Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Pulley shifter
Reexamination Certificate
1999-12-08
2002-10-15
Hannon, Thomas R. (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Pulley shifter
C474S112000, C474S135000
Reexamination Certificate
active
06464604
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to tensioners for tensioning engine driven elements such as timing belts or chains. In particular, the present invention is primarily concerned with timing belt tensioners, although the principles of the present invention may also be applied to accessory belt and chain tensioners and timing chain tensioners.
BACKGROUND OF THE INVENTION
In prior art tensioners, the tensioner geometry and characteristics of the tensioner's spring are selected to ensure that the belt tension required to move the tensioner through its range of operating positions remains relatively constant throughout the range. That is, these tensioners are designed so that as belt tension increases due to engine conditions, such as thermal expansion or increased operational belt loads, the tensioner moves under the increased belt tension to compensate for such increases and maintain the belt tension relatively constant.
Prior art tensioners are normally provided with a pair of stops, one at the maximum travel position of the tensioner arm and one at the free arm position of the tensioner arm. These stops restrict the pivotal movement of the tensioner arm and provide the same with a limited range of movement. Because the belt tension required through the range is relatively constant, increases in belt tension can cause the tensioner arm to travel through the range of operating positions until tensioner arm contacts the stop at the maximum travel position thereof. When the increase in belt tension is rapid, the contact between the tensioner arm can create undesirable noises or, in the worst case scenario, damage-the tensioner. This type of increase occurs most commonly as a result of engine kickback at shutdown. If the tensioner is damaged, the engine itself may suffer extensive damage as a result of the timing belt or chain failing to operate the component(s) connected thereto in proper timing with respect to the engine cycles.
Consequently, there exists a need in the art for a tensioner that can be used in combination with vehicle engine that eliminates the problems discussed above with respect to prior art tensioners.
SUMMARY OF THE INVENTION
It is an object of the present invention to meet the above-described need. To achieve this object, one aspect of the present invention provides a combination comprising a vehicle engine, an endless flexible driving element driven by the engine, and a tensioner. The tensioner comprises a fixed structure mounted on the engine, a pivot structure pivotally mounted on the fixed structure for pivotal movement about a pivot axis, spring structure constructed and arranged to apply a tensioning torque to the pivot structure that tends to pivot the pivot structure in a tension applying direction, and a rotatable member rotatably mounted on the pivot structure for rotation about a rotational axis spaced radially from the pivot axis by a radius. The rotatable member engages the driving element in a tension applying relationship such that the driving element is tensioned and in reaction applies a hub load force to the rotatable member at an angle with respect to the radius.
The tensioner is mounted on the engine such that when the engine is in an initial condition the pivot structure is angularly positioned at an initial angular position spaced from a perpendicular angular position at which the hub load force would be applied to the rotatable member perpendicularly to the radius. The initial angular position is spaced from the perpendicular angular position in an opposite direction opposite the tension applying direction. In the initial angular position, the spring structure applies the tensioning torque to the pivot structure such that the driving element is tensioned to a first mean dynamic tension.
As the engine thermally expands to its hot engine condition, the mean dynamic tension in the driving element increases so that the hub load force applied by the driving element pivots the pivot structure in the opposite direction away from the initial angular position thereof to a hot engine angular position. In the hot engine angular position, the spring structure applies the tensioning torque to the pivot structure such that the driving element is tensioned to a second mean dynamic tension greater than the first mean dynamic tension. The tensioner is constructed and arranged such that, as the pivot structure is pivoted from the initial angular position thereof to the hot engine angular position thereof, the angle between the hub load force and the radius continually increases and the spring structure is continually increasingly stressed so that the mean dynamic tension in the driving element continually increases from the first mean dynamic tension to the second mean dynamic tension during the thermal expansion of the engine. The tensioner is also constructed and arranged such that the mean dynamic tension of the driving element required to continue pivoting the pivot structure in the opposite direction from the hot engine position thereof continually increases as a result of the angle between the hub load force and the radius continually increasing and the spring structure being continually increasingly stressed the further the pivot structure is pivoted in the opposite direction from the hot engine position.
The key feature to note of this aspect to the invention is that in the initial angular position of the pivot structure is spaced from the perpendicular angular position in the opposite direction. As a result, as the pivot structure is pivoted from the initial angular position thereof to the hot engine angular position thereof, the angle between the hub load force and the radius continually increases beyond 90 degrees and the spring structure is continually increasingly stressed so that the mean dynamic tension in the driving element continually increases from the first mean dynamic tension to the second mean dynamic tension during the thermal expansion of the engine. Likewise, the mean dynamic tension of the driving element required to continue pivoting the pivot structure in the opposite direction from the hot engine position thereof continually increases as a result of the angle between the hub load force and the radius continually increasing and the spring structure being continually increasingly stressed the further the pivot structure is pivoted in the opposite direction from the hot engine position. In prior art tensioners, the initial angular position of the pivot structure is spaced from the perpendicular angular position in the tension applying direction. Because the torque acting against the spring structure is related to the sine of the angle between the hub load force applied to the rotatable member and the radius, the sine of this angle increases as the pivot structure approaches the perpendicular angular position, thus maximizing the contribution of the tensioner's geometry to that torque. By spacing the initial angular position of the pivot structure in the opposite direction from the perpendicular angular position, the contribution offered to that torque by the tensioner's geometry is reduced, and this reduction increases as a function of the angle between the hub load force and the radius continuing to increase (and hence the sine of that angle decreasing).
In another way to achieve the object of the present invention, another aspect of the present invention provides a vehicle engine, an endless belt driven by the engine, and a tensioner. The engine is capable of applying a maximum tension to the driving element during operation thereof. This maximum tension is the known maximum tension which the engine is capable of creating, and is normally determined from either manufacturer specifications or testing.
The tensioner comprises a fixed structure mounted on the engine, a pivot structure pivotally mounted on the fixed structure for pivotal movement about a pivot axis within a range of angular positions, spring structure constructed and arranged to apply a tensioning torque to the pivot structure th
Bytzek Klaus K.
Frankowski Marek
Gajewski Witold
Lehtovaara Jorma J.
Stepniak Jacek
Hannon Thomas R.
Johnson Vicky A.
Litens Automotive Partnership
Pillsbury & Winthrop LLP
LandOfFree
Tensioner does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Tensioner, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tensioner will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2946740