FI59054C - PNEUMATIC DAECK - Google Patents

Description

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VvM Patent meddelat> SV / (51) Kv.m.3 / W «.c · .3 B 60 c 9/18, 7/22 SUOMI — FINLAND (21) 750 ^ 98 (22) Hak« mi «patvt - AnaOknlnctdig 21.02.75 (23) AHcupUvl — Glki (h * tsda | 21.02.75 (41) TuHut julktMkii - Blivlt offantllg 27.08.75 ritwKtl- ja raklatarihallltiie / 44)

HrtMt och regleteretyrelswi '' AraMon uthgd odi utUkrtfWn pub «c« r * d 27.02.81

(32) (33) (31) Requested * toik «i« —8 «gini priority 26.02.7U

England-England (GB) 08566/7 ^ (71) Dunlop Limited, Dunlop House, Hyder Street, St. James's, London SW1, England-England (GB) (72) William Lewis Jackson, Sutton Coldfield, West Midlands, England The present invention relates to pneumatic tires comprising a tread of elastic material, the sides, an annular belt having a tread reinforcement having an axial width of 5 mm). Pneumatic Tires - Pneumatic Tires substantially the same as the width of the tread and located radially immediately within it and substantially inextensible in both the axial and circumferential directions, as well as a rubber extension strip or extensions substantially radially located inside the reinforcing belt as a tread width.

However, this type of tire, which does not have a tread reinforcement belt, has been described e.g. British Patent 229,886. This tire uses a ribbed member made of flexible rubber positioned radially inwardly of the tread from the tire. The purpose of this rib member is to counteract the tendency of the tire to distort when the tire is loaded. When the tire is inflated, the rib member is under tensile stress and thus tends to resist deformation of the tread under load. This rib member is thus intended to be under tensile stress in a pressurized tire and thus has no effect on the bearing of radial loads on the tire.

59054

A pneumatic tire of the above-mentioned type (no reinforcement belt) is also known from U.S. Pat. No. 3,734,157. This tire provides a solution by which the load-bearing capacity of the tire can be substantially maintained even if the tire is under-pressurized or even empty. As a solution, it has been proposed that several circumferentially extending annular spring members are arranged in the interior of the tire, below the tread. The spring members are shown to be embedded in rubber, whereby the elements thus obtained can either be glued to the inner surface of an ordinary tire or alternatively vulcanized directly to the tire during its manufacture. In this tire structure, the spring members are only subjected to a load when a load is placed on the tire. When the tire is at rest, the spring members are tension-free. In the case of a tire load, the spring members transfer the load stress to the rim via the sidewalls of the tire.

According to the invention, it has now been realized that the load-bearing capacity of such a reinforced tire as shown in the introduction can be significantly improved by shaping the expansion ring and placing it in the ring so that it is compressed by the surrounding reinforcing belt in the unloaded and unpressurized state of the tire. The incorporation of a pre-compressed rubber circumferential rim into the tire results in a higher tire bearing capacity while minimizing the subsequent heat generation problems that are usually caused by the incorporation of additional rubber into the tires.

At the same time, it is possible to maintain and in some cases improve the driving comfort of the tire, i.e. the ability of the tire to dampen road bumps without transmitting unpleasant vibrations to the axle and thus to the vehicle and its occupants.

The invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 shows the installation of a circumferential rim on a braided ring.

Figure 2 is a graph showing the effect of pre-compressed rubber on the development of vertical and horizontal vibration of a pneumatic tire.

The speed and support performance of elastomeric rings is limited by the hysteresis effect of the material used in their construction. This is especially true for solid rubber tires. The restrictions are broadly in line with the following formula: 3 59054 2

T T. HS

- ^ <limit value where R = radial thickness of the tire, L = vertical shell acting on the tire, H = hysteresis loss of the tire, S = speed (deviation periods / unit of time), M = modulus of elasticity of the rubber, A = effective area of contact area.

The limit value mentioned above depends on the the effective cooling rate of the tire.

The object of the present invention is to improve the load-bearing capacity of tires by pre-pressing a rubber circumferential rim in a pressed tire.

The value of the pre-compression generally appears from the formula presented above, because the effect of the pre-compression in the rubber increases the modulus of elasticity (M) without increasing the hysteresis loss factor (H). Pre-compression thus reduces the value of the formula T L HS and thus also allows it

MA

that the tire supports a higher load (L) without exceeding the limit value.

