CA1219798A - Pneumatic radial tire for use in muddy road and/or snow road - Google Patents
Pneumatic radial tire for use in muddy road and/or snow roadInfo
- Publication number
- CA1219798A CA1219798A CA000462653A CA462653A CA1219798A CA 1219798 A CA1219798 A CA 1219798A CA 000462653 A CA000462653 A CA 000462653A CA 462653 A CA462653 A CA 462653A CA 1219798 A CA1219798 A CA 1219798A
- Authority
- CA
- Canada
- Prior art keywords
- tire
- carcass
- line
- bead
- cords
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C3/00—Tyres characterised by the transverse section
- B60C3/04—Tyres characterised by the transverse section characterised by the relative dimensions of the section, e.g. low profile
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
- B60C9/02—Carcasses
- B60C9/0292—Carcass ply curvature
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
- Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Tires In General (AREA)
Abstract
Abstract of the Disclosure Disclosed herein is a pneumatic radial tire for use in a muddy road and/or a snow road, which comprises a pair of annular side wall portions each provided with a bead portion, a tread portion exten-ded over the side wall portions outside in the radial direction of the tire, and a reinforcement consisting of a carcass composed of at least one cord ply containing organic fiber cords therein, which cord ply being wound around a bead core embedded in each of the bead portions from the inside to the outside of the tire, and a belt composed of at least two ply layers superimposed around the crown portion of the carcass and containing rubberized cords of a high elasticity arranged at a relatively small inclination angle with respect to the mid-circumferential plane of the tire, the cords of which being crossed with each other, and rubber fillers each filled between the carcass and the turn-up portion thereof for hardening the bead por-tion. The carcass radial profile is varied by enlarging the negative ratio with use of a block pattern, and deepening the grooves of the pattern in the tread.
Description
31~Z~7~3 The present invention relates to a pneurnatic radial tire for use in passenger cars, and more particularly the invention is to provide an improved pneumatic radial tire suitable for use in a muddy road 05 and/or a snow road.
In order to improve a traction performance of a tire for use in the muddy road and/or the snow road, it is generally adopted to use a block pattern, increase a negative ratio, that is, the ratio of the total area of the groove (space) portions on the tread to the area of the whole tread portion, and deepen the grooves. r~
When these countermeasures are emp]oyed, however, the following defects ordinarily come out in the case of the conventional reinforcement of the radial tires:
(l) The rigidity of the tread portion lowers, the cornering power (CP) and the self-aligning torque of the tire decreases to deteriorate the cornering stability.
In order to improve a traction performance of a tire for use in the muddy road and/or the snow road, it is generally adopted to use a block pattern, increase a negative ratio, that is, the ratio of the total area of the groove (space) portions on the tread to the area of the whole tread portion, and deepen the grooves. r~
When these countermeasures are emp]oyed, however, the following defects ordinarily come out in the case of the conventional reinforcement of the radial tires:
(l) The rigidity of the tread portion lowers, the cornering power (CP) and the self-aligning torque of the tire decreases to deteriorate the cornering stability.
(2) Since it is necessary to use a thick tread rubber so as to deepen the grooves, this causes the increase in the compression and the shearing deformation of the tread rubber, so that the rolling resistance of the tire is increased by the increased deformation-energy loss of the tread rubber.
Under the circumstances, the cornering stability and the rolling resistance can not help be ~2~975~
sacrificed so as to secure the traction performance.
It is therefore an object of the invention to provide a pneumatic radial tire in which the rolling resistance and the cornering stability are improved by 05 reinforcing the tire, particularly, by appropriately varying the radial profile of the carcass without deteriorating the traction performance, which can advantageously overcome the problems inevitably encountered by the prior art when the traction perform-ance as the pneumatic radial tire for use in the muddyroad and/or the snow road is secured by enlarging the negative ratio with use of a block pattern, and deepening the grooves of the pattern.
