Patent Application
20170313137
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2016-090135, filed Apr. 28, 2016, the entire contents of which is incorporated herein by reference.
The present technology relates to a stud pin to be installed into a tread portion of a pneumatic tire, a pneumatic tire in which the stud pin has been installed, a method for manufacturing a pneumatic tire, and a method for installing a stud pin.
Conventional snow tires provide grip on icy road surfaces via stud pins installed into the tread portions of pneumatic tires.
Typical stud pins are embedded in pin embedding holes (hereinafter also referred to simply as “holes”) provided in the tread portion. When a stud pin is embedded in the hole, the diameter of the hole is spread and the stud pin is inserted. As such, the stud pin is firmly embedded in the hole. As a result, release of the stud pins from the holes due to breaking, accelerating, and lateral forces from the road surface during rolling motion of the pneumatic tire is prevented.
When a stud pin is released from a pneumatic tire, the stud pin releases while rotating relative to the hole. Therefore, in order to prevent the releasing of stud pins, it is preferable that the stud pins do not rotate relative to the hole. As such, there are many cases where the upper flange and the lower flange of the stud pin are provided with polygonal shapes.
For example, technology is known in which side surfaces of an upper flange and a lower flange, of a stud pin, that have polygonal shapes, are provided with curved recesses, and rotation of the stud pin is suppressed due to tread rubber pressing into the curved recesses (International Patent Application Publication No. WO/2015/114813).
While pin release resistance is improved with the technology in which curved recesses are provided in the side surfaces of the upper flange and the lower flange of a stud pin, insertion of the stud pins is difficult. When installing stud pins in a pneumatic tire, the hole in the tread portion is spread while a stud pin is gripped by the gripping part of an insertion apparatus, and the stud pin is pressed into the spread hole. What is meant by insertion of the stud pins being difficult is that there are increasing cases where the stud pin cannot be pressed into the hole.
The present technology provides a stud pin that is easy to insert and has superior pin release resistance; a pneumatic tire installed with this stud pin; a method for manufacturing a pneumatic tire; and a method for installing a stud pin.
One aspect of the present technology is a stud pin to be embedded into a pin embedding hole provided in a tread portion of a pneumatic tire.
The stud pin includes:
a tip having a tip end surface configured to contact a road surface; and
a trunk portion holding the tip and extending in one direction.
The trunk portion includes:
an upper flange fixing the tip at a first end of the trunk portion; and
a lower flange provided at a position of the trunk portion on a side opposite the upper flange; an edge defining a peripheral shape of the lower flange, when the lower flange is viewed in an extending direction of the trunk portion, having:
a first side of a shape protruding roundly toward an outer side of the lower flange, protruding in a first direction orthogonal to the extending direction of the trunk portion, and
a second side provided on an opposite side to the first side with respect to a tip disposal position where the tip is provided, the second side extending in a second direction orthogonal to the first direction and the extending direction, and being provided with a recess that is recessed toward an inner side of the lower flange.
When the lower flange is viewed from the first direction, both ends of the lower flange that are separated the farthest in the second direction from the tip disposal position are preferably closer to the second side in the first direction than to the first side from the tip disposal position.
The edge of the lower flange includes a pair of third sides extending in the first direction that connect the first side and the second side; wherein
a first distance between connection points that connect the third sides and the first side is preferably shorter than a second distance between connection points that connect the third sides and the second side.
The second distance is preferably not less than 1.05 times and not greater than 1.3 times the first distance.
Each of the third sides preferably includes a recess that is recessed toward the inner side of the lower flange.
Another aspect of the present technology is a pneumatic tire.
The pneumatic tire includes:
a tread portion provided with a stud pin embedding hole; and
a stud pin installed in the stud pin embedding hole.
The stud pin includes:
a tip having a tip end surface configured to contact a road surface; and
a trunk portion holding the tip and extending in one direction.
