Airless tire

Abstract

The invention discloses an airless tire mounted on a rim. The airless tire includes: a ground contact portion that at least partially contacts the ground when the tire rotates, has a predetermined width, and extends in the circumferential direction of the tire; the combination part is combined with the rim; the side surface parts extend to the combining part from the two sides of the grounding part along the surface of the tire; and a plurality of side grooves arranged radially with respect to the center of rotation of the tire and forming recesses in the side surface portion. Through the structure, the airless tire has the advantages of light weight and low rolling resistance, the surface area can be increased to improve the heat dissipation performance, and the air flow flowing along the side surface of the tire is improved in the driving process, so that the air resistance is reduced.

Description

Technical Field

[0001] This invention relates to a pneumatic tire.

[0002] This invention was supported by the Ministry of Trade, Industry and Energy of South Korea's "Leisure Equipment Industry Development Support" project, "Airless tire for electric mobility under 45W rolling resistance to maximize energy efficiency by improving rolling stability and heat resistance" (Project No.: 2022-1-025 / Announcement No.: 2022-234 / Professional Agency: Small and Medium Enterprises Promotion Agency / Research and Development Period: June 23, 2022 to June 22, 2023). Background Technology

[0003] Generally speaking, airless tires for bicycles are a type of tire designed to solve the problem of punctures. They are characterized by the absence of an inner tube; instead, the tire is fitted to the rim of the bicycle wheel by filling it with materials such as rubber, or by using a spoke structure that disperses impacts from the ground. This prevents air leakage even if the tire is punctured or compressed by an external object.

[0004] While using airless tires can prevent bicycle tires from being punctured, the increased tire weight leads to a decrease in overall performance, and the problem of increased rolling resistance remains. Rolling resistance refers to the resistance experienced by a circular object (such as a tire) as it rolls on a surface, primarily generated by tire deformation and friction with the ground. Generally, the rolling resistance of a tire is less than kinetic friction, but the greater the rolling resistance, the more energy is required to overcome it.

[0005] Therefore, there is a need for a pneumatic tire that can reduce tire weight to lower rolling resistance, minimize air resistance acting on its surface when the tire is rotating, and improve heat dissipation by increasing surface area. Summary of the Invention

[0006] The problem that the invention aims to solve The present invention aims to solve the problems in the prior art mentioned above, and provides a pneumatic tire, comprising: a contact portion having a predetermined width and extending circumferentially along the tire when the tire rotates, at least partially contacting the ground; a joint portion engaging with the rim; sidewall portions extending from both sides of the contact portion along the tire surface to the joint portion; and a plurality of side grooves arranged radially with respect to the tire's rotation center and forming recesses on the sidewall portions. With the above structure, tire weight reduction is achieved, thereby reducing rolling resistance, and advantages in heat dissipation performance are gained through increased surface area, thus providing an improved pneumatic tire.

[0007] The present invention also aims to provide a pneumatic tire, wherein the side groove extends from one end on the circumferential side formed at the center of the tire cross section along the side portion to the other end on the rotational center side formed at the center of the cross section, thereby improving airflow along the tire side during driving and reducing air resistance.

[0008] Another object of the present invention is to provide a pneumatic tire in which the airflow characteristics are improved by changing the length and depth of the side grooves formed on the tire so that the airflow along the side of the tire is smoother.

[0009] Another object of the present invention is to provide a pneumatic tire, wherein the inner wall of the side groove is formed in a curved shape on the side surface of the tire, so that air in front of the tire can flow naturally to the rear along the inner wall of the side groove.

[0010] Another object of the present invention is to provide a pneumatic tire, wherein an outer peripheral groove is formed in the circumferential direction of the tire between the ground contact portion and the side portion, so that air in front of the tire can flow to the rear along the vertical direction of the tire, thereby further improving airflow.

[0011] It should be understood that the technical challenges to be addressed by the embodiments of the present invention are not limited to those described above, and other technical challenges may also exist.