According to the present invention, there is a provision of the pneumatic radial tire for use in the muddy road and/or the snow road which comprises a pair of annular side wall portions each provided with a bead portion, a tread portion extended over the side wall portions outside in the radial direction of the tire, and a reinforcement consisting of a carcass composed of at least one cord ply containing organic fiber cords therein, which cord ply being wound around a bead core embedded in each of the bead portions from the inside to the outside of the tire, and a belt composed of at least two ply layers superimposed around the crown portion of the carcass and containing rubberized cords of a high elasticity arranged at a relatively small inclination angle with respect to the mid-circumferential ~97~
plane of the tire, the cords of which being crossed with each other, and rubber fillers each filled between the carcass and the turn-up portion thereof for hardening the bead portion, wherein a carcass line of 05 said tire body at a mounted state of the tire on a normal rim under a normal internal pressure depicts such a radial profile in tire section that a ratio of R/R' is within a range of 0.65-0.85 and f is within a range of 5-lO mm, where R' is a radius of a reference arc which passes an intersection B between the carcass line and a straight line passing through an alienating point A of the outer surface of the bead portion from a flange of the rim and being in parallel with the rotational axis of the tire, an intersection C between the carcass line and a line segment being perpendicular to the above straight line and extending from the intersection B, and point E is an intersection of a line extending through a middle point D of the line segment BC as a chord and in parallel with the rotating axis and a line extending through a maximum width point E of the carcass line and perpendicular to the rotating axis and in parallel with the line segment BC, and R is a radius of curvature of a contour curve in a shoulder portion of the carcass line extending to the inter-section C; and f is a maximum distance between thereference arc and a contour curve in the remaining portion of the carcass line smoothly connecting to the above contour curve and having a single inflection 79~
point toward the intersection B; and the tread portion is provided with a pattern of a block type having a negative ratio of 33-40%, and the pattern is formed with relatlvely deep grooves.
05 These and other objec-ts, features, and advantages o:E the invention will be well appreciated upon reading of the following description of the invention when taken in conjunction with the accompanying drawings with understanding that some modifica-tions, variations and changes could be easily made by the skilled in the art to which the invention pertains without departing from the spirit of the invention or the scope of the claims appended hereto.
The invention will be explained more in detail below with reference to the accompanying drawings, wherein:
Fig. 1 is a schematic view illustrating the relation between a radial proEile (solid line) of a tire according to the present invention and that (a dotted line) of a reference arc;
Fig. 2 is a sectional view of the tire in Example 1 according to the invention;
Fig. 3 is a sectional view of a tire in Example 2 according to the invention; and Fig. 4 is a sectional view of a tire in Comparative Example 1 to which an internal pressure is applied.
The tire according to the present invention is provided with a block pattern having a negative ratio of 33-40% and relatively deep grooves of around 130-140% of the depth of the grooves of the conven-tionally ordinary tire. If the negative ratio is less 05 than 33% and the depth of the grooves is less than 130%, the traction performance on the muddy road or snow road is insufficient, while if the negative ratio is over 40% and the groove depth is 140%, the rigidity of the tread portion becomes too low, so that the cornering stability in running on the general road is deteriorated. According to the invention, as shown by the solid line in Fig. 1, the tire is designed in a profile intentionally deviated from the natural equilibrium profile by appropriately changin~ the radial profile of the carcass.
That is, the curvature of the contour curve at the shoulder portion of the carcass corresponding to the upper zone of the side wall portion is so set that the ratio R/R' may be in a range of 0.65-0.85 in which R' is the radius of the reference circle shown in Fig. 1. In addition, it is important that the curvature at the lower portion of the side wall portion is designed small or to be in an inverted R profile, while the maximum distance f between the carcass line FB and the arc BE is 5-10 mm.
What is to be noted here is that although the arc BEC is merely a reference arc which is different from the carcass radial profile based on the natural ~Z~8 equilibrium profile, since the upper zone of the side wall is a relatively thin portion with its own rigidity being low, the carcass radial profile based on the natural equilibrium profile extremely closely approaches 05 the portion EC of this arc.
