Tilting vehicle tire

Abstract

This tilting vehicle tire comprises: a tire case that extends over a pair of bead portions; and a tread that is provided on the outer side in the tire radial direction of the tire case. A groove formed on the tread surface has a greater groove depth on the vehicle-mounted inner side than on the vehicle-mounted outer side.

Description

Tilting vehicle tires

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to tires for leaning vehicles.

[0002] Japanese Patent Application Laid-Open Publication No. 2023-51041 discloses a vehicle that has three or more wheels and turns while leaning like a two-wheeled vehicle.

[0003] An example of such a vehicle is the Lean Multi Wheel (LMW) vehicle, which has no restrictions on the maximum lean angle during turning, unlike motorcycles. Unlike motorcycles, an LMW vehicle maintains its lean angle through a balance between the center of gravity and centrifugal force, so the wheels on the outside and inside of a turn are approximately equal.

[0004] On the other hand, in the case of tilting mobility vehicles (hereinafter referred to as "tilting vehicles") that have been proposed recently, the maximum tilt angle when turning is limited to prevent tipping over when stationary, and when turning at high speed, an imbalance occurs between the ground contact conditions of the wheels on the inside and outside of the turn.

[0005] Specifically, a greater load acts on the inside shoulder of the wheel on the outside of a turn than on the outside shoulder of the wheel on the inside of a turn. As a result, the inside shoulder wears out faster than the outside shoulder. In other words, a difference in the amount of wear occurs between the inside shoulder and the outside shoulder. Moreover, because the shoulders only come into contact with the ground during turns, the difference in wear cannot be reduced during straight-line driving, and the difference in wear continues to widen as driving progresses.

[0006] The present disclosure aims to improve the wear resistance of the shoulder portion on the inside of the vehicle mounting surface.

[0007] The tilting vehicle tire according to the first aspect has a tire case spanning a pair of bead portions and a tread provided on the tire radially outer side of the tire case, and the groove depth on the inner side mounted on the vehicle of the grooves formed on the tread surface is greater than the groove depth on the outer side mounted on the vehicle.

[0008] In this tilting vehicle tire, the groove depth on the inside of the tread surface is greater than the groove depth on the outside of the tread surface, so even if the inside of the tread surface wears faster than the outside of the tread surface, the difference between the remaining groove depth on the inside of the tread surface and the remaining groove depth on the outside of the tread surface is prevented from widening.

[0009] In a second aspect, in the tilting vehicle tire according to the first aspect, when the length of the contour of the tread surface in the tire axial cross section is L and the position of L / 8 along the contour from the tire equatorial plane is taken as the 1 / 8 point, the maximum groove depth on the vehicle mounting inner side is greater than the maximum groove depth on the vehicle mounting outer side, at least within the contact area in the region axially outward from the 1 / 8 point.

[0010] In this tilting vehicle tire, the difference between the remaining grooves on the inside of the vehicle mounting surface and the remaining grooves on the outside of the vehicle mounting surface is prevented from widening, mainly in the area from the 1 / 8 point where the tire contacts the ground during cornering to the outside in the axial direction of the tire.

[0011] According to the present disclosure, it is possible to improve the wear resistance of the shoulder portion on the inside of the vehicle mounting surface.

[0012] FIG. 1 is a front view schematically showing the state of a tilting vehicle when cornering. FIG. 2 is a development view showing a tread pattern of the tire for a tilting vehicle according to the present embodiment. FIG. 3 is a cross-sectional view taken along arrow 3-3 in FIG. 2 , showing the tire for a tilting vehicle according to the present embodiment. FIG. 4 is a diagram showing the difference in tread gauge in the tire axial direction for Examples and Comparative Examples. FIG. 5 is a diagram showing the difference in wear energy in the tire axial direction for Examples and Comparative Examples due to differences in groove depth. FIG. 6 is a diagram showing the difference in wear energy in the tire axial direction for Examples and Comparative Examples due to differences in negative rate. FIG. 7 is a diagram showing the difference in wear energy in the tire axial direction for Examples and Comparative Examples due to differences in tread gauge.

[0013] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing are the same or similar components. Note that duplicated explanations and reference numerals may be omitted in the embodiments described below. Furthermore, all drawings used in the following description are schematic, and the dimensional relationships, ratios, etc. of each element shown in the drawings do not necessarily match those in reality. Furthermore, the dimensional relationships, ratios, etc. of each element between multiple drawings do not necessarily match.

[0014] In the drawings, the direction of arrow C indicates the tire circumferential direction, the direction of arrow R indicates the tire radial direction, and the direction of arrow W indicates the tire width direction. The tire radial direction means the direction perpendicular to the tire rotation axis (not shown). The tire width direction means the direction parallel to the tire rotation axis (arrow X direction). The tire width direction can also be referred to as the tire axial direction. Furthermore, "IN" indicates the inner side when mounted on a vehicle, and "OUT" indicates the outer side when mounted on a vehicle.

