JP3455666B2 - Tube for motorcycle tire used for buggy or motocross, etc., and assembly of tire and rim using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire for a motorcycle , which is suitable for a buggy vehicle or a motocross and is suitable for changing a spring constant by a load acting on a tire assembly .
Tube (hereinafter, simply referred to as a tire tube
And a tire-rim assembly using the same.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional tire tube t has a tire inner surface c formed by a tire a and a rim b.
It is arranged inside and has a function of holding the filled air, and is expanded by the filled air to uniformly apply air pressure to the tire inner surface c. Further, since the tube t is extremely thin and has a small rubber modulus, its rigidity is substantially negligible.

Therefore, the spring constant of the tire assembly in which the tire a is assembled to the rim b is substantially dependent on the rigidity due to the structure of the tire a and the air pressure received from the tube t, regardless of the load acting on the tire a. The difference between the spring constant when the load is low and the spring constant when the load is high is very small.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, for example, a buggy car traveling on rough terrain such as a rocky place, rubble, sandy land ,
Alternatively , in a tire assembly for a motorcycle that travels on a motocross road, it may be preferable that the spring constant is different depending on the load.

That is, while the tires of these vehicles are in contact with the road surface and running (at a low load), it is necessary to absorb the unevenness of the road surface, so that the spring constant of the tire assembly is smaller. However, when the vehicle jumps and touches the road surface, a very large load acts on the tire assembly. Therefore, it is desirable that the spring constant be large to some extent at this time.

Here, as shown in FIG. 7, when the tube t is relatively smaller than the tire inner surface c and the tube t does not sufficiently contact the tire inner surface c, the tire a When air pressure cannot act on the load and the load is low,
As shown in (A), the spring constant of the tire assembly is almost due to the structure of the tire a itself, but at a high load, as shown in FIG. Due to the deformation, the tire inner surface of the tread portion comes into contact with the tube t, and the air pressure and the structural rigidity of the tire a act as a spring, so that the spring constant of the tire assembly is made relatively higher than that under a low load. be able to.

However, with such a small tube t, it is substantially the same as no air pressure acting on the tire a, so that the tire a is easily separated from the rim b and the lateral rigidity of the tire assembly is increased. However, it is not practicable because it cannot be secured.

The invention according to claims 1 to 3 is different from the tube shown in FIGS. 7 and 8 in that the size of the tube is appropriately set with respect to the inner surface of the tire. A tube for a tire suitable for changing the substantial spring constant of the tire assembly depending on the load acting on the tire assembly by creating the tube in the intermediate state of two examples, and the tube for the tire It is intended to provide a tire and rim assembly used.

In particular, according to the first aspect of the invention , by setting the outer peripheral length of the cross section including the central axis of the tube, the spring effect due to the air pressure under a low load is reduced, and the substantial spring of the tire assembly is reduced. It is an object of the present invention to provide a tube for tire suitable for changing the constant.

The invention according to claim 1 balances most of the air pressure with the film force of the tube by giving the tube itself rigidity and appropriately setting the rigidity of the tube, and acts on the tire assembly. It is an object of the present invention to provide a tube for a tire which is suitable for reducing the pressure applied to the tire, and particularly for reducing the spring constant under a low load.

[0011]

The invention according to claim 1 is
A buggy vehicle or a vehicle which is arranged in the inner surface of the tire surrounded by the tire and the rim for assembling the tire and expands when pressurized.
Is a tube for a motorcycle tire , wherein the tube has a measured outer peripheral length Ltn in a cross section including a central axis in a measurement state in which the tube is filled with a minimum air pressure that eliminates depressions on the tube surface, in a natural state. The expansion outer peripheral length Lti in a cross section including the central axis in a usage state in which the tube is 0.8 to 0.9 times the circumferential length T of the cross section of the inner surface of the tire and the tube is filled with working air pressure is in a natural state. At 1.05 to 1.20 times the circumferential length T of the cross section of the inner surface of the tire , and
The tube is 100% modular with a tube thickness G.
And the radius rn of the cross section including the central axis in the measurement state
And the working air pressure P,
It is a sign.

0.20 ≦ P · rn / 4G · E ≦ 0.35

The invention according to claim 2 is the tube
But the cross-sectional center diameter Rn to the cross-sectional center of the tube from the central axis in the measurement state is you and satisfies the following equation.

Rr + 0.45Hc≤Rn≤Rr + 0.5
5Hc, where Rr: rim radius Hc: height of tire bore cross section which is the height from the rim radial line in the natural state to the outermost end of the tire bore surface in the tire radial direction

According to the third aspect of the present invention , a tire inner surface surrounded by a tire and a rim for assembling the tire into a rim,
It is an assembly of a tire and a rim in which the tube for the tire according to claim 1 or 2 is arranged.