Namely, it is to be noted that the range of 0.65-0.85 of the ratio R/R' is not at-tained unless the carcass radial profile is intentionally deviated from the natural equilibrium profile.
lo Since the carcass is turned up around each of the bead cores outwardly in the radial direction of the tire and the rubber filler is filled between the carcass and the turn-up portion for fixing the bead portion, the lower portion of the side wall has a relatively large rigidity, and the carcass radial profi.le based on the natural equilibrium form is ordinarily present inside of the arc BE. However, the value f being 5-10 mm given in the present invention can not be attained unless the carcass profile is deviated from the natural equilibrium profile, while the curvature of the carcass at the lower zone of the side wall portion is designed smaller or the inverted R
profile is given to the lower zone of the carcass.
Thus, it is completely discernible from the conventional natural equilibrium profile.
The reason why the rolling resis-tance of the tire having the above carcass radial profile deviated from the natural equilibrium profile is improved is as 37~
mentioned in Japanese Patent Application No. 158,013/1982, and a process as mentioned in the prior Japanese Patent Application No. 40,231/1982 is necessary to produce such a tire.
05 If the R/R' is larger than 0.85, as shown in the above Japanese Patent Application No. 158,013/1982, the effects that the carcass radial profile is inten-tionally deviated from the natural equilibrium profile to decrease the shearing deformation a-t the upper portion of the tire side portion and improve the rolling resistance can not be satisfac-torily obtained. On the other hand, iE the R/R' is less than 0.65, the bending deformation concentrates in relatively thick buttress portion to cancel the effect for reducing the rolling resistance resulting from the reduced shearing deforma-tion.
Further, iE the value f is less than 5 mm, according to the principle shown in Japanese Patent Application No. 158,013/1982, the effect of lessening the energy consumption can not be fully obtained, while if the value f is over 10 mm, the tension of the carcass at the lower zone of the side wall when the internal presswre is applied to the tire becomes too large, which causes the defects that the durability is inversely affected, and the outer face of the tire is located at a relatively inner position as the carcass enters the inside of the tire to deteriorate the fitting between the tire and the rim.
The above-mentioned specified profile of the carcass line causes the tension of the carcass at the upper portion of the side wall to be relatively lower, and reversely causes that of the carcass at the lower 05 portion of the side wall to be relatively higher.
It is the characteristics of the tension behaviour that gives improvement on the cornering stability performance in addi-tion to the impro-vement on the rolling resistance in the tread pattern suitable for the muddy road and/or snow road.
That is, when a slip angle is given to the tire, and a lateral force acts upon the tire to cause the lateral deformation of the tire, since the tension of the carcass is high and the apparent rigidity is large in the vicinity of the bead portion in the case of the tire according to the present invention, the high cornering power is developed. Further, the tension of the carcass at the upper portion of -the side wall is relatively low at that time, which increases the pneumatic trail, that is, the distance between the ground contacting center and the force-exerting point of the cornering force which is located rearwardly therefrom, so that a restoring torque are increased synergistically with the high cornering power.
The effects of the invention will be explained more in detail with reference to specific examples.
The specification of tires in Examples and Comparative Examples are shown in Table l. The tires ~Z~79~3 of the invention in Examples are shown in Figs. 3 and 4, while that in Comparative Examples is shown in Fig. ~l. In the drawings, a reference numeral 1 is a bead portion, a numeral 2 an annular side wall portion, a numeral 3 a tread portion, a numeral 4 a carcass, a numeral 5 a belt, a numeral 6 a rubber filler, a numeral 7 a rim, and a numeral 8 a flange of the rim.
Table 1 Specification of tires in Examples and Comparative Examples . __ ~ons truc- Negative Depth of \ tion R/R' f ratio of groove of Tread rubber Tire \ (mm) pattern pattern structure kind \ (/O) (mm) ~ ....__ Example 1 1.02 3.0 30 7.5 Single layer Comparative 1.023.0 36 10.5 Single layer E~ample l 0.80 6.0 36 10.5 Single layer ,..
