GB2485636A

GB2485636A - Chain tensioning means using a leaf spring

Info

Publication number: GB2485636A
Application number: GB1115590.0A
Authority: GB
Inventors: Peter Tyroller
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2010-11-19
Filing date: 2011-09-09
Publication date: 2012-05-23
Also published as: DE102010051951A1; GB201115590D0; CN102537241B; CN102537241A

Abstract

A tensioning means for tensioning an endless traction means in an engine of a vehicle. The tensioning means having a leaf spring 1 which is arranged between a vehicle mounted locating face and a tensioning rail (7, Figure 4). The leaf spring 1 being installed in a pre-tensioned position and the leaf spring 1 being formed with two arms 3. Suspension points 4 of arms 3 may be arranged offset relative to one another and the arms 3 may be of differing lengths and have different bending radii. Preferably a guide pin (5, Figure 4) is provided on the tensioning means and is laterally encompassed by the leaf spring 1. Optionally the leaf spring 1 has a linear spring characteristic and the arms 3 may be of different width.

Description

Tensioning means The invention relates to a tensioning means according to the preamble of Claim 1.

In a force transmission mechanism which is configured for transmitting the rotary movement of a crankshaft via an endless traction means, such as a chain, to one or more camshafts or other assemblies of an internal combustion engine of a motor vehicle, the tension of the endless traction means is kept constant by a tensioning means being provided which exerts a tensioning force on the endless traction means.

This tensioning force, which is transmitted to the endless traction means for example via a tensioning rail, may for example be provided by a leaf spring. Such a tensioning means with a leaf spring can be inferred from publication DE 11 2006 001 473 T5, the leaf spring here being rectangular, and being preshaped into an arc, so that upon installation it is deformed counter to the arc and thereby exerts a pre-tensioning force on the tensioning rail. In order to increase the spring characteristic of the leaf spring, it is conventional to arrange a plurality of layers of metal sheets one above another.

In the case of tensioning means it is often advantageous to use particularly small components in order for example to provide particularly light tensioning means of optimised weight. The known leaf springs for tensioning means, owing to their size, require a large amount of space, which causes the size of the tensioning means to increase accordingly overall.

It is therefore the object of the invention to provide a leaf spring for a tensioning means which can be installed in particularly space-saving manner.

The invention achieves this object with the features of Claim 1. Further preferred configurations of the invention can be inferred from the dependent claims, the figures

and the associated description.

In order to achieve the object, according to the invention a tensioning means for tensioning an endless traction means in an engine of a vehicle is proposed, the tensioning means having a leaf spring which is arranged between a vehicle-mounted locating face and a tensioning rail and is installed in a pre-tensioned position, and the leaf spring being formed with two arms.

Owing to the pre-tensioned two-armed leaf spring, sufficient spring force can be provided with small installation space in order to tension the endless traction means in the engine. This results in the possibility of making the tensioning means overall smaller and thus saving weight. Further, the spring force can be increased without additional assembly costs, since the proposed solution permits the use of two leaf springs acting in parallel in a single assembly step.

Preferably the suspension points of the arms are arranged offset relative to one another. Due to offset suspension points, i.e. suspension points which are at different distances from the base section connecting the arms, the spring characteristic of the leaf spring can be changed and thus readily adapted to the requirements of the respective use. The individual arms preferably have different spring characteristics, the spring behaviour of the leaf spring being yielded from a combination of the two arm properties and thus being able to be adapted for a large number of uses due to the individual possibilities of configuration of the arms. Preferably such an adaptation takes place in that the arms have different lengths and/or widths and/or bending radii.

Preferably the leaf spring has a substantially linear spring characteristic. Such a linear spring characteristic is advantageous for application in a tensioning means for tensioning an endless traction means, and can be attained only with difficulty in the case of multi-layer leaf springs.

Preferably a guide pin is provided on the tensioning means, which pin is laterally encompassed by the leaf spring with the arms and thereby laterally fixes the leaf spring. The guide pin accordingly on one hand permits guidance of the leaf spring, such that the leaf spring is fixed in its longitudinal axis and laterally to the longitudinal axis and is stably installed. Additionally, the leaf spring can be pre-tensioned better by the guide pin, since the leaf spring preferably lies against the guide pin with a base section connected the arms and thus can advantageously be pre-tensioned between the base section and the suspension points counter to the curvature of the spring.

