WO2007051788A1

WO2007051788A1 - Tensioning device for a drawing means, in particular a belt

Info

Publication number: WO2007051788A1
Application number: PCT/EP2006/067957
Authority: WO
Inventors: Rainer Pflug; Thomas Mennerat
Original assignee: Schaeffler Kg
Priority date: 2005-11-03
Filing date: 2006-10-31
Publication date: 2007-05-10
Also published as: DE102005052453A1

Abstract

Tensioning device for a drawing means, in particular a belt, having a base part which is to be arranged in a stationary manner and a tensioning lever which can be rotated relative to the former counter to a helical spring and has a tensioning element which acts on the drawing means, wherein the torsion spring is mounted with one end on the base part and with the other end on the tensioning lever, wherein at least one supporting element (14, 22) is arranged on at least one winding (16, 23) of the helical spring (9, 24) which is arranged so as to open in the event of a lever movement, which supporting element (14, 22) is pressed against a housing-like lever section (7, 29) which surrounds the helical spring (9, 24) or a housing-like base-part section as a consequence of the spring prestress or in the event of a lever movement, and which supporting element (14, 22) is arranged offset by an angle (α) between 60° - 120°, as viewed in the winding direction, with respect to the bearing location of the helical spring (9, 24) on the base part (2, 26).

Description

Name of the invention

Clamping device for a traction means, in particular a belt

description

Field of the invention

The invention relates to a tensioning device for a traction means, in particular a belt, with a fixedly arranged base part and a rotatable relative to this against a coil spring tensioning lever with a tensioning means acting on the tensioning means, wherein the torsion spring mounted with one end on the base part and the other end on the tension lifting is.

Background of the invention

A tensioning device of the type described serves to continuously tension a traction means, for example a belt or a chain of an internal combustion engine, in order to compensate for length variations due to operation or aging. For this purpose, the clamping device is attached via a base part, for example, to an engine block, wherein the base part is stationary and secured against rotation. A tensioning lever, on which a tensioning roller or a tensioning shoe is arranged, over which the traction means runs, is rotatably coupled to the base part via a helical spring about a central axis. The helical spring is prestressed, so that a tensioning force is exerted on the traction means via the tensioning lever, wherein the tensioning lever can also be moved via the traction means, for example during a change of the run, against the helical spring.

The clamping element, so for example, the tension roller or the clamping shoe is located - axially seen - outside the bearing plane in which the clamping lever on the base part or a central, connected to the base bolt is rotating, in particular sliding. As a result of the eccentric introduction of the clamping force on the traction means, the bearing is not only loaded radially, but in addition with a tilting moment. As a result, the outer bearing edges are overloaded and the bearing or sliding layer can not be exploited in its full width, resulting in a shortened bearing life. About the inevitably resulting bearing wear, the tilt increases steadily, whereby the specified limit for the maximum allowable tilt of the clamping lever is achieved relatively early.

Summary of the invention

The invention is thus based on the problem of providing a clamping device with a possibility for reducing or compensating the operationally acting overturning moment.

To solve this problem is provided according to the invention in a clamping device of the type mentioned that at least one turn of the lever spring opening arranged at least one supporting element is arranged, which due to the spring bias or a lever movement against a coil spring surrounding the housing-like lever portion or housing-like Base section is pressed, and the storage location of the coil spring on the base part by an angle between 60 ° - 120 ° - seen in the winding direction - offset.

The invention is based on the idea of generating a Gegenkippmoment for compensating the Hebelkippmoments what purpose, according to the invention a support member is provided, via which the coil spring is supported on the housing-like lever portion, while it is itself a torque transmitted to the base part set. While in known Spanneinrichtun- gene in which the coil spring is mounted with an outer and an inner Abstützpunkt on the base part, the spring torque acts as a pair of forces with the same direction and the same amount alone on the base part, from which - because the distance of these forces to the fulcrum tipping is equal to - no significant Gegenkippmoment results, the inventive decoupling of the two forces offers the opportunity to build a targeted Gegenkippmoment. As a result of the decoupling which acts on a force on the stationary base part, on which the coil spring is counteracted. A second force component is exerted due to the support of the coil spring on the support member on the lever portion and thus on the lever itself, said support is offset at a position relative to the storage location of the coil spring on the base part. In this case, the support basically due to the spring preload in opening spring arranged, which thus increases radially under load or expanded in radius, take place, ie, the support member is continuously applied to the lever portion. It is also conceivable, however, for the support element to be pressed against the lever section only when the lever moves.