Example 2 0.80 6.0 36 10.5 Double layer Note: Tire size: P 175/70R 13 Normal rim: 5J-13 In all the tested tires, a carcass consisted of one ply containing polyester cords of 1, sao d/2 crossed at 90 with respect to the equator of the tire, and a belt consisted of two plies containing steel cords (twisting construction: lx5x0.25 mm) crossed at 79~
an angle of 20 with respect to the tire equator and intersected with each other. A tread rubber had a loss tangent of 0.23 as measured by means of a spectrometer, made by Iwamoto Selsakusho, under conditions of 50 Hz, 1% tensile strain and 60C, and a Shore A hardness (Hd)=59, and an under tread rubber in the double layer structure in Example 2 had a ].oss tangent of 0.06, and a Shore A hardness (Hd)=56. The traction performance test were carried out in the following manner. Results are shown in Table 2.
Test Method:
A time necessary for a 100 m running from the starting on a snow road of the average inclination angle of 3 was measured and compared taking the -time in Comparative Example 1 as 100. The larger the index, the shorter the time necessary for the above running, and the more excellent the traction performance.
Table 2 ~esults on traction performance test . . -- , kind Example 1 Comparative Example 1 Example 2 ~ .
Index of 100 140 142 143 running time ... . .
Note: The tire internal pressure was 1.7 kg/cm2 in all the tires.
~Z~98 Examples of the invention had the overwhelrningly excellent traction performances with a larger negative ratio. Even as compared with Comparative Example 2 having a deeper grooves, the traction performance is 05 slightly better.
Next, rolling resistance test was carried out in the following manner, and results are shown in Table 3.
Rolling resistance test condi-tions:
A test tire was rotated on a steel drum of 1,707 mrn in diameter by the driving of a motor up to a specified speed and then the driving of the motor was stopped to run the drum by inertia, during which the rolling resistance was calculated from the degree of deceleration speed of the drum. Then, tire perform-ance was compared by index taking the rolling resistance of Comparative Example 1 as 100. The larger the index, the smaller -the rolling resistance.
Under the circumstances, the cornering stability and the rolling resistance can not help be ~2~975~
sacrificed so as to secure the traction performance.
It is therefore an object of the invention to provide a pneumatic radial tire in which the rolling resistance and the cornering stability are improved by 05 reinforcing the tire, particularly, by appropriately varying the radial profile of the carcass without deteriorating the traction performance, which can advantageously overcome the problems inevitably encountered by the prior art when the traction perform-ance as the pneumatic radial tire for use in the muddyroad and/or the snow road is secured by enlarging the negative ratio with use of a block pattern, and deepening the grooves of the pattern.
According to the present invention, there is a provision of the pneumatic radial tire for use in the muddy road and/or the snow road which comprises a pair of annular side wall portions each provided with a bead portion, a tread portion extended over the side wall portions outside in the radial direction of the tire, and a reinforcement consisting of a carcass composed of at least one cord ply containing organic fiber cords therein, which cord ply being wound around a bead core embedded in each of the bead portions from the inside to the outside of the tire, and a belt composed of at least two ply layers superimposed around the crown portion of the carcass and containing rubberized cords of a high elasticity arranged at a relatively small inclination angle with respect to the mid-circumferential ~97~
plane of the tire, the cords of which being crossed with each other, and rubber fillers each filled between the carcass and the turn-up portion thereof for hardening the bead portion, wherein a carcass line of 05 said tire body at a mounted state of the tire on a normal rim under a normal internal pressure depicts such a radial profile in tire section that a ratio of R/R' is within a range of 0.65-0.85 and f is within a range of 5-lO mm, where R' is a radius of a reference arc which passes an intersection B between the carcass line and a straight line passing through an alienating point A of the outer surface of the bead portion from a flange of the rim and being in parallel with the rotational axis of the tire, an intersection C between the carcass line and a line segment being perpendicular to the above straight line and extending from the intersection B, and point E is an intersection of a line extending through a middle point D of the line segment BC as a chord and in parallel with the rotating axis and a line extending through a maximum width point E of the carcass line and perpendicular to the rotating axis and in parallel with the line segment BC, and R is a radius of curvature of a contour curve in a shoulder portion of the carcass line extending to the inter-section C; and f is a maximum distance between thereference arc and a contour curve in the remaining portion of the carcass line smoothly connecting to the above contour curve and having a single inflection 79~
point toward the intersection B; and the tread portion is provided with a pattern of a block type having a negative ratio of 33-40%, and the pattern is formed with relatlvely deep grooves.
