GB2157239A

GB2157239A - Tyres

Info

Publication number: GB2157239A
Application number: GB08507414A
Authority: GB
Inventors: Christian Casper; Konrad Wilkening
Original assignee: Metzeler Kautschuk GmbH; Metzeler Kautschuk AG
Current assignee: Metzeler Kautschuk GmbH; Metzeler Kautschuk AG
Priority date: 1984-03-23
Filing date: 1985-03-21
Publication date: 1985-10-23
Also published as: IT8519896A0; FR2561588B1; GB8507414D0; ES285564U; IT1187639B; JPS60213504A; FR2561588A1; JPH0657483B2; DE3410857A1; ES285564Y; IT8521081V0; DE3410857C2; GB2157239B

Abstract

A tyre (10) for a motor cycle has a casing (14, 16), preferably a radial or semi-radial casing, a belt (22) and a tread region (24) extending into the lateral wall of the casing. A damping layer composed of crossed cord layers (18, 20) of which the threads enclose an angle of from 60 to 90 DEG and have a modulus of elasticity greater than 6000N/mm<2> is arranged between the casing (14, 16) and belt (22). The rubber mixture of the two cord layers acting as damping layer has an extremely high damping capacity, in other words the loss angle tan delta of the rubber mixture (>0.3) <IMAGE>

Description

SPECIFICATION Radial ply tyre The invention relates to a radial ply tyre for a motor cycle.

A radial ply tyre of this type is known from DE OS 3 005 543 and has a casing, namely a biasbelted casing, a belt, a tread region extending into the lateral wall of the casing, and a rubber-containing damping layer arranged symmetrically to the centre of the tyre. This damping layer which is known as a "stress-relieving" or "vibration- absorbing" layer is composed of rubber and is arranged between the two layers of the casing. It extends over a region amounting to about 10 to 50% of the tread.

This damping layer should eliminate the feared "oscillation" of the motor cycle. This oscillation occurs if the motor cycle which is travelling straight at high speed is disturbed by external influences, for example, by driving over road markings or unevenness in the ground and is thus set into vibration. These influences can lead to considerable vibration of the handle bar about the steering shaft, which dies down realtively slowly. The motor-cyclist often panics in this situation, so that accidents may occur.

The damping layer composed of pure rubber which is arranged between the two layer of the casing provides one way of shortening the time required for the oscillation to subside, but gives rise to new problems because torque is produced between the two layers of the casing and increases as the distance between the two layers increases.

As the damping layer is arranged between the two layers, the torque becomes relatively high and the two layers of the casing can come apart so that the casing no longer has the desired strength. This is particularly noticeable at high speeds.

An object of the invention, therefore, is to provide a radial ply tyre in which the above-mentioned problems are eliminated or mitigated. In particular, a radial ply tyre is to be provided in which the oscillations discussed above are damped to the desired extent without the strength of the casing being impaired.

According to the invention there is provided a radial-ply tyre for a motor cycle, comprising a casing, a belt, a tread region extending into the lateral wall of the casing, and a rubber-containing damping layer arranged symmetrically to the centre of the tyre, wherein the damping layer is arranged between the casing and the belt and comprises two crossed cord layers of which the threads enclose between them an angle of from 60 to 90 , and the rubber mixture of the two cord layers has high damping properties.

The tyre according to the invention enables the oscillations to be significantly damped in the desired manner because the damping layer is located at a point where relatively marked movements occur. These movements are converted in the damping layer into heat which can easily be carried away outwardly since the damping layer is located not in the casing but relatively close to the tread.

The casing is forcibly deformed when passing through the contact surface of such radial-ply tyre.

The threads of the various layers which are prestressed by the internal pressure of the tyre and the centrifugal force occuring during driving are relaxed and compression can even occur. The deformation of a casing composed of the cord threads and the change in the angle of the cord threads to the circumferential direction. This change of angle is accompanied by a deformation of the rubber located between the cord threads. When using cord threads having a high modulus of elasticity, only limited cord elongation occurs whereas a marked change of angle and resulting deformation of the rubber occurs.By using a high-damping rubber mixture having loss angle tan 3 greater than 0.30 in the damping layer it is possible to produce a tyre of which the damping properies are superior to those of the conventional radial ply tyre, i.e. the oscillations subside much more rapidly.

