Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Tension adjuster has surface in sliding contact with belt
Patent
1998-03-20
1999-10-19
Graysay, Tamara L.
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Tension adjuster has surface in sliding contact with belt
474140, F16H 708
Patent
active
059679220
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a tensioning device for the chain or the toothed belt of a camshaft drive of an internal combustion engine comprising a guide rail for guiding the chain or the toothed belt in the tensioned portion thereof, a pivoted tension lever for transmitting the pre-tension by acting on the slack portion of the chain or the toothed belt and a tension element which exerts a tensioning force on the tension lever through a compression spring.
BACKGROUND OF THE INVENTION
Modern internal combustion engines with unchanged or even enhanced performances are being constructed with ever decreasing outer dimensions. Besides this, due to the employment of multi-valve techniques, more and more engines have an increasing number of camshafts. This results in a considerable reduction of the design space disposable for the control gear. Many known tensioning devices are too large and therefore not usable.
Tensioning devices are known from the documents GB,A, 1 206 705 and DE,C, 3 623 903. In the device of the latter document, a tensioner housing for lodging the tension element, a guide rail for the chain and a pivoted sliding block are arranged separately from one another on the engine casing. The space requirement of this tensioning device is therefore considerable and its assembly complicated.
SUMMARY OF THE INVENTION
The object of the invention is to create a tensioning device for a control gear which is usable in a very small mounting space and can compensate a large chain elongation.
The invention achieves this object by the fact that two sliding blocks acting in different directions on the chain or the toothed belt are arranged on the tension lever which has a fixed axis of pivot. In this way, due to the two sliding blocks arranged behind each other and acting in opposite directions, the tensioned region of the chain tensioned by the tension lever acquires a slightly sinusoidal shape with only small deflections.
The axis of pivot of the tension lever can be arranged on the bearing cap of the bearing of a camshaft. However, it is also possible to arrange the axis of pivot of the tension lever, i.e. its fulcrum, on the guide rail or at another point on the engine. The guide rail can be arranged in the cylinder head of the internal combustion engine and can be fixed there detachably by screws. In this case, the entire tensioning device can be fixed as one single unit at two screwing points on the engine so that a quick and simple mounting is assured.
The tension element can be arranged in a tensioner housing formed on the guide rail. The guide rail and/or the tension lever can be configured as metal elements. If an aluminium alloy is used for this purpose, the advantage of a very light structure is obtained.
A slide lining of a polymeric material for the chain can be applied to the guide rail and the sliding blocks for the chain can likewise be made of a polymeric.
BRIEF DESCRIPTION OF THE DRAWINGS
Examples of embodiment of the invention are represented in the drawings and will be described more closely below. The drawings show:
FIG. 1, a tensioning device installed in the cylinder head of an internal combustion engine, comprising a tension lever which is pivoted on a fixed guide rail;
FIG. 2, a section through the tension lever along line II--II of FIG. 1;
FIG. 3, a view of the tension lever following the direction of the arrow III--III of FIG. 2;
FIG. 4, a section through the guide rail and the tension lever mounted thereon, along line IV--IV of FIG. 1;
FIG. 5, a top view of the guide rail;
FIG. 6, a further embodiment of the tensioning device, mounted in the cylinder head of the internal combustion engine with the tension lever mounted separately from the guide rail.
DETAILED DESCRIPTION OF THE DRAWINGS
A tensioning device of the invention shown in FIG. 1 is installed in a cylinder head 1 of an internal combustion engine. The installing space is closed in outward direction by a cylinder head cover 2. The function of the tensioning device is to produce a pre-tension in a
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Patent Abstract of Japanese Patent 59-20850(A).
Schuseil Bolko
Ullein Thomas
Charles Marcus
Graysay Tamara L.
Ina Walzlager Schaeffler OHG
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