The trunk portion includes:
an upper flange fixing the tip at a first end of the trunk portion; and
a lower flange provided at a position of the trunk portion on a side opposite the upper flange, an edge defining a peripheral shape of the lower flange, when the lower flange is viewed in an extending direction of the trunk portion, having:
a first side of a shape protruding roundly toward an outer side of the lower flange, protruding in a first direction orthogonal to the extending direction of the trunk portion, and
a second side provided on an opposite side to the first side with respect to a tip disposal position where the tip is provided, the second side extending in a second direction orthogonal to the first direction and the extending direction, and being provided with a recess that is recessed toward an inner side of the lower flange.
The stud pin is installed in the stud pin embedding hole such that the first direction corresponds to a tire circumferential direction of the pneumatic tire.
Preferably, the pneumatic tire is provided with an information display member designating a rotational direction for advancing, and the stud pin is installed in the stud pin embedding hole such that the first direction corresponds to the rotational direction of the pneumatic tire.
Another aspect of the present technology is a method for manufacturing a pneumatic tire installed with a stud pin.
The stud pin used in the manufacturing method includes:
a tip having a tip end surface configured to contact a road surface; and
a trunk portion holding the tip and extending in one direction; and
the trunk portion includes:
an upper flange fixing the tip at a first end of the trunk portion; and
a lower flange provided at a position of the trunk portion on a side opposite the upper flange,
an edge defining a peripheral shape of the lower flange, when the lower flange is viewed in an extending direction of the trunk portion, having:
a first side of a shape protruding roundly toward an outer side of the lower flange, protruding in a first direction orthogonal to the extending direction of the trunk portion, and
a second side provided on a side, based on a tip disposal position where the tip is provided, opposite the first side, the second side extending in a second direction orthogonal to the first direction and the extending direction, and being provided with a recess that is recessed toward an inner side of the lower flange.
The manufacturing method includes the steps of:
fabricating a pneumatic tire including a tread portion in which a stud pin embedding hole is provided;
installing the stud pin in the stud pin embedding hole by holding three positions on the edge of the lower flange of the stud pin by three holding members of a stud pin insertion apparatus and spreading the stud pin embedding hole using end portions of the three holding members, the holding members holding the lower flange at the first side and the second side.
Holding positions where the edge of the stud pin is held by the holding members preferably include two positions on the first side and one position on the recess of the second side.
The holding positions at the two positions on the first side preferably correspond to two peaks of an isosceles triangle, while the holding position on the second side corresponds to the other peak of the isosceles triangle.
The stud pin is preferably installed in the stud pin embedding hole such that the first direction corresponds to the tire circumferential direction of the pneumatic tire.
Preferably, the pneumatic tire is provided with an information display member designating a rotational direction, and the stud pin is installed in the stud pin embedding hole such that the first direction corresponds to the rotational direction of the pneumatic tire for advancing.
Another aspect of the present technology is a method for installing a stud pin in a pneumatic tire.
The stud pin used in the stud pin installation method includes:
a tip having a tip end surface configured to contact a road surface; and
a trunk portion holding the tip and extending in one direction; and
the trunk portion includes:
an upper flange fixing the tip at a first end of the trunk portion; and
a lower flange provided at a position of the trunk portion on a side opposite the upper flange,
an edge defining a peripheral shape of the lower flange, when the lower flange is viewed in an extending direction of the trunk portion, having:
a first side of a shape protruding roundly toward an outer side of the lower flange, protruding in a first direction orthogonal to the extending direction of the trunk portion, and
a second side provided on an opposite side to the first side with respect to a tip disposal position where the tip is provided, the second side extending in a second direction orthogonal to the first direction and the extending direction, and being provided with a recess that is recessed toward an inner side of the lower flange.
The stud pin installation method includes the steps of:
disposing a pneumatic tire including a tread portion in which a stud pin embedding hole is provided at a predetermined position of a stud pin insertion apparatus; and
installing the stud pin in the stud pin embedding hole by holding three positions on the edge of the lower flange of the stud pin by three holding members of the stud pin insertion apparatus and spreading the stud pin embedding hole using end portions of the three holding members,
the holding members holding the lower flange at the first side and the second side.
Holding positions where the edge of the stud pin is held by the holding members preferably include two positions on the first side and one position on the recess of the second side.
The holding positions at the two positions on the first side preferably correspond to two peaks of an isosceles triangle, while the holding position on the second side corresponds to the other peak of the isosceles triangle.
