FR2653846A1 - SELF - ADJUSTING TENSION DEVICE. - Google Patents

Abstract

An automatically adjustable tensioning device is provided for damping by friction of the rotational movement varying as a function of the temperature. For this purpose, the members 2.5 movable in rotation with respect to one another are applied with friction against each other and put under stress. The stress is produced by means for example of bimetallic springs reacting as a function of the temperature, such as, for example, spring washers 11. Thus, from the cold phase to the hot phase of the engine, a constant or increasing friction damping is obtained. temperature.

Description

The invention relates to an automatically adjustable tension device for

  drive belt or the like comprising a tensioner roller movable in the direction of the tension and in the direction of the rebound applied with preload by means of a spring against the drive belt and means of friction damping

  movement at least in the direction of trigger.

  Automatic tensioning devices are most often fitted with a spring which applies the roller

  mobile tensioner in rotation or translation with pre-

  slides against the drive belt. This is constantly kept taut regardless of dynamic or quasi-stationary variations such as for example wear due to aging or elongation, variations in tension due to temperature, or elongations.

  partial belts under pulsating loads, etc ...

  In the presence of pulsating loads, especially in the direction of expansion, moments of inertia among others of the tensioning device occur with the consequence that the drive belt is relaxed for a short time, or works with reduced tension. For this reason, the adjustment movement of the tensioning device is damped at least in the direction of expansion. this is

  obtained for example by means of friction elements.

  A tensioning device of this type is known from document DE-OS 2.608. 277. An oscillating arm carries at one of its ends a tension roller and is articulated movable in rotation by its other end which is clamped between friction discs. A free wheel causes a displacement without damping, therefore instantaneous in the direction of the tension and a damped displacement in the direction of relaxation. The damping force should be constant under all operating conditions. This is however not the case with the known tensioning device given

  that the friction elements usable at a reasonable cost

  ble have coefficients of friction varying as a function of the operating temperature. In addition, the springs used for the production of the friction force are

tire as you get older.

  The object of the invention is to create a device for

  voltage of the defined type which presents, for all conditions

  operating conditions, a damping of the regular and increasing rotational movement with the temperature of

operation.

  This objective is achieved by means of an element regulating the friction damping according to the

engine temperature.

  It is thus possible to compensate in a simple manner for the greater damping coming for example when the engine is cold, higher coefficients of friction of the friction surfaces, or the production of greater friction forces resulting from a

  stiffening of the springs, or even variations

  of the elements under the effect of the cold. This allows for example to produce a constant damping effort under all operating conditions. It is also possible, by a corresponding dimensioning, to produce an overportional behavior, for example a lower damping when the engine is cold. If a particular construction, an inverse characteristic is obtained, that is to say a higher damping when the engine is hot, it can be kept constant, or its evolution can be modified in the necessary temperature range, thanks to the characteristics according to the 'invention. In a preferred embodiment, the elements are produced in the form of bimetallic strips to which predetermined behavior characteristics can be given by the

  judicious choice of materials, shape and dimensions.

  Other materials or elements whose dimensions vary as a function of temperature, such as for example expansion capsules filled with fluid or the like,

  can be advantageously used.

  These and other characteristics

  ticks are described using the examples shown on

the drawing.

  Figure 1 shows the partial longitudinal section of an automatic tensioning device comprising an axially acting friction damper and a washer

bimetallic elastic.

  Figure 2 shows the partial longitudinal section of an automatic tensioning device comprising

  bimetallic shells acting radially.

  Figure 3 shows the cross section

  partial along line A-A according to Figure 2.

  The tensioning devices shown in the figures mainly consist of a support pin 2 fixed on a support 1 or directly on an engine block and a

  tensioner roller 3 mounted to rotate on the support axis.

  The roller is mounted via the inner ring 4 of the bearing on an eccentric sleeve 5 which is mounted

  mobile in rotation on the support axis 2. The eccentric bushing

  that 5 comprises an axial stud 6 which engages in the outer end of the spiral spring 7. The inner end of the spiral spring is fixed by means of a pin 8 on the support 1. The tensioning roller 3 is applied with prestressing against a drive belt not represented by the

spiral spring 7.

  In the arrangement shown in Figure 1, a friction disc 9 is applied against the front face of the eccentric sleeve 5. The disc is prestressed in the axial direction by means of an elastic washer 11 and an adjusting nut 10 and produces friction damping of the oscillating movement. The elastic washer 11 is produced in the form of a bimetallic strip, the axial tension force of which varies in

  temperature function. The initial value of the depreciation

  friction friction can be adjusted by means of the adjusting nut 10. A sliding sleeve 12 is mounted between the

  eccentric sleeve 5 and the support axis 2.

  In the example shown in Figures 2 and 3, radially acting friction damping is used in place of the axially acting damping. For this purpose, an annular groove 13 is machined in the support axis 2. This extends axially over a part of the surface of the bore 14 of the eccentric sleeve 5. Shoulders 15 of the support axis 2 extending axially on either side of the groove serve as a guide surface

  to the eccentric sleeve 5 in its oscillating movement.

  In the groove 13 are arranged, as best seen in Figure 3, four bimetallic shells 16 distributed over the circumference. They are applied elastically to the bottom of the groove 13 and against the surface of the bore 14 of

  the eccentric sleeve 5 and their efficiency increases significantly

  with temperature. This results in an increase in the application force and as a result of the damping by friction of the oscillation movement. The eccentric sleeve 5 is blocked axially by means of a washer 17, an elastic washer 18 and a locking nut 19

with washer.

Claims (6)

  1. Tensioning device with automatic adjustment for drive belt or the like comprising a tensioning roller movable in the direction of the tension and in the direction of the relaxation applied with pre-stress against the belt by means of a spring and means amortization of   movement at least in the direction of relaxation, characteristic   laughed at by an element (11, 16) regulating the amortization by   friction as a function of engine temperature.   2. Tensioning device according to claim 1, characterized by elements of material with coefficient of high temperature.   3. Tensioning device according to claim 1,   characterized by bimetallic elements.   4. Tension device according to at least one   any of claims 1 to 3, characterized by a disc (11) acting axially.   5. Tension device according to at least one   any of claims 1 to 4, characterized by a elastic washer (11).   6. Tension device according to at least one   any of claims 1 to 3, characterized by   shells (16) acting radially, the curvature of which changes.