[0012] means for solving problems To address the aforementioned technical challenges, a pneumatic tire according to an embodiment of the present invention includes: a ground contact portion that is at least partially in contact with the ground when the tire rotates, has a predetermined width and extends circumferentially along the tire; a joint portion that engages with the rim; sidewall portions that extend from both sides of the ground contact portion along the tire surface to the joint portion; and a plurality of side grooves that are radially arranged with respect to the tire's rotation center and have recesses formed on the sidewall portions.

[0013] According to an embodiment of the present invention, the side groove can extend along the side portion from one end on the circumferential side formed at the center of the tire cross section to the other end on the rotational center side formed at the center of the cross section.

[0014] In a pneumatic tire according to an embodiment of the present invention, the depth of the side groove can gradually increase as it extends from one end of its circumferential side along the side portion toward the center of the cross section.

[0015] According to an embodiment of the present invention, the side groove extends from the intersection point of the tire cross-section center and the straight line extending parallel to the tire rotation axis, along the side portion to the other end of the side groove located on the rotation center side, and its depth can gradually decrease.

[0016] According to an embodiment of the present invention, the side groove extends along the side portion from the intersection point of the tire cross section and the straight line extending parallel to the tire rotation axis to the other end of the side groove located on the rotation center side, and its depth can gradually increase.

[0017] According to an embodiment of the present invention, the airless tire includes a first segment forming an inner wall on one side of the side groove and a second segment forming an inner wall on the other side, wherein at least a portion of the first segment and the second segment extend with different curvatures.

[0018] According to an embodiment of the airless tire of the present invention, as the side groove extends from one end of the circumferential side along the side portion to the other end of the rotation center side, the distance between the first segment and the second segment can gradually increase and then decrease.

[0019] According to an embodiment of the airless tire of the present invention, the maximum recess depth of the side groove toward the center of the cross section can be 5 mm or more.

[0020] According to an embodiment of the airless tire of the present invention, the extension length of the side groove may be more than 1 / 4 of the length from the circumferential end of the grounding portion to the end of the side joint portion.

[0021] According to an embodiment of the present invention, a plurality of side grooves formed on both sides of the grounding portion are symmetrically recessed relative to the grounding portion.

[0022] According to an embodiment of the present invention, a plurality of side grooves formed on both sides of the grounding portion can be alternately recessed relative to the grounding portion.

[0023] According to an embodiment of the present invention, the airless tire may further include an outer peripheral groove formed between the ground contact portion and the side portion along the tire circumferential direction.

[0024] The technical means described above for solving the problem are merely illustrative and should not be construed as limiting the present invention. In addition to the exemplary embodiments described above, other embodiments may exist as shown in the accompanying drawings and detailed description of the invention.

[0025] Invention Effects Based on the above-described solutions to the problems of the present invention, the present invention aims to solve the problems in the prior art and provide a pneumatic tire. This pneumatic tire includes: a contact portion that at least partially contacts the ground when the tire rotates, has a predetermined width, and extends circumferentially along the tire; a joint portion that engages with the rim; sidewall portions extending from both sides of the contact portion along the tire surface to the joint portion; and a plurality of side grooves arranged radially with respect to the tire's rotation center and forming recesses on the sidewall portions. With this structure, tire weight can be reduced, thereby lowering rolling resistance, and by increasing the surface area, it has advantages in heat dissipation performance, thus achieving an improved pneumatic tire effect.

[0026] Furthermore, according to the above-described solution of the present invention, the side groove extends from one end on the circumferential side formed at the center of the tire cross section along the side portion to the other end on the rotation center side formed at the center of the cross section, thereby improving the airflow along the tire side during driving, reducing air resistance, and thus providing a tire with better aerodynamic performance.

[0027] Furthermore, according to the above-described solution to the problem of the present invention, the side channel improves airflow characteristics by changing the length and depth formed on the tire, thereby making the airflow along the side of the tire smoother.

