JPH05196105A - Stretcher for belt driving device - Google Patents

Abstract

PURPOSE: To obtain a tensioning device for a driving belt so that it runs evenly in whole ranges of rotating speed without vibration. CONSTITUTION: In a low temperature state of an engine, a tension pulley 7 positioned by spring force against a drive belt 6 is set in such a manner that the connecting line 9 between the pivoting axis S of the tension roller 8 and the rotation axis D of the pulley forms, relative to the line of direction 10 of the resultant reactive force RF issuing from the drive belt 6, a pivoting angle β less than 70 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided with a tension roller which is pressed against a non-loaded portion of a drive belt via a spring element during operation, and a rocking bearing of the tension roller is arranged inside a radius of the tension roller bearing. Drive belt device tensioning device.

[0002]

BACKGROUND OF THE INVENTION A tensioning device in which an oscillating bearing is located inside the radius of a tensioning roller bearing is known from DE-A 26 17 368.
The tension roller is generally arranged in the unloaded part of the drive belt, for example in the part between the two drive wheels of the camshaft and crankshaft of the internal combustion engine. The tensioning roller tensions the drive belt through the spring element even during operation and keeps it balanced against any fluctuating operating conditions caused by operating temperature, rotational speed, impact load and the like. In the case of an ordinary passenger car internal combustion engine, a rocking motion of about 10 to 15 mm occurs. Therefore, a very compact tensioning device can be constructed. Due to the short swing radius in this tensioning device, the swing axis is usually arranged on a cylindrical support which is fitted in the bore of the tension roller bearing. Furthermore, spring elements and damping devices are also incorporated in this area.

As a result of experiments, it has been confirmed that natural resonance occurs at one or more predetermined rotational speeds within the engine rotational speed range. At this natural resonance, the load portion of the drive belt vibrates greatly.

Empirically, this natural resonance occurs at particularly high rotational speeds and is originally dependent on the length of the vibrating part of the drive belt and its tension. In that case, an engine having two camshafts has a particularly strong tendency to generate a plurality of resonance speeds.

The vibration causes the load portion of the drive belt to loosen somewhat. This slack must be compensated by the tensioning device in the unloaded part of the drive belt. The drive belt is tensioned at this point and moves the tensioning roller against the force of the spring element.

However, this does not eliminate the vibration of the load part of the drive belt. This vibration causes terrible noise and makes the angular position of the camshaft and crankshaft rather irregular. This drawback is extremely pronounced in the case of two camshafts having an angular deviation from each other.

It has been found that increasing the tension in the drive belt can reduce at least the intensity of the vibration. In principle, however, maintaining a high tension increases wear and damage to the components of the drive and is therefore unacceptable.

[0008]

SUMMARY OF THE INVENTION The object of the invention is to provide a tensioning device of the type mentioned at the outset which ensures a uniform operation of the drive belt over the entire rpm range.

[0009]

According to the present invention, it is an object of the present invention to provide a drive belt with a connecting line passing through the swing axis and the rotation axis of the tension roller when the tension device is installed at a low temperature of the engine. This is achieved by forming an oscillating angle of 70 ° or less in the direction against the tension of the spring element with respect to the line of reaction of the reaction force acting on the tension roller by the unloaded portion of

By means of the device according to the invention, when the tension roller has to follow strongly against the force of the spring element during the natural resonance of the belt drive, the rocking axis and the rotation axis of the tension roller are required. The length of the lever of the oscillating arm connecting the two is geometrically shortened.

In that case, the tensioning roller is pressed in a direction that increases the rocking movement from a preferred rest position, for example about 65 °.

When the line (swing arm) connecting the swing axis and the rotation axis extends perpendicular to the line of action of the reaction force, the entire length of the swing arm acts as it is and the spring Along with the force, it creates tension on the drive belt.

Also, when the entire length of the swing arm extends parallel to this line of action, the effective lever length becomes infinitely short, and the tension roller acts in this respect as if it were a fixed tension roller. However, the rocking movement is limited in this respect.

Between these two extreme swing points, the length of the lever changes depending on the angle between the oscillating arm and the line of action.

Within the advantageous swing range according to the invention, a tension which theoretically increases infinitely against the tension direction is obtained.

For example, in the preferred rest position where the angle is 65 °, almost the entire length of the swing arm acts as the lever length. In that case, the drive belt is subjected to an allowable tension with respect to normally changing operating conditions such as load switching change and operating temperature change. At the time of natural resonance that occurs under a predetermined rotation speed and in that case, when the tension roller is further moved against the tension direction, the tension increases extremely, which effectively suppresses the vibration of the drive belt. To be done.

