CA2027643A1 - Heavy duty tire - Google Patents
Heavy duty tireInfo
- Publication number
- CA2027643A1 CA2027643A1 CA 2027643 CA2027643A CA2027643A1 CA 2027643 A1 CA2027643 A1 CA 2027643A1 CA 2027643 CA2027643 CA 2027643 CA 2027643 A CA2027643 A CA 2027643A CA 2027643 A1 CA2027643 A1 CA 2027643A1
- Authority
- CA
- Canada
- Prior art keywords
- tread
- radius
- tire
- curvature
- extending
- 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.)
- Abandoned
Links
Abstract
ABSTRACT OF THE DISCLOSURE
A belted radial tire for heavy duty use in which the tread profile is composed of a central part (CS) extending from the tire equator (C) toward the both sides thereof and having a curvature of a radius (CR) having a center on the tire equator and a pair of tread edge parts (SS) extending one from each edge of the central part (CS) toward the sidewall portion and having a curvature of a radius (SR) smaller than the radius (CR), the radius (SR) of the curvature of the tread edge parts (SS) being 0.03 to 0.06 times the tread width (TW), the tread portion provided with a circumferentially extending wide main groove (G) and a pair of circumferentially extending narrow grooves (S), the center line (L) of each narrow groove positioned near and axially outward of the boundary line (P) between the tread central part and each edge part (SS) on the tread surface, and the center line (L) inclined axially inwardly toward the tire equator (C) at an angle (.beta.) of 2 to 10 degrees with respect to the normal direction to the tread face, the depth (HG) of the narrow groove (S) being not less than 60%
of the depth (HG) of the main groove (G).
A belted radial tire for heavy duty use in which the tread profile is composed of a central part (CS) extending from the tire equator (C) toward the both sides thereof and having a curvature of a radius (CR) having a center on the tire equator and a pair of tread edge parts (SS) extending one from each edge of the central part (CS) toward the sidewall portion and having a curvature of a radius (SR) smaller than the radius (CR), the radius (SR) of the curvature of the tread edge parts (SS) being 0.03 to 0.06 times the tread width (TW), the tread portion provided with a circumferentially extending wide main groove (G) and a pair of circumferentially extending narrow grooves (S), the center line (L) of each narrow groove positioned near and axially outward of the boundary line (P) between the tread central part and each edge part (SS) on the tread surface, and the center line (L) inclined axially inwardly toward the tire equator (C) at an angle (.beta.) of 2 to 10 degrees with respect to the normal direction to the tread face, the depth (HG) of the narrow groove (S) being not less than 60%
of the depth (HG) of the main groove (G).
Description
2 ~ 2 ~
The present inYention relates to a pneumatlc tire for heavy duty use in which the tread is provided ln shoulder regions thereof with narrow grooves.
In a heavy duty tire for large si~ed vehicles such as truck, bus and the like ot which tread portion is reinrorced by a Stirr belt layer, due to the increased rigidity of the tread shoulder portions, a wandering phenomenon of vehicle is apt to occur when, tor example, the tire runs across a rut at a small angle.
As a countermeasure ~or the wandering phenomenon, it has been employed to increase camber thrust by (1) decreasing the tread radius (tr) (2) rounding the tread edges with a small radius (r) and (3~ torming axial cuts (s) at the tread edges However, the measure (1) inYolves a problem that the dltference in circumterence between the center and shoulder of the tread is large, which causes a great shoulder wear.
The measure (2) can make deformation ot the tire shoulder portion easy, which can reduce wandering phenomenon, but can not prevent shoulder wear.
The measure (3) can make deformation ot the tire shoulder portion easy, which reduce wandering phenomenon, but partial wear called heal and toe wear is apt to occur which shorten the tire lite.
Further, the following technique has been proposed.
7apanese patent application JP-A-58-194606 discloses a tread provided in each shoulder region with a narrow .. ~ . .
- . . . , ~
2 ~ 62 ~ 3 circumferential groove to rorm a side rib axlally outside the groove, and the outer prof ile Or the side rib being parallel with that of the central region of the tire, and rurther the profile located radially inward of that Or the central region of the tire.