[0028] Furthermore, according to the above-described solution of the present invention, the inner wall of the side groove is formed in a curved shape on the side surface of the tire, so that the air in front of the tire can flow naturally to the rear along the inner wall of the side groove, thereby providing a tire with smooth airflow.

[0029] Furthermore, according to the above-mentioned solution to the problem of the present invention, the present invention includes an outer peripheral groove formed between the grounding portion and the side portion along the tire circumferential direction, which allows air in front of the tire to flow to the rear along the vertical direction of the tire, thereby further improving airflow characteristics and enhancing overall aerodynamic performance. Attached Figure Description

[0030] Figure 1 This is a schematic perspective view of a pneumatic tire according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic cross-sectional view of a pneumatic tire along line AA′ according to an embodiment of the present invention.

[0032] Figure 3 This is a partially enlarged cross-sectional schematic diagram of a pneumatic tire according to an embodiment of the present invention.

[0033] Figure 4 This is a schematic cross-sectional view of a pneumatic tire along line AA′ according to another embodiment of the present invention.

[0034] Figure 5This is an enlarged view of the surface portion of a pneumatic tire according to an embodiment of the present invention.

[0035] Figure 6 This is a schematic diagram of a side groove formed in the side portion of a pneumatic tire according to an embodiment of the present invention.

[0036] Figure 7 This is a front view of a pneumatic tire according to an embodiment of the present invention.

[0037] Figure 8 This is a front view of a pneumatic tire according to another embodiment of the present invention. Detailed Implementation

[0038] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Furthermore, for the sake of clarity, parts unrelated to the description have been omitted in the drawings, and the same or similar reference numerals are used throughout the specification.

[0039] In this specification, when a part is referred to as being “connected” to another part, this includes not only the case of “direct connection” but also the case of “electrical connection” indirectly through other components.

[0040] In this specification, when a component is described as being "above", "over", "upper end", "lower", "below", or "lower end" of another component, this includes not only cases where the two components are in contact with each other, but also cases where there are other components between them.

[0041] In this specification, when a part is described as "including" a constituent element, this does not preclude the possibility of including other constituent elements, unless otherwise stated.

[0042] Furthermore, in the description of embodiments of the present invention, terms related to direction or position (such as "upper side") are defined based on the arrangement of the components in the accompanying drawings. For example, referring to... Figure 1 At that time, the 12 o'clock position can generally be considered as the upper side.

[0043] Furthermore, in the description of the embodiments of the present invention, the term "circumferential side" ( Figure 2 The 12 o'clock direction can be understood as the direction of the outer circumference of the tire, while the so-called "rotation center side" ( Figure 2 The 6 o'clock direction can be understood as the direction of the tire's rotation center (X).

[0044] This invention relates to a pneumatic tire, which is lightweight, has low rolling resistance, and an increased surface area that provides advantages in heat dissipation. Furthermore, it improves the airflow along the tire sidewall during driving, thereby reducing air resistance.

[0045] The following describes a pneumatic tire (10) according to an embodiment of the present invention. The interior of the pneumatic tire (hereinafter referred to as the "tire") may be filled with materials such as rubber or synthetic resin, or may have structures such as shear bands and spokes. In the embodiment described in the present invention, the tire may be a solid tire filled with rubber, synthetic resin or equivalent materials. The tire is coupled to a rim, wherein the so-called "coupling" of the tire to the rim can be understood as the tire being supported on a part of the rim, and at least a part of the rim being coupled or connected to a part of the tire to prevent the tire from falling off the rim. This includes situations where a part of the tire is housed in a part of the rim, or where a part of the tire is in direct contact with a part of the rim to prevent falling off, and also includes a structure that fixes the tire (10) to the rim (30) without falling off by a separately provided coupling unit (not shown).