The integration and positioning of the support element offset from the storage location of the coil spring on the base part, a significant Gegenkippmoment be generated, which leads to a reduction or in favorable cases, even to a complete compensation of the caused by the belt clamping force overturning moment. This means that the asymmetric, wear-promoting stress of the plain bearing is significantly reduced, that is, the life of the bearing can be significantly increased. The sliding layer, after only a reduced or no tilting moment acts, can be exploited in its surface much more extensive, there is also the possibility to increase the contact area between the lever and the plain bearing bushing. Although due to the support, the force acting on the plain bearing radial force increases, but this acts symmetrically on the bearing, so does not lead to a tilting moment.

Another considerable advantage of the integration of the support element is that the force acting on the support element force can be used for friction generation. Because the pressed against the lever portion support member which is preferably secured against rotation, but arranged radially movable, for example, in a radially extending groove on the base part, rubs during the lever movement on the lever, thus dampening the lever movement. Thus, an additional friction element is created parallel to the mechanical friction of the friction disk usually provided and the sliding bearing, the height of which depends on the angle of rotation of the spring and thus on the operating position of the tensioner.

The angle at which the support element is offset with respect to the storage location of the coil spring on the base part, should be in a development between 70 ° - 110 °, even a smaller interval of 80 ° - 100 ° is conceivable. Preferably, the support element is arranged at approximately 90 ° relative to the storage location, in which context it should be noted that the support element itself, of course, has a certain length, so that the 90 ° position, for example, refers to the longitudinal center of the support element. The support element itself preferably has an outer abutment surface adapted to the curved shape of the lever section, which extends at a certain angle, for example between 5 ° and 60 °, that is to say the support element has an outer friction surface which is finite in its length.

In addition to the use of a plurality of individual support elements, which may be arranged on individual turns of the coil spring, it is also conceivable to form the support element oblong and in one piece, so that it rests against one or more further turns and can be pressed over its length to the lever portion. As a result, so the counter bearing surface increases as well as the friction surface. It is also expedient in this embodiment that, as a result of the at least temporary contact of the helical spring windings on the lever section, vibrations are damped or avoided perpendicular to the spring longitudinal axis via the support element.

Alternatively, however, it is also conceivable to provide an elongate section on the support element, which bears against one or more further windings for vibration damping. That is, it is an axially or parallel to the axis of rotation extending portion provided on which abut the one or more further turns, which thus antires this and so any vibration dampens.

For ease of assembly, the support member is preferably clipped or glued to the respective turn. Further attachment is not required as a result of the determination or guidance in a corresponding groove or the like on the base part.

Conveniently, the support element made of plastic, preferably a sliding bearing material such as PA 4.6 PTFE 15.

With regard to the abutment of the coil spring on the base part, different embodiments are conceivable. A particularly advantageous embodiment provides for counteracting the helical spring with its end face against the base part. So here is a dull Auflagerung realized, the force or torque introduction takes place directly on the front side of the spring. In conjunction with the inventive arrangement of the support element, offset by the angle described above, this results in an optimal Momentenbzw. Force distribution and support against the clamping lever, so that the zugmittelkraftbedingte overturning moment can be largely compensated.

However, it is also conceivable to provide an abutment of the helical spring with an end section bent inwards or outwards or axially angled, with which the spring is abutted against an abutment on the base part. Here as well, there is a punctual spring bearing which allows the introduction of high moments or forces and, in conjunction with the positioning of the support element according to the invention, permits the generation of a high counter-overturning moment.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of an embodiment and with reference to the drawings. Showing: 1 is an exploded view of a clamping device according to the invention,

2 shows the assembled clamping device of FIG. 1 in section,

3 is a plan view of the base part laterally mounted spring end with arranged support element,

Fig. 4 is a partial view of a clamping device with a differently shaped support element.