Japanese patent application JP-A-61-143205 discloses a tire having a squared shoulder, and a shoulder rib provided with narrow zigzag circumferential grooves in a region axially outslde of the rib center, and the groove width in the range of 0.003 to 0.02 times the tread width.
Japanese patent application ~P-A-55-44028 discloses a tire having a squared shoulder, and a tread shoulder region having a width Or about 25% Or the tread width and provided with a circumrerential groove, and the circumrerential groove inclined toward the axially outside Or the tire at angle Or 5 to 60 degrees with respect to the normal direction to the tread race.
Japanese patent application JP-A-63-106112 discloses a shoulder rib provided with a circumferential groove, and the circumrerential groove inclined at angle of 10 to 60 degrees with respect to the normal direction to the tread face, and circumferentially spaced sipes each extending axially across a portion Or the rib axially outward Or the groove.
However, In the tire disclosed in Japanese patent application JP-A-58-194606, wandering phenomenon can be prevented, but shoulder wear is apt ~o occur.
In the tires disclosed in Japanese patent applications JP-A-61-2 ~ 3 143205 and JP-A-55-4402~, shoulder wear can be lessened, but wandering phenomenon can not be effectively prevented.
In the tire dlsclosed ~n Japanese patent application JP-A-63-106112, wandering phenomenon on well paved roads can be efrectiYely prevented. However, when rubbing against a curb and when running on rough roads or unpaved roads, the groove bottom is easily cracked, and tread edge rubber is apt to be torn off at the cracked part. That is, so called rib-tear is apt to occur.
It ls, therefore, an object Or the present invention to provide a heavy duty tire, in which a wanderlng phenomenon, shoulder wear and rib tear are effectively prevented.
According to one aspect Or the present invention, a heavy duty tire comprises a carcass ply extending between bead portions through sidewall portions and a tread portlon Or the tire and turned up around bead cores dispose one in each bead portion, and a belt layer disposed radially outside the carcass in the tread portion, the tread portion having a profile composed of a central part (CS) extending from the tlre equator (C) toward the both sides thereor and having a curvature Or a radius (CR) having a center on the tire equator and a pair Or tread edge parts (SS) extending one rrom each edge ot the central part (CS) toward the sidewall portion and having a curvature or a radius (SR) smaller than the radius (CR), the radius (SR) of the curvature Or the tread edge parts (SS) being 0.03 to 0.06 tlmes the tread width (TW), the tread portion provided with a circumferentially extending wide main groove (G) and a pair of circumferentially extending narrow grooves (S), in a cross section including the tire axis, the center line (L) of each narrow groove positioned near and axially outward of the boundary line (P) between the tread central part and each edge part (SS) at the tread face, and the center line (L) Incllned axially lnwardly toward the tire equator (C) at an angle (~) of 2 to 10 degrees with respect to the normal direction to the tread face, the depth (HG) Or the narrow groove (S) being not less than 60% Or the depth (HG~ of the main groove (G).
Accordingly, the tread portion contacts with the ground mainly by the central part and the ground pressure is decreased in the tread edge parts, thereby improving anti-wandering performance Or the tire.
In terms of movement or deformation during running, the tread edge part is separated trom the central part by the narrow grooves, whereby shoulder wear is prevented.
Due to the Inclination of the narrow groove, the rubber axially outside the narrow groove is increased in thickness toward the the groove bottom, whereby the strength of the tread edge portion is maintained, and further due to the specific depth of the narrow groove, shoulder wear is further prevented, and rib tear is prevented.
An embodiment of the present invention will now be described in detail with reference to the accompanying drawin^gs, in which:
~ ~ 2 i~
Fig.1 is a cross sectional view showing an embodiment Or the present In~ention;
Fig.2 is a cross sectional view diagramlr atically showing the tread portion thereo~:
Fig.3 is a deYeloped plan view showing the tread pattern thereof;
Fig.4 is a side view showing the side face of the tire shoulder; and Figs.5-7 are diagrams showing prior art tires.