[0046] First, such as Figure 1 and Figure 2 As shown, the rim (30) is annular in shape and has a joint in the circumferential direction with respect to the rotation center (X) of the tire, so as to engage with at least a portion of the tire (10). The rim (30) may have a partially concave shape to accommodate or fit the tire joint (13) described later, but its shape is not limited to this, as long as it can engage and securely fix the tire (10) to the rim (30).

[0047] Reference Figure 1 The tire (10) has a recessed side groove structure formed along the sidewall of the tire, which is arranged radially on the tire surface. This structure reduces the overall weight of the tire to lower rolling resistance, and allows air from the front of the tire to flow smoothly to the rear of the tire through the side grooves formed on the sidewall of the tire when the tire rotates, thereby further increasing the tire surface area to improve heat dissipation performance. The tire (10) may include a contact patch (11), a sidewall (12), a contact patch (13), and side grooves (15).

[0048] The contact patch (11) is the portion of the tire that at least partially contacts the ground when the tire rotates, and has a predetermined width extending circumferentially along the tire. Although not shown, tread patterns or protrusions may be formed on the contact patch (11) to improve driving performance (e.g., increasing traction, preventing slippage). See reference... Figure 2 The cross-sectional view shown indicates that the grounding portion (11) may be formed on the circumferential side of the tire. Figure 2(at the 12 o'clock direction), and the first axis in the vertical direction passing through the center (O) of the tire section ( Figure 2 Based on the axis at the 12 o'clock and 6 o'clock directions, it has a certain width and extends symmetrically. Under normal driving conditions, the grounding portion (11) located between the outer peripheral grooves (19) described below can contact the ground. However, under conditions of heavy load, the side portion (12) extending beyond the outer peripheral grooves (19) may also contact the ground, and this situation is not excluded from the scope of the claims.

[0049] The side portion (12) is a structure that extends from both sides of the ground contact portion (11) along the tire surface to the joint portion (13). As described later, the joint portion (13) can be accommodated or fitted inside the rim (30) to achieve a joint. Therefore, the side portion (12) actually refers to the area not covered by the rim (30) in the portion extending from one end or near the end of the ground contact portion (11) along the tire surface towards the tire rotation center. In other words, one end of the side portion (12) can be the end of the ground contact portion (11) or its vicinity, and the other end of the side portion (12) can be the part where the tire surface contacts one end of the rim (30).

[0050] Reference Figure 2 The side portion (12) may have a first point (121), which is the location where the center of the tire section (O) intersects the side portion (12) with a straight line extending parallel to the tire rotation axis. In one embodiment, the center of the section (O) may be the midpoint of the length (H) from the circumferential end of the ground contact portion to the end of the side portion joint portion, and also the midpoint of the width of the tire in the left-right direction.

[0051] In one embodiment, the first point (121) may be the most prominent part of the side portion (12) in the left-right direction of the tire. In other words, the most prominent first point (121) and the center of the cross section (O) may be located on a straight line parallel to the tire's axis of rotation. However, the first point (121) does not necessarily have to be the most prominent part, and the present invention does not impose this limitation.

[0052] The joining portion (13) is the part that engages with the rim (30), and at least part of it is accommodated or fitted inside the rim (30) to achieve engagement. The joining portion (13) is formed on the rotation center side of the tire. Figure 2 The surface of the wheel (6 o'clock direction) can be designed as a curved surface or a shape to accommodate the connecting unit (not shown) to ensure a more secure connection with the rim (30).

[0053] Figure 2 for Figure 1 AA′ cross-section. (Refer to...) Figure 1 and Figure 2According to an embodiment of the present invention, the side groove (15) is arranged radially with respect to the center of rotation of the tire, and can form a depression from the side portion (12) toward the center of the tire cross section (O). The side groove (15) can extend from one end (15a) formed on the circumferential side at the center of the tire cross section (O) along the side portion to the other end (15b) formed on the center of rotation side. Thus, the center of the tire cross section (O) is located between one end on the circumferential side and the other end on the center of rotation side of the side groove (15).