[0015] 1, the tilting vehicle 100 tilts when turning, but the maximum tilt angle when turning is limited to prevent tipping over when stationary, and has the characteristic that when turning at high speed, an imbalance occurs between the ground contact state of the wheel 12 on the inside of the turn and the ground contact state of the wheel 14 on the outside of the turn. For this reason, the load F14 acting on the shoulder portion 26 on the inside of the vehicle mounting of the wheel 14 on the outside of the turn is greater than the load F12 acting on the shoulder portion 26 on the outside of the vehicle mounting of the wheel 12 on the inside of the turn.

[0016] In FIG. 2 , the tire 10 for a tilting vehicle according to this embodiment has a tire case 18 spanning a pair of bead portions 16 and a tread 20 provided on the tire radial direction outer side of the tire case 18.

[0017] As shown in FIG. 2 , grooves 22A, 22B, 24A, and 24B are formed on the surface of the tread 20. As shown in FIG. 3 , the groove depth D on the vehicle-mounted inner side of the grooves 22A, 22B, 24A, and 24B formed on the tread surface is set to be greater than the groove depth on the vehicle-mounted outer side. In FIG. 2 , the length of the contour of the tread surface in the tire axial cross section is defined as L, and the position along the contour at L / 8 from the tire equatorial plane is defined as ⅛ point T. The region axially outward from ⅛ point T is referred to as a shoulder portion 26. As an example, within at least the contact zone of the region axially outward from ⅛ point T (shoulder portion 26), the maximum groove depth Dimax on the vehicle-mounted inner side is set to be greater than the maximum groove depth Domax on the vehicle-mounted outer side. Here, groove depth D is measured in the normal direction to the tread surface. The contact zone is the area that contacts the ground at a certain inclination angle, and is indicated by an ellipse in FIG. 2 , for example. When the left and right tires 10 are inclined at the same inclination angle, there are contact areas on the vehicle-mounted inner side and on the vehicle-mounted outer side. In comparing the two contact areas, it is sufficient that the maximum groove depth Dimax on the vehicle-mounted inner side is set larger than the maximum groove depth Domax on the vehicle-mounted outer side. The same applies to the thickness and negative ratio of the tread 20, which will be described later.

[0018] In FIG. 4 , squares indicate the outer side of the example, circles indicate the inner side of the example, and crosses indicate the inner side of the comparative example. The thickness (tread gauge) of the tread 20 on the inner side may be greater than the thickness of the tread 20 on the outer side. As an example, in at least the contact area in the region (shoulder portion 26) axially outward from the ⅛ point T, the thickness of the tread 20 on the inner side is greater than the thickness of the tread 20 on the outer side. In the example shown in FIG. 4 , the maximum thickness Timax of the tread 20 is greater than the maximum thickness Tomax of the tread 20 on the outer side (Timax > Tomax). Note that the thickness distribution of the tread 20 is not limited to this and can be changed as desired.

[0019] In Figure 2, if the ratio of the area of ​​the grooves 22A, 22B, 24A, and 24B on the tread surface to the area of ​​the tread surface is defined as a negative ratio, the negative ratio on the vehicle-mounted inner side may be set to be smaller than the negative ratio on the vehicle-mounted outer side. As an example, in the region (shoulder portion 26) axially outward from the ⅛ point T, the negative ratio on the vehicle-mounted inner side is smaller than the negative ratio on the vehicle-mounted outer side. In other words, the proportion of land areas without grooves on the tread surface is larger on the vehicle-mounted inner side than on the vehicle-mounted outer side, and the tread rigidity is higher.

[0020] In this embodiment, on the vehicle-mounted inner side, the groove 22A is provided on the side closer to the tire equatorial plane CL, and the groove 22B is provided on the side farther from the tire equatorial plane CL. The grooves 22A and 22B are provided alternately in the tire circumferential direction.

[0021] On the vehicle-mounted outer side, the groove 24A extends from the tread edge side past the 1 / 8 point T to near the tire equatorial plane CL. The groove 24B terminates from the tread edge side further outward in the tire width direction than the 1 / 8 point T. The positions of the ends of the grooves 24A and 24B on the tread edge side are equal in the tire width direction. The groove width of the groove 24B at the end on the tire equatorial plane CL side is partially expanded. The grooves 24A and 24B are alternately provided in the tire circumferential direction. The arrangement and shape of each groove are not limited to the example shown in the figure and can be changed as desired.

