JP2024076453A - tire - Google Patents

Abstract

[Problem] To provide a tire that makes it possible to improve the measurement performance of tire information by increasing the sensing sensitivity of a functional part. [Solution] In a tire equipped with a functional part 20 having a sensor function for detecting tire information on the back surface of a tread part 1, the functional part 20 has a contact surface 21 that contacts the back surface side of the tread part 1, and when a first projection area S0 is defined by projecting the contact surface 21 onto the tread surface of the tread part 1, a groove area ratio GR0 within the first projection area S0 in a new tire condition is in the range of 0.0%≦GR0<50.0%. [Selected Figure] Figure 2

Description

The present invention relates to a tire equipped with a functional component having a sensor function for detecting tire information, and more specifically, to a tire that makes it possible to improve the measurement performance of tire information by increasing the sensing sensitivity of the functional component.

In order to obtain tire information, functional components (e.g., a sensor unit including a sensor) are installed on the inner surface of the tire (see, for example, Patent Documents 1 to 3). Such functional components are used to detect not only the temperature and inner pressure of the tire, but also the impact force and acceleration received from the road surface while the tire is traveling, as tire information.

However, tire information such as the impact force and acceleration received from the road surface while the tire is traveling is greatly affected by the structural characteristics of the part where the functional parts are installed. Therefore, depending on the mounting position of the functional parts, it may not be possible to ensure sufficient sensing sensitivity of the functional parts.

JP 2021-146875 A JP 2021-60401 A JP 2018-512333 A

The object of the present invention is to provide a tire that enables improved tire information measurement performance by increasing the sensing sensitivity of functional components.

In order to achieve the above object, the present invention provides a tire having a functional part having a sensor function for detecting tire information on a back surface of a tread portion,
The functional part has a contact surface that contacts the back side of the tread portion, and when a first projection area S0 is defined by projecting the contact surface onto the tread surface of the tread portion, a groove area ratio GR0 within the first projection area S0 in a new tire condition is in the range of 0.0%≦GR0<50.0%.

The inventors conducted extensive research into the functional parts installed on the underside of the tread, based on evaluations of actual tires and simulations, and discovered that the positional relationship between the grooves formed in the tread and the functional parts significantly affects the measurement results, which led to the invention.

In other words, in the present invention, when functional parts are installed on the back surface of the tread portion, the functional parts are installed in a position where the overlap with the grooves is as small as possible, so that the impact from the road surface when the tire touches the ground is efficiently transmitted to the functional parts, thereby increasing the sensing sensitivity of the functional parts and improving the measurement performance of tire information. Sensing sensitivity refers to the ability to sensitively detect changes in physical quantities caused by impacts from the road surface, and improving the sensing sensitivity increases the peak-to-peak value of the output waveform, making it possible to accurately grasp the timing at which physical quantities change due to impacts from the road surface.

In the present invention, the functional part has a sensor element that detects tire information, the sensor element is disposed in the contact surface, and when a second projection area S formed by projecting the sensor element onto the tread surface of the tread portion is defined, it is preferable that the groove area ratio GR within the second projection area S in a new tire state is in the range of 0.0%≦GR<20.0%. By thus locating the sensor element in a position where the overlap with the groove is as small as possible, the impact received from the road surface when the tire touches the ground is efficiently transmitted to the sensor element, thereby increasing the sensing sensitivity of the functional part.

When the first projection area S0 is moved from the tread position of a new tire toward the contact surface by the thickness of the rubber in the tread portion to define the first three-dimensional area V0 formed by the path, it is preferable that the groove volume ratio GRV0 in the first three-dimensional area V0 is in the range of 0.0%≦GRV0<30.0%. In this way, by making the volume of the grooves present directly above the functional parts as small as possible, the impact received from the road surface when the tire touches the ground is efficiently transmitted to the functional parts, thereby improving the sensing sensitivity of the functional parts.

