Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Guide roll mounted for movement of its axis along...
Patent
1999-02-02
2000-12-05
Hannon, Thomas R.
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Guide roll mounted for movement of its axis along...
474101, 474110, 474136, F16H 710
Patent
active
061559423
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention presented here involves a device for tensioning a tension element, preferably a chain, having a traction wheel, preferably a sprocket, rotatably mounted on a hollow axle, and having a hollow piston element arranged within the hollow axle and sprung against the hollow axle using a spring element, preferably a coil spring. The hollow piston element is arranged in a piston chamber such that the longitudinal axis of the piston element is arranged perpendicular to the traction wheel axis, and such that hydraulic fluid, preferably motor oil, arranged in the inner space of the hollow piston element, is provided for hydraulic damping of the piston element.
A device of this general type is known, for example, from the U.S. Pat. No. 5,366,417. The spring element is arranged in the aforementioned inner space for the hydraulic fluid and supported on one side, on the piston chamber, and on the other side, on a circular ring shaped disc of the piston element, which closes the inner space. At present, the parameters that are decisive for the design of this spring element can make a radially and axially enlarged construction space necessary for the spring element. In these types of cases, the known device can, under certain circumstances, no longer be applied, since with the radial enlargement of the piston, the oil throughput increases in the hydraulic part, when the inner space is used as a pressure chamber for the hydraulic fluid.
SUMMARY OF THE INVENTION
The object of the invention presented here is thus to further construct the device forming the generic type in such a way that the use of spring elements requiring increased construction space is possible, particularly without an enlargement of the inner space of the piston element.
This object is achieved according to the invention in that the piston element contains an outer piston, which is sprung against the hollow axle by the spring element, and an inner piston that is arranged concentrically with the outer piston and provided on the face side with a contact surface for bearing on the hollow axle.
In comparison to the known device, the device according to the invention has distinct advantages: first, the design of the inner space can be made independent from the spring component. The outer piston can be constructed to be very short in the axial direction, such that on the one hand, the masses moved are reduced, and on the other hand, more axial construction space, and thus a greater spring path, are made possible for the spring element. By the introduction of the outer piston, a larger coil diameter than in the known device is possible when using a coil spring, for example.
Preferably, the inner piston is provided with a check valve that closes in the direction towards the inner space on its face side located opposite to the contact surface. By the check valve arranged according to the invention, it is made certain that the inner space is impinged upon with a comparably small pressure. The inner space is used only as a supply chamber for the hydraulic fluid in the device according to the invention. When the motor is started, the hydraulic fluid is thus immediately available to be sucked into the high pressure chamber. According to a further embodiment of the invention, a cylindrical separation wall is provided between the outer piston and the inner piston, which on the one hand, forms a guide for the inner piston, and on the other hand, forms the boundary of an annular space, in which the coil spring is arranged. The annular space is dimensioned so that the coil spring can not be subject to an undesired excursion perpendicular to its longitudinal axis. The piston chamber preferably contains the annular space for the outer piston and a cylinder space for the inner piston. The separation wall is preferably formed by the barrel of a hollow cylinder that is supported axially on the piston chamber.
According to a further embodiment according to the invention, hydraulic fluid conveyed into the annular space gets into the in
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Hannon Thomas R.
Ina Walzlager Schaeffler OHG
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