Noise-reducing tire

Abstract

To provide a noise-reducing tire significantly reducing noise caused by the tire.SOLUTION: A noise-reducing tire comprises: side wall portions on both sides; a tread portion 10 integrally connecting outer circumferences of the side wall portions; a longitudinal groove 20 concavely formed in the tread portion 10 along a driving direction; and a lateral groove 30 concavely formed from the longitudinal groove 20 towards the side wall portion in the lateral direction, where the lateral groove 30 expands in width towards the side wall portion in the form of multiple sidewall steps 51.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vehicle tire, and more particularly to a noise reduction tire having a noise reduction structure.

Background Art

[0002] During driving, a motor vehicle generates noise due to its own air resistance, mechanical movements of drive systems such as engines and transmissions, and road surface friction of tires.

[0003] Such noise not only reduces the riding comfort of the driver and passengers but also induces discomfort, and efforts have been continuously made to reduce noise by using vehicle soundproofing materials or sound-absorbing materials.

[0004] The Ministry of the Environment has clarified that it will introduce the "Tire Noise Performance Labeling System" currently in force in the European Union (EU) since 2019, and domestic and foreign automotive industries are making great efforts to reduce noise in anticipation of the implementation of this system. Conventionally, efforts have been concentrated on reducing noise generation inside the vehicle such as engines, but in order to minimize noise generated outside the vehicle such as tires, the number of cases applying new low-noise technologies from the initial stage of tire development is increasing.

[0005] In particular, tires for electric vehicles, whose market share has been rapidly increasing recently, are required to have different noise performance from that of internal combustion engine vehicles. Since electric vehicles do not have an engine, the overall noise level is low, and the contribution of noise due to friction between the tire and the road surface is high, making the tires more important.

[0006] Among tire noises, the peak of the pipe resonance in the 1KHz frequency range and the pitch noise caused by the pitch (the blocks divided in the running direction) account for a very large proportion of the overall tire noise. While in contact with the ground, a pipe shape is formed, and impacts are applied to each block, generating impact noise in the frequency range related to the pipe resonance sound and the pitch number in the 1KHz band.

[0007] Common tires further have lateral grooves for drainage. The lateral grooves formed in the tire come into contact with the ground and generate noise due to impacts or other reasons.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, the present invention is for solving the above-mentioned problems of the prior art. In order to minimize the unpleasant noise generated between the road surface and the tire, it is a technical problem to provide a noise-reducing tire that reduces the noise energy generated by the lateral grooves and reduces the peak of the pipe resonance sound affected in relation to the pitch noise, thereby reducing the noise energy.

[0010] Specifically, the present invention aims to solve the technical problem of providing a noise-reducing tire that reduces noise by designing the lateral groove to have a lateral expansion part and a bottom surface step part, narrowing the air channel, and dispersing the contact mechanism with the road surface to reduce the noise energy.

Means for Solving the Problems

[0011] One embodiment of the present invention for achieving the above object includes side wall portions 5 on both sides, a tread portion 10 integrally connecting between the outer circumferences of the side wall portions 5, a longitudinal groove 20 recessed along the traveling direction in the tread portion 10, and a transverse groove 30 recessed laterally from the longitudinal groove 20 toward the side wall portion 5 side. The transverse groove 30 is formed such that the width expands toward the side wall portion 5, and a noise reduction tire is provided.

[0012] The transverse groove 30 may be formed to communicate with the longitudinal groove 20 at an end on the longitudinal groove 20 side.

[0013] The transverse groove 30 may be formed by a lateral expansion portion 50 in which one or more side walls of both side walls include one or more side wall steps 51 and the width expands in multiple steps.

[0014] The widths of the respective multi-stage side wall steps 51 in the longitudinal direction (X-direction) of the transverse groove 30 may be configured to gradually widen in the range of 0.01 mm to 0.1 mm with respect to the width of the transverse groove 30.

[0015] The side wall step 51 may be configured to have a side surface inclination that is narrow on the longitudinal groove 20 side and wider toward the side wall portion 5.

[0016] The transverse groove 30 may communicate with the longitudinal groove 20 at an end on the longitudinal groove 20 side, and the depth of the bottom surface of the transverse groove 30 may be configured such that the longitudinal groove 20 side is shallower and the side wall portion 5 side is deeper with respect to the surface of the tread portion 10.

