JPH0288304A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve operation stability and convergency in riding across projections by prescribing, with particular requirements, the outer profile of a tire which is filled with air to regular inner pressure and whose tread developing width is less than 140-280mm and SH is 90-120mm to increase profile effects. CONSTITUTION:The outer profile of a tire is preset so that the following requirements (1-4) may be met - (1) a/a+b=0.35-0.45 (however, a=SDH-c, d=(SH-SDH)-b, where b: height of P1 form P2, c: height of a rim flange), SDH: a side height, (2) alpha=60 deg.-75 deg., where alpha: angle of the connecting line of P1 with P2 in the axial direction of a tire, (3) beta=50 deg.-70 deg., where beta: angle of the connecting line of P2 with P3 in the axial direction of a tire and (4) alpha/beta=0.95-1.15. This increases lateral rigidity by profile effects.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pneumatic radial tire that has excellent steering stability and convergence in driving over bumps.

[Prior art]

Previously, JP-A-54-40406, JP-A-54-6
4303, JP 55-47903, JP 56-146401, JP 56-14640
As shown in Publication No. 2, a technique has been proposed in which the carcass line of a tire is defined as an "equilibrium carcass line" (including a combination with a natural cross-sectional shape) in order to improve durability.

However, these are not sufficient at present when a high balance between steering stability and convergence of overcoming bumps (phase delay of cornering force) is required.

Furthermore, in Japanese Patent Application Laid-open No. 59-11996, durability is improved by increasing the tire side height so that a part of the shoulder becomes lower after the internal pressure is filled.

However, in this case, the lateral rigidity due to the profile effect decreases, resulting in poor handling stability. Japanese Patent Publication No. 58-1616
No. 03, JP-A-59-48204, JP-A-Sho. 5
In JP 9-75810 and JP 59-186702 G, the side height is similarly increased to reduce rolling resistance, but the lateral rigidity due to the profile effect also decreases, resulting in poor handling stability. Gender becomes inadequate.

Here, the profile effect refers to the effect that lowering the side hide makes it possible to ensure high rigidity due to air pressure. That is, in general, a tire can only perform its basic functions when it is inflated. The required rigidity is achieved not only by the rigidity of the tire's own constituent parts (together with the rigidity due to air pressure).However, if the side height is high, the stiffness due to air pressure cannot be utilized as much. It becomes impossible to secure the necessary rigidity, and the steering stability deteriorates.On the other hand, by lowering the side height, it becomes possible to secure high rigidity due to air pressure.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire that improves the profile effect by devising the outer surface profile of the tire, and improves the steering stability and convergence of driving over bumps.

[Structure of the invention]

For this reason, the present invention has a tread development width of 140 mm to 28 mm when assembled on a regular rim and filled with a regular internal pressure.
Section height SH is less than 0 mm and 90 to 120 m
m tire, the shoulder point is P1, the maximum width position on the tire outer surface is PZ, the position inside the bead corresponding to the rim flange height C at the rim inner width end is P3, and the side height is SDH, from the P2 position of P+. When the height of is b, a=sDHC1d= (SH-3DH)-b
Furthermore, when the angle between the connecting line between Pl and P2 and the tire width direction is α, and the angle between the connecting line between P2 and P and the tire width direction is β, the following relationship is satisfied. This article focuses on pneumatic radial tires.

a/(a+b)=0.35~0.45α=
60'' to 75° β = 50° to 70' α/β = 0.95 to 1.15 Hereinafter, the structure of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory diagram of the outer surface profile of the pneumatic radial tire of the present invention. In Figure 1, the tread development width TDW when assembled on a regular rim and filled with the regular internal pressure is 1.
Indicates a tire with a section height SH of 90 to 120 inches with a length of 40 mm to less than 280 mm. Here, "filled with the normal internal pressure" means that the normal internal pressure (for example, 0.5 kg/
−) This means that air is filled into the tire so that the tire is filled with air.

P is the shoulder point. The shoulder point is an extension of the circular arc (radius R1) that shapes the tread surface and the circular arc (radius R2) that shapes the surface from the side part to the shoulder part in the meridian direction cross section of the tire.
The point where the extension line intersects with the extension line. P2 is the maximum width position of the tire outer surface. P3 is a position within the bead portion corresponding to the rim flange height C at the end of the rim inner width T.

SH is the section height (tire cross-sectional height), SDR is the side height (height at the tire maximum width position), and b is the height of Pl from the position of P2. a=sDH−c, d=
(SH-3DH)-su.

α is the connection line between P and P2 and the tire width direction (i.e.
β is the angle between the connection line between P2 and P3 and the tire width direction.

In the present invention, the following requirements (1) to (4) are defined in the outer surface profile of the tire when inflated with the normal internal pressure. Note that the rim flange height C, side height SDI, and section height SH are each height from the bead base.

The rim flange height C remains unchanged regardless of the section height SH, and is usually about 20 mm.

(1) a/ (a + b) = 0.35 to 0.4
Must be 5. Preferably it is 0.40.

When a/(alb) exceeds 0.45, the lateral rigidity due to the profile effect decreases, and the steering stability decreases. 0.3
If it is less than 5, it will be difficult to manufacture a tire, and even if it can be manufactured, the durability of the obtained tire will deteriorate.

Note that the outer surface of the tire corresponding to section d is the tread surface, and the outer surface of the tire corresponding to section C is fixed by the rim flange, so the profile effect is related to (al
b) Since the side portion is a section, the d section and the C section are not particularly defined in the present invention.

(2) α=60° to 75°.