05 These and other objec-ts, features, and advantages o:E the invention will be well appreciated upon reading of the following description of the invention when taken in conjunction with the accompanying drawings with understanding that some modifica-tions, variations and changes could be easily made by the skilled in the art to which the invention pertains without departing from the spirit of the invention or the scope of the claims appended hereto.
The invention will be explained more in detail below with reference to the accompanying drawings, wherein:
Fig. 1 is a schematic view illustrating the relation between a radial proEile (solid line) of a tire according to the present invention and that (a dotted line) of a reference arc;
Fig. 2 is a sectional view of the tire in Example 1 according to the invention;
Fig. 3 is a sectional view of a tire in Example 2 according to the invention; and Fig. 4 is a sectional view of a tire in Comparative Example 1 to which an internal pressure is applied.
The tire according to the present invention is provided with a block pattern having a negative ratio of 33-40% and relatively deep grooves of around 130-140% of the depth of the grooves of the conven-tionally ordinary tire. If the negative ratio is less 05 than 33% and the depth of the grooves is less than 130%, the traction performance on the muddy road or snow road is insufficient, while if the negative ratio is over 40% and the groove depth is 140%, the rigidity of the tread portion becomes too low, so that the cornering stability in running on the general road is deteriorated. According to the invention, as shown by the solid line in Fig. 1, the tire is designed in a profile intentionally deviated from the natural equilibrium profile by appropriately changin~ the radial profile of the carcass.
That is, the curvature of the contour curve at the shoulder portion of the carcass corresponding to the upper zone of the side wall portion is so set that the ratio R/R' may be in a range of 0.65-0.85 in which R' is the radius of the reference circle shown in Fig. 1. In addition, it is important that the curvature at the lower portion of the side wall portion is designed small or to be in an inverted R profile, while the maximum distance f between the carcass line FB and the arc BE is 5-10 mm.
What is to be noted here is that although the arc BEC is merely a reference arc which is different from the carcass radial profile based on the natural ~Z~8 equilibrium profile, since the upper zone of the side wall is a relatively thin portion with its own rigidity being low, the carcass radial profile based on the natural equilibrium profile extremely closely approaches 05 the portion EC of this arc.
Namely, it is to be noted that the range of 0.65-0.85 of the ratio R/R' is not at-tained unless the carcass radial profile is intentionally deviated from the natural equilibrium profile.
lo Since the carcass is turned up around each of the bead cores outwardly in the radial direction of the tire and the rubber filler is filled between the carcass and the turn-up portion for fixing the bead portion, the lower portion of the side wall has a relatively large rigidity, and the carcass radial profi.le based on the natural equilibrium form is ordinarily present inside of the arc BE. However, the value f being 5-10 mm given in the present invention can not be attained unless the carcass profile is deviated from the natural equilibrium profile, while the curvature of the carcass at the lower zone of the side wall portion is designed smaller or the inverted R
profile is given to the lower zone of the carcass.
Thus, it is completely discernible from the conventional natural equilibrium profile.
The reason why the rolling resis-tance of the tire having the above carcass radial profile deviated from the natural equilibrium profile is improved is as 37~
mentioned in Japanese Patent Application No. 158,013/1982, and a process as mentioned in the prior Japanese Patent Application No. 40,231/1982 is necessary to produce such a tire.
05 If the R/R' is larger than 0.85, as shown in the above Japanese Patent Application No. 158,013/1982, the effects that the carcass radial profile is inten-tionally deviated from the natural equilibrium profile to decrease the shearing deformation a-t the upper portion of the tire side portion and improve the rolling resistance can not be satisfac-torily obtained. On the other hand, iE the R/R' is less than 0.65, the bending deformation concentrates in relatively thick buttress portion to cancel the effect for reducing the rolling resistance resulting from the reduced shearing deforma-tion.
