JP2895538B2 - Pair of motorcycle pneumatic tires - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic tire for a pair of motorcycles (including motorcycles for racing) comprising a front wheel and a rear wheel having excellent steering stability. is there.

(Prior Art) The progress of motorcycles in recent years has been remarkable, and tires have been required to have characteristics as high-performance tires, that is, high grip.

By the way, conventionally, tread rubbers having different characteristics are generally used for front and rear wheels in motorcycles, but in recent tires called high grip tires, the difference in tread rubber characteristics between front and rear wheels is further increased. . Actually, the front wheels are made of tread rubber with higher gripping force than the rear wheels in consideration of braking stability when entering a corner, while the rear wheels are compared with the front wheels in consideration of the large load. Tread rubber with poor grip but good wear resistance is used.

(Problems to be Solved by the Invention) In pneumatic tires for motorcycles, it is required to maintain a grip balance between the front and rear wheels. Has become extremely difficult.

The only way to check the grip balance (steering stability) of the front and rear wheels was to use an actual vehicle test. For this reason,
It has been known that the steering stability of a motorcycle can be improved by changing the characteristics of each tread rubber at the front wheel and the rear wheel of the motorcycle.However, what kind of tread rubber characteristics are changed and how much the steering stability is improved It was not known to what extent it could be improved. Therefore, in order to improve steering stability, we pay too much attention to this point,
Others have designed tread rubber that compromised other properties such as ride comfort and, as a result, lacked a balance of overall performance.

On the other hand, it is widely known that the friction characteristics of rubber are related to dynamic viscoelasticity, but the relationship between the steering stability of motorcycles and the dynamic viscoelasticity of tread rubber is No attempt has been made to develop tires with balanced front and rear wheels.

Therefore, an object of the present invention is to balance the grip of the front and rear wheels by optimizing the viscoelastic characteristics of the tread rubber of the front and rear wheels of the motorcycle, thereby achieving excellent steering stability without impairing other characteristics. It is an object of the present invention to provide a pair of motorcycle pneumatic tires having the following.

(Means for Solving the Problems) The present inventor has proposed a pneumatic tire for a motorcycle,
We thought that the viscoelastic properties of tread rubber could represent the balance of the grip force of the front and rear wheels of the tire, and as a result of intensive research on this point, the ratio of the dynamic elastic modulus of tread rubber to the internal loss coefficient was further increased It has been found that a combination of tread rubbers within a certain range exerts excellent steering stability (grip balance between front and rear wheels), and has completed the present invention.

That is, the present invention relates to a pair of motorcycle pneumatic tires comprising a front wheel and a rear wheel, wherein the dynamic elastic modulus E 'of the tread rubber of the front wheel at a frequency of 50 Hz and a dynamic strain of 3% is obtained.
(Tanδ / E ') _F , the ratio between the dynamic elastic modulus E' and the internal loss coefficient tanδ of the tread rubber of the rear wheel under the same conditions (tanδ / E ') _R Is 0 ° C ~ 1
In the temperature range of 00 ° C., And a pair of pneumatic tires for motorcycles, characterized by satisfying a relationship represented by:

(Action) Generally, it is known that high grip characteristics can be obtained by a tread rubber having high hysteresis loss,
With that alone, satisfactory high grip performance cannot be obtained.
That is, it is necessary that the elastic modulus is low at the same time, and that the deformation of the rubber follows irregularities on the road surface. From the above, it is considered that a tread rubber having a large tan δ / E ′ exhibits excellent grip performance.

Therefore, the present inventors, in a motorcycle pneumatic tire, the following formula as an indicator of the tread rubber grip balance of the front and rear wheels, We thought that the relationship represented by was appropriate, and as a result of intensive research on it, we were able to prove it.

In the present invention, the value represented by the above expression is set to 1.5 or more because if it is less than 1.5, the grip force of the front wheel is inferior, resulting in understeer. Also, the value
The reason for setting the ratio to less than 3.5 is that when the ratio is 3.5 or more, the grip force of the rear wheel is inferiorly deteriorated, resulting in oversteer. Eventually, if the value deviates from the above range of the present invention, slippage of either of the front and rear wheels becomes large, and it takes time to correct the slip, and it is impossible to quickly take a stable running.

The reason why the temperature specified in the present invention is 0 ° C to 100 ° C is as follows.

In other words, the grip is generated at a very high frequency. Even if the actual tire temperature is high, the wet grip is expressed by dynamic viscoelasticity of 0 ° C and the dry grip by 30 ° C in terms of WLF, but the rolling resistance Those generated at a relatively low frequency as described above are represented by dynamic viscoelasticity at 60 ° C. close to the actual tire temperature.

On the other hand, a high steering stability requires that the vehicle body generate little vibration at a low frequency in addition to high grip performance, in other words, that the tread rubber deforms little.

From the above, to evaluate the steering stability, the temperature inside the tire in the actual vehicle was changed from 0 ° C. which is the grip region.
It will have to be measured up to 100 ° C.

(Examples) Next, the present invention will be specifically described with reference to examples.

Table 1 below shows the composition (parts by weight) of the various tread rubbers used in this example, and the dynamics of these rubbers at a frequency of 50 Hz, a static stress of 1.7 kg / cm ² and a dynamic strain of 3%. The elastic modulus E 'and the internal loss coefficient (tan δ) are shown. The viscoelastic characteristics of the rubber were measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. on a sample cut from a tire and having a width of 4.7 mm, a thickness of 2 mm, and a length of 20 mm.

The compounded rubbers shown in Table 1 were used in combinations shown in Table 2 below as tread rubbers of pneumatic tires for front and rear wheels of a motorcycle, and the steering stability of the motorcycle was evaluated.

Driving stability was evaluated by using a 2km circuit
The test was performed by indexing the standard deviation of the lap time of 20 laps with the control tire (Comparative Example 2 in Table 2 below) as 100. If the value is smaller than 100, the dispersion of the orbiting tires is small, indicating that the steering stability is excellent. If the value is larger than 100, the dispersion of the surrounding tires is large, and the steering stability is inferior. Along with the index evaluation, the steer characteristics were also evaluated.

 The test results obtained are shown in Table 2 below.

(Effects of the Invention) As is clear from the test results shown in Table 2, in the pair of motorcycle pneumatic tires comprising the front wheel and the rear wheel of the present invention, the (tan δ /
As a result of combining the ratio of E ′) _F / (tan δ / E ′) _R to be 1.5 or more and less than 3.5, an effect of exhibiting extremely stable steering stability was obtained.

Claims (1)

(57) [Claims] 1. A pair of motorcycle pneumatic tires comprising a front wheel and a rear wheel, wherein the tread rubber of the front wheel has a dynamic elastic modulus E 'and an internal loss coefficient tan δ under a frequency of 50 Hz and a dynamic strain of 3%. Ratio (tanδ /
E ratio between ') _F and the dynamic elastic modulus E under the same conditions in the tread rubber of the rear wheel' and internal loss factor tanδ (tanδ / E ') temperature range of the ratio of the _R is 0 ° C. to 100 ° C. In the following equation, A pair of pneumatic tires for motorcycles, characterized by satisfying a relationship represented by: