JPS62137201A - Pneumatic tire pair - Google Patents

Abstract

PURPOSE:To enhance the controllability during middle and low rotational speed running and the stability during high rotational speed running of a vehicle, by selecting the distribution of the belt rigidity so that the difference between the heights of the center section of each of front and rear wheels, which are obtained during high rotational speed running and during middle and low rotational speed running, respectively, and the similar difference between the heights of the shoulder section thereof are specified, and therefore cornering powers at a specific speed satisfy a predetermined relationship. CONSTITUTION:Estimating that the difference between the height H8CL of the center section of a front wheel 1 during high speed running and the height H7CL thereof during middle and low speed running is DELTAFC, and the difference between the height H8Sh of the shoulder section thereof during high speed running and the height H7Sh thereof during middle and low speed running is DELTAFSh, and estimating that the similar differences between the heights of the center section and the shoulder section of a rear wheel 1' are DELTARC, DELTARSh, respectively, the distribution of the belt rigidity is so selected that the ratio DELTAFC/DELTAFSh of the front wheel 1 is set to be greater than the ratio DELTAFC/DELTAFSh of the rear wheel 1'. Further, the relationships F1/F2 and R1/R2 of the cornering powers F1, F2, R1, R2 of the front and rear wheels 1, 1', which are obtained during running at speeds of 50km/h and 150km/h, respectively, are set so as F1/F2>=1.00 and R1/R2<=0.95. With this arrangement it is possible to the controllability during low and middle speed running of the vehicle and the stability during high speed running of the vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a pair of pneumatic tires, particularly a tire with a running speed of 59+
The present invention relates to a pair of pneumatic tires for a passenger car having a front tire and a rear tire, which improves the handling performance and stability performance of a vehicle that travels at medium speeds of about m/h or less to high speeds of 1100 k/h or more.

(Prior Art) Generally, when a passenger car travels at a high speed of approximately 100 kffi/h or more, the stability of the vehicle cannot be said to be sufficient. To improve this problem with tires, it is effective to improve the cornering power of the rear tires, but if the cornering power of the rear tires is improved, the vehicle will Maneuvering performance becomes insufficient. (Problem to be Solved by the Invention) Therefore, by changing the characteristics of pneumatic tires, it is possible to simultaneously improve the stability performance of a vehicle at high speeds and the maneuverability at low and medium speeds. The problem is that it cannot be done. In particular, in recent front-wheel drive vehicles (so-called front-engine, front-drive front-wheel drive vehicles), the load on the rear wheels is light, so cornering power from the rear tires is low, and the vehicle stability at high speeds is not sufficient. However, there is a problem in that it is extremely difficult to simultaneously improve both the stability performance of the vehicle when running at high speeds and the maneuverability performance when running at medium speeds.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a pair of pneumatic tires having a front tire and a rear tire, which improve the stability performance of a vehicle during high speed travel while sufficiently ensuring the maneuverability of the vehicle during low and medium speed travel. With the goal.

