Internal combustion engine belt drive

ES 2 182 802 T3

DESCRIPTION

Belt drive for an internal combustion engine.

Field of the invention

The present invention relates to a belt drive for an internal combustion engine. In particular, the invention relates to belt drives, in which a device called a starter-generator is placed in the drive mechanism of the belt. The starter-generators of this class perform two functions: firstly the starting of the internal combustion engine and secondly the generation of the electric current during the operation of the internal combustion engine. Due to the double function of the starter-generator, in a belt drive device the actuator branch (working) and the driven branch (no-load) alternate, depending on the operating mode of the starter-generator. All the auxiliary devices generally placed on the belt drive device, such as the water pump or the servo pump, can be operated electrically with the electrical energy produced by the starter-generator. It is possible that the pulley for the belt that reaches the crankshaft and the pulley for the starter-generator belt are positioned on the belt drive.

Background of the invention

Tensioning devices having two tensioning arms can be used in such a belt drive. Each tensioning arm was elastically supported against a branch or section of the belt. From patent document DE-42 43 451 -A1, which is considered to be the closest state of the art, for example, a tensioning device for tensioning means, such as belts or chains, has been disclosed in which Two clamping arms are provided which can be pivoted on a common axis of rotation and each one is elastically held against a branch of the belt. This known tensioning device, however, is not suitable for use for a belt drive with generator-starter, since both tensioning arms can swivel together around the axis of rotation without a relative displacement relative to each other during the operation of the internal combustion engine. Thus, there is a danger that the entire system may undergo large vibrations due to dynamical excitation in the field of natural frequency, which in turn will negatively influence the operation of the tensioning system.

Object of the invention

The object of the present invention, therefore, is to avoid these drawbacks. Summary explanation of the invention

With the present invention, a belt drive for an internal combustion engine is proposed, in whose crankshaft a first pulley for the belt is placed, with a starter-generator, on whose shaft a second pulley for the belt was placed, with a belt. , in particular a toothed belt or a V-belt with internal teeth, which surrounds the two mentioned pulleys, with a tensioning device, whose two tensioning arms each press on a section or branch of the belt, which acted as an actuator branch (working) or as a driven branch (in vacuum) and which extends between the pulleys adjacent to each other for the belt, in such a way that the two tensioning arms pivot respectively around an axis of rotation preferably located within the surface surrounded by the belt, the tensioning rollers being held in the tensioning arms, preferably positioned outside this surface surrounded by the belt and elastically supported against the belt, so that the tensioning arm positioned on the working actuator branch is pressed by the force of the belt to a stop position.

The invention takes advantage of the effect that a resultant force of the belt acted on the working actuator branch, which is greater than the force on the idle driven branch. The belt drive carried out according to the invention was constructed in such a way that, under this resultant force of the belt with a higher value in the working drive branch, the respective tensioning arm is pressed inwards to this stop position and is held. there. This means that the tensioning roller located on this tensioning arm works only as a reverse roller in the direction of the belt. This also means that only the tensioning arm located on the trailing branch is working properly.

This stop position, according to an advantageous variant of the invention, was formed in such a way that a distance between the axis of rotation of the tensioning arm and the fulcrum of the tensioning roller on the belt is smaller than a distance in perpendicular to this axis of rotation and a tangent, which passes tangentially over the two pulleys adjoining each other for the belt. If a branch of the belt acted as a working actuator branch, this branch approaches the aforementioned tangent so that the useful lever arm becomes smaller, which produces a torque directed against the tensioning spring together with the resulting force. of the strap. The tensioning arm, therefore, moves to a neutral position, in which no lever arm acted or in any case only a very small lever arm for the resulting tensioning force of the belt. This means that the resultant force from the belt acted only as a pulling force on this tensioning arm. In other words, the axis of rotation of the tensioning arm is positioned in the belt drive so that the tensioning arm is swung to one side, under the resultant force of the belt on the work actuator branch, until the resultant belt force is at least roughly aligned with the tensioning arm.

The belt drive carried out according to the invention may comprise auxiliary devices or rollers for reversing the direction of passage. However, preferably the starter2 is placed on the belt drive alone.

ES 2 182 802 T3 generator.