When the second projection area S is moved from the tread position of a new tire toward the contact surface by the thickness of the rubber in the tread portion to define the second three-dimensional area V formed by the trajectory, it is preferable that the groove volume ratio GRV in the second three-dimensional area V is in the range of 0.0%≦GRV<20.0%. In this way, by making the volume of the grooves present directly above the sensor element as small as possible, the impact from the road surface when the tire touches the ground is efficiently transmitted to the sensor element, thereby improving the sensing sensitivity of the functional component.

The rate of change RGR0 of the groove area ratio GR0 in the first projection area S0 when the tread is 80% worn relative to the groove area ratio GR0 in the first projection area S0 when the tire is new is preferably within ±10%. The groove area ratio GR0 in the first projection area S0 changes as the tread wears, and decreases in typical tires. By specifying the rate of change RGR0 as described above, the change in the groove area ratio GR0 in the first projection area S0 due to wear becomes smaller, so the effect of increasing sensing sensitivity continues from when the tire is new until it is worn, and high sensing sensitivity can be continuously obtained throughout the tire's wear life.

It is preferable that the rate of change RGR of the groove area ratio GR in the second projection area S when the tread is 80% worn relative to the groove area ratio GR in the second projection area S when the tire is new be within ±5%. The groove area ratio GR in the second projection area S changes as the tread wears, and decreases in typical tires. By specifying the rate of change RGR as described above, the change in the groove area ratio GR in the second projection area S due to wear becomes smaller, so that the effect of increasing sensing sensitivity continues from when the tire is new until it is worn, and high sensing sensitivity can be continuously obtained throughout the tire's wear life.

In tires that employ pitch variation in which grooves formed in the tread portion have a repetitive structure along the tire circumferential direction and the pitch of the repetitive structure varies along the tire circumferential direction, it is preferable that the second projection area S is disposed in a portion where a pitch larger than the intermediate pitch among multiple types of pitches is applied. In other words, by disposing the sensor element in a portion with relatively high rigidity in the tread portion where pitch variation is applied, the impact received from the road surface when the tire touches the ground is efficiently transmitted to the sensor element, thereby increasing the sensing sensitivity of the functional component.

In a tire in which a belt layer is embedded in the tread portion, it is preferable that the second projection area S is disposed within the extension area of the belt layer. By disposing the sensor element within the extension area of the belt layer, deformation of the tread portion due to contact with the ground can be efficiently detected.

The tire of the present invention has markings in the tire side area that allow the position of the sensor element to be identified, and the markings are preferably arranged within a range of ±10° in the tire circumferential direction from the center position of the second projection area S around the tire rotation axis. This allows the position of the sensor element to be recognized from outside the tire, improving the workability of installing and maintaining functional parts.

In the present invention, it is preferable that a container for housing functional parts is fixed to the back surface of the tread portion, and the functional parts are housed in the container. It is preferable that the container is fixed to the back surface of the tread portion with an adhesive. It is preferable that the container is made of vulcanized rubber. Even when such a container is used, the above-mentioned excellent effects can be obtained.

Furthermore, it is preferable that the functional component has a sensor function using a piezoelectric element as the sensor element. When using a functional component having a sensor function using such a piezoelectric element, a remarkable effect can be obtained.

The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. In the case of a pneumatic tire, the inside of the tire can be filled with air, an inert gas such as nitrogen, or other gases.

1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view showing a tread portion of the pneumatic tire of FIG. 1 . FIG. 2 is a plan view showing an installation portion of a functional component in the pneumatic tire of FIG. 1 . 4 is a cross-sectional view taken along the line IV-IV in FIG. 3. FIG. 2 is a perspective view showing a functional part and a housing thereof; FIG. 2 is a perspective cross-sectional view showing a tread portion of the pneumatic tire of FIG. 1 . FIG. 2 is a side view showing a sidewall portion of the pneumatic tire of FIG. 1 . FIG. 4 is a diagram showing an example of an output waveform from a piezoelectric element.

The configuration of the present invention will be described in detail below with reference to the attached drawings. Figures 1 to 7 show a pneumatic tire according to an embodiment of the present invention.