Further, iE the value f is less than 5 mm, according to the principle shown in Japanese Patent Application No. 158,013/1982, the effect of lessening the energy consumption can not be fully obtained, while if the value f is over 10 mm, the tension of the carcass at the lower zone of the side wall when the internal presswre is applied to the tire becomes too large, which causes the defects that the durability is inversely affected, and the outer face of the tire is located at a relatively inner position as the carcass enters the inside of the tire to deteriorate the fitting between the tire and the rim.
The above-mentioned specified profile of the carcass line causes the tension of the carcass at the upper portion of the side wall to be relatively lower, and reversely causes that of the carcass at the lower 05 portion of the side wall to be relatively higher.
It is the characteristics of the tension behaviour that gives improvement on the cornering stability performance in addi-tion to the impro-vement on the rolling resistance in the tread pattern suitable for the muddy road and/or snow road.
That is, when a slip angle is given to the tire, and a lateral force acts upon the tire to cause the lateral deformation of the tire, since the tension of the carcass is high and the apparent rigidity is large in the vicinity of the bead portion in the case of the tire according to the present invention, the high cornering power is developed. Further, the tension of the carcass at the upper portion of -the side wall is relatively low at that time, which increases the pneumatic trail, that is, the distance between the ground contacting center and the force-exerting point of the cornering force which is located rearwardly therefrom, so that a restoring torque are increased synergistically with the high cornering power.
The effects of the invention will be explained more in detail with reference to specific examples.
The specification of tires in Examples and Comparative Examples are shown in Table l. The tires ~Z~79~3 of the invention in Examples are shown in Figs. 3 and 4, while that in Comparative Examples is shown in Fig. ~l. In the drawings, a reference numeral 1 is a bead portion, a numeral 2 an annular side wall portion, a numeral 3 a tread portion, a numeral 4 a carcass, a numeral 5 a belt, a numeral 6 a rubber filler, a numeral 7 a rim, and a numeral 8 a flange of the rim.
Table 1 Specification of tires in Examples and Comparative Examples . __ ~ons truc- Negative Depth of \ tion R/R' f ratio of groove of Tread rubber Tire \ (mm) pattern pattern structure kind \ (/O) (mm) ~ ....__ Example 1 1.02 3.0 30 7.5 Single layer Comparative 1.023.0 36 10.5 Single layer E~ample l 0.80 6.0 36 10.5 Single layer ,..
Example 2 0.80 6.0 36 10.5 Double layer Note: Tire size: P 175/70R 13 Normal rim: 5J-13 In all the tested tires, a carcass consisted of one ply containing polyester cords of 1, sao d/2 crossed at 90 with respect to the equator of the tire, and a belt consisted of two plies containing steel cords (twisting construction: lx5x0.25 mm) crossed at 79~
an angle of 20 with respect to the tire equator and intersected with each other. A tread rubber had a loss tangent of 0.23 as measured by means of a spectrometer, made by Iwamoto Selsakusho, under conditions of 50 Hz, 1% tensile strain and 60C, and a Shore A hardness (Hd)=59, and an under tread rubber in the double layer structure in Example 2 had a ].oss tangent of 0.06, and a Shore A hardness (Hd)=56. The traction performance test were carried out in the following manner. Results are shown in Table 2.
Test Method:
A time necessary for a 100 m running from the starting on a snow road of the average inclination angle of 3 was measured and compared taking the -time in Comparative Example 1 as 100. The larger the index, the shorter the time necessary for the above running, and the more excellent the traction performance.
Table 2 ~esults on traction performance test . . -- , kind Example 1 Comparative Example 1 Example 2 ~ .
Index of 100 140 142 143 running time ... . .
Note: The tire internal pressure was 1.7 kg/cm2 in all the tires.
~Z~98 Examples of the invention had the overwhelrningly excellent traction performances with a larger negative ratio. Even as compared with Comparative Example 2 having a deeper grooves, the traction performance is 05 slightly better.
Next, rolling resistance test was carried out in the following manner, and results are shown in Table 3.
Rolling resistance test condi-tions:
A test tire was rotated on a steel drum of 1,707 mrn in diameter by the driving of a motor up to a specified speed and then the driving of the motor was stopped to run the drum by inertia, during which the rolling resistance was calculated from the degree of deceleration speed of the drum. Then, tire perform-ance was compared by index taking the rolling resistance of Comparative Example 1 as 100. The larger the index, the smaller -the rolling resistance.