(Means for Solving the Problems) A pair of pneumatic tires according to the present invention includes: a tread passing through the crown center of the tire and extending beyond both shoulders; a belt provided on the radially inner side of the tread; In a pair of pneumatic tires having a front tire and a rear tire with The front wheel center difference ΔFc is larger than the center height from the crown center of the surface, and the shoulder height from the axis of rotation to the shoulder of the tread surface during high speed rotation is the same as the shoulder height from the axis of rotation to the shoulder of the trend surface during low speed rotation. Equipped with a belt having a belt stiffness distribution that increases by the front wheel shoulder difference ΔF0, the rear tire has a belt whose center height from the rotation axis of the rear tire at high speed rotation to the crown center of the tread surface is the rotation axis at low speed rotation. Rear wheel center difference Δ from the center height from to the crown center of the tread surface
Belt rigidity that increases by Rc and that the shoulder height from the rotation axis to the shoulder on the tread surface during high-speed rotation is greater than the shoulder height from the rotation axis to the shoulder on the tread surface during low-speed rotation by the rear wheel shoulder difference ΔR□ Equipped with a belt having a distribution, front wheel center difference ΔFc
The ratio ΔFc/ΔFsh between the front wheel shoulder difference ΔFsh and the rear wheel center difference ΔRc is the ratio ΔFsh between the rear wheel center difference ΔRc and the rear wheel shoulder difference ΔRih.
It is larger than Rc/Rsh, and the front tires and rear tires have cornering power that varies depending on the speed when filled with the normal internal pressure and when the normal load is applied, and the cornering power of the front tires and the rear tires at a speed of 5Q km/h is expressed as Fl and Rsh, respectively. R1, speed 150km/h
When the cornering power at the time is F2 and R2, respectively, the front tire and the rear tire are characterized in that they are within the range of the following formula %. Further, as one method, the belt is made of a rubber-coated cord, and an acute angle formed between the tire circumferential direction of the front tire and the cord direction of the belt seen from the tread side is the same as that between the tire circumferential direction of the rear tire and the tread side. It is larger than the acute angle formed with the cord direction of the viewed belt, and the following formula, Fl/F2≧1.00.
It is desirable to have a relationship of R1/R2≦0.95.

Here, 2Fl/F2≧1.00, R1/R2≦0゜9
It was limited to 5 when Fl/F2 was less than 1.00 and
When R1/R2 exceeds 0.95, the driving speed is 59km/
This is because it is not possible to simultaneously obtain sufficient maneuverability at speeds of about 150 km/h and sufficient stability at speeds of 150 km/h or more.

In addition, the acute angle between the tire circumferential direction of the front tire and the belt cord direction as seen from the tread side is made larger than the acute angle between the tire circumferential direction of the rear tire and the belt cord direction as seen from the tread side. This is because the speed dependence of the code direction and the cornering power Cp has the relationship shown in FIG. In Fig. 1, the angle θ between the belt cord direction and the tire circumferential direction is 15 degrees and 2 degrees.
This is because, when the cord angle θ is 0 degrees, the cornering power Cp increases as the running speed increases, and when the cord angle θ is 25 degrees, the cornering power Cp decreases as the running speed increases.

(for production) Next, the effect will be explained.

The pneumatic tire pair of the present invention has a belt rigidity distribution in which the center part of the tread of the front tire protrudes radially outward from the center part of the rear tire during high-speed rotation, and a part of the shoulder of the rear tire is a part of the front tire. The belt stiffness distribution extends radially outward from a portion of the shoulder of the tire. Therefore, the front tires and the rear tires have different ground pressure distributions depending on the running speed, and have different cornering power depending on the running speed. The cornering power of the front tires is greater when driving at medium speeds (about 5Q km/h) than when driving at high speeds (over 100 km/h). Therefore, when driving at medium speeds, the front tires have a strong grip on the road and the vehicle's maneuverability during steering is excellent, and when driving at high speeds, the rear tires have a strong grip on the road and prevents wobbling. The stability of the vehicle is excellent.

(Example) Hereinafter, one example of a pneumatic tire pair according to the present invention will be described based on the drawings.

2 to 6 show examples of a pair of pneumatic tires according to the present invention, and FIG. 2 is a partial sectional view thereof. In Figure 2, 1 is the front tire (tire size is 195/70
R14), and this front tire 1 has a central portion 2a passing through the crown center CL of the front tire 1 and a central portion 2a.
Trend 2 and Trend 2 having shoulder portions 2b that are continuous at both ends of and extend beyond the pair of shoulders sh.
It has a belt 3 provided on the radially inner side of the belt. The belt 3 is made of a cord 6 covered with rubber 5 (a steel cord in this embodiment), and the acute front wheel cord angle θ between the tire circumferential direction and the cord direction of the belt 3 as seen from the tread 2 side is 25 degrees. The rest of the structure is the same as a normal radial tire for passenger cars. The rear tire paired with the front tire 1 is the same as the front tire 1 except that the rear wheel cord angle 0 position of the acute angle of the belt as seen from the tire circumferential direction and the tread 2 side is 15 degrees. The front wheel cord angle θ is larger than the rear wheel cord angle θ.