In the drawings, heavy duty tire 1 according to the present invention has a pair Or bead portions 3, a pair Or sidewall portlons 4 each extending radially outwardly rrom each bead portion, and a tread portion extending between the radially outer edges o~ the sidewall portions, and the tire comprises a pair Or bead cores 2 disposed one In each bead portion, a carcass 6 extending between the bead portions through the tread portion and the sidewall portions and turned up around the bead cores, a rubber tread 5 disposed radially outslde the carcass, and a belt layer 7 having at least one ply or stir~ organic fiber cords or steel cords disposed between the carcass and the tread.
Fig.2 is a left half Or a cross section including the tire axis, oi' the tread portion. As shown in Fig.2, the surface 10 Or the tread portion is curved such that:
a region CS, which extends between two points (p) positioned one on each side Or the tire equator C and near the respective tread edges E, has a curvature of a single radius CR having a center on the tire equator C; and a regions SS, which extends from the point (p) toward the sidewall portion 4 beyond the tread edge E, has a curvature o~ a single radius SR.
Thus, the point (p) in Fig.2 shows a boundary line between the central region CS and each of the edge regions SS.
The radius CR is set in the range Or not less than 2 times and not more than S times the tread wldth TW.
The radius SR should be not less than 0.02 times and not more than 0.08 times the tread width TW, and preîerably the radlus SR is set In the range of not less than 0.03 times and not more than 0.06 times the tread width TW.
Here, the tread width TW is a given width according to the tire size. In practice, however, it is def ined as the axial length between the imaginary tread edges E each Or which is derined as the intersection between an extension of the proflle Or the central region CS which has the radius CR and an extension of the profile of the upper sidewall portion 11 which has a curvature of a single radius having the center outside the tire.
At the above-mentioned point (p), the curvature o~ the tread edge region SS Is smoothly joined to the curvature Or the tread center region CS. Also, the curvature of the tread edge region SS is smoothly joined to the curvature Or the upper sidewall portion 11 at its axially outer edge.
The tread portion is provided with a plurality of circumferentially extending main grooves G.
Further, lateral grooves extending between the adjac^ent main --, . , grooves are provided.
In this embodiment, four straight main grooves Go and Gi having a substantially identical depth HG are provided so as to divide the tread into rive straight ribs, as shown in Fig.3.
The lateral grooves Fl extend between the ad~acent main grooves Gi and Gi to divide the central rlb into blocks, and the lateral grooves F2 extend between the ad~acent main grooves Gi and Go to divide the middle rlb into blocks.
However, the axially ou$ermost shoulder ribs are not provided with any lateral groove not to divide them in the circumferential direction o~ the tire.
The tread portion is further provided with a narrow groove S
at a position near each of the tread edges E. The narrow groove extends around the tire continuously in the circumferential direction of the tire.
The width WS Or the narrow groove is set to be not more than the tread width TW multiplied by the ratio SR/CR of the radius SR
of the tread edge region SS to the radius CR of the tread central region CS, that is, WS S 11W(SR/CR).
If the width WS is more than TW(SR/CR), the tread edge portion is liable to crack and durability is ~mpaired, and further small stones or other ob~ects are liable to be entrapped in the groove which damages the groove sidewall and bottom and durability is further impaired.
The narrow groove S extends radially inwardly from the tread surface, and the depth H is set to be not less than 0.6 times the depth HG of the main groove G.
When the depth H is not more than 0.6 times the main groove depth, movement of the rubber in the region SS near the surîace thereof Is less and shoulder wear Is caused. Further, the camber thrust and the camber torque can not be increased and as a result the anti-wandering performance can not be improved.
The narrow groove S is positioned as follows:
the center of the groove top is positioned at almost the point (p) but slightly axially outward Or the point (p), that is, positioned in the above-mentioned region SS;
the center line L Inclines axially inwardly at an angle ~ being In the range of 2 to 10 degrees with respect to the normal line n to the tread face which is drawn from the groove top center; and the center of the groove bottom is positioned on or slightly axially inward of the normal line and axially inside the groove top center.
Further, as shown in Fig.4, a shallow groove 13 extending continuously in the circumferential dlrection o~ the tire is provided on the above-mentioned upper sidewall face 11, but no groove or sipe Is f ormed in the tread edge reglons SS.