3~ 7~8 Table 3 Results on rolling resistance measurement Tire Comparati~e Comparative Speed ~ Example 1 Example 2 Example 1 Example 2 _ ~ ~ . __ 50 ~n/~l lO0 89 98 103 _ .__ 80 km/~l lO0 88 98 102 100 km/H 100 88 103 105 Note: The tire internal pressure was 1.7 kg/cm2 in all the tires.
Despite that the tire of the present invention in Example 1 had deeper grooves with a larger negative ratio, it showed the rolling resistance substantially equivalent to that of Comparative Example 1 in which the grooves were shallow. As compared with the tire in Comparative Example 2 in which the radial profile of the carcass was not properly changed, the rolling resistance was improved by 10-15% through paying due attention to the carcass line.
Example 2 showed the more improved rolling resistance than the Comparative Example 1 with a shallower grooves, and it was revealed that Example 2 is more preferable in practicing the invention.
The following tests were carried out with respect to the cornering stability, and results are shown in Table 4.
~Z~9~
Test Method:
A slip angle was given to a tire while the tire being pushed against a drum of 1,707 mm in diameter, and a cornering power and a restoring torque were measured. The maximum value of the restoring torque was determined, and the comparison was made by index -taking the result of Comparative Example 1 as 100.
The larger the index, the larger the cornering power and the restoring ~orque, and the more excellent the cornering stability.
Table 4 Results on cornering stability tests __ - Compa~ative Compara-tive Example 1 Examp].e 2 Item \ Example 1 Example 2 . _ Cornering power 100 94 99 99 Restoring torque 100 90 101 103 Note: The internal pressure was 1.7 kg/cm2 in all the -tires.
Despite that the tires of the invention had deeper grooves with a larger negative ratio, they exhibited the cornering stability performance which was substantially equivalent to or more excellent than that of Comparative Example 1 having a shallower grooves with a smaller negative ratio.
Comparing Example 1 and Comparative Example 2, it is understood that the cornering stability was far ~Z~7~E~
improved by appropriately changing the radial profile of the carcass.
As mentioned above, according to the present invention, the traction performance of the tire for use 05 in the muddy road and/or snow road which has a block pattern of an increased negative ratio with grooves of a relatively larger depth can be advantageously improved by appropriately changing the radial profile of the carcass. The results given in the above shown that the tire according to the present invention can be suited for the use as all-weather type tire.
Despite that the tire of the present invention in Example 1 had deeper grooves with a larger negative ratio, it showed the rolling resistance substantially equivalent to that of Comparative Example 1 in which the grooves were shallow. As compared with the tire in Comparative Example 2 in which the radial profile of the carcass was not properly changed, the rolling resistance was improved by 10-15% through paying due attention to the carcass line.
Example 2 showed the more improved rolling resistance than the Comparative Example 1 with a shallower grooves, and it was revealed that Example 2 is more preferable in practicing the invention.
The following tests were carried out with respect to the cornering stability, and results are shown in Table 4.
~Z~9~
Test Method:
A slip angle was given to a tire while the tire being pushed against a drum of 1,707 mm in diameter, and a cornering power and a restoring torque were measured. The maximum value of the restoring torque was determined, and the comparison was made by index -taking the result of Comparative Example 1 as 100.
The larger the index, the larger the cornering power and the restoring ~orque, and the more excellent the cornering stability.
Table 4 Results on cornering stability tests __ - Compa~ative Compara-tive Example 1 Examp].e 2 Item \ Example 1 Example 2 . _ Cornering power 100 94 99 99 Restoring torque 100 90 101 103 Note: The internal pressure was 1.7 kg/cm2 in all the -tires.
Despite that the tires of the invention had deeper grooves with a larger negative ratio, they exhibited the cornering stability performance which was substantially equivalent to or more excellent than that of Comparative Example 1 having a shallower grooves with a smaller negative ratio.
Comparing Example 1 and Comparative Example 2, it is understood that the cornering stability was far ~Z~7~E~
improved by appropriately changing the radial profile of the carcass.