The stud pin is preferably installed in the stud pin embedding hole such that the first direction corresponds to the tire circumferential direction of the pneumatic tire.
Preferably, the pneumatic tire is provided with an information display member designating a rotational direction for advancing, and
the stud pin is installed in the stud pin embedding hole such that the first direction corresponds to a rotational direction of the pneumatic tire.
According to the aspects of the stud pin, the pneumatic tire, the method for manufacturing a pneumatic tire, and the method for installing a stud pin described above, stud pins can be easily inserted and superior pin release resistance can be obtained.
Below, a studded tire of the present embodiment is described.
The tire 10 is a tire with stud pins embedded in a tread portion (the stud pins are not illustrated in
The tire 10 is, for example, a tire for a passenger vehicle. A tire for a passenger vehicle refers to a tire defined according to Chapter A of the JATMA Yearbook 2012 (standards of The Japan Automobile Tyre Manufacturers Association, Inc.). The tire 10 can also be a small truck tire as defined in Chapter B or a truck tire or bus tire as defined in Chapter C.
Below, values of the dimensions of various pattern elements are described in detail as an example values for a tire for a passenger vehicle. However, the studded tire of the present technology is not limited to these example values.
A tire circumferential direction C in the following description is defined as a direction the tread surface rotates (both rotational directions) when the tire 10 is rotated around a tire rotational axis (see
The tire 10 includes a carcass ply layer 12, a belt layer 14, and bead cores 16 as skeleton members. The tire 10 mainly includes a tread rubber 18, a sidewall rubber 20, a bead filler rubber 22, a rim cushion rubber 24, and an inner liner rubber 26, around these skeleton members.
The carcass ply layer 12 includes carcass ply members 12a and 12b that are formed from organic fibers covered with rubber and that are wound between a pair of bead cores 16 of an annular shape so as to be formed into a toroidal shape. In the tire 10 illustrated in
The tread rubber 18 is provided on the outer side of the belt layer 14 in the tire radial direction. The tread rubber 18 has both end portions thereof connected with the side rubber 20, to thereby form sidewall portions. The tread rubber 18 is made of two layers of rubber, namely an upper layer tread rubber 18a provided on the outer side in the tire radial direction and a lower layer tread rubber 18b provided on the inner side in the tire radial direction. The rim cushion rubber 24 is provided at the end of the side rubber 20 on the inner side in the tire radial direction, and comes into contact with a rim on which the tire 10 is mounted. The bead filler rubber 22 is provided on the outer side of the bead core 16 in the tire radial direction so as to be interposed between a portion of the carcass ply layer 12 prior to being wound around the bead core 16 and a portion of the carcass ply layer 12 after being wound around the bead core 16. The inner liner rubber 26 is provided on an inner surface of the tire 10 facing a tire cavity region that is filled with air and is surrounded by the tire 10 and the rim.
In addition, the tire 10 includes a belt cover layer 28 formed from organic fiber covered with rubber that covers the belt layer 14 from the outer side in the tire radial direction of the belt layer 14.
The tire 10 has such a tire structure, but the tire structure of the present embodiment is not limited to the tire structure illustrated in
The tread pattern 30 includes an inclined groove 32, a circumferential direction communicating grove 34, a protruding groove 36, and a sipe 38.
The inclined groove 32 is formed in plurality at a predetermined pitch in the tire circumferential direction (the vertical direction in
The inclined groove 32 extends in a direction opposite (the up direction in
A groove width of the inclined groove 32 gradually increases from the starting edge near the tire equator line CL. The inclination with respect to the tire width direction W of the inclined groove 32 is smallest near the tire equator line CL including the starting edge and, after crossing the tire equator line CL, bends so that the angle of inclination with respect to the tire width direction W increases, and advances outward in the tire width direction in a direction opposite the tire rotational direction X. Furthermore, the inclination angle gradually decreases with advancement outward in the tire width direction. The inclined groove 32 configured as described above is provided on both sides across the tire equator line CL.