By provision oî shallow groove 13, heat radiation f rom the tire shoulder portion is enhanced, and the anti-wandering perf ormance of the tire is further improved.
Test tires of size lO.OOR20-14PR including a working example tire of the present invention and reference tires 1 and 2 were prepared and sub~ected to comparison tests. The test results are shown ln Table 1.
The working example tire had the above-expla~ned structure 6 ~L 3 shown in Figs.1-4, and the following specirications:
Tread width TW 208 mm Central region's radius CR 275 Edge region's radius SR 8 mm Main groove depth HG 15.7 ~
Narrow groove depth H 15.7 nnn Narrow groove widtn WS 2 mm Narrow groove's angle ~ 2 degrees The reference tire 1 had the same structure as the working example tire with the exception that the narrow grooves S and the shallow grooves 13 were omitted.
The reference tire 2 had the same structure as the working example tire with the exception that the tire was provided with a squared shoulder In which the tread ~ace has a single radius of curvature CR all over the tread width instead o~ the rounded shoulder with the edge regions SS, and narrow grooves S were inclined reversely toward the tread edge side.
.
________________________________ __________________ Ex. Ref . 2 Re~ . 1 ___________________________________________________ Ant i -wander lng perf ormance Camber thrust *1 210 170 100 Camber torque *1 300 22Q 100 Self alignment *2 180 150 100 f orce Ride feeling *3good not good bad ___________________________________ _______________ , Rlb tear *4 none observed none _________________________________._________________ Shoulder wear *5 none none observed ___________________________________________________ *1: measured with a tire tester under the following conditions:
Camber angle 6 degrees Tire load 2750 kg, Air pressure 7.25 kgf/sq.cm *1 ~ *2: Indicated by an index base on the assumptlon that the reference tire 2 Is 100. The larger the index the better the performance.
*2 ~ *3: evaluated with using a 2-D-D type truck.
(Tire load: 2750 kg, Air pressure: 7.25 kgf/sq.cm) *3 anti-wandering performance of the tire agalnst a deep rut was evaluated by the driver's feeling.
*4 the tire was inspected after the tire had run on a rib-tear promoting road formed on a test course at a predetermined slow speed for a predetermined distance.
*5 the tire was installed on a 2-D-D type truck and inspected after a B0,000 km running.
(Tire load: 2750 kg, Air pressure: 7.25 kgf/sq.cm)
The present inYention relates to a pneumatlc tire for heavy duty use in which the tread is provided ln shoulder regions thereof with narrow grooves.
In a heavy duty tire for large si~ed vehicles such as truck, bus and the like ot which tread portion is reinrorced by a Stirr belt layer, due to the increased rigidity of the tread shoulder portions, a wandering phenomenon of vehicle is apt to occur when, tor example, the tire runs across a rut at a small angle.
As a countermeasure ~or the wandering phenomenon, it has been employed to increase camber thrust by (1) decreasing the tread radius (tr) (2) rounding the tread edges with a small radius (r) and (3~ torming axial cuts (s) at the tread edges However, the measure (1) inYolves a problem that the dltference in circumterence between the center and shoulder of the tread is large, which causes a great shoulder wear.
The measure (2) can make deformation ot the tire shoulder portion easy, which can reduce wandering phenomenon, but can not prevent shoulder wear.
The measure (3) can make deformation ot the tire shoulder portion easy, which reduce wandering phenomenon, but partial wear called heal and toe wear is apt to occur which shorten the tire lite.
Further, the following technique has been proposed.
7apanese patent application JP-A-58-194606 discloses a tread provided in each shoulder region with a narrow .. ~ . .
- . . . , ~
2 ~ 62 ~ 3 circumferential groove to rorm a side rib axlally outside the groove, and the outer prof ile Or the side rib being parallel with that of the central region of the tire, and rurther the profile located radially inward of that Or the central region of the tire.
Japanese patent application JP-A-61-143205 discloses a tire having a squared shoulder, and a shoulder rib provided with narrow zigzag circumferential grooves in a region axially outslde of the rib center, and the groove width in the range of 0.003 to 0.02 times the tread width.
