JPS59209902A - Combination of front and rear wheel tires in front-drive four-wheeled vehicle - Google Patents

Abstract

PURPOSE:To improve both of drivability and running stability, by using a front wheel tire carrying such a tire characteristic as being larger in the maximum value of side force against a slip angle than that of a rear wheel tire, in case of a radial tire provided for both front and rear wheels. CONSTITUTION:Radial tires to be used in both front and rear wheels for a front- drive four-wheeled vehicle have at least a one-ply radial carcass 1 and a belt 2 layered with at least two sheets of card cloth in the cord arrangement crossed with each other with a relatively small angle to the equator surface of a tire surrounding this carcass 1 as body reinforcement. In this case, the maximum value of side force against a slip angle at the front wheel should be larger than that of the rear wheel, if possible, it is desirable to use such one as in a tire characteristic of 2-10% in caliberation difference. With this constitution, in time of the abrupt turnabout of a car, comfortable drivability is securable.

Description

[Detailed description of the invention] (Technical field) Passenger cars, especially front-wheel drive four-wheel vehicles (so-called F,
Here, we will discuss the matching of pneumatic tires to the driving performance of high-performance passenger cars (F, cars).
F. Concerning the combination of front and rear tires that makes a significant contribution to improving the maneuverability and furthermore the stability of a vehicle.
Therefore, high performance passenger F, F.

It is located in the field of technology related to improving characteristics specific to cars.

(Technical background) Generally, as tires for passenger cars, it is customary to use the same tire on all four wheels, regardless of whether it is a radial tire or a bias tire.

When installing different types of tires on the rear wheels, be careful to use tires with lower maneuverability than the rear wheels on the front wheels. For example, when using a mixture of bias tires and radial tires, it is important to use bias tires on the front wheels. It was only necessary for safety reasons.

Improving the performance of tires that are suitable for passenger cars, especially high-performance F, F, cars1 Until now, development has been focused exclusively on improving the tires themselves.
F, F, to improve maneuverability during sharp turns, which is unique to cars, without impeding stability, and furthermore, to improve steering responsiveness and associated stability under minute steering angles when driving at high speeds. There is still room for improvement in achieving this, and further improvements are increasingly required, especially with the spread of F, F, cars and their increasing performance. However, it can be said that improvements in this respect for individual tires have already reached their limits.

(Problem to be solved by the invention) The following points are pointed out as characteristics of the dynamic characteristics of the F, F, car.

(1) When making a sharp turn, the driving force is applied to the front wheels that control the steering, so while stability is good, the steering wheel does not always sharply turn the steering wheel when driving lightly, resulting in poor maneuverability.

(2) When performing minute steering while driving at high speeds, although the steering wheel may turn well, stability may be lacking.

In this way, sharp turning steering and small angle steering, especially at high speeds, exhibit contradictory motion characteristics.・F, F
, from a new perspective that takes into account the unique tendencies of cars and the fact that the front wheels are used for driving as well as steering as described above, and in particular, the maneuverability during sharp turns is improved. ” to take measures to improve without worsening;
Furthermore, simultaneously ensuring stable maneuverability during high-speed driving is an important issue for high-performance passenger cars.

(Purpose of the Invention) In view of the current situation where improvements in the performance of tires themselves have already reached their limits regarding the above-mentioned problem, a solution is provided by providing a difference in performance characteristics, especially when so-called radial tires are used for front and rear wheels. The purpose of this invention is to newly propose the results of research and development that attempted the following.

(Structure of the invention) The above objectives are advantageously met by the following.

In a front-wheel drive four-wheel vehicle, both the front and rear wheels have at least one ply radial carcass in which the fiber cords are arranged substantially parallel to the radial plane of the tire including the axis of rotation thereof, and the carcass is surrounded by at least one ply of fiber cords. A belt consisting of at least two layers of cord cloth laminated in a cord arrangement that intersects each other at a relatively small angle with respect to the equatorial plane of the tire is provided as body reinforcement, and a tread is formed by an integral rubber skin surrounding the belt. A tire with a radial structure has a patterned crown, a pair of sidewalls and bead parts connected to the crown in a toroidal manner, and the maximum value of the side force relative to the slip angle at the front wheel is higher than that at the rear wheel. The difference is also large, preferably 2 to 10%.
70 combinations of F, F, front and rear tires for cars, which are used based on the tire characteristics.

That is, the above configuration provides light maneuverability even when making sharp turns, with sharp steering operation.

In addition, the stability at very small steering angles, especially during high-speed driving, is less desirable as the side force based on the steering is smaller than that of the rear tires under very small slip angles, usually less than 40. These problems can be simultaneously and effectively solved by making the tire characteristics such that the difference between them is 8 to 12%.

FIG. 1 shows an example of the relationship between the side force SF (vertical axis) and the slip angle SA (horizontal axis), divided into cases where the maximum value SFmax is large (solid line) and cases where it is slightly small (broken line).

This relationship shows how the side force SF of the test tire attached to the test shaft inclined with respect to the axis on the circumference of the test drum depends on the increase in the inclination angle of the test shaft, that is, the slip angle SA. , and when SA exceeds approximately 4o, S
It is almost saturated at Fmax.

When making a sharp turn, the SA of both the front and rear tires of the vehicle is approximately 4.
On the other hand, as shown in the figure, a general pneumatic tire exhibits SFmax at SA of 40 or more.