[0017] The transverse groove 30 may communicate with the longitudinal groove 20 at an end on the longitudinal groove 20 side and may include a bottom surface step portion 40 having one or more bottom surface steps 41 in which the bottom surface of the transverse groove 30 gradually deepens toward the side wall portion 5.

[0018] The bottom step 41 may be configured to have an inclination such that the side closer to the longitudinal groove 20 is shallow and gradually becomes deeper as it goes toward the side wall portion 5.

[0019] The transverse groove 30 may further include tie bars 14, 15 that communicate with the longitudinal groove 20 at the end on the longitudinal groove 20 side and are formed to have a height lower than that of the tread portion 10 so as to project in the circumferential direction of the tire and connect the side surfaces of the tread pattern blocks 11 on the connected end side.

[0020] The transverse groove 30 may further include either non-separating tie bars 14 that connect the inner side walls of the transverse groove 30 without being separated from the longitudinal groove 20 or separating tie bars 15 that connect the inner side walls of the transverse groove 30 while being separated from the longitudinal groove 20.

[0021] The non-separating tie bars 14 or the separating tie bars 15 may have a flat surface or a shape that becomes deeper in a parabolic shape.

Advantages of the Invention

[0022] The noise-reducing tire according to one embodiment of the present invention described above reduces the noise energy generated in the transverse grooves and reduces the peak of the air column resonance sound affected in relation to the pitch noise in order to minimize the unpleasant noise generated between the road surface and the tire, thereby reducing the noise energy and providing the effect of significantly reducing the noise caused by the tire.

[0023] Also, the noise-reducing tire according to one embodiment of the present invention described above is designed such that the transverse groove has a lateral expansion portion and a stepped shape, narrowing the air channel and dispersing the contact mechanism with the road surface to reduce the noise energy, thereby providing the effect of significantly reducing the noise caused by the tire.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

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Figure 5B

Figure 5C

Figure 5D

Figure 5E

Figure 5F

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Figure 7

Best Mode for Carrying Out the Invention

[0025] In the following description of the present invention, when it is determined that a specific description of a related known function or configuration would unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

[0026] Examples according to the concept of the present invention can be modified in various ways and can have various forms. Therefore, specific examples are illustrated in the drawings and described in detail in this specification or the application documents. However, this is not intended to limit the examples according to the concept of the present invention to a specific disclosed form, and the present invention should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0027] When it is mentioned that a certain component is "connected" or "attached" to another component, it should be understood that it can be directly connected or attached to the other component, but other components can also exist between them. On the other hand, when it is mentioned that a certain component is "directly connected" or "directly attached" to another component, it should be understood that no other components exist between them. Other expressions for explaining the relationship between components, such as "between", "immediately between", or "adjacent to", "directly adjacent to", etc., should be interpreted in the same way.

[0028] The terms used in this specification are merely used to explain specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "including" or "having" are intended to specify the existence of the described features, numbers, steps, operations, components, parts, or combinations thereof, and should be understood not to preclude the possibility of the existence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0029] Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings showing embodiments of the present invention.

[0030] FIG. 1 is a partial plan view (a) of a tread portion showing the longitudinal grooves 20 and transverse grooves 30 of a tire according to an embodiment of the present invention, and a partial inclined view (b) of the tread portion. FIG. 2 is a side end view (a) of the longitudinal grooves 20 and transverse grooves 30 of a tire 1 according to an embodiment of the present invention, a plan view (b) of the longitudinal grooves 20 and transverse grooves 30 in which a lateral expansion portion 50 is formed on one side wall of the transverse groove, and a plan view (c) of the longitudinal grooves 20 and transverse grooves 30 in which lateral expansion portions 50 are formed on both side walls of the transverse groove.

[0031] As shown in FIGS. 1 and 2, the noise reduction tire 1 according to an embodiment of the present invention includes sidewall portions 5 on both sides, a tread portion 10 integrally connecting between the outer circumferences of the sidewall portions 5, longitudinal grooves 20 recessed along the traveling direction in the tread portion 10, and lateral grooves (LG, Lateral Groove) 30 recessed laterally from the longitudinal grooves 20 toward the sidewall portions 5. The lateral grooves 30 are formed such that the width expands as they go toward the sidewall portions 5.

[0032] The lateral grooves 30 may be formed to communicate with the longitudinal grooves 20 at the end portions on the longitudinal groove 20 side.

[0033] The lateral grooves 30 may be formed as a lateral expansion portion 50 in which one or more sidewalls of both sidewalls include one or more sidewall steps 51 and the width expands in multiple steps.