Figure 3 is a conceptual cross-sectional diagram (model) of a pneumatic tire l.
and the tread surface 2C of the tread 2 in FIG.
The approximate shape line is shown. In Fig. 3, 7 (double-dashed line) is filled with the normal internal pressure, and at low speed (about 50 km/h,
(same below), 8 (solid line) is when front tire 1 rotates at high speed (
The speed is approximately 150 ko+/h (the same applies hereafter), and the 8" (dotted line) is the rear tire 1' (hereinafter, the configuration of the rear tire is indicated by a dash) at high speed (approximately 150 km/h).
/h, hereinafter the same). As shown in FIG. 3, when the front tire 1 rotates at high speed, the central portion 2a and shoulder portion 2b of the tread 2 protrude radially outward A due to centrifugal force when the front tire I rotates at high speed, and the rotational axis of the front tire I (see FIG. (not shown, the same applies hereafter) to tread surface 2
The center height HscL from the crown center CL of C (shape line 8) is from the rotating wheel at low speed rotation to the tread surface 2C.
Center height H to crown center CL of (shape line 7)
'lCL larger than front wheel center difference ΔFc, and tread surface 2c from rotation axis at high speed rotation (shape vA8)
The shoulder height H8Sh from the rotation axis at low speed rotation to the shoulder sh of the tread surface 2c (shape line 7) is the shoulder height H8Sh? The belt 3 is provided with a belt stiffness distribution that is larger than sh by a front wheel shoulder difference ΔFSk.

Further, when the rear tire 1' rotates at high speed, the tread 2. The central part 2'a and the shoulder part 2'b of 2' protrude radially outward A, and the tread surface (8' of the shape line) extends from the rotation axis of the rear tire 1'.
The center height F3・eL from the rotation axis to the crown center CL of the tread surface (shape lines 7', 7'
is approximately the same as 7), the center height H1 to the crown center CL is greater than the rear wheel center difference ΔRc, and the shoulder from the axis of rotation at high speed rotation to the shoulder sh of the tread surface shape line 8') Belt rigidity distribution such that s'sh is greater than the shoulder height Hl, h from the rotation axis at low speed rotation to the shoulder sh of the tread surface (shape line 7') by the rear wheel shoulder difference ΔR5h The belt 3' has a belt 3'.

When a pneumatic tire pair consisting of a front tire 1 and a rear tire 1' having such a belt stiffness distribution is mounted on a vehicle and the vehicle is running at high speed, the tread 2 of the front tire 1 makes contact with the ground on the inside of the cornering. As shown in Fig. 4 (al, (b)), the pressure changes as shown in curve 11 in Fig. 4 (al) from the stepping point B to the kicking point C at a running speed of 50 km/h. At a speed of 150 kffi/h, curve 12 of Figure 4 (Mountain)
The ground pressure on the outside of the cornering of the front tire 1 is as low as shown in Fig. 5 (a
) changes as shown in curve 13, but at a running speed of 150 km.
/h, there is little change due to speed as shown by curve 14 in FIG. 5 Tb). In addition, the ground contact pressure of the tread of the rear tire during cornering is as follows: on the inside of the corner, when the speed is 50 km/h, the ground contact pressure is as shown in curve 11' in Figure 4 (a), and when the speed is + m/h to 150 km/h, the ground contact pressure is as shown in Figure 4 (b). ), the ground contact pressure increases, and on the outside of cornering, at a speed of 50 km/h, the curve m13' in Figure 5(a) increases.
, when the speed is 150 km/h, the ground pressure increases as shown by curve 14' in FIG. 5(b).

