Patent Description:
<CIT> proposes a tire having a recessed mark provided on a sidewall portion. In the tire, a bottom surface of the recessed mark is divided into a shadow region where a shadow is formed by a wall portion of the recessed mark and a main region other than the shadow region. The shadow region has a plurality of micro projections to impart contrast between the shadow region and the main region, thereby enhancing the visibility of the recessed mark.

In the tire in <CIT>, part of the contour of the main region is defined by the micro projections adjacent thereto, and thus the contour is not smooth, so that the appearance tends to deteriorate.

<CIT> discloses a pneumatic tire comprising the features according to the preamble of claim <NUM>.

<CIT> discloses a pneumatic tire comprising features according to a related technology.

<CIT> also discloses a pneumatic tire comprising features according to a related technology.

The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a pneumatic tire having improved appearance of a marking portion on a sidewall portion.

This object is satisfied by a pneumatic tire comprising the features of claim <NUM>.

The pneumatic tire includes a pair of sidewall portions. In the pneumatic tire, at least one of outer surfaces of the pair of sidewall portions includes at least one marking portion, the marking portion includes a first region forming a mark including at least one character, at least one graphic, or at least one symbol, a second region that is a background portion of the mark, and a fringing portion that demarcates the first region from the second region and fringes a contour of the mark, the first region is formed as a smooth surface, the second region is a projection-recess region where a plurality of micro projections are arranged, and the fringing portion is a rib projecting from the first region.

As a result of adopting the above-described configuration, the pneumatic tire according to the present invention can improve the appearance of the marking portion of the sidewall portion.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. <FIG> is an enlarged perspective view of a sidewall portion <NUM> of one embodiment of a pneumatic tire <NUM> (hereinafter, also referred to simply as "tire <NUM>") according to the present invention. The tire <NUM> of the present invention has a pair of sidewall portions <NUM>, and <FIG> shows a part of an outer surface of one of the sidewall portions <NUM>. As shown in <FIG>, the tire <NUM> of the present invention is, for example, used as a pneumatic tire for a passenger car. The present invention may be applied to a motorcycle tire or a heavy-duty tire, for example.

In the description herein, unless otherwise specified, dimensions of components of the tire <NUM> are measured in the standardized state. The "standardized state" represents a state in which a tire is fitted on a standardized rim and is inflated to a standardized internal pressure and no load is applied to the tire when the tire is a pneumatic tire for which various standards are defined. For tires for which various standards are not defined, the standardized state represents a standard use state, corresponding to a purpose of use of the tire, in which no load is applied to the tire.

The "standardized rim" represents a rim that is defined by a standard for each tire, in a standard system including the standard on which the tire is based, and is, for example, "standard rim" in the JATMA standard, "Design Rim" in the TRA standard, or "Measuring Rim" in the ETRTO standard.

The "standardized internal pressure" represents an air pressure that is defined by a standard for each tire, in a standard system including the standard on which the tire is based, and is "maximum air pressure" in the JATMA standard, the maximum value recited in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or "INFLATION PRESSURE" in the ETRTO standard.

As shown in <FIG>, the sidewall portion <NUM> has a visible outer surface. The visible outer surface is a surface that is visible from the outside when the tire <NUM> is used. At least one of the outer surfaces of the pair of sidewall portions <NUM> is provided with at least one marking portion <NUM>. A mark <NUM> is formed on the marking portion <NUM>. The mark <NUM> includes at least one character, at least one graphic, or at least one symbol. The mark <NUM> of the present embodiment includes "R", "S", and "F" as one example, but the present invention is not limited thereto.

<FIG> is an enlarged view of the marking portion <NUM> in <FIG>. As shown in <FIG>, the marking portion <NUM> includes a first region <NUM> forming the mark <NUM>, a second region <NUM> that is a background portion of the mark <NUM>, and a fringing portion <NUM> that demarcates the first region <NUM> from the second region <NUM> and fringes the contour of the mark <NUM>. In <FIG>, the first region <NUM> is shown as a blank region, and the second region <NUM> is dotted. The fringing portion <NUM> is shown by thin double lines.

<FIG> is an enlarged perspective view of a region A in <FIG>. As shown in <FIG>, the first region <NUM> is formed as a smooth surface. On the other hand, the second region <NUM> is a projection-recess region where a plurality of micro projections <NUM> are arranged. The smooth surface of the first region <NUM> means an even surface enabling a sufficient contrast to be imparted with respect to the second region <NUM> described below. In a preferable aspect, the first region <NUM> has an arithmetic mean roughness Ra of not greater than <NUM>, for example.