[0034] The sidewall steps 51 may be configured to have a side surface inclination such that the longitudinal groove 20 side is narrow and it becomes wider as it goes toward the sidewall portion 5.

[0035] The sidewall steps 51 in the longitudinal direction of the lateral grooves 30 may be configured in multiple steps such as one step, two steps, three steps, etc.

[0036] In the longitudinal direction of the lateral grooves, the criteria for setting the number of steps of each sidewall step 51 may be gradually widened in the range of 0.01 mm to 0.1 mm with respect to the width of the lateral grooves 30 at the connection portion of the longitudinal grooves 20.

[0037] In the longitudinal direction of the lateral grooves, the criteria for setting two or three steps are all cases where it becomes wider by 0.01 mm or more with respect to the width of the lateral grooves at the main groove connection portion.

[0038] In the above configuration, the sidewall step difference between the adjacent sidewall steps 51 may be formed to have a range of 0.5 mm to 4 mm.

[0039] The extended form and the changing position of the stepped form of the side wall step 51 may be freely changed according to the size of the lateral groove 30. When mixing the extended form and the stepped form of the side wall step 51, the appropriate position must consider the contact width of the actual tire's contact shape. Taking three steps as an example, the starting point of the second step must be the same as the contact width during steady running (about 90-95% of the tread width (TW)), and the starting point of the third step must be the same as the contact width during proper turning (about 100-105% of the tread width (TW)).

[0040] The lateral groove 30 communicates with the longitudinal groove 20 at the end on the longitudinal groove 20 side, and the bottom surface of the lateral groove 30 may be configured such that the side on the longitudinal groove 20 side is shallower and the side on the sidewall portion 5 side is deeper with respect to the surface of the tread portion 10.

[0041] The lateral groove 30 may include a bottom step portion 40 having one or more bottom steps 41 that communicate with the longitudinal groove 20 at the end on the longitudinal groove 20 side and whose bottom surface gradually becomes deeper as it goes towards the sidewall portion 5.

[0042] In the above configuration, the height difference between the adjacent bottom steps 41 may be formed to have a range of 0.5 mm to 4 mm.

[0043] The bottom step 41 may be configured to have an inclination such that the side on the longitudinal groove 20 side is shallower and gradually becomes deeper as it goes towards the sidewall portion 5.

[0044] The lateral groove 30 may further include a tire 15 that communicates with the longitudinal groove 20 at the end on the longitudinal groove 20 side and is formed to have a height lower than that of the tread portion 10 so as to project in the circumferential direction of the tire and connect the side surfaces of the tread pattern blocks 11 on the connected end side.

[0045] The bottom surface 31 of the lateral groove of the lateral groove 30 is not limited to the stepped portion described above, and may be formed of a flat surface or an inclined surface such as a parabolic surface having a variable inclination, as described in FIG. 5 below.

[0046] Further, the side wall of the side direction expansion part 50 of the lateral groove 30 is not limited to the stepped portion described above, and may be formed in a straight line having a certain angle with respect to the side direction center line toward the side wall part 5 of the tread part 10, as described in FIG. 3 below.

[0047] The noise reduction tire 1 of an embodiment of the present invention having the above-described configuration forms a bottom step portion 40 on the bottom surface in the depth direction of the lateral groove 30 functioning as a drainage groove, and forms a side direction expansion part 50 in the cross section in the traveling direction of the tread part 10, thereby reducing the amount of noise generated during straight running, and dispersing the impact of the lateral groove 30 when grounding on the road surface to provide an effect of reducing pitch noise.

[0048] Hereinafter, FIGS. 3 to 7 are diagrams showing the results of experiments on the noise reduction performance of the noise reduction tire 1 of an embodiment of the present invention.

[0049] FIG. 3 is a result graph of a sound power change experiment based on the width and depth of the lateral groove 30 of the tire and the depth of the tie bar 15 during traveling at a speed of 80 kph. (a) is a graph showing the sound power change according to the width of the lateral groove of the tire, (b) is a graph showing the sound power change according to the depth of the lateral groove of the tire, and (c) is a graph showing the sound power change according to the depth of the tie bar of the tire.

[0050] FIG. 3 basically shows the results of comparing the tire noise according to the width, depth, and form of the tie bar 15 of the lateral groove 30 of the tire.