In this way, since the ground contact pressure changes depending on the speed, the front tires 1 and the rear tires 1' have cornering power cp that differs depending on the running speed, and the normal internal pressure (1.7ks
r/cd) Speed of front tire 1 and rear tire 1 when filled and with normal load (470 kg) 50 km/
The cornering power Cp of h is Fl and R1, respectively.
The cornering power Cp at a speed of 150 km/h is
are F2 and R2, respectively, then the front tire and the rear tire are within the range of the following formula %. In this example, each of the legacy ratios is
As shown in Figure 6, the cornering power Cp for the front tires at a speed of 50 ktm/h is almost equal to that at 150 ktm/h, and for the rear tires, Speed 50km/
The cornering power Cp at h is 5% smaller than that at 150 km/h. Also, at a speed of 501 am/h,
The cornering power F1 of the front tires is greater than the cornering power R1 of the rear tires, and the speed is 150 km/h.
Sometimes, the cornering power F2 of the front tires is smaller than the cornering power R2 of the rear tires.

Therefore, when driving at medium speeds of around 50 km/h, the front tires have a large road grip and good steering performance, and when driving at high speeds of 150 km/h or more, the rear tires have a large road grip. Less light-headedness,
Excellent stability performance.

(Effect) Next, a pair of test tires (tire size 195/70R14
) were prepared in three types M (Example, Comparative Examples ■ and ■),
The effects of the present invention were confirmed.

The tire of the example is as described above. Comparative example! and Comparative example ``are conventional tires, and the cord angle of the belt is 20 degrees, and the difference in tread rubber and bead structure makes it 7th tire.
It has load dependence as shown in the figure. The cornering power of Comparative Examples ■ and ■ does not change much depending on the speed. That is, in Comparative Example (2), there is a load dependence of cornering power, and in the case of the above-mentioned FF vehicle, the cornering power of the rear wheels is small.

The load dependence of cornering power in the example is as shown in FIG. 7, with the front tires having a tendency as in Comparative Example I, and the rear tires having a tendency as in Comparative Example (2).

In the test, four test tires were attached to the front and rear wheels of a passenger car (front wheel drive vehicle), and run step steering was performed as shown in Figure 8 during medium speed driving (speed 50 kffl/h) and high speed driving (speed 150 km/h). We measured the yaw rate and compared the behavior of the car in the following cases.

The test results are shown in FIG. 9 (at a speed of 150 km/h) and FIG. 10 (at a speed of 501 ua/h). When driving at high speed (
At a speed of 150 km/h), as shown in FIG. 9, the example shows a smaller change in yaw rate than comparative examples (2) and (2), and the stability performance of the vehicle is very excellent. In comparative example ■, the cornering power of the rear wheels is small, so the yaw rate changes greatly and the stability performance is significantly lower. When traveling at low speed (speed 50 kntZh), as shown in FIG. 10, the example has superior maneuverability during run-step steering shown in FIG. 8, compared to comparative examples (2) and (2).

Furthermore, using a passenger car equipped with the above-mentioned test tires, a feeling test of steering stability performance was conducted by driving at medium speeds and high speeds. The evaluation used a 5-point evaluation method, and the evaluation results of each test driver were averaged. The higher the score, the better the score. The evaluation results are shown in the table below.

(Hereinafter, the margin of this page) As shown in the previous table, Examples are Comparative Examples ■ and ■
It has excellent handling stability performance both at low to medium speeds and at high speeds.

In addition, when the absolute value of cornering power is low, in order to increase the absolute value of the level of cornering power, reinforcing belt layers, so-called hollow belt layers, are usually added to both sides of the radial outside of the belt layer, or reinforcing belt layers are added to both sides of the belt layer. Even with the addition of a belt layer, the effects of the present invention can be achieved.

As described above, according to the present invention, it is possible to significantly improve the stability performance of the vehicle during high-speed driving while sufficiently maintaining the maneuverability of the vehicle during low-speed and medium-speed driving.