As mentioned above, according to the present invention, the traction performance of the tire for use 05 in the muddy road and/or snow road which has a block pattern of an increased negative ratio with grooves of a relatively larger depth can be advantageously improved by appropriately changing the radial profile of the carcass. The results given in the above shown that the tire according to the present invention can be suited for the use as all-weather type tire.
Claims
1. A pneumatic radial tire for use in a muddy road and/or a snow road which comprises a pair of annular side wall portions each provided with a bead portion, a tread portion extended over the side wall portions outside in the radial direction of the tire, and a reinforcement consisting of a carcass composed of at least one cord ply containing organic fiber cords therein, which cord ply being wound around a bead core embedded in each of the bead portions from the inside to the outside of the tire, and a belt composed of at least two ply layers superimposed around the crown portion of the carcass and containing rubberized cords of a high elasticity arranged at a relatively small inclination angle with respect to the mid-circumferential plane of the tire, the cords of which being crossed with each other, and rubber fillers each filled between the carcass and the turn-up portion thereof for hardening the bead portion, a carcass line of said tire body at a mounted state of the tire on a normal rim under a normal internal pressure depicts such a radial profile in tire section that a ratio of R/R' is within a range of 0.65-0.85 and f is within a range of 5-10 mm, where R' is a radius of a reference arc which passes an inter-section B between the carcass line and a straight line passing through an alienating point A of the outer surface of the bead portion from a flange of the rim and being in parallel with the rotational axis of the tire, an intersection C between the carcass line and a line segment being perpendicular to the above straight line and extending from the intersection B, and point E
is an intersection of a line extending through a middle point D of the line segment BC as a chord and in parallel with the rotating axis and a line extending through a maximum width point F of the carcass line and perpendicular to the rotating axis and in parallel with the line segment BC, and R is a radius of curvature of a contour curve in a shoulder portion of the carcass line extending to the intersection C; and f is a maximum distance between the reference arc and a contour curve in the remaining portion of the carcass line smoothly connecting to the above contour curve and having a single inflection point toward the intersection B; and the tread portion is provide with a pattern of a block type having a negative ratio of 33-40%, and the pattern is formed with relatively deep grooves.
is an intersection of a line extending through a middle point D of the line segment BC as a chord and in parallel with the rotating axis and a line extending through a maximum width point F of the carcass line and perpendicular to the rotating axis and in parallel with the line segment BC, and R is a radius of curvature of a contour curve in a shoulder portion of the carcass line extending to the intersection C; and f is a maximum distance between the reference arc and a contour curve in the remaining portion of the carcass line smoothly connecting to the above contour curve and having a single inflection point toward the intersection B; and the tread portion is provide with a pattern of a block type having a negative ratio of 33-40%, and the pattern is formed with relatively deep grooves.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58168321A JPS6060004A (en) | 1983-09-14 | 1983-09-14 | Pneumatic radial tire for muddy area or snow area |
| JP168,321/83 | 1983-09-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1219798A true CA1219798A (en) | 1987-03-31 |
Family
ID=15865864
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000462653A Expired CA1219798A (en) | 1983-09-14 | 1984-09-07 | Pneumatic radial tire for use in muddy road and/or snow road |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS6060004A (en) |
| CA (1) | CA1219798A (en) |
| GB (1) | GB2148214B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2824052B2 (en) * | 1986-12-25 | 1998-11-11 | 株式会社ブリヂストン | Radial tires for heavy loads |
| GB9813965D0 (en) | 1997-07-05 | 1998-08-26 | Hankook Tire Manufacturing Com | Radial tyre |
-
1983
- 1983-09-14 JP JP58168321A patent/JPS6060004A/en active Pending
-
1984
- 1984-09-07 CA CA000462653A patent/CA1219798A/en not_active Expired
- 1984-09-14 GB GB08423240A patent/GB2148214B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6060004A (en) | 1985-04-06 |
| GB2148214B (en) | 1987-03-04 |
| GB2148214A (en) | 1985-05-30 |
| GB8423240D0 (en) | 1984-10-17 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |