The invention relates to a tensioner, and more particularly, to an orbital tensioner having a carrier engaged with a base and revolvable about a first axis, a pivot arm mounted to the carrier, the pivot arm pivotable about a second axis, the second axis orbitally movable about the first axis.
Belt tensioners are used to impart a load on a belt. Typically the belt is used in an engine application for driving various accessories associated with the engine. For example, an air conditioning compressor and alternator are two of the accessories that may be driven by a belt drive system. A belt tensioner may include a pulley journalled to an arm which is pivotable on a base. A spring is connected between the arm and a base. The spring may also engage a damping mechanism. The damping mechanism may include frictional surfaces in contact with each other. The damping mechanism damps an oscillatory movement of the arm caused by operation of the belt drive. This in turn enhances a belt life expectancy and the tensioner life expectancy, by minimizing wear on movable components.
Dual tensioners have been applied to single belt drives which have load reversals, such as starter-generator applications, in order to tension either or both of two spans of the same belt. Since such tensioners work in concert on a single belt, they typically have a single torsion spring. Market demands can include reduction of emissions and increases in fuel economy by lowering the weight of the automobile and reducing the number of under-the-hood components. An approach taken toward these goals involves combining the function of the starter motor and the function of the alternator into a single device, a motor/generator or a gen-star. Also toward the goal of increasing fuel economy, the gen-star promotes the use of a feature called “stop-in-idle”. This feature is where the engine is allowed to die when it would ordinarily idle, then be restarted when the automobile is expected to resume motion. This feature substantially increases the demands placed upon accessory belt drives. In this type of application the starter/generator is placed in mechanical communication with the crankshaft via the accessory belt drive.
Representative of the art is EPO patent no. 2128489B1 which discloses a belt tensioning device for a belt drive which comprises a driving machine with a driving belt pulley drivable by a driveshaft around a driving axis, and a plurality of further belt pulleys, and with an infinite belt which is wrapped around the driving belt pulley and the further belt pulleys, wherein the belt tensioning device comprises a housing in which two tensioning arms are supported so as to be pivotable around a common pivot axis, in which tensioning arms there are supported tensioning rollers with axes of rotation extending parallel to the driving axis, wherein the tensioning arms are supported relative to one another by spring means, wherein the housing can be mounted, in presence of the driving belt pulley being mounted at the driving machine, in that the housing is contact-free relative to the driving machine in an annular region surrounding the driveshaft of the driving belt pulley, characterized in that the pivot axis of the tensioning arms is arranged inside the diameter of the driving belt pulley.
What is needed is an orbital tensioner having a carrier engaged with a base and revolvable about a first axis, a pivot arm mounted to the carrier, the pivot arm pivotable about a second axis, the second axis orbitally movable about the first axis. The present invention meets this need.
The primary aspect of the invention is to provide an orbital tensioner having a carrier engaged with a base and revolvable about a first axis, a pivot arm mounted to the carrier, the pivot arm pivotable about a second axis, the second axis orbitally movable about the first axis.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises an orbital tensioner comprising a base, a carrier engaged with the base and revolvable about an axis A-A, a first pulley journalled to the carrier, a pivot arm mounted to the carrier, the pivot arm pivotable about an axis B-B, a second pulley journalled to the pivot arm, the axis B-B is orbitally movable about axis A-A, a spring engaged between the carrier and the pivot arm, and a damping mechanism frictionally engaged between the carrier and the base to damp a carrier movement.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.
Carrier 103 is engaged with base 101 to move with a revolving motion about axis A-A. Pulley 104 is journalled to carrier 103 on bearing 118. Pulley 104 may be referred to as an idler pulley. Pulley 104 moves orbitally about axis A-A on member 103. Axis A-A does not engage or intersect any physical portion of the tensioner. Each of base 101 and carrier 103 encircle but do not intersect axis A-A. In particular, carrier 103 comprises hole 124 disposed in a plane when viewed edge-on that is coplanar with section 13-13, and which axis A-A intersects normally. Base 101 comprises hole 125 disposed in a plane when viewed edge-on that is coplanar with section 13-13, and which axis A-A intersects normally. Each of carrier 103 and base 101 encircle but do not intersect axis A-A. Hole 124 and hole 125 are coaxial and parallel.
Pivot arm 105 is pivotably connected to carrier 103 about axis B-B. Pulley 106 is journalled to pivot arm 105 on bearing 119. Axis A-A and axis B-B are parallel and are not coaxial. Pivot arm 105 and axis B-B orbit in a partial arc about axis A-A. Axis B-B is disposed a distance from axis A-A and also orbits with a constant radius (R3) about axis A-A. The range a for an orbital movement of axis B-B about axis A-A can be up to approximately 90 degrees, but is typically less than approximately 50 degrees. Radius (R1) of the rotational axis of pulley 106 to axis A-A is variable given the pivoting action of pivot arm 105 about axis B-B. Radius (R2) of the rotational axis of pulley 104 to axis A-A is constant. The rotational axis of pulley 104 and the rotational axis of pulley 106 are both disposed within an outside diameter (D) of the base, thereby rendering the tensioner very compact.
Damping mechanism 111 is enclosed between base 101 and cover 109. Damping mechanism 111 is disposed between carrier 103 and base 101. Damping mechanism 111 damps an oscillatory movement of carrier 103 by a frictional engagement between the damping mechanism 111 and base 101. Damping mechanism 111 is fixedly attached to carrier 103 at member 112.
Carrier 103 engages bushing 116. Bushing 116 is disposed between carrier 103 and base 101. Bushing 117 is disposed between cover 109 and carrier 103.
In this embodiment a cantilever pivot arm 1050 is used. Spring 2010 is mounted by end 2011 to the carrier 103 mounting portion 1030. The other end 2012 of spring 2010 engages a cantilever end 1051 of pivot arm 1050. Spring 2019 urges end 1051 radially outward from axis A-A which in turn urges pulley 106 toward pulley 104, thereby loading a belt (not shown). Pivot arm 1050 pivots about bolt 1052. Retaining member 1014 holds carrier 103 in engagement with base 101.
Damping member 1012 frictionally engages carrier 103 in order to damp movements of carrier 103. Spring member 1010 provides the normal force to press damping member 1012 against carrier 103.
Spring 401 is engaged between pivot arm 1050 and pivot arm 2050. Ends of spring 401 engages slot 1070 and slot 2070. Spring 401 acts upon pivot arm 1050 and pivot arm 2050 thereby urging pulley 106 toward pulley 104, which in turn loads a belt, see
Although forms of the invention have been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts and method without departing from the spirit and scope of the invention described herein.