Patent Application
20230191836
The present invention generally relates to vehicle tires and, more particularly, to non-pneumatic tires based on reinforced rubber.
The pneumatic tire has been the solution of choice for vehicular mobility for over a century and is still dominant on the tire market today. Pneumatic tires are efficient at carrying loads because all of their structure is involved in carrying the load. Pneumatic tires are also desirable because they have low contact pressure, resulting in lower wear on roads due to the distribution of the load of the vehicle. Pneumatic tires also have low stiffness, which ensures a comfortable ride in a vehicle. The primary drawback to a pneumatic tire is that it requires compressed fluid (e.g., air or an inert gas). A conventional pneumatic tire is rendered useless after a complete loss of inflation pressure.
A tire designed to operate without inflation pressure may eliminate many of the problems and compromises associated with a pneumatic tire. Neither pressure maintenance nor pressure monitoring is required. Structurally supported tires such as solid tires or other elastomeric structures to date have not provided the levels of performance required from a conventional pneumatic tire. A structurally supported tire solution that delivers pneumatic tire-like performance would be a desirous improvement.
Non pneumatic tires are typically defined by their load carrying efficiency. So-called “bottom loaders” are essentially rigid structures that carry a majority of the load in the portion of the structure below the hub. “Top loaders” are designed so that all of the structure is involved in carrying the load. Top loaders thus have a higher load carrying efficiency than bottom loaders, allowing a design that has less mass.
US 2017/0297371 A1 discloses a non-pneumatic tire, which includes a ground contacting annular tread portion, a shear band, and a connecting web positioned between a hub and the shear band. US 2017/0297371 A1 specifically relates to the shear band, which is preferably comprised of a three-dimensional spacer fabric having a first and second layer connected by connecting members. The three-dimensional spacer fabric has a defined depth. The three-dimensional spacer structure further includes a plurality of cells formed between the connecting members, and wherein one or more of the cells are filled with a filler material. The filler material may be foam or a thermoplastic elastomer.
The purpose of a shear band is to transfer the load from contact with the ground through tension in the spokes to the hub, creating a top loading structure. When the shear band deforms, its preferred form of deformation is shear over bending. The shear mode of deformation occurs because of the inextensible membranes located on the outer portions of the shear band. Non-pneumatic tires may have a shear band made from rubber materials sandwiched between two or more layers of inextensible belts or membranes. One may find disadvantages in such sandwich construction, which is the reason why alternatives are investigated.
WO 2021/061323 A1 relates to a non-pneumatic tire having a looped support structure. The proposed non-pneumatic tire includes an inner ring, an outer ring, and a plurality of loops extending between the inner ring and the outer ring. The plurality of loops includes at least a first loop and a second loop, the first and second loops being each in direct contact with both the inner ring and the outer ring. The first loop has a single reinforcement layer disposed therein and includes a first extent that extends between the inner ring and the outer ring and a second extent that extends between the inner ring and the outer ring. The second loop has a single reinforcement layer disposed therein and includes a third extent that extends between the inner ring and the outer ring and a fourth extent that extends between the inner ring and the outer ring. The second extent is in direct contact with the third extent. In other words, the loops are placed one adjacent the other in the annular section between the inner and outer rings and spokes are formed by the radial extents of two adjacent loops.
According to an aspect of the invention, a non-pneumatic tire comprises a radially inner ring for contacting a vehicle rim, a radially outer ring and a support structure including spokes extending from the radially outer ring to the radially inner ring. The support structure is effective to transfer load from the radially inner ring to the radially outer ring. The spokes delimit openings in the support structure, which extend in a width direction (transversal direction) of the non-pneumatic tire. The non-pneumatic tire further comprises a reinforcement structure. The reinforcement structure comprises loops of reinforcement cord, each loop extending around one of the openings. Each spoke has arranged therein radial reinforcement cord segments extending radially between the inner ring and the outer ring. The radial reinforcement cord segments are lined up parallel to one another along the width direction of the non-pneumatic tire. Along the width direction, the reinforcement cord segments in a spoke belong alternately to a first loop extending around an opening on a first side of the spoke and to a second loop extending around an opening on a second side of the spoke, opposite to the first side.