Japanese patent application ~P-A-55-44028 discloses a tire having a squared shoulder, and a tread shoulder region having a width Or about 25% Or the tread width and provided with a circumrerential groove, and the circumrerential groove inclined toward the axially outside Or the tire at angle Or 5 to 60 degrees with respect to the normal direction to the tread race.
Japanese patent application JP-A-63-106112 discloses a shoulder rib provided with a circumferential groove, and the circumrerential groove inclined at angle of 10 to 60 degrees with respect to the normal direction to the tread face, and circumferentially spaced sipes each extending axially across a portion Or the rib axially outward Or the groove.
However, In the tire disclosed in Japanese patent application JP-A-58-194606, wandering phenomenon can be prevented, but shoulder wear is apt ~o occur.
In the tires disclosed in Japanese patent applications JP-A-61-2 ~ 3 143205 and JP-A-55-4402~, shoulder wear can be lessened, but wandering phenomenon can not be effectively prevented.
In the tire dlsclosed ~n Japanese patent application JP-A-63-106112, wandering phenomenon on well paved roads can be efrectiYely prevented. However, when rubbing against a curb and when running on rough roads or unpaved roads, the groove bottom is easily cracked, and tread edge rubber is apt to be torn off at the cracked part. That is, so called rib-tear is apt to occur.
It ls, therefore, an object Or the present invention to provide a heavy duty tire, in which a wanderlng phenomenon, shoulder wear and rib tear are effectively prevented.
According to one aspect Or the present invention, a heavy duty tire comprises a carcass ply extending between bead portions through sidewall portions and a tread portlon Or the tire and turned up around bead cores dispose one in each bead portion, and a belt layer disposed radially outside the carcass in the tread portion, the tread portion having a profile composed of a central part (CS) extending from the tlre equator (C) toward the both sides thereor and having a curvature Or a radius (CR) having a center on the tire equator and a pair Or tread edge parts (SS) extending one rrom each edge ot the central part (CS) toward the sidewall portion and having a curvature or a radius (SR) smaller than the radius (CR), the radius (SR) of the curvature Or the tread edge parts (SS) being 0.03 to 0.06 tlmes the tread width (TW), the tread portion provided with a circumferentially extending wide main groove (G) and a pair of circumferentially extending narrow grooves (S), in a cross section including the tire axis, the center line (L) of each narrow groove positioned near and axially outward of the boundary line (P) between the tread central part and each edge part (SS) at the tread face, and the center line (L) Incllned axially lnwardly toward the tire equator (C) at an angle (~) of 2 to 10 degrees with respect to the normal direction to the tread face, the depth (HG) Or the narrow groove (S) being not less than 60% Or the depth (HG~ of the main groove (G).
Accordingly, the tread portion contacts with the ground mainly by the central part and the ground pressure is decreased in the tread edge parts, thereby improving anti-wandering performance Or the tire.
In terms of movement or deformation during running, the tread edge part is separated trom the central part by the narrow grooves, whereby shoulder wear is prevented.
Due to the Inclination of the narrow groove, the rubber axially outside the narrow groove is increased in thickness toward the the groove bottom, whereby the strength of the tread edge portion is maintained, and further due to the specific depth of the narrow groove, shoulder wear is further prevented, and rib tear is prevented.
An embodiment of the present invention will now be described in detail with reference to the accompanying drawin^gs, in which:
~ ~ 2 i~
Fig.1 is a cross sectional view showing an embodiment Or the present In~ention;
Fig.2 is a cross sectional view diagramlr atically showing the tread portion thereo~:
Fig.3 is a deYeloped plan view showing the tread pattern thereof;
Fig.4 is a side view showing the side face of the tire shoulder; and Figs.5-7 are diagrams showing prior art tires.
In the drawings, heavy duty tire 1 according to the present invention has a pair Or bead portions 3, a pair Or sidewall portlons 4 each extending radially outwardly rrom each bead portion, and a tread portion extending between the radially outer edges o~ the sidewall portions, and the tire comprises a pair Or bead cores 2 disposed one In each bead portion, a carcass 6 extending between the bead portions through the tread portion and the sidewall portions and turned up around the bead cores, a rubber tread 5 disposed radially outslde the carcass, and a belt layer 7 having at least one ply or stir~ organic fiber cords or steel cords disposed between the carcass and the tread.