The inclined groove 32 provided on one side across the tire equator line CL of the tread portion is offset in the tire circumferential direction C with respect to the inclined groove 32 provided on the other side; and the starting edge of the inclined groove 32 provided on one side are configured so as not to connect with the inclined groove 32 provided on the other side.
Of the plurality of inclined grooves 32 provided in the tire circumferential direction C, the inclined grooves 32 that are adjacent are in communication via the circumferential direction communicating groove 34. More specifically, the circumferential direction communicating groove 34 extends in the tire circumferential direction C from a position partway along one of the inclined groove 32, crosses a second inclined groove 32 that is adjacent to the one inclined groove 32 in the tire circumferential direction C, and advances to a third inclined groove 32 that is adjacent to the second inclined groove 32. That is, the starting edge of the circumferential direction communicating groove 34 is located at one of the inclined grooves 32; and a terminating edge is located at the second inclined groove 32 along the tire circumferential direction C from the inclined groove 32 containing the starting edge. As described above, the circumferential direction communicating groove 34 is provided so as to connect three of the inclined grooves 32 that are adjacent along the tire circumferential direction C. The circumferential direction communicating groove 34 are inclined with respect to the tire circumferential direction C so as to approach the tire equator line CL with advancement in the direction opposite to the tire rotational direction X.
The protruding groove 36 protrudes in a direction toward the tire equator line CL from the circumferential direction communicating groove 34, and is provided so as to terminate prior to reaching the tire equator line CL.
A land portion of the tread portion is separated into a center region and shoulder regions by the inclined grooves 32 and the circumferential direction communicating grooves 34. A plurality of the sipes 38 connected to the inclined grooves 32 and the circumferential direction communicating grooves 34 is provided in the center region and both of the shoulder regions of the tread portion.
Furthermore, the plurality of the pin embedding holes 29 is provided in the center region and both of the shoulder regions of the tread portion.
A groove depth of the inclined groove 32, the circumferential direction communicating groove 34, and the protruding groove 36 is, for example, from 8.5 to 10.5 mm, and a maximum groove width is 12 mm. The tread pattern illustrated in
The stud pin 50 includes a tip 52 and a trunk portion 54. The trunk portion 54 includes an upper flange 56, a lower flange 58, and a shank portion 60. When installed in the pin embedding holes 29 of the tire 10, the trunk portion 54 is installed in the tread rubber 18 (
The tip 52 has a tip end surface that contacts a road surface. The tip 52 is formed from tungsten carbide or a similar cemented carbide. Additionally, the tip 52 may be formed from a cermet material. The tip 52 is fixed in a hole provided in the upper end surface of the trunk portion 54. The tip 52 of the stud pin 50 is configured so as to protrude from the tread surface when the stud pin 50 is installed in the tire 10.
The trunk portion 54 holds the tip 52 and is provided around a central axis Z.
The upper flange 56 of the trunk portion 54 is configured so that, when embedded in the tread portion of the tire 10, the tip 52 protrudes from the tread surface. The tip 52 is fixed to a first end of the trunk portion 54, namely an end of the upper flange 56.
The lower flange 58 is configured so as to be in contact with a bottom of the pin embedding hole 29, when embedded in the tread portion of the tire 10. The lower flange 58 is provided at a position on a side opposite the first end of the trunk portion 54.
The shank portion 60 is a portion that connects the upper flange 56 with the lower flange 58. A cross-section of the shank portion 60 orthogonal to the central axis Z is narrower than each of a cross-section of the upper flange 56 and a cross-section of the lower flange 58.
Material of the trunk portion 54 is not particularly limited and, for example, the trunk portion 54 may be formed from aluminum alloy or the like in order to reduce the weight of the stud pin 50.
The central axis Z passes through the centroid of a cross-section orthogonal to the extending direction along which the trunk portion 54 extends. Accordingly, an axial direction of the central axis Z is the extending direction of the trunk portion 54.
Here, the upper flange 56 and the lower flange 58 of the trunk portion 54 include side surfaces extending in parallel in the axial direction of the central axis Z of the stud pin 50.