[0054] The extension length (L) of the side groove (15) from one end to the other can be more than 1 / 4 of the length (H) from the circumferential end of the ground contact portion (11) to the end of the side surface portion (12) at the joint portion (13). Compared with the case where only a hole-like depression is formed in a specific area of ​​the side surface portion (12), the side groove extending along the tire rotation direction can reduce air resistance and reduce tire weight. Here, the extension length of the side groove and the length from the circumferential end of the ground contact portion to the end of the side surface portion at the joint portion can be regarded as the length of the first axis in the vertical direction through the center of the cross section (O). Refer to Figure 2 When the side groove (15) extends from one end (15a) on the circumferential side along the side portion to the other end (15b) on the rotation center side, the tire volume decreases, and the thickness of the portion forming the side groove decreases relative to the portion not forming the side groove. When the tire rotates and propels the vehicle (such as a bicycle) forward, air from the front or circumferential side of the tire flows along the side groove (15) towards the rear or rotation center side of the tire. As the air flows along the tire surface, when the length from the circumferential end of the contact patch to the end of the side portion joint is defined as H, the side groove extension length (L) should be in a certain proportion relative to H, preferably more than 1 / 4, so that air can substantially flow along the side groove and produce an effect of improved airflow.

[0055] Continue to refer to Figure 2 The side groove (15) may have different depths at different locations. As it extends along the side surface (12) from one circumferential end (15a) towards the center of the cross-section, the depth of the side groove gradually increases. Furthermore, the side groove (15) may have an intersection point (15c), which is the location where a straight line extending parallel to the tire's axis of rotation intersects at the center of the tire cross-section (O). As it extends along the side surface from this intersection point (15c) to the other end (15b) on the center of rotation side, the depth of the side groove gradually decreases. In other words, in Figure 2 In the illustrated embodiment, as the side groove (15) extends along the side portion (12) from one end (15a) on the circumferential side to the other end (15b) on the rotation center side, its depth gradually increases and then gradually decreases. In one embodiment, the depth (w1) of the groove from the first point (121) on the side portion to the intersection point (15c) of the side groove can be the maximum value.

[0056] On the other hand, such as Figure 3As shown, each position of the side portion (12) can be defined as the distance (t) from the first axis extending vertically through the center of the cross section (O). a 、t_b). In the direction parallel to this, the depth of depression (w) at each position of the lateral groove (15) a 、w_b) can also be defined. In one embodiment, the side portion (12) recessed by the side groove (15) can be formed into a shape with left and right protrusions. That is, the difference in distance (t_b - t) between the side portion (12) and the first axis at the position of the cross-section center (O) is... a This can be greater than the distance difference (w_b - w) between the side ditch and the first axis at the center of the cross-section. a ), that is, (t_b - t a )>(w_b - w a Alternatively, the difference (t_b - w_b) between the distance of the side portion (12) from the first axis at the center (O) side of the cross section and the distance (t_b - w_b) between the corresponding position of the side groove and the first axis can be greater than the difference (t_b) at the circumferential side position. a - w a Therefore, when air flows from the circumferential side of the tire towards the center of rotation, airflow is improved and excessive negative pressure is prevented from forming on the tire sidewall.

[0057] like Figure 4 As shown, the side groove (16) according to another embodiment of the present invention may have different recess depths at various locations. The recess depth may gradually increase as it extends along the side surface portion (12) from one circumferential end (16a) of the side groove towards the center of the cross-section. Furthermore, the recess depth may continue to gradually increase as it extends along the side surface portion from the intersection point (16c) where it intersects a straight line extending parallel to the tire's rotation axis at the center of the tire cross-section to the other end (16b) on the rotation center side. Here, the recess direction of the side groove (16) may be from the side groove towards the center of the cross-section (O). In other words, in Figure 3 In the illustrated embodiment, the depth of the side groove (16) gradually increases as it extends along the side portion (12) from one end (16a) on the circumferential side to the other end (16b) on the rotation center side. In this embodiment, the depth of the groove (w2) from the first point (121) on the side portion to the intersection point (16c) of the side groove can be less than the depth of the groove (w3) at the other end (16b) on the rotation center side.