[0051] Specifically, (a) of FIG. 3 is a graph showing the sound power change according to the width of the lateral groove 30 of the tire 1, and it was confirmed that the sound power decreases as the width of the lateral groove 30 becomes narrower.

[0052] Figure 3(b) is a graph showing the change in sound power due to the depth of the lateral groove 30 of the tire 1. It was confirmed that the noise performance of the single tire 1 is more advantageous as the depth of the lateral groove 30 becomes shallower.

[0053] Figure 3(c) is a graph showing the change in sound power due to the depth of the tie bar 15, which is the distance from the upper surface of the tie bar 15 formed on the longitudinal groove 20 side of the lateral groove 30 of the tire 1 to the tread portion 10. It was confirmed that the noise performance of the single tire 1 is more advantageous as the depth of the tie bar 15 becomes shallower.

[0054] Figure 4 is a result graph of an experiment on the change in sound power due to the change in the width of the lateral groove of the tire during driving at a speed of 80 kph. (a) is a photograph of a tire (Ref tire) in which the width of the lateral groove on the longitudinal groove side of the tire is the same as the width of the lateral groove on the sidewall side. (b) is a photograph of a tire (Extended LG Small) configured such that the width of the lateral groove on the sidewall side of the tire spreads to a width of 1.5 times or more and less than 2 times the width of the lateral groove on the longitudinal groove side. (c) is a photograph of a tire (Extended LG Large) configured such that the width of the lateral groove on the sidewall side of the tire spreads to a width of 2 times or more and 6 times or less the width of the lateral groove on the longitudinal groove side. (d) is a graph showing the change in sound power for each of the Ref tire, Extended LG Small, and Extended LG Large tires, and (e) is a graph showing the change in sound power of the 1 / 3 octave band for each tire.

[0055] The experiment in Figure 4 is the result of conducting the sidewall step 51 in two steps.

[0056] When driving at 80 kph, as shown in Fig. 4(d), it was confirmed that in the case of the small extended tire (Extended LG Small, Fig. 4(b)) and the large extended tire (Extended LG Large, Fig. 4(c)), it is advantageous for noise reduction compared to a general Ref tire (Fig. 4(a)). Also, it was confirmed that the effect affects up to 800 - 2500 Hz based on the frequency range. Further, it was confirmed that the impact noise due to pitch decreases, and as a result, the noise decreases generally around 1 KHz.

[0057] Fig. 5 shows tires having combinations of different tires and lateral groove depths for conducting an experiment on the change in sound power due to the combination of the tire and the lateral groove depth during driving at a speed of 80 kph. (a) shows a tire with a non - separated tire / large - depth lateral groove (Tiebar0mm_Large Depth), (b) shows a tire with a non - separated tire / middle - depth lateral groove (Tiebar0mm_MIddle Depth), (c) shows a tire with a non - separated tire / small - depth lateral groove (Tiebar0mm_Small Depth), (d) shows a tire with a separated tire / large - depth lateral groove (Tiebar3mm_Large Depth), (e) shows a tire with a separated tire / middle - depth lateral groove (Tiebar3mm_MIddle Depth), and (f) shows a tire with a separated tire / small - depth lateral groove (Tiebar3mm_Small Depth).

[0058] Fig. 6 is a graph showing the noise measurement results of tires having combinations of different tires and lateral groove depths for conducting an experiment on the change in sound power due to the combination of the tire and the lateral groove depth during driving at a speed of 80 kph. (a) is a graph showing the sound power measurement values of the tires in Fig. 5, and (b) is a graph measuring the change in sound power for each center frequency of the 1 / 3 - octave band of the tires in Fig. 5.

[0059] FIG. 7 is a graph showing the noise measurement results for each depth of the lateral groove 30 and the tire 15 of the tire having a combination of different tires and the depth of the lateral groove for performing an experiment on the change in sound power due to the combination of the tire and the depth of the lateral groove during traveling at a speed of 80 kph. (a) is a sound power measurement graph of the tire (Tiebar0mm_Large Depth) having a non-separated tire / large-depth lateral groove, the tire (Tiebar0mm_MIddle Depth) having a non-separated tire / medium-depth lateral groove, and the tire (Tiebar0mm_Small Depth) having a non-separated tire / small-depth lateral groove in FIG. 5, and (b) is a sound power measurement graph of the tire (Tiebar3mm_Large Depth) having a separated tire / large-depth lateral groove, the tire (Tiebar3mm_MIddle Depth) having a separated tire / medium-depth lateral groove, and the tire (Tiebar3mm_Small Depth) having a separated tire / small-depth lateral groove in FIG. 5. FIGS. 5 to 7 show an experiment on the noise reduction effect when combining a tire and an extended form based on a cross-sectional view in the depth direction, and the results thereof.

[0060] In FIG. 5, the non-separated tire 14 means a tire without separation from the longitudinal groove 20, and the separated tire 15 means a tire with separation from the longitudinal groove 20. Further, the tires 14 and 15 may have a flat surface and a shape that becomes deeper in a parabolic shape.

[0061] The non-separated tire 14 is configured to connect the inner walls of the lateral groove 30 to each other without separation from the longitudinal groove 20.

[0062] The separated tire 15 is configured to connect the inner walls of the lateral groove 30 to each other while being separated from the longitudinal groove 20.

[0063] The tires 14 and 15 may be located on the inner bottom surface of the lateral groove 30 whose starting position is from 0 to 3 mm from the longitudinal groove 20.

[0064] The tire with non-separated tie bar / lateral groove of large depth (Tiebar0mm_Large Depth) in Fig. 5(a) is configured such that the non-separated tie bar 14 is not separated from the lateral groove 30, and the region of the bottom surface of 2 - 3 mm on the longitudinal groove 20 side of the lateral groove 30 is located 2 - 3 mm below the surface of the tread pattern block 11, and the subsequent bottom surface has a flat surface having substantially the same height as the bottom surface of the longitudinal groove 20.

[0065] The tire with non-separated tie bar / lateral groove of medium depth (Tiebar0mm_MIddle Depth) in Fig. 5(b) is configured such that the non-separated tie bar 14 is not separated from the lateral groove 30, and the region of the bottom surface of 2 - 3 mm on the longitudinal groove 20 side of the lateral groove 30 is located 2 - 3 mm below the surface of the tread pattern block 11, and the subsequent bottom surface is configured to be parabolic and deepen with a maximum depth of about 5 - 7 mm from the surface of the tread pattern block 11.

[0066] The tire with non-separated tie bar / lateral groove of small depth (Tiebar0mm_Small Depth) in Fig. 5(c) is configured such that the non-separated tie bar 14 is not separated from the lateral groove 30, and the region of the bottom surface of 2 - 3 mm on the longitudinal groove 20 side of the lateral groove 30 is located 2 - 3 mm below the surface of the tread pattern block 11, and the subsequent bottom surface is configured to be parabolic and deepen with a maximum depth of about 3 - 4 mm from the surface of the tread pattern block 11.

[0067] The tire with separated tie bar / lateral groove of large depth (Tiebar3mm_Large Depth) in Fig. 5(d) is formed with a separated tie bar 15 whose upper surface is located 2 - 3 mm below the surface of the tread pattern block 11, and the region of the bottom surface of 3 mm after the separated tie bar 15 on the longitudinal groove 20 side of the lateral groove 30 is located 2 - 3 mm below the surface of the tread pattern block 11, and the subsequent bottom surface has a flat surface having substantially the same height as the bottom surface of the longitudinal groove 20.

[0068] The tire with a separating tie bar / middle-depth lateral groove in Fig. 5(e) (Tiebar3mm_MIddle Depth) is formed with a separating tie bar 15 whose upper surface is located 2 - 3 mm below the surface of the tread pattern block 11. The region of the bottom surface 2 - 3 mm after the separating tie bar 15 on the longitudinal groove 20 side of the lateral groove 30 is located 2 - 3 mm below the surface of the tread pattern block 11, and the subsequent bottom surface is configured to deepen in a parabolic shape with a maximum depth of about 5 - 7 mm from the surface of the tread pattern block 11.

[0069] The tire with a separating tie bar / small-depth lateral groove in Fig. 5(f) (Tiebar3mm_Small Depth) is formed with a separating tie bar 15 whose upper surface is located 2 - 3 mm below the surface of the tread pattern block 11. The region of the bottom surface 2 - 3 mm after the separating tie bar 15 on the longitudinal groove 20 side of the lateral groove 30 is located 2 - 3 mm below the surface of the tread pattern block 11, and the subsequent bottom surface is configured to deepen in a parabolic shape with a maximum depth of about 3 - 4 mm from the surface of the tread pattern block 11.