Detailed description of the drawings

Fig. 1 shows an inventive clamping device 1 in the form of an exploded view. The clamping device 1 comprises a base part 2, which passes through a fastening screw, which is not shown here, and which provided on the base part 2 sleeve 3, for example, is screwed to an engine block. About a pin 4, which engages a motor block-side recess, the base part 2 is secured against rotation. Further, a clamping lever 5 is provided, comprising a bearing portion 6 for a tension roller not shown in detail, and a housing-like lever portion 7. Further provided is a sliding bearing 8, which causes the mounting of the clamping lever 5 on the sleeve 3. The movement of the clamping lever 5 relative to the base part 2 takes place against the restoring force of a coil spring 9, which is arranged with one end on an abutment 10 on the base part 2 and with the other end to a counter-bearing not shown here on the clamping lever 5. Further, a friction plate 11 is provided and an upper end plate 12 which is snapped onto the sleeve 3 in a corresponding annular recess 13 and the clamping device is locked in the mounting position with axially biased coil spring 9. Also provided is a support element 14, which has a clamping groove 15, via which the support element 14 is placed on the first turn 16, which follows the bearing section of the coil spring 9 at the base end portion thereof. Fig. 2 shows the clamping device 1 in the mounted state. Although not shown in this sectional view, the tension spring 9 is stumped on the counterbearing 10 with its base-part-side free end or end face 17, cf. Fig. 3. With its opposite end it is connected in a conventional manner known with the tensioning lever 5. During the movement of the clamping lever 5 against the restoring force of the spring, this opens, ie, the turns will move outwards due to the lever movement, over which the spring torque is built up. The lever movement relative to the base part 2 is mounted on the slide bearing 5, which - as described - between the sleeve 3 and a bearing portion 18 of the clamping lever 5 is arranged. During this rotational movement, damping is realized relative to the tensioning lever 5 moved past it via the friction disk 11, which is arranged, for example, against the closing disk 12.

The support member 14 is, as shown in FIG. 3 in plan view, placed on the first turn 16. The angle α between the abutment point of the coil spring 9 on the base part, ie the point where the end face 17 is counter-mounted, and the position at which the support member 14 is disposed on the winding 16, is - with respect to the center of the support member - shown Embodiment 90 °. However, this angle can vary between 60 ° - 120 ° or in a slightly limited interval between 70 ° - 110 ° and can be selected depending on the design.

In any case, this arrangement causes the support member 14 is pressed with its outer abutment surface 19 against the inner side 20 of the housing-like lever portion 7 at a lever movement caused opening of the coil spring 9 in which the turns and the winding 16 are moved radially outward is, wherein the shape of the contact surface 19 corresponds to the shape of the inner side 20 of the lever portion 7. As a result, on the one hand, the possibility of the transmission of force from the coil spring 9 on the lever portion 7, on the other hand can also be increased thereby the friction and thus damping of the system. Visible here are the location of the abutment of the coil spring and thus the force or torque introduction into the base part and the location of the abutment of the coil spring on the housing-like lever portion 7 separated and offset by the angle α, ie, the respective forces are in two different components , namely once the base part 2, on the other hand, the lever portion 7 and thus the lever itself initiated. This makes it possible to generate a Gegenkippmoment to the tipping moment generated by the Zugmittelspannkraft that acts on the clamping lever 5.

In Fig. 2, the forces are shown, which act on the clamping lever and generate torques and resulting tilting moments in the cutting plane. On the one hand, the tension force Fz _ug exerted by the traction means is shown. This force will produce a tilting moment on the bearing 8 due to the off-center application of force. To counteract this, the support element 14 is provided on the opposite side, which is arranged on the opposite side with respect to the pivot point of the clamping lever by which this would be rotated via the Zugmittelspannkraft Fz _U g. About this support element, a supporting force F _{Stutz is} generated, from which a Gegenkippmoment results, which prevents the clamping lever 5 is tilted and therefore given an unbalanced position stress. From the two forces Fz _ug and Fstutz results in a bearing force Fι_ _a ger, which is opposite to the two forces. Although this is higher than without the use of the support member 14, but it acts symmetrically, ie, there are no asymmetric forces or tilting moments on the bearing 8, resulting in longer lifetimes.