[0058] In one embodiment, the maximum depth of the side groove (15) can be 5 mm or more. For conventional pneumatic tires with an inner tube inside, the sidewall thickness is relatively thin, making it difficult to form side grooves with such a large depth. However, for pneumatic tires filled with materials such as synthetic resin or formed from a single material, side grooves with a depth of 5 mm or more can be formed on the tire sidewall. This can minimize the air resistance caused by the tire shape. In a tire according to one embodiment of the present invention, as shown in Table 1 below, its drag coefficient (Cd) can be reduced to below 0.1. Table 1 below shows the drag coefficient (Cd) obtained according to the variation of the width and depth of the side groove (15) formed on the sidewall (12).

[0059] Table 1

[0060] [Tire performance based on bore structure and size] Reference Figure 5 and Figure 6 The side groove (15) may include a first segment (151) forming the inner wall of one side of the side groove and a second segment (153) forming the inner wall of the other side. The first segment (151) and the second segment (153) may extend as curves with at least partial different curvatures. When the tire rotates, air from the circumferential side of the tire enters the space between the first segment (151) and the second segment (153) and flows along the side groove toward the center of rotation. Figure 5 As shown, when the tire rotates, air first contacts the circumferential side of the tire. Therefore, the first and second sections can be shaped to allow air to flow smoothly towards the rear of the tire, i.e., the center of rotation, along the direction of tire rotation. When the tire rotates downwards, the first section (151) and the second section (153) can have an upward convex shape. In other words, when the tire is viewed from one side, as the tire rotates counterclockwise, the first section (151) and the second section (153) can convex upwards from the circumferential side of the tire. Figure 5 (left side) towards the center of rotation ( Figure 5 Extending to the right, it forms a clockwise curve.

[0061] Furthermore, as the side groove (15) extends along the side surface from one end (15a) on the circumferential side to the other end (15b) on the rotation center side, the distance (d) between the first segment (151) and the second segment (153) can gradually increase and then decrease.

[0062] Reference Figure 6The first segment (151) and the second segment (153) may each include a first diverging portion (1511) and a second diverging portion (1531) extending separately from one end (15a) of the side groove. The first diverging portion (1511) and the second diverging portion (1531) may extend from one end (15a) of the side groove to the intersection point (15c) or the portion forming the first point (121), and at least partially extend with different curvatures. Here, the radius of curvature (r1) of the circle (c1) formed by a portion of the first diverging portion (1511) may be smaller than the radius of curvature (r2) of the circle (c2) formed by a portion of the second diverging portion (1531). Therefore, as the side groove extends from one end (15a) to the intersection point (15c), the distance (d) between the first segment and the second segment may gradually increase. From the circumferential side of the tire ( Figure 6 When the tire extends from the left side of the cross-section towards the center (O), the tire thickness ( Figure 6 The depth gradually increases, and this shape allows air to flow smoothly along the surface of the side grooves.

[0063] like Figure 7 As shown, according to one embodiment of the present invention, the side portions (12) are respectively arranged on both sides of the grounding portion (11), and the side grooves (15) are radially formed on the side portions (12) with reference to the rotation center of the tire. Here, the plurality of side grooves (15) formed on the two side portions (12) can be formed symmetrically with respect to the grounding portion (11).

[0064] like Figure 8 As shown, according to another embodiment of the present invention, a plurality of side grooves (15) formed on the side surfaces (12) on both sides of the grounding portion (11) can be alternately recessed relative to the grounding portion.