In the present specification, the term "the inner surface of the tire in a natural state" means that the tire is assembled into a rim together with a tube whose air pressure is zero, and the outer surface of the bead portion of the tire comes into contact with the rim flange on the tube. It is defined as the tire inner surface filled with the air pressure. Further, the air pressure at the time of measuring the tube is set to 20 g / cm ² or less, and the dimension measurement is performed without denting the tube.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A case where the tube for a tire of the present invention is used in an assembly of a tire and a rim for a motorcycle will be described below with reference to the drawings. As shown in FIG. 1, the tire tube 5 of the present embodiment is used for a buggy vehicle.
Alternatively, in a tire for a motorcycle, for example, a tire 2 for a motorcycle and for running on rough terrain used for motocross or the like.
Is used in the tire inner surface 4 surrounded by the tire 2 and the rim 3 assembled to the tire 2 and is expanded by pressurization.

The tire 2 has a tread portion T which is in contact with the road surface and has a maximum tire width in this example, side wall portions S and S extending inward in the tire radial direction from both ends of the tread portion T. The wall portion S has a toroidal shape having a bead portion B and a bead portion B located on the inner side in the radial direction. Although not shown, the tire 2 is appropriately reinforced by a carcass of 1 ply or more, which is formed of a fiber cord in which cords are folded back from the tread portion T through the sidewall portion S and the bead core of the bead portion B and arranged in parallel.

The rim 3 has a ring shape in which a pair of rim seat portions 3a, 3a on which the bottom surfaces of the beads formed on the radially inner ends of the bead portions B, B are seated are connected,
The tire inner surface 4 may be formed by the tire 2 and the rim 3.

The tube 5 includes a central axis in a measurement state in which the tube 5 is filled with a minimum air pressure which eliminates the depression on the tube surface without being incorporated in the tire inner cavity, in this embodiment, an air pressure of 5 g / cm ^2. The measured outer peripheral length (so-called outer peripheral contour length of the cross section) Ltn in the cross section is 0.8 to 0 of the peripheral length T (so-called inner peripheral contour length of the cross section) of the tire bore surface 4 in the natural state. One of the features is that it is 9 times.

In this way, the measured outer peripheral length Lt of the tube 5 is
By bringing n close to the circumferential length T of the cross section of the tire bore surface 4 in the natural state, for example, by filling the working air pressure,
Since the extension amount of the tube 5 can be reduced when the tube 5 expands to the circumferential length L of the cross section of the tire inner surface 4, the effect of air pressure transmitted to the tire 2 via the tube 5 is reduced. As a result, the spring effect of pneumatic pressure can be relatively suppressed under low load compared to under high load, and the spring constant of the tire assembly can be changed by the load.

If the measured outer peripheral length Ltn of the tube 5 is less than 0.8 times the peripheral length T of the cross section of the tire bore surface 4, the expansion amount when the tube 5 is filled with air pressure tends to increase. Therefore, there is a tendency that the durability of the tube 5 is lowered, and conversely, if it is larger than 0.9 times, the tube is likely to be bitten during the rim assembly work, which is not preferable. In the present embodiment, the cross-sectional shape of the tube 5 including the central axis is substantially circular in the measurement state.

Further, the tube 5 has an expanded outer peripheral length in a cross section including a central axis in a usage state in which the tube 5 is filled with working air pressure while satisfying the stipulated dimensional value in the measurement state and without being incorporated in the tire inner cavity. Lti is 1.05 to 1.20 of the circumferential length T of the cross section of the tire bore surface 4 in the natural state.
It is desirable that the amount is 1.0 times, more preferably 1.05 to 1.10 times.

As described above, the expansion outer peripheral length Lti of the tube 5 when the working air pressure is filled, and the tire inner surface 4
By optimally setting the difference from the perimeter T of the cross section of
The amount of extension can be made as small as possible while preventing the rim from coming off, and the effect of air pressure on the tire 2 can be reduced.
When the load is low, the spring effect of the air pressure is relatively suppressed as compared to when the load is high, and the spring constant of the tire assembly can be changed by the load.

The expansion outer peripheral length Lti of the tube 5
However, if it is less than 1.05 times the circumferential length L of the cross section of the tire bore surface 4, there is a risk of tube misalignment when running in the state of being incorporated in the tire 2, and the tire 2
Tends to be difficult to hold the bead portion B of the
On the other hand, if it exceeds 1.20 times, the air pressure share of the tube 5 decreases, and the air pressure of the tube 5 tends to act on the tire 2 as it is, and it is difficult to expect a change in the spring constant due to a load change.