As shown in FIG. 1, the pneumatic tire of this embodiment has a tread portion 1 that extends in the circumferential direction of the tire and forms an annular shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged on the radially inner side of the sidewall portions 2.

A carcass layer 4 is fitted between a pair of bead portions 3, 3. This carcass layer 4 includes multiple reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around a bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition with a triangular cross section is arranged on the outer periphery of the bead core 5.

On the other hand, multiple belt layers 7 are embedded on the outer periphery of the carcass layer 4 in the tread portion 1. These belt layers 7 include multiple reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to a range of, for example, 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layers 7. At least one belt cover layer 8 is arranged on the outer periphery of the belt layers 7, in which reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction, with the aim of improving high-speed durability. Organic fiber cords such as nylon and aramid are preferably used as the reinforcing cords of the belt cover layer 8.

The above-mentioned tire internal structure shows a typical example of a pneumatic tire, but is not limited to this.

As shown in FIG. 2, four circumferential grooves 11 extending in the tire circumferential direction are formed on the tread surface of the tread portion 1. The circumferential grooves 11 include, for example, three circumferential main grooves 11A and one circumferential narrow groove 11B. The circumferential main groove 11A has a groove width in the range of 6.5 mm to 20.0 mm, a groove depth in the range of 5.0 mm to 8.5 mm, and is equipped with a wear indicator. The circumferential main groove 11A and the circumferential narrow groove 11B each have a chamfered portion 12A, 12B, which constitute a part of the circumferential main groove 11A and the circumferential narrow groove 11B, respectively. Therefore, the chamfered portions 12A, 12B are included in the groove area and groove volume.

The tread portion 1 is divided into five rows of land portions 13 by the above-mentioned circumferential grooves 11. Each land portion 13 has a plurality of lug grooves 14 extending in the tire width direction and spaced apart in the tire circumferential direction. Groove components such as sipes may be added to the tread portion 1 as necessary.

In the above pneumatic tire, grooves such as circumferential grooves 11 and lug grooves 14 are formed on the tread surface of the tread portion 1, while as shown in FIG. 1, a cylindrical functional part 20 having a sensor function for detecting tire information is installed on the back surface of the tread portion 1.

As shown in Figures 3 to 5, the functional part 20 is housed inside the housing 30. The housing 30 has a flat bottom 31 fixed to the back surface of the tread 1, a cylindrical side wall 32 protruding from the bottom 31, a housing section 33 formed by the bottom 31 and the side wall 32, and an opening 34 communicating with the housing section 33. The housing 30 is preferably a molded body made of vulcanized rubber. The housing 30 thus configured is fixed to the back surface of the tread 1 by, for example, an adhesive, and the functional part 20 is housed in the housing 30. The functional part 20 is preferably installed on the tread surface of the tread 1 via the housing 30, but may be directly attached to the back surface of the tread 1 without the housing 30. In either case, the functional part 20 has a contact surface 21 that contacts the back surface side of the tread 1. That is, the contact surface 21 is a surface that contacts the back surface of the tread 1 or the surface of the bottom 31 of the housing 30.

The functional part 20 has a structure in which various electronic components are housed inside a housing. The electronic components can be configured to include various sensors, transmitters, receivers, control circuits, batteries, etc. for acquiring tire information. Examples of tire information acquired by the sensors include the internal temperature and internal pressure of the pneumatic tire, and the amount of wear in the tread portion. For example, a temperature sensor or a pressure sensor is used to measure the internal temperature and internal pressure. When detecting the amount of wear in the tread portion, for example, a sensor element 22 made of a piezoelectric element is disposed on the contact surface 21 of the functional part 20, and the sensor element 22 detects an output voltage corresponding to tire deformation during driving, and detects the amount of wear in the tread portion 1 based on the output voltage. In addition, an acceleration sensor or a magnetic sensor can also be used.

As shown in FIG. 2, when a first projection area S0 is defined by projecting the contact surface 21 of the functional part 20 onto the tread surface of the tread portion 1, the groove area ratio GR0 within the first projection area S0 in a new tire state is set in the range of 0.0%≦GR0<50.0%. The groove area ratio GR0 within the first projection area S0 in a new tire state is the ratio of the groove area to the total area of the first projection area S0 projected onto the tread surface of the new tire state.

When the functional part 20 is placed on the back surface of the tread portion 1 in this way, the functional part 20 is placed in a position that minimizes the amount of overlap with the grooves. This allows the impact from the road surface when the tire touches the ground to be transmitted to the functional part 20 efficiently, thereby increasing the sensing sensitivity of the functional part 20 and improving the tire information measurement performance.

Here, if the groove area ratio GR0 in the first projection region S0 in a new tire state is 50% or more, the groove components existing between the road surface and the contact surface 21 of the functional part 20 will increase, and the effect of increasing the sensing sensitivity of the functional part 20 will decrease. In particular, the groove area ratio GR0 in the first projection region S0 in a new tire state is preferably in the range of 0.0%≦GR0≦20.0%, and more preferably in the range of 0.0%≦GR0≦5.0%.

As shown in FIG. 2, when the second projection area S formed by projecting the sensor element 22 onto the tread surface of the tread portion 1 is defined, it is preferable that the groove area ratio GR within the second projection area S in the new tire state is in the range of 0.0%≦GR<20.0%. The groove area ratio GR within the second projection area S in the new tire state is the ratio of the groove area to the total area of the second projection area S projected onto the tread surface in the new tire state. By installing the sensor element 22 in such a position that the overlap with the groove is as small as possible, the impact received from the road surface when the tire touches the ground is efficiently transmitted to the sensor element 22, thereby improving the sensing sensitivity of the functional component 20.

Here, if the groove area ratio GR in the second projection region S in a new tire state is 20% or more, the groove components existing between the road surface and the sensor element 22 of the functional part 20 will increase, and the effect of increasing the sensing sensitivity of the functional part 20 will decrease. In particular, it is preferable that the groove area ratio GR in the second projection region S in a new tire state is in the range of 0.0%≦GR0≦10.0%.

As shown in FIG. 6, when the first projection area S0 is moved from the tread position of the tire in a new state toward the contact surface 21 by the rubber thickness of the tread portion 1 to define the first three-dimensional area V0 formed by the trajectory, the groove volume ratio GRV0 in the first three-dimensional area V0 is preferably in the range of 0.0%≦GRV0<30.0%. The rubber thickness of the tread portion 1 is the thickness of the tread rubber layer laminated on the outside of the reinforcing layer such as the belt layer 7 and the belt cover layer 8 embedded in the tread portion 1, and is the thickness from the tread surface of the tread portion 1 to the reinforcing layer. The groove volume ratio GRV0 in the first three-dimensional area V0 is the ratio of the groove volume to the total volume of the first three-dimensional area V0. In this way, by making the volume of the grooves present in the area directly above the functional part 20 as small as possible, the impact received from the road surface when the tire touches the ground is efficiently transmitted to the functional part 20, so that the sensing sensitivity of the functional part 20 can be improved.

Here, if the groove volume ratio GRV0 in the first three-dimensional region V0 is 30% or more, the groove components existing between the road surface and the contact surface 21 of the functional part 20 will increase, and the effect of increasing the sensing sensitivity of the functional part 20 will decrease. In particular, it is preferable that the groove volume ratio GRV0 in the first three-dimensional region V0 is in the range of 0.0%≦GR0≦10.0%.

As shown in FIG. 6, when the second projection area S is moved from the tread position of a new tire by the rubber thickness of the tread portion 1 toward the contact surface 21, the groove volume ratio GRV in the second three-dimensional area V is preferably in the range of 0.0%≦GRV<20.0%. The groove volume ratio GRV in the second three-dimensional area V is the ratio of the groove volume to the total volume of the second three-dimensional area V. By making the volume of the grooves present in the area directly above the sensor element 22 as small as possible, the impact from the road surface when the tire touches the ground is efficiently transmitted to the sensor element 22, thereby improving the sensing sensitivity of the functional component 20.