Fig.2 is a left half Or a cross section including the tire axis, oi' the tread portion. As shown in Fig.2, the surface 10 Or the tread portion is curved such that:
a region CS, which extends between two points (p) positioned one on each side Or the tire equator C and near the respective tread edges E, has a curvature of a single radius CR having a center on the tire equator C; and a regions SS, which extends from the point (p) toward the sidewall portion 4 beyond the tread edge E, has a curvature o~ a single radius SR.
Thus, the point (p) in Fig.2 shows a boundary line between the central region CS and each of the edge regions SS.
The radius CR is set in the range Or not less than 2 times and not more than S times the tread wldth TW.
The radius SR should be not less than 0.02 times and not more than 0.08 times the tread width TW, and preîerably the radlus SR is set In the range of not less than 0.03 times and not more than 0.06 times the tread width TW.
Here, the tread width TW is a given width according to the tire size. In practice, however, it is def ined as the axial length between the imaginary tread edges E each Or which is derined as the intersection between an extension of the proflle Or the central region CS which has the radius CR and an extension of the profile of the upper sidewall portion 11 which has a curvature of a single radius having the center outside the tire.
At the above-mentioned point (p), the curvature o~ the tread edge region SS Is smoothly joined to the curvature Or the tread center region CS. Also, the curvature of the tread edge region SS is smoothly joined to the curvature Or the upper sidewall portion 11 at its axially outer edge.
The tread portion is provided with a plurality of circumferentially extending main grooves G.
Further, lateral grooves extending between the adjac^ent main --, . , grooves are provided.
In this embodiment, four straight main grooves Go and Gi having a substantially identical depth HG are provided so as to divide the tread into rive straight ribs, as shown in Fig.3.
The lateral grooves Fl extend between the ad~acent main grooves Gi and Gi to divide the central rlb into blocks, and the lateral grooves F2 extend between the ad~acent main grooves Gi and Go to divide the middle rlb into blocks.
However, the axially ou$ermost shoulder ribs are not provided with any lateral groove not to divide them in the circumferential direction o~ the tire.
The tread portion is further provided with a narrow groove S
at a position near each of the tread edges E. The narrow groove extends around the tire continuously in the circumferential direction of the tire.
The width WS Or the narrow groove is set to be not more than the tread width TW multiplied by the ratio SR/CR of the radius SR
of the tread edge region SS to the radius CR of the tread central region CS, that is, WS S 11W(SR/CR).
If the width WS is more than TW(SR/CR), the tread edge portion is liable to crack and durability is ~mpaired, and further small stones or other ob~ects are liable to be entrapped in the groove which damages the groove sidewall and bottom and durability is further impaired.
The narrow groove S extends radially inwardly from the tread surface, and the depth H is set to be not less than 0.6 times the depth HG of the main groove G.
When the depth H is not more than 0.6 times the main groove depth, movement of the rubber in the region SS near the surîace thereof Is less and shoulder wear Is caused. Further, the camber thrust and the camber torque can not be increased and as a result the anti-wandering performance can not be improved.
The narrow groove S is positioned as follows:
the center of the groove top is positioned at almost the point (p) but slightly axially outward Or the point (p), that is, positioned in the above-mentioned region SS;
the center line L Inclines axially inwardly at an angle ~ being In the range of 2 to 10 degrees with respect to the normal line n to the tread face which is drawn from the groove top center; and the center of the groove bottom is positioned on or slightly axially inward of the normal line and axially inside the groove top center.
Further, as shown in Fig.4, a shallow groove 13 extending continuously in the circumferential dlrection o~ the tire is provided on the above-mentioned upper sidewall face 11, but no groove or sipe Is f ormed in the tread edge reglons SS.
By provision oî shallow groove 13, heat radiation f rom the tire shoulder portion is enhanced, and the anti-wandering perf ormance of the tire is further improved.
Test tires of size lO.OOR20-14PR including a working example tire of the present invention and reference tires 1 and 2 were prepared and sub~ected to comparison tests. The test results are shown ln Table 1.