[0026] Also, tubing 5, to increase than the thickness G of the rubber to the conventional and, by increasing the 100% modulus E of the rubber, further by combining these, the tube is relatively high itself It shows that it is formed to have rigidity. The rigidity of the tube 5 can be specified from the stress acting on the tube 5.

First, as shown in FIG. 1, at the tube outer peripheral point U passing through the equatorial plane of the tube 5 and the tube inner peripheral point L, the circumferential strains εU and εL generated when the working air pressure P is filled are , Which can be expressed by the following equations 1 and 2 (this equation is described, for example, in Hideo Sakai, “Tire Engineering” (Grand Prix Publishing), page 67, (5.1.37), (5.1.
38) and the like. ).

[0028]

[Equation 1]

[Equation 2]

In these equations, G is the thickness of the rubber of the tube, E is the 100% modulus of the rubber constituting the tube, Rn is the cross-sectional center diameter up to the cross-sectional center of the tube in the above measurement state, and rn is the measurement state. Is the radius of the cross section of the tube at.

From the equations (1) and (2), the radius RU of the outer peripheral point U of the tube when the working air pressure P is filled and expanded.
i and the radius RLi of the inner peripheral point L can be obtained by Equations 3 and 4.

[0031]

[Equation 3]

[Equation 4]

If the cross-sectional shape of the tube 5 when filled with air pressure without being placed in the tire lumen is a circle, the radius r of the cross-section of the tube 5 when filled with the working air pressure P is r.
The rate of change of the radius in the cross section of the tube 5 (ri / r, which is represented by the ratio of i to the radius rn of the cross section of the tube in the measurement state
n) can be calculated by the equation 5.

[0033]

[Equation 5]

Then, by substituting Equations 1 to 4 into this Equation 5 and arranging, Equation 6 can be expressed.

[0035]

[Equation 6]

On the other hand, as described above, the measured outer peripheral length Ltn of the tube 5 can be represented as 2π · rn by approximating the section to a circle, and the expanded outer peripheral length Lti of the tube 5 can be represented as 2π · ri. Can be specified as Equations 7 and 8 from the relationship with the circumferential length L of the cross section of the tire bore surface in the natural state.

[0037]

[Equation 7]

[Equation 8]

From these equations 7 and 8, the tube 5
The change rate (ri / rn) of the radius of 1.17 to 1.38 is obtained, but according to the experiments of the present inventors, a more preferable range of 1.20 to 1.35 was obtained. Therefore, by using these values and the expression 6, it can be expressed as in the expression 9 and can be expressed as in the expression 10 by subtracting 1 from each term.

[0039]

[Equation 9]

[Equation 10]

In this way, the shape of the tube 5 is specified,
Also, by giving the tube itself high rigidity,
As conceptually shown in FIG. 2, by balancing most of the air pressure P filled in the tube 5 with the film force F of the tube 5, the pressure p acting on the tire inner surface 4 can be reduced. . Therefore, the tube 5 of the present embodiment and the tire-rim assembly using the same can reduce the action of the air pressure of the tube 5 relating to the spring constant as much as possible at the time of low load. The spring constant can be changed.

In the above formula 10, P · rn / 4G
The more preferable range of E is 0.20 to 0.30, and the more preferable range is 0.20 to 0.25. As a result, the rigidity of the tube 5 is further enhanced, and the change in spring constant can be increased.

The ratio (K2 / K1) of the spring constant K1 of the tire assembly under a low load to the spring constant K2 of a high load is preferably 1.4 or more , more preferably 1.5 or more. Is desirable. It should be noted that, for example, the low load can be defined as being equivalent to 1 G of the vehicle to be mounted (operating state including the occupant), and the high load can be defined as being equivalent to 2 G.

Further, in the tube 5, it is desirable that the cross-sectional center diameter Rn of the tube from the central axis to the cross-sectional center of the tube in the measurement state satisfies the following equation.

Rr + 0.45Hc≤Rn≤Rr + 0.5
5Hc, where Rr: rim radius Hc: height of tire bore cross section which is the height from the rim radial line in the natural state to the outermost end of the tire bore surface in the tire radial direction

That is, since it is preferable that the tube 5 be uniformly expanded by the filling of the working air pressure, the center of the cross section of the tube 5 in the measurement state is set to the substantial center position of the tire bore surface 4. Is there.