When the upper flange 56 is viewed from the extending direction of the trunk portion 54, an edge defining a peripheral shape of the upper flange 56 forms a deformed hexagonal shape in which the six points are rounded and a portion of four of the sides is recessed. This shape is only an example and, as illustrated in
Regarding the lower flange 58, when the lower flange 58 is viewed from the extending direction of the trunk portion 54 (the axial direction of the central axis Z), as illustrated in
The first side 58a has a shape roundly protruding toward an outer side of the lower flange 58, and protrudes in a first direction A orthogonal to the extending direction of the trunk portion 54 (the axial direction of the central axis Z). As illustrated in
In the edge defining the peripheral shape of the lower flange 58, a pair of third sides 58c are provided that connect the first side 58a and the second side 58b. Each of the third sides 58c extends in the first direction A. As illustrated in
Additionally, a pair of points 58f, where the edge of the lower flange 58 meets a straight line 58e, is formed as the edges of the second side 58b. The straight line 58e is parallel to the second direction B and passes through a position where the recess provided in the second side 58b is most recessed. Accordingly, in the example illustrated in
As illustrated in
The rounded shape of the first side 58a is preferably an arc shape of a perfect circle or an oval having the center position 52c as a center as damage to the walls of the pin embedding holes (the stud pin installation holes) 29 will be suppressed, but other curved shapes are also allowable.
The second side 58b may be of a shape including two straight lines and a recessed portion positioned between the two straight lines, or the shape of the portions on either side of the recess may be a curved shape forming a shape that protrudes toward the outer side of the lower flange 58, instead of being a straight line shape. Additionally, the recess of the second side 58b may be formed as a curving recessed shape, or may be formed as a recessed shape in which two straight lines are combined to form a V shape. The recesses of the third sides 58c may be formed as curving recessed shapes, or may be formed as recessed shapes in which two straight lines are combined to form a V shape.
In the stud pin 50 of the present embodiment, when the lower flange 58 is viewed from the first direction A, both ends 58g of the lower flange 58 that are separated the farthest in the second direction B from the tip disposal position (the center position 52c) are preferably closer to the second side 58b, in the first direction A, than to the first side 58a from the tip disposal position (the center position 52c). Particularly, a distance L1 between connection points that connect the third sides 58c and the first side 58a (distance between the points 58d) is preferably shorter than a distance L2 between connection points that connect the third sides 58c and the second side 58b (distance between the points 58f). That is, the second side 58b is disposed on a back side in the rotational direction X because the length in the second direction B of the second side 58b is relatively greater than the first side 58a. As a result, pin release resistance of the tire during braking can be improved.
In this case, the distance L2 is preferably not less than 1.05 times and not greater than 1.3 times the distance L1.
Additionally, a length along the second direction B of the recess of the second side 58b is preferably from 30 to 70% of the distance L2. Additionally, a depth of the recess of the second side 58b (length along the first direction A between the starting point of the recess and the most recessed point of the recess) is preferably from 5 to 20% of the distance L2.
Additionally, a length along the first direction A of the recesses of the third sides 58c is preferably from 60 to 90% of a length along the first direction A between each of the points 58d and each of the points 58f. Additionally, a depth of the recesses of the third sides 58c (length along the second direction B between the starting point of the recesses and the most recessed point of the recesses) is preferably from 5 to 20% of the length along the first direction A between each of the points 58d and each of the points 58f.
The stud pin 50 described above is preferably installed in the pin embedding hole 29 such that the first direction A corresponds to the tire circumferential direction C of the pneumatic tire 10. More specifically, preferably, the pneumatic tire 10 is provided with an information display member (information display member displaying an arrow symbol or the like indicating the rotational direction X) designating the rotational direction for advancing, and the stud pin 50 is installed in the pin embedding hole (the stud pin installation hole) 29 such that the first direction A corresponds to the designated rotational direction X of the pneumatic tire 10. Here, the stud pin 50 is prone to being released from the tread portion during braking. At such a time, due to breaking forces applied to the stud pin 50 from the road surface, a force is generated that causes the second side 58b to lift up from the bottom of the pin embedding hole 29. However, because the second side 58b, which has a greater side length because it includes the recess, is positioned on the back side in the rotational direction X, the lifting up of the second side 58b from the bottom of the pin embedding hole 29 can be suppressed. As a result, pin release resistance is improved. Additionally, due to breaking forces applied to the stud pin 50 from the road surface, the first side 58a is prone to bite into the wall of the pin embedding hole 29 and damage the wall. However, because the shape of the first side 58a is rounded, damaging of the wall of the pin embedding hole 29 by the first side 58a can be suppressed.