Here, if the groove volume ratio GRV in the second three-dimensional region V is 20% or more, the groove components existing between the road surface and the sensor element 22 of the functional part 20 will increase, and the effect of increasing the sensing sensitivity of the functional part 20 will decrease. In particular, it is preferable that the groove volume ratio GRV in the second three-dimensional region V is in the range of 0.0%≦GR0≦10.0%.

Furthermore, the change rate RGR0 of the groove area ratio GR0 in the first projection area S0 in the 80% worn state of the tread portion 1 (i.e., 20% of the remaining tread) relative to the groove area ratio GR0 in the first projection area S0 in the new tire state is preferably within ±10%. For example, if the groove area ratio GR0 in the first projection area S0 in the new tire state is 25%, the groove area ratio GR0 in the first projection area S0 in the 80% worn state of the tread portion 1 is preferably within the range of 22.5% to 27.5%. The groove area ratio GR0 in the first projection area S0 changes as the wear of the tread portion 1 progresses, and decreases in a typical tire. By specifying the change rate RGR0 as described above, the change in the groove area ratio GR0 in the first projection area S0 due to wear is reduced, so that the effect of increasing the sensing sensitivity continues from when the tire is new until it is worn, and high sensing sensitivity can be continuously obtained within the tire wear life.

Here, if the rate of change RGR0 of the groove area ratio GR0 in the first projection area S0 when the tread portion 1 is in an 80% worn state relative to the groove area ratio GR0 in the first projection area S0 when the tire is new falls outside the range of ±10%, the fluctuation in sensing sensitivity within the tire's wear life will increase.

Similarly, the rate of change RGR of the groove area ratio GR in the second projection area S when the tread portion 1 is 80% worn relative to the groove area ratio GR in the second projection area S when the tire is new should be within ±5%. For example, if the groove area ratio GR in the second projection area S when the tire is new is 15%, the groove area ratio GR in the second projection area S when the tread portion 1 is 80% worn should be within the range of 14.25% to 15.75%. The groove area ratio GR in the second projection area S changes as the wear of the tread portion 1 progresses, and decreases in a typical tire. By specifying the rate of change RGR as described above, the change in the groove area ratio GR in the second projection area S due to wear is reduced, so that the effect of increasing the sensing sensitivity continues from when the tire is new until it is worn, and high sensing sensitivity can be continuously obtained within the tire wear life.

Here, if the rate of change RGR of the groove area ratio GR in the second projection area S when the tread portion 1 is in an 80% worn state relative to the groove area ratio GR in the second projection area S when the tire is new falls outside the range of ±5%, the fluctuation in sensing sensitivity within the tire's wear life will increase.

2, the grooves formed in the tread portion 1 have a repeating structure along the tire circumferential direction, and a pitch variation is adopted in which the pitch of the repeating structure varies along the tire circumferential direction. For example, the lug grooves 13 are repeatedly arranged at intervals along the tire circumferential direction, but the size of the circumferential pitch P of the tire varies along the tire circumferential direction. In a tire adopting such pitch variation, it is preferable that the second projection area S (i.e., the sensor element 22) is arranged in a portion where a pitch larger than the intermediate pitch among the multiple types of pitches is applied. For example, if the size of the pitch P is five types and P1<P2<P3<P4<P5, the second projection area S is arranged in a portion where the pitch P4 or P5 is applied. Also, if the size of the pitch P is four types and P1<P2<P3<P4, the second projection area S is arranged in a portion where the pitch P3 or P4 is applied.

In the tread portion 1 to which pitch variation is applied in this manner, the sensor element 22 is disposed in a portion having a relatively high rigidity, so that the impact received from the road surface when the tire touches the ground is efficiently transmitted to the sensor element 22, thereby improving the sensing sensitivity of the functional component 20. For the same reason, it is preferable that the JIS-A hardness of the tread rubber layer constituting the tread portion 1 is 62 or more. The JIS-A hardness referred to here is the durometer hardness measured in accordance with JIS-K6253 using an A-type durometer at a temperature of 20°C.