[0046]

Examples Tire size 110 / 90-19 (rim 2.
19-19) For a motorcycle tire, a plurality of types of tubes as shown in Table 1 were prototyped, and a tire-rim assembly (tube air pressure 0.8 kgf / cm ² ) was prepared using these tubes. The spring constant was measured when a low load and a high load were applied to this and the vibration was applied by a vibration machine at a frequency of 1 Hz and an amplitude of ± 1 mm. The low load is 150
kgf and high load were 300 kgf. These correspond to 1G equivalent and 2G equivalent, respectively, when a 250cc off-road motorcycle is used by one person.

The test results are shown in Table 1.

[0048]

[Table 1]

As a result of the test, it can be confirmed that the tire-rim assembly of the embodiment has a larger change in spring constant due to the load than the conventional example. In particular, in Examples 1 to 3, the spring constant ratio (K2 / K1) at a low load and at a high load are both 1.5 or more, and it is clear that Examples 1 to 3 are very excellent.
Further, FIGS. 3 to 5 show CT scan radiographic cross sections of the tire and rim assembly of Example 3, FIG. 3 shows no load, FIG. 4 shows low load, and FIG. 5 shows high load. Shows.

[0050]

As described above, in the invention according to claim 1, since the extension of the tube can be reduced,
The effect of pneumatic pressure on the tire can be reduced, the spring effect of pneumatic pressure can be suppressed at low load, and the spring constant of the tire assembly can be changed by the load. Also tube
The rigidity of the tube itself can be increased by setting the relationship between the used air pressure P, the tube thickness G, and the 100% modulus E, and most of the filled air pressure is balanced with the film force of the tube. In addition, by reducing the pressure acting on the tire, especially by reducing the spring constant of the tire at low load, it can be useful for changing the spring constant of the tire assembly at high load and low load. it can.

In addition to the above effects, in the invention according to claim 2, the center of the cross section of the tube in the measurement state is set to the substantial center position of the inner surface of the tire. It is possible to prevent the tube from wrinkling and lowering its durability when it is filled.

Further, in the invention according to claim 3, the tube for the tire according to any one of claims 1 and 2 is arranged in a tire bore surface surrounded by the tire and a rim for assembling the tire. By using the tire and rim assembly described above, it is possible to provide the tire and rim assembly in which the spring constant can be changed in accordance with the applied load.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire-rim assembly showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a tire and rim assembly illustrating the membrane force of a tube.

FIG. 3 is a cross-sectional view of a tire-rim assembly under no load taken by CT scanning.

FIG. 4 is a cross-sectional view taken by CT scanning of an assembly of a tire and a rim under a low load.

FIG. 5 is a cross-sectional view of a tire and rim assembly under a high load, which is taken by a CT scan.

FIG. 6 is a cross-sectional view illustrating a conventional tube.

FIG. 7 is a cross-sectional view illustrating another tube.

FIG. 8A is a cross-sectional view in which a low load is applied and FIG. 8B is a cross-sectional view in which a high load is applied.

[Explanation of symbols]

2 tires 3 rims 4 Tire inner surface 5 tubes

Claims (3)

(57) [Claims] 1. A tube of a tire for a buggy vehicle or a motorcycle, which is arranged in a tire inner surface surrounded by a tire and a rim for assembling the tire, and expands by pressurization, wherein the tube is a tube. The measured outer peripheral length Ltn in the cross section including the central axis in the measurement state in which the minimum air pressure is filled to eliminate the hollow on the tube surface is 0.8 to 0.8 of the peripheral length T of the cross section of the tire inner surface in the natural state. The expansion outer peripheral length Lti in the cross section including the central axis in the used state, which is 0.9 times and the tube is filled with the used air pressure, is 1. of the circumferential length T of the cross section of the tire bore surface in the natural state. 05 to 1.20 times, and the tube has a thickness G of the tube and 100%.
A tire for a motorcycle, which is used in a buggy vehicle, a motocross, or the like, characterized in that a modulus E, a radius rn of a cross section including a central axis in the measurement state, and an operating air pressure P satisfy the following expressions. Tube. 0.20 ≦ P · rn / 4G · E ≦ 0.35 2. The tube has a cross-section center diameter Rn from the central axis to the cross-section center of the tube in the measurement state,
A tube for a tire of a motorcycle tire used in a buggy vehicle, a motocross or the like according to claim 1, which satisfies the following formula. Rr + 0.45Hc ≦ Rn ≦ Rr + 0.55Hc where Rr: rim radius Hc: height of the tire bore cross section which is the height from the rim radial line in the natural state to the outermost end of the tire bore surface in the tire radial direction. 3. A tire in which a tube of a tire for a motorcycle used for a buggy vehicle or a motocross according to claim 1 or 2 is arranged in a tire inner surface surrounded by a tire and a rim for assembling the tire. And rim assembly.