The invention will be explained in greater detail below with reference to a preferred example of embodiment. In the figures, there can be recognised in detail: Fig. 1: isometric representation of a one-layer leaf spring according to the prior art; Fig. 2: isometric representation of a leaf spring according to the invention; Fig. 3: side view of a leaf spring according to the invention; Fig. 4: isometric representation of a tensioning means according to the invention with built-in leaf spring.

Figure 1 shows a leaf spring as can be inferred for example from publication DE 11 2006 001 473 T5. The leaf spring is rectangular and designed pre-curved in an arc. In the installed state, the leaf spring is deformed counter to the arc shape and thereby exerts a pre-tensioning force on a tensioning rail.

Figure 2 shows a two-armed leaf spring I according to the invention. The two arms 3 of the leaf spring 1 have one suspension point 4 in each case. The suspension points 4 form the end sections of the arms 3 and are substantially at a right-angle to the arms 3, they in each case being oriented in the direction of the other section 3. The suspension points 4 are arranged offset to one another, and therefore are at a different distance from the base section 2 which connects the arms 3.

In Figure 3, the leaf spring 1 of Figure 2 can be seen in a side view. In this view it can be seen that the arms 3 have different bending radii 8 and different lengths. Owing to the different bending radii 8 and lengths and the offset suspension points 4 of the arms 3, different spring characteristics are yielded for the individual arms 3.

Figure 4 shows a tensioning means according to the invention with installed two-armed leaf spring 1. The leaf spring I is arranged between a vehicle-mounted body, such as an engine section 6, and a tensioning rail 7, which is provided for tensioning an endless traction means (not shown), the arms 3 of the leaf spring enclosing a guide pin 5. The tensioning rail 7 and the engine section 6 are connected together via an articulation, the leaf spring I exerting a spring force on the tensioning rail 7 and thereby moving it in a rotation about the articulation in the direction of the endless traction means and tensioning the endless traction means.

Owing to the suspension points 4 which are arranged offset and the different bending radii 8 or lengths of the arms 3, pre-tensioning of the leaf spring 1 is yielded already in the installed situation. This pre-tensioning has the advantage that a high spring characteristic can be provided even with a small spring excursion, and thus the endless traction means can be tensioned with weight-saving components of small dimensions. The spring characteristics required for the respective case of use can be set in simple manner by small changes in geometry of the arms 3 of the leaf spring 1.

In order to provide increased pre-tensioning, for example a greater curvature, i.e. a smaller bending radius of an arm 3 or more greatly offset suspension points 4, can be provided.

One difference between the tensioning means according to the invention and a tensioning means known from the prior art, for example a tensioning means in accordance with DE 11 2006 001 473 T5, is that the pre-tensioning of the leaf spring I does not lead to the tensioning rail 7 already being moved in the direction of the endless traction means by the installation of the leaf spring. On the contrary, a high pre-tensioning of the two-armed leaf spring 1 according to the invention even results in less spring excursion being required for the same spring force, and thus the tensioning means being able to be designed overall more compactly and in particularly space-saving manner, since only a very small distance between the endless traction means and engine section is required for applying the necessary pre-tensioning force.

List of reference numerals 1 leaf spring 2 base section 3 arm 4 suspension points guide pin 6 engine section 7 tensioning rail 8 bending radius

Claims

Claims 1. A tensioning means for tensioning an endless traction means in an engine of a vehicle, the tensioning means having a leaf spring (1) which is arranged between a vehicle-mounted locating face and a tensioning rail (7), and the leaf spring (1) being installed in a pre-tensioned position, characterised in that the leaf spring (1) is formed with two arms.
2. A tensioning means according to Claim 1, characterised in that that suspension points (4) of the arms (3) are arranged offset relative to one another.
3. A tensioning means according to Claim I or 2, characterised in that the arms (3) have different lengths.
4. A tensioning means according to one of the preceding claims, characterised in that the arms (3) have different bending radii.
5. A tensioning means according to one of the preceding claims, characterised in that the arms (3) have different widths.
6. A tensioning means according to one of the preceding claims, characterised in that the leaf spring (1) has a substantially linear spring characteristic.
7. A tensioning means according to one of the preceding claims, characterised in that a guide pin (5) is provided on the tensioning means, which pin is laterally encompassed by the leaf spring (I) with the arms (3) and thereby laterally fixes the leaf spring.
8. A tensioning means according to Claim 7, characterised in that the leaf spring (1) lies against the guide pin (5) with a base section (2) connecting the arms (3).
9. A tensioning means substantially as hereinbefore described with reference to figures 2 to 4 of the drawings.