It is obvious that this formula represents a simplified approximation of the state prevailing in the ring. Depending on the method of manufacturing the tire, the degree of pre-compression may not be the same for the entire compressed rubber. In general, however, it is most convenient that no part of the circumferential rim of pre-compressed rubber is pre-compressed by more than 30%. The average pre-compression in the circumferential rim of the pre-compressed rubber is preferably in the range of 10-20%, although smaller pre-compressions are also important, especially in a pneumatic tire, as will be explained below.

It is also apparent that the higher the modulus of elasticity of the rubber, the lower the pre-compression required to produce a particular effect on the bearing capacity.

Figure 1 (a) shows a cross section of a pneumatic rim tire mounted on a rim.

Figure 1 (b) shows a cross section of an elastomeric circumferential rim with a diameter larger than the inner surface of the buffer layer region.

Figure 1 (c) shows a circumferential rim attached in place on the inner surface.

59054 4

To the extent shown, this modification is able to increase the bearing capacity of the tire by about 20% without the large hysteresis energy loss that usually occurs when thick inner linings are used.

The effect of a pre-compressed rubber rim on the ride comfort of a pneumatic tire is illustrated by the following example.

Two 155-12 Dunlop SP Sport textile belt tires were fitted with rubber rims that were placed below the law area on the inner surface of the tire. In one case the circumferential rim was not pre-compressed and in the other it was. In the latter case, the prestress was in the order of 4%. The rubber used in the rim was a natural rubber compound, the composition of which is shown in the table below.

Table

Weight part SMR 20 100

Flectol flakes 2.5

Nonax ZA 1.0

Mineral oil 5.0

ZnO 4.0

Stearic acid 1.0 GPF black 65.0

Broken 3.0

Santocure 1.0 PVI 0.8 SMR 20 is a standard Malaysian natural rubber.

Flectol flakes is a trademarked product comprising (2,2,4-trimethyldihydroquinoline).

Nonos ZA is phenylisopropyl-p-phenylenediamine (IPPD).

Santocure is N-cyclohexylbenzthiazole sulfenamide (CBS).

PVI 50 is 50% cyclohexylthiophthalimide + 50% inert inorganic filler.

2

The hardness of the compound was 64 ° BS and its modulus of elasticity was 7.00 MN / m measured dynamically at 15 Hz and 10% frequency, i.e. the oscillation was between 0 and 10% elongation.

For both tires, the load elasticity curves were recorded and it was found that at a standard pressure of 0.14 MPa (1.4 kp / cm) the load elasticity curve of a tire with a prestressed circumferential rim was about 7% steeper than that of a reference without prestressing, i.e. a tire with a preloaded rubber rim was less than

Claims (2)

59054 heiranan resilient with a certain hump than the reference ring. The vibration transmission capacity of the tires was measured by fitting air-inflated tires to 0.14 MPa in the laboratory for Machpherson-type suspension, and the tire was rotated with a 2450 N (250 kp) load on a bar drum to vibrate the tires. The induced acceleration of the wheel axle on which the tire was mounted was measured over a wide frequency range. For both the radial (i.e., vertical) acceleration VA and the longitudinal acceleration LA, the results of the prestressed circumferential rim are plotted in Figure 2, which shows the relationships between the accelerations transmitted by the tires when the tire has pre-compressed rubber. the tires were exposed, i.e. exciter. The beveled areas of the figure show those parts of the frequency range in which the ring containing the prestressed rubber had better results. Longitudinal acceleration is particularly important because vehicle designers are subject to greater constraints in designing suspension stiffness in this direction than in the vertical direction. A biased circumferential rim is clearly more advantageous because it reduces the transmission of vibration over almost the entire frequency range in the case of a longitudinal effect. A pneumatic ring (10) comprising a tread (13) of elastic material, sides, an annular tread reinforcement belt (11) having an axial width substantially equal to the width of the tread and disposed radially immediately inside it and which is substantially inextensible both in the axial direction and in the circumferential direction, and a rubber expansion strip or extension ring (12) substantially radially inside the reinforcing belt (11) as the tread (13) wide, characterized in that the extension ring is thus shaped and positioned in the ring (10), that it is compressed by the surrounding reinforcing belt (11) in the unloaded and unpressurized state of the tire. A tire according to claim 1, characterized in that the average compression in the expansion strip or