[0065] Refer again Figure 1 as well as Figures 7 to 8 According to an embodiment of the present invention, the tire (10) may further include a peripheral groove (19). The peripheral groove (19) is formed between the contact patch (11) and the sidewall portion (12), and is recessed along the circumferential direction of the tire. The peripheral groove (19) substantially separates the contact patch (11) from the sidewall portion (12) and allows air from the front of the tire to flow along the peripheral groove (19) in the vertical direction of the tire. Figure 7 and Figure 8 (The 12 o'clock and 6 o'clock directions). With the formation of the outer peripheral groove (19), the air blown from the front of the tire can flow to the left and right directions of the tire through the side groove (15). Figure 7 and Figure 8 On the one hand, the airflow is directed at the 3 o'clock and 9 o'clock positions, and on the other hand, it flows vertically, thereby further improving airflow on the tire surface and increasing the tire surface area to improve heat dissipation performance.

[0066] The above description of the present invention is for illustrative purposes only. Those skilled in the art should understand that other specific modifications can be easily made without altering the technical concept or essential features of the invention. Therefore, the above embodiments should be understood as exemplary in all respects and not restrictive. For example, components described as a single structure can be implemented separately, and similarly, components described as separate structures can be implemented in combination.

[0067] The scope of protection of this invention should be defined by the following claims, rather than by the detailed description above, and should be interpreted to include all modifications or variations derived from the meaning, scope and equivalent concepts of the claims.

Claims

1. A pneumatic tire mounted on a wheel rim, characterized in that, The airless tire includes: The ground contact portion, which has a predetermined width and extends circumferentially along the tire, is at least partially in contact with the ground when the tire rotates. The joint portion that engages with the rim; The side portions extending from both sides of the grounding portion along the tire surface to the joint portion; and Multiple side grooves are arranged radially with respect to the center of rotation of the tire and are recessed on the side surface.

2. The airless tire according to claim 1, characterized in that, The side groove extends along the side surface from one end on the circumferential side formed at the center of the tire cross section to the other end on the rotational center side formed at the center of the cross section.

3. The airless tire according to claim 2, characterized in that, As the side groove extends from one end on its circumferential side along the side portion toward the center of the cross section, its depth gradually increases.

4. The airless tire according to claim 3, characterized in that, The side groove extends from the intersection point at the center of the tire cross section with a straight line extending parallel to the tire's axis of rotation, along the side surface to the other end of the side groove located at the center of rotation, with its depth gradually decreasing.

5. The airless tire according to claim 3, characterized in that, The side groove extends along the side surface from the intersection point of the straight line extending parallel to the tire's axis of rotation at the center of the tire cross section to the other end of the side groove located at the center of rotation, with its depth gradually increasing.

6. The airless tire according to claim 3, characterized in that, The side groove includes a first segment forming the inner wall of one side of the side groove and a second segment forming the inner wall of the other side. At least a portion of the first and second segments extend with different curvatures.

7. The airless tire according to claim 6, characterized in that, As the side groove extends from one end of the circumferential side along the side surface to the other end of the rotation center side, the distance between the first segment and the second segment gradually increases and then decreases.

8. The airless tire according to claim 2, characterized in that, The maximum depth of the side groove towards the center of the cross-section is 5 mm or more.

9. The airless tire according to claim 2, characterized in that, The extension length of the side groove is more than 1 / 4 of the length from the circumferential end of the grounding portion to the end of the side joint portion.

10. The airless tire according to claim 2, characterized in that, Multiple side grooves are formed on both sides of the grounding part, symmetrically recessed with the grounding part as the reference.

11. The airless tire according to claim 2, characterized in that, Multiple side grooves are formed on both sides of the grounding part, with the grounding part as the reference, and are alternately recessed.

12. The airless tire according to claim 2, characterized in that, It also includes an outer peripheral groove formed by a circumferential recess between the grounding portion and the side portion of the tire.

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