JPH1058920A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce radial force variation in the straight travel of a vehicle, by arranging the tread patterns of the most part of a tread at equal pitches in the peripheral direction of the tread, and arranging the tread patterns of the remained area with the combination of the various kinds of pitches. SOLUTION: The tread patterns of, for example, 30-50% of tread width CW from the central position of the tread width to each side, of a tread 1, is formed in an equal pitch area 2 in which the patterns are arranged at equal pitches P in the peripheral direction of the tread. On the other hand, the tread pattern of the remained part of the tread 1 is formed in a variable pitch area 3 in which at least two kinds (five kinds in the drawing) of pitches P11 -P15 are combined in the peripheral direction. Thereby the vibration in the vertical direction, of the area caused by the radial force variation, can be effectively inhibited under the straight travelling condition of the car. Further the generation of the pattern noise in the turning of the car, is effectively reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of effectively reducing radial force variation (hereinafter referred to as "RFV") while suppressing pattern noise, especially pattern noise entering a vehicle interior. But it's about the tread pattern of the tire.

[0002]

2. Description of the Related Art In order to reduce pattern noise generated by a tread pattern of a tire, a plurality of pitches are formed by combining two or more types of pitches in the circumferential direction of the tread over the entire area of the tread surface. The arrangement (hereinafter referred to as “pitch variation”) has been widely and generally performed in the past, and according to this, the noise component was made more noticeable by widely dispersing the frequency components of the generated noise and lowering the peak value. Can be eliminated.

[0003]

However, when such a pitch variation over the entire area of the tread surface is adopted, the RFV as one of the evaluation criteria of the uniformity of the tire becomes large and the ride comfort to the vehicle is increased. There was a problem that was damaged.

[0004] Here, as one factor that the pitch variation increases the RFV, as shown in FIG. 6, a belt BE located on the radially inner peripheral side of the tread portion TR as illustrated in a circumferential cross section of the tread portion. Is forced to be deformed in a direction radially inwardly recessed at a position corresponding to each groove GR due to the formation of the grooves GR extending in the tread width direction. , Each pitch P
_In the case of a pattern arrangement in which ₁ , P ₂ and P ₃ are combined, the depression RE of the belt BE is generated irregularly in the circumferential direction, and the irregularity itself is caused by the radius of the rolling tire. The direct effect on the fluctuation of the directional reaction force is raised, and another factor is that the volume of the tread rubber in each pitch changes depending on the size of the pitch due to the adoption of the pitch variation. As a result, in addition to the difference in stiffness between the respective pitches, the difference in the stiffness between the pitches is further increased under the tendency that the tread rubber thickness increases as the pitch becomes larger. The difference in compression elastic modulus between them is large.

[0005] The inventor of the present invention has sought to achieve a balance between the suppression of pattern noise and the improvement of RFV, which are in conflict with each other.
Regarding how to perceive the intrusion of pattern noise into the cabin and the reduction in ride comfort due to RFV, apply a tire with a pattern arrangement in which the entire tread tread portion has the same pitch and apply a pitch variation to the whole An actual vehicle survey was conducted for each of the tested tires. When the vehicle was running straight, and the ground contact state, load load state, and the like of each of the four tires were stable and steady, the vertical vibration caused by RFV was reduced. While the occupant's sense is sharp and the vertical vibration is uncomfortable,
With regard to pattern noise that enters the cabin, the sound insulation effect of the vehicle body itself has been improved in recent years with higher performance of the vehicle, so that the pattern noise cannot be clearly distinguished from the noise generated by the engine etc. In addition, since the pattern noise integrates with the engine noise generated in response to the engine rotation based on the driver's conscious accelerator operation, the occupant extracts only the pattern noise from the integrated noise The pattern noise itself was hardly perceived as a peculiar and unpleasant sound.

On the other hand, when the vehicle is turning,
In addition to the unstable contact state of each tire of the four wheels, when the load state changes over time, the occupant's sense of vibration caused by RFV becomes dull. Regarding pattern noise that enters the cabin, since each tire generates various pattern noises of frequency components according to the ground contact state, etc., the occupant may not have the sound insulation performance of the body itself. It became clear that unpleasant sounds, such as unrecognizable and humming sounds, were felt.

Therefore, according to the survey results, it is effective to reduce the RFV mainly when the vehicle is traveling straight, and to reduce the pattern noise when the vehicle is turning, in order to effectively balance both of them. There will be.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention aims to separate the function of the tread surface of the tire between a portion that contacts the ground when the vehicle is running straight and a portion that contacts the ground when turning the vehicle. The part that mainly touches the ground functions to reduce the RFV, and the part that mainly touches the ground when turning makes it function to reduce the pattern noise. Specifically, of the tread contact surface, when the vehicle travels straight, A tread pattern in an area of 30 to 50% of the tread width is arranged at equal pitches in the tread circumferential direction from most or all of the tread width including the central portion, preferably from the center of the tread width to each side. And the remaining tread pattern is a pattern arrangement of a plurality of pitches in which at least two types of pitches are combined in the tread circumferential direction.

Here, the "contact width when the vehicle travels straight ahead" means that the tire is mounted on the applicable rim,
The contact width when traveling straight ahead under the condition that the load applied to the tire is 100% of the load capacity at the time of filling the maximum specified internal pressure, and means the contact width under normal use conditions .

As described above, in this pneumatic tire, many portions within the tread contact width when the vehicle travels straight ahead are arranged in a pattern of an equal pitch, so that the depressions generated in the belt are formed in the circumferential direction of the tread. RF caused by irregular occurrence in the circumferential direction of the depression
V can be effectively improved, and the multiple pitch pattern arrangement can sufficiently remove the RFV due to the difference in the tread rubber volume in each pitch, and as a result, the straight running of the vehicle Occurrence of vertical vibration that sometimes causes discomfort to the occupant is sufficiently prevented.

[0011] By the way, as described above, due to the improvement of the sound insulation performance of the vehicle body itself, the pattern noise at the time of straight running is a peculiar and unpleasant to the occupants in the vehicle compartment even if the pattern arrangement is at the same pitch. It is not perceived as noise.

Further, in the pneumatic tire, in addition to an increase in the contact area when the vehicle turns, the tread shoulder region where the load is particularly large is arranged in a plurality of pitches in a pattern arrangement, so that the pneumatic tire inherently has a pitch variation. This makes it possible to effectively prevent the generation of unpleasant noise such as a beat noise and the intrusion of the noise into the vehicle interior.

At the time of turning, the ground contact state, load state, etc. of each tire change with time, and the running state itself becomes unsteady. Therefore, even if vibration caused by RFV occurs, It does not independently cause any particular discomfort to the occupant, and the vibration will be included in the vibration caused by the driving condition.

In this pneumatic tire, by separating the function of the tread surface of the tread tread when the vehicle is traveling straight ahead and when the vehicle is turning, the pneumatic tire has a pattern that is in a trade-off relationship with each other. Noise suppression and RFV
Can be achieved at a high level.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a development view of a tread pattern showing one embodiment of the present invention. The pneumatic tire shown here is 225/50 R in size
16 and the ground contact width of the vehicle when traveling straight ahead is 170 mm.

In this embodiment, most or all of the tread width CW of the tread surface 1 when the vehicle travels straight ahead, preferably 30 to 50 of the tread width CW from the center of the tread width to each side. % range, for example, the tread pattern in the range of 32.35%, while the equal pitch region 2 that the pattern sequence of a constant pitch P ₁₀ in the tread circumferential direction, the tread pattern of the remainder of the tread surface 1, at least two In the figures, the variable pitch area 3 is a pattern arrangement formed by combining five types of pitches P _{11 to} P ₁₅ in the circumferential direction.

[0017] In such a tread pattern configuration of the pneumatic tire, the tire is moved within the equal pitch range 2.
When the cross section is formed in the tread circumferential direction in a relatively short widthwise extending portion of the widthwise groove 4 in the central region of the tread tread, as shown in FIG. 5 are regularly formed in the circumferential direction at an interval of a pitch P ₁₀ , which means that the recesses 6 on the inner side in the radial direction are formed in the same pitch area 2 where the width direction grooves exist. Since the same is true in the circumferential cross section at the position, in this equi-pitch region 2, the generation of RFV due to the irregular presence of the recess 6 in the circumferential direction can be effectively prevented, Further, it is possible to effectively prevent the occurrence of RFV due to the difference in tread rubber volume in each pitch and the difference in tread rubber thickness in each pitch. On the other hand, in the variable pitch area 3, although the generation of RFV is inevitable, the effective reduction of the pattern noise can be realized.

Here, if the width of the equal pitch area 2 is less than 30% of the contact width from the center position of the contact width when the vehicle is traveling straight, the variable pitch area 3 occupying the contact surface when the vehicle is traveling straight. Is too large, it is difficult to effectively reduce RFV. On the other hand, if it exceeds 50%, the proportion of the equal pitch area 2 occupying the ground contact surface during turning of the vehicle becomes too large, resulting in a pattern noise. It is difficult to effectively suppress the above.

FIG. 3 is a diagram showing the footprint of a tire having the above-described tread pattern when the vehicle is running straight, for each of the four tires. According to this, under the straight running state of the vehicle, in which both the contact state of each tire and the load state of the load on the tire are sufficiently stable, the equal pitch area 2 corresponds to the tread central area of the tire where the contact pressure is the highest. It is evident that it occupies a significant portion of each footprint, including:
, Vibration of the vehicle, mainly in the vertical direction, is effectively suppressed. According to the figure, although the variable pitch area 3 also occupies a part of the footprint, the occupation amount is extremely small, and the ground pressure of the variable pitch area 3 is considerably low. The RFV generated in the variable pitch area 3 hardly affects the riding comfort of the vehicle. By the way, as described above, the pattern noise in the equal pitch area 2 generated in this running state is not recognized as annoying noise by the occupant of the vehicle.

FIG. 4 shows a case where the vehicle turns to the left.
FIG. 3 is a diagram showing a footprint of each tire. In this case, a particularly large load is applied to an outer tread edge portion of a tire located outside of the turn, and a contact state of each tire and a state thereof are shown. The state of the load on the vehicle greatly changes with the progress of the vehicle.

In this case, in each tire, the contact area of the variable pitch area 3 outside the turn increases as compared with the straight running, and the contact pressure of the contact portion is the contact pressure of the other portion. Since the variable pitch area 3 is much higher, the variable pitch area 3 can realize the effective reduction of the pattern noise generated mainly by the variable pitch area 3 based on its original function.

Even in this case, the ratio of the equal pitch area 2 in each footprint becomes larger than that of the variable pitch area 3, but here, the ratio of the variable pitch area is smaller than that in the straight running. In addition to the increase, in any tire, the ground pressure in the equi-pitch area 2 is extremely small, so that the pattern noise generated in that portion does not become so loud. When the generated noise is close to that when the vehicle is traveling straight, it is effectively shielded by the vehicle body. Further, the vibration caused by the generation of the RFV in the variable pitch area 3 during the turning traveling is taken in during the vibration caused by the unsteady traveling of the vehicle, and the vibration causes a particular discomfort to the occupant. Never.

Thus, with the pneumatic tire, the RFV can be reduced to improve the riding comfort of the vehicle when the vehicle travels straight, particularly by the action of the equi-pitch region 2. In particular, under the action of the variable pitch region 3, the pattern noise can be effectively suppressed, which can also enhance the riding comfort of the vehicle.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a tire having a tread pattern as shown in FIG. 1 and a size of 225/50 R16, the contact width CW of the vehicle when traveling straight ahead is 170 mm, and the width of the equal pitch area 2 is as follows.
From the center position of the contact width to each side, the contact width CW
In the range of 32.35%, also each pitch P ₁₀ in an equal pitch region 2 27.96Mm, each pitch P ₁₁ to P ₁₅ in the variable pitch region 3, 27.57Mm, 31.5
The vehicle interior noise and RFV of the inventive tires of 2 mm, 35.46 mm, 39.39 mm, and 43.33 mm during straight running and cornering were measured, and the results were as shown by the index values in Table 1.