In a tire in which the belt layer 7 is embedded in the tread portion 1, it is preferable that the second projection area S is disposed within the extending area of the belt layer 7. That is, in the tire meridian cross section shown in FIG. 1, it is preferable that the sensor element 22 of the functional part 20 is disposed within the extending area of the belt layer 7. By adopting such an arrangement, deformation of the tread portion 1 due to contact with the ground can be efficiently detected. In particular, as shown in FIG. 2, it is preferable that the distance in the tire width direction between the tire center line CL and the center position O of the second projection area S is 20% or less of the maximum width of the belt layer 7.

As shown in FIG. 7, the pneumatic tire described above may have a marking 23 in the tire side region (the region where the brand is displayed on the outer surface of the sidewall portion 2) that allows the position of the sensor element 22 to be identified. Such marking 23 may be arranged within a range of ±10° in the tire circumferential direction from the center position O of the second projection region S around the tire rotation axis A. This allows the position of the sensor element 22 to be recognized from outside the tire, improving the workability in installing and maintaining the functional component 20. Note that the marking 23 is preferably a dedicated display for identifying the position of the sensor element 22, but in some cases, it is also possible to use an existing display such as a wear indicator mark as the marking 23.

In a tire having a tire size of 225/45ZR18 and equipped with a functional part having a sensor function for detecting tire information on the back surface of the tread portion, the functional part having a sensor function using a piezoelectric element as a sensor element, a first projection area S0 formed by projecting the contact surface of the functional part onto the tread surface of the tread portion, a second projection area S formed by projecting the sensor element of the functional part onto the tread surface of the tread portion, a first three-dimensional area V0 formed by the trajectory when the first projection area S0 is moved from the tread position of the tire in a new state toward the contact surface by the rubber thickness of the tread portion, and a second projection area S formed by the trajectory when the second projection area S is moved from the tread position of the tire in a new state toward the contact surface by the rubber thickness of the tread portion. When the second three-dimensional region V is defined, the groove area ratio GR0 in the first projection region S0 in the new tire state, the groove area ratio GR in the second projection region S in the new tire state, the groove volume ratio GRV0 in the first three-dimensional region V0, the groove volume ratio GRV in the second three-dimensional region V, the rate of change RGR0 of the groove area ratio GR0 in the first projection region S0 in the 80% worn state of the tread portion relative to the groove area ratio GR0 in the first projection region S0 in the new tire state, and the rate of change RGR of the groove area ratio GR in the second projection region S in the 80% worn state of the tread portion relative to the groove area ratio GR in the second projection region S in the new tire state were set as shown in Table 1. The tires of the comparative example and examples 1 to 8 were manufactured. The functional parts were attached to the back surface of the tread portion via a container.

The sensing sensitivity of these test tires was evaluated when new and when worn using the test method below, and the results are shown in Table 1.

Sensing Sensitivity:
Each test tire was mounted on a wheel with a rim size of 18×7.5JJ and attached to a drum testing machine, and a running test was performed with an air pressure of 230 kPa, a load of 60% of the maximum load capacity, and a speed of 30 km/h, and the output detected by the sensor element (piezoelectric element) was recorded. FIG. 8 shows an example of an output waveform from a piezoelectric element. In this output waveform, when the part where the functional part is installed in the tread part touches the ground, a negative peak and a positive peak are formed in the output of the piezoelectric element with the passage of time T, and a peak-to-peak value V is obtained. Then, the average value of the peak-to-peak value V of the output waveform obtained in each of the 10 measurements was calculated. The evaluation results were shown as an index using the average value of the peak-to-peak value V of the output waveform, with the comparative example being 100. The larger the index value, the better the sensing sensitivity. Such sensing sensitivity was evaluated when the tire was new and when the tread part was 50% worn. The sensing accuracy when new is an index value based on the comparative example when new, and the sensing accuracy when worn is an index value based on the comparative example when worn.

As can be seen from Table 1, the tires of Examples 1 to 8 had better sensing sensitivity of the functional parts compared to the comparative example.