In a method for manufacturing the pneumatic tire 10 in which the stud pin has been installed described above, first, a pneumatic tire including a tread portion in which the pin embedding holes 29 are provided is fabricated. The pin embedding holes 29 are formed by a die used in the vulcanization process of the tire.
A stud pin insertion apparatus is used to install the stud pin 50 in the tire 10.
As illustrated in
Here, as illustrated in
Here, the holding positions at the two positions on the first side 58a preferably correspond to two peaks of an isosceles triangle, while the holding position on the second side 58b corresponds to the other peak of the isosceles triangle.
Additionally, the stud pin 50 is preferably installed in the pin insertion hole (stud pin installation hole) 29 such that the first direction A corresponds to the tire circumferential direction C of the pneumatic tire 10. Additionally, the stud pin 50 is preferably installed in the pin embedding hole 29 such that the first direction A corresponds to the rotational direction X for advancing the pneumatic tire 10.
As described above, in the method for manufacturing the pneumatic tire and the method for installing the stud pin, the stud pin 50 of the present embodiment is used and, as a result, a method can be realized where installation failures of the stud pin 50 are few.
Various stud pins having lower flanges of differing shapes were fabricated. The fabricated stud pins were embedded in the tire 10 illustrated in
The size of each fabricated tire was 205/55R16. The passenger vehicle used was a front-wheel drive sedan with an engine displacement of 2000 cc. The internal pressure condition of the tires was 230 (kPa) for both the front wheels and rear wheels. The load condition of the tires was a 450 kg load on the front wheels and a 300 kg load on the rear wheels.
Stud pin insertion stability was determined by calculating the probability of insertion success when inserting stud pins into 10 tires using an existing stud pin insertion apparatus. The probabilities of the Working Examples and the like were indexed with, of the probabilities, the probability of Conventional Example being set as a standard (index value of 100). Accordingly, higher index values indicate higher stud pin insertion stability.
Pin release occurs only rarely on icy road surfaces and occurs readily on dry road surfaces including asphalt road surfaces and concrete road surfaces. Accordingly, in the pin release resistance tests, the proportion of the number of stud pins remaining in the tread rubber to the total number of installed stud pins was obtained after the passenger vehicle described above traveled 10,000 km on a dry road surface. The proportion of remaining stud pins was indexed with the proportion of remaining stud pins in Comparative Example 1 being set as a standard (index value of 100). Accordingly, higher index values indicate better pin release resistance.
Specifications of the fabricated stud pins and evaluation results for the same are shown in Table 1 below.
In Conventional Examples 2 and 3 and Working Examples 1 and 2, L1and L2 were both 6 mm, and in Working Examples 3 and 4, L1 was 5 mm and L2 was 7 mm. In Working Example 5, L1 was 7 mm and L2 was 5 mm. In the insertion stability testing, insertion failures at an index value of 98 were low to the point of being substantially indistinguishable from an index value of 100.
It is clear from Table 1 that Working Examples 1 to 5 have superior pin release resistance compared to Conventional Examples 1 to 3, while realizing the same superior insertion stability displayed by Conventional Example 1.
By comparing Working Examples 3 and 4, it becomes clear that superior insertion stability can be obtained by changing the number of holding positions of the stud pin from 4 to 3. By comparing Working Examples 1 and 2, it becomes clear that pin release resistance is improved by providing the recesses in the third sides. By comparing Working Examples 2, 3, and 5, it becomes clear that pin release resistance is improved by configuring the distance L2 to be greater than the distance L1.
The stud pin, the pneumatic tire, the method for manufacturing the pneumatic tire, and the method for installing the stud pin of the present technology have been described in detail above. However, no limitation of the present technology to the above-described embodiment and working examples is intended. Various improvements and variations are of course applicable within the scope of the present technology.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-090135 | Apr 2016 | JP | national |
