Resilient tires and wheels – Tires – resilient – Anti-skid devices
Patent
1980-03-07
1982-07-20
Ball, Michael W.
Resilient tires and wheels
Tires, resilient
Anti-skid devices
156129, 264126, 264326, B60C 1100, B29H 1702
Patent
active
043401031
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The present invention concerns a vehicle tire with reduced rolling noise emission and a method for its manufacture.
A considerable environmental problem in todays society is noise emission from roads and streets. At lower speeds and high acceleration, the noise from the power unit dominates at the receiver point in most cases compared to the rolling noise.
At speeds exceeding 50 km/h, however, rolling noise created by the tire contact with the road will dominate. This means that a great portion of the noise problems that exist along streets and roads even in urban areas are caused by tire/road noise. For those areas it would not help much to further reduce the noise emission from the power units. The fact that the tire/road rolling noise dominates the total noise emission for most conditions at speeds exceeding 50 km/h contributes to a certain understandable disinclination of car manufacturers to further reduce the noise emission from the power unit. A reduction of the tire/road rolling noise would thus contribute directly to solve noise problems at streets and highways where speed is higher than 50 km/h and also contribute to a general reduction of the road traffic noise at lower speeds, as reduced rolling noise would increase motivation also for power unit noise reduction. There are mainly three known methods up to now on how to reduce tire/road rolling noise.
1. Changing the tread pattern. The length of different tread blocks is varied in the direction of rotation so that the tonal components of the noise emission is spread around the mean frequency.
2. Changing the rubber compound so that higher compliance is obtained.
3. Influencing the texture of the road surface to obtain an optimal texture depth with respect to noise.
The first method can probably not give any further noise reduction because of an already well developped technique. The tonal contribution to the total noise emission is less dominating for coarse road surfaces, as the random road surface excitation of the tire would dominate noise emission in these cases. The second method can not be used without some increase of tire wear. It gives noise reduction but is not acceptable from an encomical point of view.
Laboratory studies have shown that the most probable cause of the far field tire/road rolling noise at higher frequencies is that tread block oscillations can excite air-resonances in acoustical resonance circuits between the tire and the road surface. A method to prevent this is to allow the air pressure differences in tread cavities to be neutralized through the tread pattern. This can be done by decreasing the tread block sizes and ensure that the air can move in open and communicating channels between the tread blocks. However, if the tread blocks are too small the road holding capabilities will decrease to an unacceptable level. The proposal according to the present invention is in contrary to make the tread blocks in a shape acceptable for road-holding or other requirements but make the entire tread with communicating air channels or pores, for example by using a porous rubber compound. Thereby air-pressure neutralization through the tread block itself can occur while the tread stability is maintained. Due to the porosity the damping characteristics (mechanical losses) of the rubber is increased which is a further advantage with respect to tire/road rolling noise emission. When a tread block is suddenly accelerated and decelerated during road contact, the aerodynamically stored energy is released in form of acoustical energy. If the tread block itself is porous, a part of the energy could be absorbed by the friction losses in the pores and thus not radiated to the surroundings. When the tread surface is made porous the radiated noise to the external far field will be reduced because
(1) radiation efficiency will be reduced,
(2) the vibration level in the tread blocks is reduced, and
(3) the stored aerodynamical energy will be absorbed during velocity changes.
An important question is how a tire with a porous tread sur
REFERENCES:
patent: 2575439 (1951-11-01), Billingsley
patent: 2960138 (1960-11-01), Chiodo
patent: 3386485 (1968-06-01), Harrison et al.
patent: 3532147 (1970-10-01), Gough et al.
patent: 3920604 (1975-11-01), Berg et al.
patent: 4290470 (1981-09-01), Williams et al.
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