Instead of the described position of the dead center of the tensioning arm, a fixed stop can also be provided on the frame, against which the tensioning arm located on the work actuator branch is pressed under the resulting force of the belt, being kept in that position. This means that also in this variant realized according to the invention it is ensured that the tensioning roller located in the working actuator branch works as an almost rigid roller to reverse the direction of passage.

A variant of the invention provides that both tensioning arms pivot around a common axis of rotation. This ensures a space-saving layout. Naturally, other variants are also possible according to the present invention, according to which the two axes of rotation of the two tensioning arms are located at a distance from each other.

Since the two tensioning rollers are preferably positioned outside the surface surrounded by the belt, a tensioning spring can be provided which acts between the two tensioning arms and pressing both tensioning arms against each other.

Brief description of the drawings

The invention is further explained in detail below by means of an embodiment example represented in two figures in the attached drawings. Specifically shown:

- in figure 1 a belt drive carried out according to the invention, in a starting phase of the internal combustion engine ^Y

- in figure 2 the belt drive carried out according to the invention and represented in figure 1, during the operation of the internal combustion engine.

Detailed description of the drawings

In a belt drive for an internal combustion engine, a crankshaft 1 and a starter-generator 2 are provided. The crankshaft 1 carries a pulley 3 for the belt, and the shaft not represented in the drawing of the starter-generator 2 carries a second pulley 4 for the strap. A belt 5 surrounds the two pulleys 3, 4. In addition, a tensioning device 6 is provided, comprising two clamping arms 7 and 8. Each clamping arm 7, 8 carries at its end a tensioning roller 9, 10. Both tensioning arms 7, 8 are pivotally positioned around a common axis of rotation 11. While the axis of rotation 11 is located within the surface surrounded by the belt 5, the two tensioning rollers 9, 10 are positioned off the belt 5.

Between the two clamping arms 7, 8 a tensioning spring (not represented in the drawing) acts, which is supported on one side on a tensioning arm 7 and on the other side on the other tensioning arm 8 and presses on both arms. tensioning 7, 8 against belt 5.

In figure 1 it can be seen that the distance l1 between the rotation axis 11 of the tensioning arms 7, 8 and the support point of the tensioning roller 10 or on the belt 5 is smaller than a distance l2 between this axis. rotation 11 and a tangent 12, which passes tangentially over the two pulleys 3 and 4 for the belt.

The starter-generator 2 rotates clockwise. Therefore, during the engine starting operation, the belt branch 5 against which the tensioning arm 8 rests elastically, acts as a working actuator branch. This means that the resultant force W2 of the belt is much greater than the force W1 of the belt on the branch driven in vacuum, against which the tensioning arm 7 is elastically supported.

In figure 1 it can be seen that the line of action W2 of the resultant force of the belt coincides in alignment at least approximately with the line of symmetry of the tensioning arm 8. This means that there is no longer any lever arm, in the one that can actuate the resultant force W2 of the belt and therefore can cause the tensioning arm 8 to tilt.

On the other hand, the resultant force W1 of the belt acts on the vacuum driven branch, which with its effective lever arm "h" generates a torque, which is directed against the force of the tensioning spring.

In the situation represented in FIG. 1, the tensioning roller 10 therefore works as a rigid roller for reversing the direction of passage.

Figure 2 now shows the operation of the internal combustion engine, which means that the starter-generator 2 produces electric current, with which the crankshaft 1 is actuated. In this situation, the working actuator branch and the driven branch are still exchanged between them. in vacuum. While no effective lever arm is now available for the resultant force W1 of the belt, the resultant force W2 of the belt, together with the lever arm “h” produces a torque that acts on the tensioning arm. 8 and that it is directed against the force of the tensioning spring. In this situation, the tensioning roller 9 works as a rigid roller of reversing the direction of passage, since the resultant force W1 of the belt coincides in alignment with the line of symmetry of the tensioning arm 7.

The advantageous position of the neutral position therefore acts as a stop for the tensioning arms 7 and 8. The described configuration of the length ratios of l1 with respect to l2 makes it possible to approach the tensioning arms 7, 8 to the position of neutral described. Drawing reference list

Crankshaft

Starter- generator

1st pulley for belt

Second pulley for belt

strap

Tensioning device

Tensioning arm

Tensioning arm

Tensioning roller

Tensioning roller

Axis of rotation

Tangent.