The change in tension occurs precisely, in particular when the swing radius, ie the length of the swing arm, is determined by the length of the expected swing or displacement movement of the tensioning roller. In fact, it has been confirmed that good results are obtained at a swing radius of 1.2 to 3 times the maximum displacement movement of the tension roller.

[0018]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. All the figures are shown schematically, and only the part important for understanding the action is shown.

FIG. 1 shows a belt drive device for an internal combustion engine having one crankshaft 1 and two camshafts 2. A guide roller 3 is provided between both cam shafts 2. The drive is performed by the crankshaft 1 in the direction of the arrow. In that case, the drive belt 6 has a loaded portion 4 and an unloaded portion 5. A tensioning device 7 is provided in the area of the unloaded part 5. The tensioning device 7 always operates and has a rocking bearing which is arranged eccentrically with respect to the rotation axis D and has a rocking axis S. The tension roller 8 supported around the rotation axis D is tensioned by a spring (not shown) so as to be rotatable around the swing bearing toward the drive belt 6. The rocking axis S is arranged inside the radius of the tension roller 8, for example in a support which receives the tension roller bearing. As a result, the swing radius R or the interval SD forming the vibrating arm is reduced. This automatically compensates for fluctuations during operation.
This is especially the case when the load part 4 oscillates due to its natural resonance at a given rotational speed (illustrated by the dashed line). Reaction force R
The action line 10 of F is a bisector of the angle formed by the load portion 5 which geometrically contacts the tension roller 8 of the drive belt 6. The connecting line 9 passing through the swing axis S and the rotation axis D forms a swing angle β = 65 ° with the action line 10. This is the rest position, even if the engine is cold, for example. When the tension roller 8 is moved against the tension of the spring by the tension of the drive belt 6, the swing angle β becomes smaller.

FIG. 2 shows the tension roller 8 at the position shown in FIG.
The relationship between the force acting on and the lever is shown. A tension roller 8 rotatably supported around a concentric rotation axis D
Can additionally move on the swing track 13 around the swing axis S in the direction of the drive belt 6 and in the opposite direction against the force of the spring (not shown). In that case, as described above, in the rest state, the swing angle β = 65 ° occurs between the connection line 9 passing through the swing axis S and the rotation axis D and the action line 10.

The reaction force RF of the drive belt 6 is
When the unloaded part 5 of the is under tension, it acts against the force of the spring. Since the lever length H effective for this force is large in the rest state in FIG. 2, that is, when the swing angle β is 65 °, a small reaction force RF is used to swing the tension roller 8. The force of the spring can be resisted.

FIG. 3 shows the tension roller 8 slightly swung against the force of the spring. In this case, the swing angle β becomes small and the effective lever length H becomes small. In this position, a fairly large reaction force RF is required to cause the oscillating movement against the force of the spring.

[0023]

In the tensioning device according to the present invention, when the tensioning device follows due to natural resonance or irregularity of the angular position between the cam shaft and the crankshaft, the swinging angle becomes small, so that the effective tension is reduced. To rise extremely. This ensures that drive belt vibrations are prevented under all operating conditions.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a tensioning device of a drive belt device in which a connection line passing through a swing axis line and a rotation axis line of a tension roller forms an angle of 65 ° with a reaction force acting line.

FIG. 2 is a force line diagram in the tensioning device of FIG.

FIG. 3 is a view showing a state where the driving belt vibrates and the tension increases.
Line diagram corresponding to.

[Explanation of symbols]

 6 Drive belt 7 Tension device 8 Tension roller 9 Connection line passing through the swing axis S and the rotation axis 10 Action line RF Reaction force β Swing angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Karl August Luking Germany, 8721 Nida Bern, Breschla Ostrasse 30 (72) Inventor Otmer Winkel Germany, 8720 Schweinfurt, Berthawüstner Strasse 31

Claims (3)

[Claims] 1. A drive in which a tension roller is provided which is pressed against a non-loaded part of the drive belt during operation by means of a spring element, the rocking bearing of the tension roller being arranged inside the radius of the tension roller bearing. In the tensioning device of the belt device, when the tensioning device (7) is installed in a low temperature condition of the engine, a connecting line (9) passing through the swing axis (S) and the rotation axis (D) of the tensioning roller (8). However, with respect to the line of action (10) of the reaction force (RF) acting on the tension roller (8) by the unloaded portion (5) of the drive belt (6), the force is 70 in the direction against the tension of the spring element. A belt drive tension device having a swing angle (β) of less than or equal to °. 2. The tensioning device for a belt driving device according to claim 1, wherein the swing angle (β) is 60 to 70 °. 3. The swing radius (R) is 1.2 of the maximum displacement of the tension roller (8) expected in all operating conditions.
The belt drive tensioning device according to claim 1 or 2, wherein the tensioning device has a size three to three times larger.