The fringing portion <NUM> of the present invention is a rib <NUM> projecting from the first region <NUM>. The "rib" is a protrusion projecting with respect to the first region <NUM>, and means one that continuously extends along the contour of the mark <NUM> to have a longitudinal direction. Owing to the above-described configuration, the present invention can improve the appearance of the marking portion <NUM> (shown in <FIG>) of the sidewall portion <NUM>. The reason for this is as follows.

As shown in <FIG> and <FIG>, in the present invention, the first region <NUM> is a smooth surface, so that more light is reflected to cause the first region <NUM> to look pale, but the plurality of micro projections <NUM> (shown in <FIG>) inhibit reflection of light on the second region <NUM> to cause the second region <NUM> to look darker. Accordingly, the contrast between the first region <NUM> and the second region <NUM> is increased, thereby improving the visibility and the appearance of the mark <NUM>. In addition to this, in the present invention, the fringing portion <NUM> is a rib projecting form the first region <NUM>, and thus can prevent the contour of the mark <NUM> from forming an irregular wavy line, thereby improving the appearance of the marking portion <NUM>.

In a conventional art, to prevent the contour of a mark from forming an irregular wavy line, a plurality of micro projections are arranged at equal intervals along the contour of a first region. However, in such a method, an arrangement of the micro projections needs to be determined for each mark, thereby increasing cost in design or processing of a vulcanization mold for a tire. In addition, the above method is relatively easily performed on a mark (e.g., "F" in the present embodiment) formed by only straight lines, but when the above method is performed on a mark (e.g., "R" or "S" in the present embodiment) including a curved line, a region where arrangement pitches of the micro projections are narrow and a region where arrangement pitches of the micro projections are wide are generated, and thus the appearance tends to deteriorate. In the present invention, the above-described fringing portion <NUM> is disposed, so that such a defect can be avoided.

Hereinafter, more detailed configurations of the present embodiment will be described. The configurations described below show a specific aspect of the present embodiment. Therefore, it is needless to say that the present invention can achieve the above-described effect even when the configurations described below are not provided. In addition, even when any one of the configurations described below is independently applied to the tire <NUM> according to the present invention having the above-described characteristics, performance improvement corresponding to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, complex performance improvement corresponding to each configuration can be expected.

<FIG> is a sectional view of the marking portion <NUM>. <FIG> corresponds to a sectional view taken along a B-B line in <FIG>. As shown in <FIG>, the marking portion <NUM> is preferably recessed with respect to a reference surface <NUM> of the outer surface of the sidewall portion <NUM> (shown in <FIG>), for example. Accordingly, the appearance of the mark <NUM> (shown in <FIG>) is improved, and a rubber volume of the sidewall portion <NUM> can be inhibited from increasing. However, the present invention is not limited thereto.

From the viewpoint of ensuring the durability of the sidewall portion <NUM>, a recessed amount d1 of the marking portion <NUM> with respect to the reference surface <NUM> is preferably not larger than <NUM>.

<FIG> is an enlarged plan view of a part of the second region <NUM>. As shown in <FIG>, the second region <NUM> preferably includes a portion where the plurality of micro projections <NUM> are arranged so as to form closest packing in a planar view. Accordingly, the amount of light reflected on the second region <NUM> is further decreased, the contrast with the first region <NUM> is increased, and thus the appearance of the marking portion <NUM> is improved.

The above-described "closest packing" at least means that the micro projections <NUM> are densely arranged in a state in which another micro projection <NUM> cannot be additionally arranged, because the contours of the adjacent micro projections <NUM> are in contact with each other. In the present embodiment, the contour of each micro projection <NUM> has a circular shape having a first maximum outer diameter D1, and the micro projections <NUM> are arranged so as to form closest packing. Accordingly, in a planar view of the second region <NUM>, a virtual triangle <NUM> with centers 13c of the contours of three micro projections <NUM> adjacent to each other, as apexes, is an equilateral triangle. However, the arrangement of the micro projections <NUM> in the second region <NUM> of the present invention is not limited thereto.

In the second region <NUM>, less than five micro projections <NUM> are arranged per mm<NUM>, and preferably one to four micro projections <NUM> are arranged. Accordingly, the appearance of the marking portion <NUM> is further improved.

As shown in <FIG> and <FIG>, each micro projection <NUM> is formed as a truncated cone in which an upper surface 13a (shown in <FIG>) is composed of a curved surface. However, the micro projection <NUM> is not limited thereto, and various forms such as a cone shape and a cylinder shape can be used. In another embodiment, in the upper surface 13a of the micro projection <NUM>, a local recess may be provided (not shown). Such micro projections <NUM> can further inhibit the reflection of light on the second region <NUM>.

As shown in <FIG>, the first maximum outer diameter D1 of each micro projection <NUM> is, for example, <NUM> to <NUM>, and preferably <NUM> to <NUM>. A maximum height h1 of the micro projection <NUM> with respect to the first region <NUM> is preferably smaller than the recessed amount d1 of the marking portion <NUM>. Specifically, the height h1 is <NUM> to <NUM>, and preferably <NUM> to <NUM>. However, the micro projection <NUM> is not limited thereto.