According to an embodiment, each spoke has the radial reinforcement cord segments lined-up therein in a single reinforcement layer. The radial reinforcement cord segments may form a substantially coplanar arrangement in each spoke.
According to an embodiment, each spoke has a median surface and the radial reinforcement cord segments lined-up therein in the median surface. As used herein, the expression “median surface” designates the locus of points that are equidistant from the side surfaces that delimit the openings on either side of the spoke. The radial reinforcement cord segments could, more generally speaking, be lined-up in an internal surface of each spoke. Such internal surface could be substantially parallel to the median surface or correspond to the locus of points that are a given distance away from one of the surfaces that delimit the openings on either side of the spoke, or to the locus of points whose distance from one of the surfaces that delimit the openings on either side of the spoke amounts to a predefined percentage of the distance from the one of the surfaces.
The spokes may be planar. According to an embodiment, however, the spokes are curved. In particular, the spokes may all be curved in the same angular direction about the tire axis, so that they deflect in the same direction when the tire is loaded.
According to an embodiment, each loop of the reinforcement structure comprises:
a first radial reinforcement cord segment extending within a first spoke from the inner ring to the outer ring,
an outer arc reinforcement cord segment extending within the radially outer ring from the first spoke to a second spoke that is an immediate neighbor of the first spoke,
a second radial reinforcement cord segment extending within the second spoke from the outer ring to the inner ring, and
an inner arc reinforcement cord segment extending within the radially inner ring from the second spoke to the first spoke.
The loops could be closed loops. In this case, the loops extending around a given opening could be arranged in parallel planes perpendicular to the tire axis. The loops extending around the neighboring openings would then be arranged between those planes, e.g., midway between those planes.
According to an embodiment, the reinforcement structure comprises windings, each winding extending around one of the openings, the loops being part of the windings. Each loop may form at least one turn of a such a winding.
The windings could all have the same chirality (handedness). Preferably, however, the windings include both left-handed and right-handed windings. According to an embodiment, in an angular direction about the tire axis, the left-handed windings alternate with the righthanded windings. Using windings of alternating handedness may be beneficial for improved dimensional stability of the tire.
According to an embodiment, the radial reinforcement cord segments are perpendicular to the tire axis. Alternatively, the radial reinforcement cord segments could be slanted with respect to the tire axis.
According to an embodiment, the radially outer ring includes a shear band and a tread.
According to an embodiment the radially inner ring, the radially outer ring and the support structure consist essentially of reinforced rubber.
According to an aspect of the invention, a non-pneumatic tire comprises:
a radially inner ring extending around the tire axis, for contacting a vehicle rim;
a radially outer ring extending around the tire axis;
a support structure including spokes extending from the radially outer ring to the radially inner ring, the support structure being effective to transfer load from the radially inner ring to the radially outer ring, the spokes delimiting openings in the support structure, the openings extending along the tire axis; and
a reinforcement structure comprising reinforcement cord arranged in windings, each winding extending around one of the openings and comprising
a first radial section extending within a first spoke from the inner ring to the outer ring;
an outer arc section extending within the radially outer ring from the first spoke to a second spoke that is an immediate neighbor of the first spoke,
a second radial section extending within the second spoke from the outer ring to the inner ring, and
an inner arc section extending within the radially inner ring from the second spoke to the first spoke.
Neighboring windings are arranged so as to interdigitate with one another within the spokes. The depth of the interdigitation (in the circumferential direction) may correspond to the thickness of the reinforcement cord.
As for the first aspect, the radially outer ring may include a shear band and a tread. The spokes may be planar. Alternatively, the spokes may be curved. In particular, the spokes may all be curved in the same angular direction about the tire axis, so that they deflect in the same direction when the tire is loaded.