If α is less than 60", the ground contact width cannot be set wide considering the tire width, and as a result, the absolute grip of the tire cannot be ensured, and the steering stability deteriorates. Also, if α is 75"
When it exceeds , the lateral stiffness due to the profile effect decreases,
Maneuvering stability is not sufficient.

(3) β = 50° to 706.

When β is less than 50°, stress concentration occurs at the inflection point of the carcass line, causing a problem in durability. Also, 70
If it exceeds 6, the rim will be extremely wide relative to the tire, causing problems in holding the bead of the rim.

(4) α/β-0.95 to 1.15.

This is because α and β are preferably approximately the same angle in order not to reduce durability.

In the present invention, by specifying the requirements (1) to (4) in this way, the lateral rigidity due to the profile effect is increased. Also, since the carcass tension in a part of the shoulder increases, lateral G
The change in lateral stiffness is linear, especially for roll,
It also improves yaw convergence and improves steering stability. moreover,
By increasing the carcass tension in a portion of the shoulder, the apparent rigidity of the belt portion is relatively reduced, thereby improving the convergence before and after getting over the protrusion. Note that the outer surface profile of the tire of the present invention can be measured by, for example, a laser profile measuring machine or a plaster molding method.

Examples are shown below.

Example A green tire with the same specifications was vulcanized using a conventional mold and an inventive mold, and assembled onto a regular rim.
The tires shown in Table 1 below were manufactured by filling the tires with the normal internal pressure.

Using these tires, side spring constants, cornering force (CF) phase lag, steering stability, and convergence in riding over bumps were evaluated. The results are shown below.

(al) Evaluation of side spring constant After mounting the tire on the rim and filling it with the normal internal pressure, the tread is crimped with a ring-shaped object to prevent it from moving.In this state, vertically from the rim, Evaluation is performed by applying displacement in the lateral and circumferential directions and measuring each spring constant.

As a result, the side longitudinal spring constant of the conventional tire was 97.6.
(kg/mm), the longitudinal spring constant of the side part of the tire of the present invention is 102.4 (kg/mm2), the lateral spring constant of the side part of the conventional tire is 36.4 (kg/mI), the lateral spring constant of the side part of the tire of the present invention is 102.4 (kg/mm). Spring constant is 41.3 (kg/
mm). Therefore, compared to the conventional tire, the tire of the present invention has a side part longitudinal spring constant that is 4% higher, a side part lateral spring constant that is 13% or more higher, and a ratio of the lateral spring constant to the longitudinal spring constant that is 8% higher. became.

(Evaluation of phase delay of blcF: A ramp waveform steering angle was input, and the temporal change in CF that occurred at that time was investigated. The results are shown in Figure 2.

As can be seen from FIG. 2, the conventional tire had a slow time to reach the CF peak and also had a significantly long convergence time, whereas the tire of the present invention had a small CF phase lag and a short convergence time. Therefore, the tire of the present invention has a CF phase delay that is 6% or more smaller than that of the conventional tire. The difference was particularly noticeable in the low load range. This is because the ratio of the horizontal spring constant to the vertical spring constant has become high as described above.

(e) Evaluation of steering stability: The conventional tire and the tire of the present invention were driven on an actual vehicle on a test course, and the feeling was evaluated.

As a result, compared to the conventional tire, the tire of the present invention has less CF phase delay as described above, and as shown in Table 2 below, the steering linearity is improved and the roll and yaw convergence mode during lane changes is improved. Significantly improved. In Table 2, "+1" indicates a slight difference, "+2" indicates a case where an experienced driver can tell, and "+3" indicates a case where an experienced driver can tell.
” indicates cases that most people can understand.

(dl Evaluation of convergence of getting over a protrusion: A diameter 20 mm
Using a protrusion tester equipped with m + * semicircular protrusions,
The axial force when the test tire passed over this protrusion by 4 degrees was detected, and its convergence was evaluated.

The results are shown in FIGS. 3(A), (B), and (C).

From these figures (A), (B), and (C), in the tire of the present invention, the frequency in the vertical direction is increased by 5%, the damping rate in the vertical direction is improved by 5%, and the impact force in the longitudinal direction is increased by 5%. It can be seen that it is 4% smaller.

Therefore, in the tire of the present invention, the impact force in the longitudinal direction when riding over a protrusion was reduced due to the relative reduction in belt tension and the profile effect, and the tire had excellent convergence in the actual vehicle feeling.

〔Effect of the invention〕

As explained above, according to the present invention, by specifying the outer surface profile of the tire, the profile effect can be enhanced, and the steering stability and the convergence of driving over a bump can be simultaneously improved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the outer surface profile of the pneumatic radial tire of the present invention, and Fig. 2 is a diagram showing the cornering force (CF).
), Figure 3 (A) is an explanatory diagram showing the temporal dependence of
,(B). (C) is an explanatory diagram showing in a graph the evaluation of the convergence of getting over the protrusion. TDW...Tread development width, T...Rim inner width, S
H...Section height, SDR...Side high
to.

Claims (1)

[Claims] In a tire with a tread width of 140 mm to less than 280 mm and a section height SH of 90 to 120 mm when mounted on a regular rim and filled with a regular internal pressure, the shoulder point is P_1, and the maximum width position on the outer surface of the tire is P
_2, the position inside the bead corresponding to the rim flange height c at the end of the rim inner width is set to P_3, and the side height is set to S
DH, the height of P_1 from the position of P_2 is b, a=
SDH-c, d=(SH-SDH)-b, and furthermore, the angle between the connecting line of P_1 and P_2 and the tire width direction is α, and the angle between the connecting line of P_2 and P_3 and the tire width direction A pneumatic radial tire that satisfies the following relationship, where the angle is β. a/(a+b)=0.35~0.45 α=60°~75° β=50°~70° α/β=0.95~1.15