초록 ▼

A pulley pivotable on the swinging member is pressed against a timing belt by the resilient force of a tension coil spring, and the retracting action of the pulley is made slow by the damper unit, having a cylinder and piston in the cylinder wherein a leak gap between the inner peripheral surface of

A pulley pivotable on the swinging member is pressed against a timing belt by the resilient force of a tension coil spring, and the retracting action of the pulley is made slow by the damper unit, having a cylinder and piston in the cylinder wherein a leak gap between the inner peripheral surface of the cylinder and the outer peripheral surface of the piston is controlled to have a larger vibration prevention effect for the timing belt.

대표청구항 ▼

An autotensioner for applying a proper tension to a timing belt in a vehicle engine, comprising; a first shaft supported on a fixed portion directly or by way of a fixed member fixed to the fixed portion, a swinging member freely swinging about the first shaft, a second shaft provided parallel to th

An autotensioner for applying a proper tension to a timing belt in a vehicle engine, comprising; a first shaft supported on a fixed portion directly or by way of a fixed member fixed to the fixed portion, a swinging member freely swinging about the first shaft, a second shaft provided parallel to the first shaft and on one part of the swinging member separated from the first shaft, a pulley supported so as to be freely rotatable about the second shaft, a tensioning spring provided between the fixed portion or the fixed member and the swinging member, for applying a resilient force to the swinging member to press the pulley towards a timing belt, and a damper unit provided between the fixed portion or fixed member and the swinging member, for providing a resistance to displacement of the swinging member against the resilient force of the tensioning spring, the damper unit comprising a cylinder in which viscous liquid is sealed, a piston having axial end faces and fitted inside the cylinder so as to be movable in an axial direction thereof, a biasing spring provided between the piston and the cylinder for biasing the piston in one direction, a plunger which protrudes increasingly from the cylinder with displacement of the piston under a resilient force of the biasing spring, an oil passage for communicating both of the axial end faces of the piston with each other, and a check valve provided in series with the oil passage and adapted to open only when the piston is displaced under the resilient force of the biasing spring, the tensioning spring provided outside of the cylinder, the autotensioner having the following dimensional relationships wherein r represents an inner diameter (mm) of the cylinder, d represents an outer diameter (mm) of the piston, h represents a leak gap width (mm) between the cylinder and the piston, wherein the width (h) of the leak gap is half the difference between the inner diameter (r) of the cylinder and the outer diameter (d) of the piston, that is h=(r-d)/2, m1 represents a total swinging inertial mass (kg) of the swinging member and members which swing together with the swinging member, m2 represents a total inertial mass (kg) of the members which move axially inside the cylinder with extension and contraction of the damper unit, n2/s) of the viscous liquid under operating conditions of the autotensioner, r3) of the viscous liquid under the operating conditions of the autotensioner, L represents an axial length (mm) of the small leak gap existing between the inner peripheral face of the cylinder and the outer peripheral face of the piston, K1 represents the spring constant (kg/s2) of the tensioning spring, K2 represents the spring constant (kg/s2) of the biasing spring, B1, B2, B4 represent movement direction coefficients for displacement between the pulley and the damper unit, related to the swinging member, B3 represents a movement direction coefficient for displacement between the pulley and the tensioning spring, related to the swinging member, a represents a half amplitude (kgㆍmm/s2) of fluctuations in the input load to the pulley, accompanying tension fluctuations in the timing belt under operating conditions, f represents a frequency (Hz) of the oscillations of the timing belt which is most detrimental under operating conditions, t represents time (s), x represents displacement (mm) of the pulley accompanying oscillations in the timing belt, dx/dt represents displacement velocity (mm/s) of the pulley accompanying oscillations in the timing belt, d2x/dt2 represents displacement acceleration (mm/s2) of the pulley accompanying oscillations in the timing belt, y represents the amplitude of the pulley displacement (mm) accompanying the oscillations in the timing belt, h1 represents the value of h (mm) if (y/2) is 0.7 mm, h2 represents the value of h (mm) if (y/2) is 0.05 mm, and the leak gap width (h) satisfies the following equation: (m1+B1m2)d2x/dt2+B2{(3pnrLd3)/4h3}dx/dt+(B3K1+B4K2)x=a sin (2pft) and is between (h1) and (h2) and equal to or greater than 0.002 mm.