[0022] (Operation) This embodiment is configured as described above, and its operation will be described below. Referring to Figures 2 and 3, in the tilting vehicle tire 10 according to this embodiment, the groove depth D on the vehicle mounting inner side is greater than the groove depth D on the vehicle mounting outer side for the grooves 22A, 22B, 24A, and 24B formed on the tread surface. In particular, in at least the ground contact region in the region (shoulder portion 26) axially outward from the ⅛ point T, the maximum groove depth Dimax on the vehicle mounting inner side is set greater than the maximum groove depth Domax on the vehicle mounting outer side. Therefore, even if the wear on the vehicle mounting inner side of the shoulder portion of the tread 20 is faster than the wear on the vehicle mounting outer side, the difference between the remaining grooves 22A and 22B on the vehicle mounting inner side and the remaining grooves 24A and 24B on the vehicle mounting outer side is prevented from widening in the region (shoulder portion 26) axially outward from the ⅛ point T that mainly comes into contact with the ground during cornering. In this way, the difference between the remaining grooves 22A, 22B on the vehicle mounting inner side and the remaining grooves 24A, 24B on the vehicle mounting outer side is unlikely to widen.

[0023] Furthermore, the thickness of the tread 20 on the vehicle-mounted inner side is greater than the thickness of the tread 20 on the vehicle-mounted outer side. In particular, the thickness of the tread 20 on the vehicle-mounted inner side is greater than the thickness of the tread 20 on the vehicle-mounted outer side, at least in the contact area in the region (shoulder portion 26) axially outward from the ⅛ point T (in FIG. 4 , Timax > Tomax). Therefore, even if the wear on the vehicle-mounted inner side of the shoulder portion of the tread 20 is faster than the wear on the vehicle-mounted outer side, the difference between the remaining thickness of the tread 20 on the vehicle-mounted inner side and the remaining thickness of the tread 20 on the vehicle-mounted outer side is prevented from widening in the region (shoulder portion 26) axially outward from the ⅛ point T that mainly contacts the tire during cornering. In this way, a difference in the amount of wear is unlikely to occur between the vehicle-mounted inner side and the vehicle-mounted outer side.

[0024] Furthermore, in Figure 2, the negative ratio on the vehicle mounting inner side is smaller than the negative ratio on the vehicle mounting outer side. In particular, in the region (shoulder portion 26) axially outward from 1 / 8 point T, the negative ratio on the vehicle mounting inner side is smaller than the negative ratio on the vehicle mounting outer side. Therefore, the tread rigidity on the vehicle mounting inner side is higher than the tread rigidity on the vehicle mounting outer side. As a result, even if a greater load acts on the vehicle mounting inner side shoulder portion 26 of the wheel 14 on the outer side of a turn than on the vehicle mounting outer side shoulder portion 26, a difference in the amount of wear is unlikely to occur between the vehicle mounting inner side and the vehicle mounting outer side in the region (shoulder portion 26) from 1 / 8 point T to the axially outward side of the tire, which mainly comes into contact with the ground during a turn. In this way, a difference in the amount of wear is unlikely to occur between the vehicle mounting inner side and the vehicle mounting outer side of the tread 20.

[0025] Figure 5 shows the results of a simulation calculation of the difference in wear energy in the tire width direction between an example having a configuration in which the groove depth on the vehicle-mounted inner side is greater than the groove depth on the vehicle-mounted outer side and a comparative example not having this configuration. Figure 6 shows the results of a simulation calculation of the difference in wear energy in the tire width direction between an example having a configuration in which the negative rate on the vehicle-mounted inner side is smaller than the negative rate on the vehicle-mounted outer side and a comparative example not having this configuration. Figure 7 shows the results of a simulation calculation of the difference in wear energy in the tire width direction between an example having a configuration in which the thickness of the tread 20 on the vehicle-mounted inner side is greater than the thickness of the tread 20 on the vehicle-mounted outer side and a comparative example not having this configuration. In both cases, it can be seen that the wear energy of the shoulder portion on the vehicle-mounted inner side is significantly reduced compared to the shoulder portion on the vehicle-mounted outer side.

[0026] As described above, according to this embodiment, it is possible to improve the wear resistance of the shoulder portion on the inside of the vehicle mounting surface, and also to provide an improved tire for a tilting vehicle.

[0027] [Other Embodiments] Although one example of an embodiment of the present disclosure has been described above, the embodiment of the present disclosure is not limited to the above, and it goes without saying that various modifications can be made without departing from the spirit of the present disclosure.

[0028] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. It is believed that one embodiment of the present disclosure can be a technology that contributes to "No. 12: Responsible Consumption and Production" and "No. 13: Take concrete measures against climate change."

[0029] The disclosure of Japanese Patent Application No. 2024-67073, filed on April 17, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A tilting vehicle tire having a tire case spanning a pair of bead portions and a tread provided on the tire radially outer side of the tire case, wherein the groove depth on the inner side of the tread surface is greater than the groove depth on the outer side of the tread surface.

2. A tilting vehicle tire as set forth in claim 1, wherein, when the length of the contour of the tread surface in the tire axial cross section is L and the position of L / 8 along the contour from the tire equatorial plane is the 1 / 8 point, the maximum groove depth on the vehicle mounting inner side is greater than the maximum groove depth on the vehicle mounting outer side, at least within the contact area in the region axially outward from the 1 / 8 point.

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