The shape of a transverse cross-section of the rib <NUM> formed as the fringing portion <NUM> is, for example, a trapezoidal shape. However, the shape of the transverse cross-section is not limited thereto, and may be a triangular shape or a semi-circular shape. In addition, the rib <NUM> has a maximum rib width W1 orthogonal to the longitudinal direction thereof. The rib width W1 is preferably larger than <NUM>/<NUM> of the first maximum outer diameter D1 of the micro projection <NUM>. Accordingly, the rib <NUM> is easily visually recognized, and the appearance of the mark <NUM> is further improved. On the other hand, when the rib width W1 is excessively large, the contour of the mark <NUM> may be unclear. Accordingly, the rib width W1 is preferably smaller than the first maximum outer diameter D1, and specifically not larger than <NUM>% of the first maximum outer diameter D1.

According to the invention, a maximum height h2 of the rib <NUM> with respect to the first region <NUM> is not smaller than <NUM>% of the maximum height h1 of the plurality of micro projections <NUM> with respect to the first region <NUM>, and not larger than <NUM>% thereof, and preferably not larger than <NUM>% thereof.

From the viewpoint of clarifying the contour of the mark <NUM>, preferably, the plurality of micro projections <NUM> adjacent to the rib <NUM> are orderly arranged along the longitudinal direction of the rib <NUM>. However, depending on the shape of the mark <NUM>, when such an arrangement is maintained, cost in design or processing of a vulcanization mold for a tire may be increased. From the viewpoint of reducing the cost, the plurality of micro projections <NUM> may include a micro projection <NUM> that is not directly connected to the rib <NUM>, or a micro projection <NUM> that is partially connected to the rib <NUM>.

<FIG> is an enlarged perspective view conceptually showing the positional relationship between the rib <NUM> and the plurality of micro projections <NUM>. In <FIG>, for easy understanding of the positional relationship, only one rib <NUM> and three micro projections <NUM> are shown, but it is needless to say that many micro projections <NUM> are actually arranged so as to be adjacent to the rib <NUM>. In <FIG>, the outer face of each micro projection <NUM> is dotted.

As shown in <FIG>, the plurality of micro projections <NUM> may include first projections <NUM> that are not directly connected to the rib <NUM> and second projections <NUM> that are partially connected to the rib <NUM>. On the other hand, the rib <NUM> includes a first side surface <NUM> on the first region <NUM> side, a second side surface <NUM> on the second region <NUM> side, and a top face <NUM> between the first side surface <NUM> and the second side surface <NUM>. The first projection <NUM> is not connected to any of the surfaces of the rib <NUM>. However, the smaller a gap <NUM> between the rib <NUM> and the first projection <NUM> is, the larger the contrast between the rib <NUM> and the second region <NUM> is. From this viewpoint, the length of the gap <NUM> (minimum length between the first projection <NUM> and the rib <NUM> at the root) is preferably smaller than a minimum width of the top face <NUM> of the rib <NUM>.

Meanwhile, each second projection <NUM> is connected only to the second side surface <NUM> of the rib <NUM>, or to both the second side surface <NUM> and the top face <NUM>. Preferably, the second projection <NUM> is, at least, not connected to the first side surface <NUM>. Accordingly, the first side surface <NUM> can be clearly observed as a contour line of the mark <NUM>, an increase in cost in design or processing of a vulcanization mold for a tire can be avoided, and the appearance of the mark <NUM> (shown in <FIG>) can also be improved.

Claim 1:
A pneumatic tire (<NUM>) comprising a pair of sidewall portions (<NUM>), wherein
at least one of outer surfaces of the pair of sidewall portions (<NUM>) includes at least one marking portion (<NUM>),
the marking portion (<NUM>) includes a first region (<NUM>) forming a mark (<NUM>) including at least one character, at least one graphic, or at least one symbol, a second region (<NUM>) that is a background portion of the mark (<NUM>), and a fringing portion (<NUM>) that demarcates the first region (<NUM>) from the second region (<NUM>) and fringes a contour of the mark (<NUM>),
the first region (<NUM>) is formed as a smooth surface,
the second region (<NUM>) is a projection-recess region where a plurality of micro projections (<NUM>) are arranged, and
the fringing portion (<NUM>) is a rib (<NUM>) projecting from the first region (<NUM>),
characterized in that
a maximum height (h2) of the rib (<NUM>) with respect to the first region (<NUM>) is <NUM>% to <NUM>% of a maximum height (h1) of the plurality of micro projections (<NUM>) with respect to the first region (<NUM>).