[0070] As a result of the experiment, when applied to the tie bars 14 and 15, the noise decreased slightly compared to a general Ref tire. Also, as a result of evaluating by forming three levels of steps in the depth direction, it was confirmed that there was a clear difference depending on the volume of the lateral groove 30.

[0071] A similar tendency was shown when changing the positions of the tie bars 14 and 15. As shown in Fig. 6(b), it was also confirmed that the noise was reduced in a wide range of 630 - 4,000 Hz based on the frequency region. In the case of changing the positions of the tie bars 14 and 15, there was the same effect according to the positions of the tie bars 14 and 15, and thereby, it was confirmed that when separating from the lateral groove 30 by 0 - 3 mm at the start positions of the tie bars 14 and 15, there was diversity and a noise reduction effect.

[0072] As a result of the experiments of FIGS. 5 to 7 described above, when the lateral groove 30 applying the bottom surface stepped portion 40 and the lateral expansion portion 50 is applied to the cross section in the depth direction and the traveling direction of the tread portion 10, the noise reduction effect is remarkable in terms of pattern noise, and it was confirmed that the noise of the indoor tire alone and the pass by noise are also reduced.

[0073] In the case of the same grounding shape and the same volume of the lateral groove 30, the larger the step difference in the step form with respect to the longitudinal direction of the lateral groove 30 (see FIG. 1), the smaller the air pumping noise generated during steady running.

[0074] The tire 1 of the embodiment of the present invention having the above-described configuration can be applied to various vehicles such as a racing car, an electric vehicle, and a general vehicle.

[0075] Although the technical idea of the present invention described above has been specifically described in the preferred embodiments, it should be noted that the above embodiments are for the purpose of explanation and not for the purpose of limitation. Also, those having ordinary knowledge in the technical field of the present invention will be able to understand that various embodiments are possible within the scope of the technical idea of the present invention. Therefore, the true technical protection scope of the present invention should be determined by the technical idea of the appended claims.

Explanation of Reference Numerals

[0076] 1: Tire 5: Sidewall portion 10: Tread portion 11: Tread pattern block 14: Non-separating tie bar 15: Separating tie bar 20: Longitudinal groove 30: Lateral groove 31: Bottom surface of the lateral groove 40: Bottom surface stepped portion 41: Bottom surface step 50: Lateral expansion portion 51: Sidewall step Extended LG Small: Small extended tire Extended LG Large: Large extended tire Tiebar0mm_Large Depth: Tire with non-separated tiebar / lateral grooves with large depth Tiebar0mm_MIddle Depth: Tire with non-separated tiebar / lateral grooves with middle depth Tiebar0mm_Small Depth: Tire with non-separated tiebar / lateral grooves with small depth Tiebar3mm_Large Depth: Tire with separated tiebar / lateral grooves with large depth Tiebar3mm_MIddle Depth: Tire with separated tiebar / lateral grooves with middle depth Tiebar3mm_Small Depth: Tire with separated tiebar / lateral grooves with small depth

Claims

1. Side wall portions (5) on both sides, A tread portion (10) integrally connecting between the outer circumferences of the side wall portions (5), A longitudinal groove (20) recessed along the running direction in the tread portion (10), A transverse groove (30) recessed in a lateral direction from the longitudinal groove (20) toward the side wall portion (5), and including: The transverse groove (30) Communicates with the longitudinal groove (20) at an end on the longitudinal groove (20) side, A bottom step portion (40) having one or more bottom steps (41) where the bottom surface of the transverse groove (30) becomes deeper as it goes toward the side wall portion (5), An uninterrupted tie bar (14) connecting the inner walls of the transverse groove (30) to each other without being separated from the longitudinal groove (20), The surface height of the uninterrupted tie bar (14) is formed lower than the height of the tire surface A noise-reducing tire, characterized in that.

2. The transverse groove (30) The noise-reducing tire according to claim 1, characterized in that one or more side walls of both side walls include one or more side steps (51) and are formed by a lateral expansion portion (50) whose width expands in multiple steps.

3. The transverse groove (30) The noise-reducing tire according to claim 2, characterized in that the widths of the multi-stage side steps (51) in the longitudinal direction (X-direction) of the transverse groove (30) are configured to sequentially expand in the range of 0.01 mm to 0.1 mm with respect to the width of the transverse groove (30).

4. The side step (51) The noise-reducing tire according to claim 2, characterized in that it has a side surface inclination such that the side on the longitudinal groove (20) side is narrow and becomes wider as it goes toward the side wall portion (5).

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