an axial thrust to decrease the width of the pulley groove. An annular belt 5 is passed on the drive and driven pulleys to drivingly connect the drive and driven pulleys. The belt is fitted in the pulley groove of each pulley. The belt includes a plurality of elements which are aligned along the periphery of the belt. A control unit is provided and configured to variably control the width of the pulley groove in accordance with a transmission ratio based on an operating condition of the vehicle under the action of shift control means 101, and set the axial thrust (Q) so that a value of (Q.times.r)/T increases as the transmission ratio becomes larger (gear becomes lower) under the action of thrust generating means 100, in which T is a transmitted torque; and r is a passed-on radius of the
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Bucci David A.
Kaness Matthew A.
Nissan Motor Co,. Ltd.
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