The index values in the table indicate the comparative tire 1 as a control, and the larger the index value, the better the result. By the way, the comparative tire 1 in the table
It is, the whole of the tread surface, the above-mentioned five kinds of pitch P ₁₁ ~
A tire having a variable pitch range of P _15, Comparative tire 2, except the entire tread surface is equal pitch region and the tire of the pitch P _10, and has a configuration similar to that of the invention tires.

[0026]

[Table 1]

Here, the vehicle interior noise is measured by measuring the sound pressure level of noise collected during traveling at a constant speed by placing a microphone at the ear position of the driver on the center side of the vehicle body and performing sensory evaluation. I asked. The sound insulation performance of the vehicle here is 40
It was about -20 dB above 0 Hz and about -30 dB below 400 Hz.
Further, RFV is defined as P- of the variation of the magnitude of the force in the tire radial direction obtained by rotating the tire on a uniformity machine, with the tire internal pressure at 2 kgf / cm ² and the load at 85% of the standard (JATMA standard). The P value was determined by measuring.

According to Table 1, in the vehicle interior noise, when the tire of the present invention is running straight, the sound insulation of the vehicle and the frequency fluctuation of the four wheels are so controlled that they are synchronized with the accelerator control of the driver, that is, the engine rotation. There was no difference in the sensory evaluation, which was inconspicuous. Also, at the time of turning, at the same pitch, the grounding conditions of the four wheels are various, and the generated noise changes every moment, and it is felt that it is felt as a beat sound. The RFV of the inventive tire has a small PP value of about 5% in a state equivalent to straight running, and the vertical vibration felt by the occupant is smaller than that of the comparative tire.

Incidentally, the frequency of the vehicle interior noise during straight running at 60 km / h was analyzed for each of the inventive tire and the comparative tire 1. As shown by the solid line in FIG. The pitch component was slightly larger than the comparative tire 1, but was smaller than the comparative tire 1 at other frequencies.

[0030]

As is apparent from the above description, according to the pneumatic tire of the present invention, the vehicle interior noise during the straight running of the vehicle is suppressed sufficiently low in combination with the sound insulation performance of the vehicle body. Well, the RFV will be effectively reduced based on the equi-pitch pattern arrangement, and
Since the vehicle interior noise during the turning of the vehicle is sufficiently reduced based on the pattern arrangement of a plurality of pitches, it is possible to achieve both a high level of the suppression of the pattern noise and the reduction of the RFV. .

[Brief description of the drawings]

FIG. 1 is a tread pattern developed view showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view in a tread circumferential direction showing a modification of the belt of the tire shown in FIG. 1;

FIG. 3 is a diagram showing a footprint of a four-wheel tire when the vehicle travels straight.

FIG. 4 is a diagram showing a footprint of a four-wheel tire when the vehicle is turning.

FIG. 5 is a graph showing a frequency spectrum of vehicle interior noise.

FIG. 6 is a cross-sectional view similar to FIG. 2, showing a modification of a belt of a conventional tire.

[Explanation of symbols]

Reference Signs List 1 tread tread surface 2 equal pitch area 3 variable pitch area 4 width direction groove 5 belt 6 depression CW contact width P _{10 to} P ₁₅ pitch

Claims (1)

[Claims] 1. The tread surface of a pneumatic tire,
The tread pattern of most or all areas including the central portion of the contact width when the vehicle travels straight ahead is arranged at a uniform pitch pattern in the tread circumferential direction, and the remaining tread pattern is treaded with at least two types of pitches. A pneumatic tire having a plurality of pitch patterns arranged in a circumferential direction.