According to an embodiment, each of the first radial section, the outer arc section, second radial section and the inner arc section comprises plural parallel segments of reinforcement cord. In particular, the first radial section may comprise plural parallel first radial reinforcement cord segments extending from the inner ring to the outer ring, the outer arc section may comprise plural parallel outer arc reinforcement cord segments extending from the first spoke to the second spoke, the second radial section may comprise plural parallel second radial reinforcement cord segments extending from the outer ring to the inner ring and the inner arc section may comprise plural inner arc reinforcement cord segments extending from the second spoke to the first spoke.
As used herein, the expression “to interdigitate” may mean that within the spokes, neighboring windings are arranged interleaved, in such a way that, along the direction of the tire axis, there is a zone of overlap containing alternatingly a turn of either winding. In particular, the plural parallel first radial reinforcement cord segments of a winding may be arranged alternatingly with the plural parallel second radial reinforcement cord segments of a neighboring winding.
The windings may have the same pitch. The pitch is preferably constant along the direction of the tire axis. Alternatively, the pitch of the windings could change as a function of a coordinate on the tire axis. This would lead to variable amount of reinforcement, in particular to variably spaced radial reinforcement cord segments. Windings with non-constant pitch could thus be used to specifically tailor the mechanical properties of the spokes.
According to an embodiment, where the neighboring windings interdigitate, the neighboring windings are regularly spaced along the direction of the tire axis. Preferably, neighboring windings interdigitate with one another in the median surface of the spoke.
In the present document, the verb “to comprise” and the expression “to be comprised of” are used as open transitional phrases meaning “to include” or “to consist at least of”. Unless otherwise implied by context, the use of singular word form is intended to encompass the plural, except when the cardinal number “one” is used: “one” herein means “exactly one”. Ordinal numbers (“first”, “second”, etc.) are used herein to differentiate between different instances of a generic object; no particular order, importance or hierarchy is intended to be implied by the use of these expressions. Furthermore, when plural instances of an object are referred to by ordinal numbers, this does not necessarily mean that no other instances of that object are present (unless this follows clearly from context). When reference is made to “an embodiment”, “one embodiment”, “embodiments”, etc., this means that these embodiments may be combined with one another. Furthermore, the features of those embodiments can be used in the combination explicitly presented but also that the features can be combined across embodiments without departing from the invention, unless it follows from context that features cannot be combined.
The invention will be described by way of example and with reference to the accompanying drawings in which:
The inner ring 102 may be mounted on a hub or rim (not shown). The outer ring 104 may include a circumferential tread 110 and a shear band 112. The tread 110 may include tread features such as, e.g., grooves, ribs, blocks, lugs, sipes, studs, etc. The shear band 112 receives the load exerted on the inner ring as tension in the spokes 108 and transfers this load to the ground, via the tread.
The reinforcement may be made of steel cords and/or cords formed from nylon fiber, polyester fiber, fiber glass, carbon fiber, aramid fiber, glass fiber, polyethylene fiber, polyethylene terephthalate fiber, or other reinforcement materials. Different reinforcement materials could be combined. It is worthwhile noting that a “cord” may include one or plural strands.
As can be seen in
Each loop 118 is continuous but not necessarily closed. According to a preferred embodiment, each loop around a given opening is connected to a series of loops around that opening, such that the series of loops forms a winding around that opening. Each loop may correspond to a turn of the winding.
As shown in
The manufacturing process may comprise assembling different preformed pieces of uncured tire material, e.g., green rubber, in a mold comprising different parts. The mold may then be heated to an elevated temperature sufficient to cure the tire material. In case of green rubber, the combination of elevated temperatures and high pressure causes vulcanization of the rubber. When the tire material is cured, the mold is disassembled, and the cured tire is removed from it.
In the embodiment illustrated in
It is worthwhile noting that, in alternative embodiments of the invention, the support structure may be built with windings having all the same chirality (handedness), provided that in such windings the second radial reinforcement cord segments 118c of the second radial section 132 are offset (preferably by a distance equal to approximately half the pitch) in the direction of the tire axis with respect to the first radial reinforcement cord segments 118a of the first radial section 128.
Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.