The working example tire had the above-expla~ned structure 6 ~L 3 shown in Figs.1-4, and the following specirications:
Tread width TW 208 mm Central region's radius CR 275 Edge region's radius SR 8 mm Main groove depth HG 15.7 ~
Narrow groove depth H 15.7 nnn Narrow groove widtn WS 2 mm Narrow groove's angle ~ 2 degrees The reference tire 1 had the same structure as the working example tire with the exception that the narrow grooves S and the shallow grooves 13 were omitted.
The reference tire 2 had the same structure as the working example tire with the exception that the tire was provided with a squared shoulder In which the tread ~ace has a single radius of curvature CR all over the tread width instead o~ the rounded shoulder with the edge regions SS, and narrow grooves S were inclined reversely toward the tread edge side.
.
________________________________ __________________ Ex. Ref . 2 Re~ . 1 ___________________________________________________ Ant i -wander lng perf ormance Camber thrust *1 210 170 100 Camber torque *1 300 22Q 100 Self alignment *2 180 150 100 f orce Ride feeling *3good not good bad ___________________________________ _______________ , Rlb tear *4 none observed none _________________________________._________________ Shoulder wear *5 none none observed ___________________________________________________ *1: measured with a tire tester under the following conditions:
Camber angle 6 degrees Tire load 2750 kg, Air pressure 7.25 kgf/sq.cm *1 ~ *2: Indicated by an index base on the assumptlon that the reference tire 2 Is 100. The larger the index the better the performance.
*2 ~ *3: evaluated with using a 2-D-D type truck.
(Tire load: 2750 kg, Air pressure: 7.25 kgf/sq.cm) *3 anti-wandering performance of the tire agalnst a deep rut was evaluated by the driver's feeling.
*4 the tire was inspected after the tire had run on a rib-tear promoting road formed on a test course at a predetermined slow speed for a predetermined distance.
*5 the tire was installed on a 2-D-D type truck and inspected after a B0,000 km running.
(Tire load: 2750 kg, Air pressure: 7.25 kgf/sq.cm)
Claims (2)
1. A heavy duty tire comprising a carcass ply extending between bead portions through sidewall portions and a tread portion Or the tire and turned up around bead cores dispose one in each bead portion, and a belt layer disposed radially outside the carcass in the tread portion, the tread portion having a profile composed of a central part (CS) extending from the tire equator (C) toward the both sides thereof and having a curvature of a radius (CR) having a center on the tire equator and a pair of tread edge parts (SS) extending one from each edge of the central part (CS) toward the sidewall portion and having a curvature of a radius (SR) smaller than the radius (CR), the radius (SR) of the curvature of the tread edge parts (SS) being 0.03 to 0.06 times the tread width (TW), the tread portion provided with a circumferentially extending wide main groove (G) and a pair of circumferentially extending narrow grooves (S), the center line (L) of each narrow groove positioned near and axially outward of the boundary line (P) between the tread central part and each edge part (SS) on the tread surface, and the center line (L) inclined axially inwardly toward the tire equator (C) at an angle (.beta.) of 2 to 10 degrees with respect to the normal direction to the tread face, the depth (H ) of the narrow groove (S) being not less than 60% of the depth (HG) of the main groove (G).
2. The tire according to claim 1 wherein the above-mentioned the radius (CR) and the radius (SR) and the width (TW) of the tread and the width (WS) of the narrow grooves (S) satisfy the following relation: WS ? TW(SR/CR).
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1-271278 | 1989-10-17 | ||
| JP27127889 | 1989-10-17 | ||
| JP2-237851 | 1990-09-07 | ||
| JP2237851A JPH03208708A (en) | 1989-10-17 | 1990-09-07 | Heavy load tire |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2027643A1 true CA2027643A1 (en) | 1991-04-18 |
Family
ID=26533404
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2027643 Abandoned CA2027643A1 (en) | 1989-10-17 | 1990-10-15 | Heavy duty tire |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2027643A1 (en) |
-
1990
- 1990-10-15 CA CA 2027643 patent/CA2027643A1/en not_active Abandoned
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