This is achieved without impairing the strength of the casing as the damping layer is no longer located between the two layers of the casing.

The above-mentioned change of angle is observed in the two crossed damping layers in the form of rhombic deformation which, in conjection with the damping properties of the rubber, leads to the desired strong damping effect.

Although the casing can in principle have any structure, particularly good results are achieved if it is semi-radial or radial casing.

The belt preferably consists of at least one cord layer of which the threads rub at an angle of from 0 to 8 to the circumferential direction. The modulus of elasticity of the cord layer of the belt is preferably at least 600 N/mm2.

The casing has a high modulus of elasticity in the circumferential direction owing to the extremely small zenith angle of the belt. The increase in the centrifugal force of the tyre is thus reduced almost completely and the contour of the tyre hardly alters even at high speeds, providing a wide contact surface. A tyre having a belt of this type therefore has a greater surface for the transmission of forces at high speed than a conventional motor cycle tyre. This increase in the contact surface, in turn, results in reduced wear and therefore a longer service life.

The invention is described in more detail below by means of an embodiment which is shown in the accompanying schematic drawing which shows a perspective view of a radial-ply tyre according to the invention which is cut away in layers.

The drawing shows a radial ply tyre 10 which has a conventional internal panel 12 of the type provided in the tubeless tyres. This internal panel 12 is surrounded by two superimposed cord layers 14 and 16 which together form a casing. This is a radial casing, i.e. the threads of the two cord layers of the casing run at an angle of 90 to the circumferential direction of the tyre.

The two cord layers 14 and 16 of the casing extend in the conventional manner from bead to bead.

As an alternative embodiment illustrated, however, it is possible to use a semi-radial or even a diagonal casing.

Two crossed cord layers 18, 20 which form a damping layer and of which the threads enclose between them an angle of from 60 to 90" are arranged on the two cord layers 14, 16 of the casing.

The threads of these two cord layers are composed of rayon, polyester or aramide and have a modulus of elasticity of at least 6000 N/mm2. The rubber mixture into which the threads of the two cords layers 18, 20 are embedded have a loss angle tan 3 of at least 0.30. The thread density, measured perpendicularly to the thread direction, should be not greater than 50 threads per dm.

As shown in the drawing, the threads on the lower cord layer 28 run approximately at an angle of 56" and the threads in the upper cord layer 20 at an angle of approximately 135" to the circumferential direction of the tyre.

The two cord layers 18, 20 are staggered in a radial direction to produce a continuous transition and they take in about 50 to 60% of the width of the tread 24 of the tyre 10 symmetrically to the centre line of the tyre.

A belt having a single belt layer 22 is arranged on the two cord layers 18, 20 of the damping layer, of which the threads run at an angle of 0" to the circumferential direction of the tyre 10. The modulus of elasticity of the threads in the belt layer 22 should be at least 6000N/mm2.

Finally, a conventional tread 24 of the tyre 10 which extends relatively far into the lateral wall of a motor cycle tyre is located on the belt 22.

Claims

1. A radial-ply tyre for amotor cycle, comprising a casing, a belt, a tread region extending into the lateral wall of the casing, and a rubber-containing damping layer arranged symmetrically to the centre of the tyre, wherein the damping layer is arranged between the casing and the belt and comprises two crossed cord layers of which the threads enclose between them an angle of from 60 to 90 , and the rubber mixture of the two cord layers has high damping properties.

2. A tyre according to claim 1, wherein the threads of cord layers have a high modulus of elasticity.

3. A tyre according to claim 2, wherein the modulus of elasticity of the threads is greater than 6000N/mm2.

4. A tyre according to claim 2 or 3, wherein the threads in the cord layers are composed of rayon, polyester or aramide.

5. A tyre according to any preceding claim wherein the rubber mixture of the two cord layers has a loss angle tan 3 greater than 0.30.

6. A tyre according to any preceing claim wherein the maximum thread density measures perpendicularly to the thread direction is 50 threads per dm.

7. A tyre according to any preceding claim wherein the belt has at least one cord layer of which the threads rub at an angle of from 0 to 8" to the circumferential direction.

8. A tyre according to claim 7, wherein the modulus of elasticity of the threads of the belt is at least 6000Nlmm2.