[Brief explanation of drawings]

1 to 6 are diagrams showing an embodiment of a pneumatic tire pair according to the present invention, and FIG. 1 is a graph showing the relationship between cornering power Cp and speed when the cord angle of the belt is changed; Figure 2 is a cross-sectional view of the tire, Figure 3 is a diagram showing changes in the shape line of the outer surface of the tire during high-speed running and low-speed running, and Figure 4 (al, (bl) is the ground contact pressure on the inside of the corner when cornering. Figure 4(a) shows the change in speed 50.
km/h, Fig. 4 (b) is a graph at a speed of 150 kIl/h, Fig. 5 (Ta), (bl shows the change in ground pressure on the outside of cornering during cornering, Fig. 5 (al is a graph at a speed of 5Q km) /h, Figure 5(b) shows the speed of 150km/h.
FIG. 6 is a graph showing changes in the cornering power Cp of the front tires and the rear tires depending on the speed. FIG. 7 is a graph showing the relationship between cornering power and load of a conventional tire. 8 to 10 are diagrams showing the effects of the present invention. FIG. 8 is a graph showing changes in steering angle of run-step steering for testing, and FIG. 9 is a graph showing changes in steering angle of run-step steering for testing.
FIG. 10 is a graph showing changes in yaw rate at a speed of 50 km/h. l...Front tire, 1'...Rear tire, 2.2'...Tread, 2a, 2''a...Central part, 2b, 2"b...Part of the shoulder, 5...
・Rubber, 6... Cord.

Claims (2)

[Claims] (1) In a pneumatic tire pair having a front tire and a rear tire, the front tire has a tread that passes through the crown center of the tire and extends beyond both shoulders, and a belt that is provided radially inward of the tread. The tires are
The center height from the rotation axis of the front tire to the crown center of the tread surface during high speed rotation is greater than the center height from the rotation axis to the crown center of the tread surface during low speed rotation by the front wheel center difference ΔF_c, and when the front tire rotates at high speed The shoulder height from the axis of rotation to the shoulder on the tread surface is greater than the shoulder height from the axis of rotation to the shoulder on the tread surface during low speed rotation. Front wheel shoulder difference ΔF_s
The rear tire is equipped with a belt having a belt stiffness distribution that increases by _h, and the center height from the rotation axis of the rear tire at high speed rotation to the crown center of the tread surface is the same as the center height of the rear tire from the rotation axis at low speed rotation to the tread surface. The rear wheel center difference ΔR_c is larger than the center height to the crown center, and the shoulder height from the rotation axis to the shoulder of the tread surface during high speed rotation is greater than the shoulder height from the rotation axis to the shoulder of the tread surface during low speed rotation. The belt has a belt stiffness distribution that increases by the rear wheel shoulder difference ΔR_s_h, and the ratio ΔF_c/ΔF_s_h between the front wheel center difference ΔF_c and the front wheel shoulder difference ΔF_s_h is the ratio ΔR_c/R_s_h between the rear wheel center difference ΔR_c and the rear wheel shoulder difference ΔR_s_h. larger, the front tires and the rear tires have cornering power that varies depending on the speed when filled with the normal internal pressure and when the normal load is applied, and the cornering powers of the front tires and the rear tires at a speed of 50 km/h are respectively F_1 and R1, speed 15
A pneumatic tire characterized in that the front tire and the rear tire are within the range of the following formula: F1/F2≧1.00 R1/R2≦0.95, where cornering power at 0 km/h is F2 and R2, respectively. versus. (2) The belt is made of a rubber-coated cord, and the acute angle between the tire circumferential direction of the front tire and the belt cord direction seen from the tread side is the acute angle between the tire circumferential direction of the rear tire and the belt cord seen from the tread side. A pair of pneumatic tires according to claim 1, wherein the angle is larger than an acute angle with a direction.