For a radial movability of the support member 14, this is radially movably guided in a groove 21 on the base part, but axially supported as well as secured against rotation. During the lever movement and the tension spring 9 which thereby opens, the support element 14 can thus be moved outwardly in the radial groove 21 into contact with the inner surface 20 of the housing-like lever section 7. A further embodiment of a usable support element 22 is shown in FIG. 4. This, like the support element 14, is clipped onto the winding 23 and at an angle α in the specified interval of 60 ° -120 °, preferably in the range of approximately 90 °, positioned relative to the storage location of the end of the coil spring 24, not shown in detail and also radially movable, but axially as well as against rotation in a groove 25 on the base member 26 is arranged. In case of a lever movement opening spring 24, the support member 22 is pressed against the housing-like lever portion 29, the Gegenkippmoment generating. In addition, here an elongated portion 27 is formed, which extends axially along the following turns 28 of the coil spring 24. About this elongated portion, a radial vibration of the coil spring 24, which is possible under external excitation, for example by the internal combustion engine, are damped.

It can be seen in this embodiment, the contact surface of the support member 22, compared with the embodiment of FIG. 1, slightly larger, resulting in a different damping behavior results. Of course, this damping behavior can also be varied by the choice of the material of the respective support element as well as its length or the length of its contact surface.

While Figures 2 and 4 show embodiments in which the support member is pressed against a housing-like lever portion, a design would be conceivable in which the support member is pressed against a housing-like base section. Starting from z. B. Fig. 2 would be in such an embodiment, the base part 2 like a housing and the coil spring executed laterally at least in the lower area, the housing-like lever portion 7 would be replaced or at least shortened. With the spring opening, the support element 14 would then be pressed against the raised, surrounding base part. reference numerals

1 clamping device

2 base part

3 sleeve

4 cones

5 tension levers

6 bearing section

7 lever section

8 plain bearings

9 coil spring

10 counter bearings

11 friction disc

12 end plate

13 annular recess

14 support element

15 clamping groove

16 turn

17 front side

18 bearing section

19 contact surface

20 inside

21 groove

22 support element

23 turn

24 spiral spring

25 groove

26 base part

27 section

28 turns

Claims

claims

1. clamping device for a traction means, in particular a belt, with a stationary to be arranged base part and a rotatable relative to this against a coil spring tensioning lever with an am

Traction means engaging clamping element, wherein the torsion spring is mounted with one end on the base part and the other end on the clamping lever, characterized in that at least one turn (16, 23) of the opening during a lever movement arranged coil spring (9, 24) at least one support element (14, 22) is arranged, which is pressed due to the spring bias or a lever movement against a coil spring (9, 24) surrounding the housing-like lever portion (7, 29) or box-like base section, and the storage location of the coil spring (9, 24) on the base part (2, 26) by an angle (α) between 60 ° - 120 ° - seen in the winding direction - is arranged offset.

2. Clamping device according to claim 1, characterized in that the angle (α) between 70 ° - 110 °, and preferably 90 °.

3. Clamping device according to claim 1 or 2, characterized in that the supporting element (14, 22) on the base part (2, 26) secured against rotation, but is arranged radially movable.

4. Clamping device one of the preceding claims, characterized in that the support element (14, 22) has a curved shape of the lever portion (7, 29) adapted outer bearing surface (19), preferably at an angle between 5 ° - 60 ° extends.

5. Clamping device according to one of the preceding claims, characterized in that the (14, 22) supporting element is elongated, to one or more further turns and is pressed over its length to the lever portion.

6. Clamping device according to one of claims 1 to 4, character- ized in that on the support element (22) has an elongated portion

(27) is provided, which bears against the vibration damping at one or more further turns (28).

7. Clamping device according to one of the preceding claims, character- ized in that the support element (14, 22) on the winding (16, 23) is clipped or glued.

8. Clamping device according to one of the preceding claims, characterized in that the support element (14, 22) made of plastic, in particular a sliding bearing material.

9. Clamping device according to one of the preceding claims, characterized in that the helical spring (9, 24) with its end face (17) is counter-supported on the base part (2, 26).

10. Clamping device according to one of claims 1 to 8, characterized in that the helical spring (9, 24) has an end, bent inwards or outwards, or axially angled portion, with which it is gegengelagert to an abutment on the base part.