The role played by the front wheels of the vehicle here is to guide the turning of the vehicle, and therefore, the larger the SF of the front wheels, the better the turning performance, that is, the maneuverability. By the way, SF generally decreases when driving force is applied to a pneumatic tire. Therefore, F, F
In a car, as shown in Figure 1, the front wheels are 3 times higher than the rear wheels.
By using tires with I'ma) (about 2 to 10% larger), maneuverability during sharp turns can be advantageously improved.

In other words, by selecting the tire characteristics described above, the steering wheel becomes sharper when making sharp turns, allowing for nimble driving.

Furthermore, Figure 2 shows that SFma under SA of over 40
While maintaining the relationship of In some cases, the amount of steering wheel steering is not so large, and therefore SA does not reach approximately 40.

The role of the rear wheels here is to stabilize turning, that is, in relation to the stability of the vehicle, as mentioned above, the SF of the rear tires is approximately 8 to 12% larger in the SA minute steering area. means an immediate increase in stability. Therefore, by using the combination of front and rear tires shown in Figure 2, stability can be improved under minute hand and wheel steering amounts when driving at high speeds. This is in addition to what has already been described in Figure 1, and thus it can be said to be more desirable as it improves the maneuverability and stability of the vehicle over the entire range from small to large steering amounts. be.

In accordance with the concept described above, we will proceed with an explanation of a case in which the effects of the invention were confirmed using the following combinations of test tires of size PSR175/70 HR18, the cross section of which is illustrated in FIG. 8. In addition, 1 in the figure is a carcass,
2 is a belt, 8 is a crown part, 4 is a side part S5 is a bead part, 6 is a tread rubber, and 7 is a nylon cord layer.

Difference factors , compared to the vertical load of the test tire.

2 Belt Structure Table 2 Driving, 8 Tread Patterns - Table 8 First, in Experiment 7761, both the front and rear wheels used the same tire with the same block pattern and tread rubber for physical properties, along with the belt of structure P. For the A2, only the front tire was changed to trend rubber with physical property B, and for the A8,
Only the front tire was changed to a belt with Structure Q, and A4 had the same tread rubber as A2 and the same belt structure as A3, A5 had the front and rear reversed from A4, Furthermore, in the same 6, the tread pattern of the front and rear tires is changed to X and Y with the same tread rubber and belt structure as the same 1.
1. We made combinations with a range of differences, and conducted a feeling evaluation based on actual vehicle driving and an evaluation based on a test called ramp/step response.

The test was conducted on a dry asphalt road using a sports car F, F, with an emission percentage of 1150 occ, and the feeling evaluation was the average value of three experienced test drivers.

The results are summarized as shown in Table 4.0 The ramp/step response test was conducted based on the yaw rate based on steering as shown in Figure 4a, that is, the degree of turning of the vehicle (in the same figure).
(shows the results of test number l), the larger the value, the smaller the turning radius, that is, the sharper the turn.
This is one of the general methods for evaluating the maneuverability and stability of a vehicle. It means a violent turning condition.

The dimensions of the yaw rate curve in Figure 4(b) are 1
゜It shows the stability of the vehicle, and the smaller the value, the better the stability. Similarly, the dimension G measures the sharpness of the steering wheel, that is, the maneuverability, and the larger the value of G, the better the maneuverability.

Ramp/step response indices listed in Table 4 C, 1, and 7
1. (Calculated by ' n , Therefore, for both indexes, the larger the value, the better the performance.

Indicates that the condition is good.

(Effects of the Invention) According to the present invention, so-called radial tires are used for both the F, F, front and rear wheels of the car, and the slip angle S is particularly high for the front wheels.
Based on the tire characteristics that the maximum side force for A, SFmaX, is larger than that of the rear wheel, a new concept that intentionally mixes F, F, and F, which is unique to cars, especially high-performance vehicles, during sharp turns, Maneuverability can advantageously be improved by 1° without deterioration of stability.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing the influence of the tire slip angle SA on the side force SF, together with a preferable difference between the front and rear wheels; Figure 8 is a cross-sectional view of the tire; Figure 4(a), ■) is a ramp/step response diagram.
...Carcass 2...Belt 8...Crown part 4...Side part 5...Bead part Patent applicant Brideston Tire Co., Ltd. Figure 4 (a) (b')

Claims (1)

[Claims] L: Front and rear of a front-wheel drive four-wheel vehicle. Tires on both axles, including their axes of rotation. a radial carcass of at least one bridle consisting of an array of fiber cords substantially parallel in the radial plane of the carcass and at least one briny radial carcass of cords surrounding the carcass and consisting of an array of cords intersecting each other at a relatively small angle to the equatorial plane of the tire; A belt made of two layers of cord cloth is provided as a body reinforcement, and a crown part with a tread pattern engraved by an integral rubber skin that wraps these belts and each belt connected in a toroidal shape to this crown part.
A tire with a radial structure in which a pair of sidewalls and a bead are formed is used with tire characteristics such that the maximum value of the side force relative to the slip angle at the front wheel is larger than that at the rear wheel. Combination of front and rear tires. A combination described in L, in which the characteristics of the tires used for the front wheels are smaller than those of the tires used for the rear wheels in terms of side force according to the slip angle at a small slip angle of S4° or less. & The combination according to 1 or λ, in which the tire characteristics used for the front and rear straight wheels differ depending on the characteristics of the rubber outer skin of the tread. 8. The tread rubber skin strength of the tires used for the front wheels is equal to or higher than that of the rear tires in terms of friction coefficient with the road surface, and the hardness due to shore A is lower.8. Combinations listed.