The present disclosure includes the following inventions [1] to [13].
Invention [1] is a tire having a functional part having a sensor function for detecting tire information on the back surface of a tread portion, the functional part having a contact surface that contacts the back surface side of the tread portion, and when a first projection area S0 is defined by projecting the contact surface onto the tread surface of the tread portion, a groove area ratio GR0 within the first projection area S0 in a new tire condition is in the range of 0.0%≦GR0<50.0%.
Invention [2] is the tire according to invention [1], characterized in that the functional part has a sensor element that detects tire information, the sensor element is arranged in the contact surface, and when a second projection area S is defined by projecting the sensor element onto the tread surface of the tread portion, a groove area ratio GR within the second projection area S in a new tire condition is in the range of 0.0%≦GR<20.0%.
Invention [3] is the tire according to invention [1] or [2], characterized in that when a first three-dimensional region V0 is defined by a trajectory when the first projection region S0 is moved from the tread position of the tire in a new state toward the contact surface by an amount equivalent to the rubber thickness of the tread portion, a groove volume ratio GRV0 within the first three-dimensional region V0 is in the range of 0.0%≦GRV0<30.0%.
Invention [4] is the tire according to Invention [2], characterized in that when a second three-dimensional region V is defined that is formed by a trajectory when the second projection region S is moved from the tread position of the tire in a new state toward the contact surface by an amount equivalent to the rubber thickness of the tread portion, a groove volume ratio GRV within the second three-dimensional region V is in the range of 0.0%≦GRV<20.0%.
Invention [5] is a tire according to any one of inventions [1] to [4], characterized in that a rate of change RGR0 of the groove area ratio GR0 within the first projection region S0 in an 80% worn state of the tread portion relative to the groove area ratio GR0 within the first projection region S0 in a new tire state is within ±10%.
Invention [6] is the tire according to invention [2] or [4], characterized in that a rate of change RGR of the groove area ratio GR within the second projection region S in an 80% worn state of the tread portion relative to the groove area ratio GR within the second projection region S in a new tire state is within ±5%.
Invention [7] is a tire according to invention [2], [4] or [6], characterized in that in a tire employing pitch variation in which grooves formed in the tread portion have a repetitive structure along the tire circumferential direction and the pitch of the repetitive structure varies along the tire circumferential direction, the second projected area S is disposed in a portion where a pitch larger than an intermediate pitch among a plurality of types of pitches is applied.
Invention [8] is the tire according to invention [2], [4], [6] or [7], characterized in that in the tire having a belt layer embedded in the tread portion, the second projected area S is arranged within the extending area of the belt layer.
Invention [9] is a tire according to invention [2], [4], [6], [7] or [8], characterized in that the tire has an engraving in the tire side region that enables the position of the sensor element to be identified, and the engraving is arranged within a range of ±10° in the tire circumferential direction around the tire rotation axis from the center position of the second projection region S.
Invention [10] is a tire according to any one of inventions [1] to [9], characterized in that a container for accommodating the functional parts is fixed to the back surface of the tread portion, and the functional parts are accommodated in the container.
Invention [11] is the tire according to invention [10], characterized in that the container is fixed to the back surface of the tread portion by an adhesive.
Invention [12] is the tire according to invention [10] or [11], characterized in that the container is made of vulcanized rubber.
Invention [13] is the tire according to any one of inventions [1] to [12], characterized in that the functional part has a sensor function using a piezoelectric element as a sensor element.

REFERENCE SIGNS LIST 1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt cover layer 11 circumferential groove 11A circumferential main groove 11B circumferential narrow groove 12A, 12B chamfered portion 13 land portion 14 lug groove 20 functional part 21 contact surface 22 sensor element 23 marking 30 container

Claims (13)

In a tire having a functional part having a sensor function for detecting tire information on the back surface of the tread portion,
The functional part has a contact surface that contacts the back side of the tread portion, and when a first projection area S0 is defined by projecting the contact surface onto the tread surface of the tread portion, a groove area ratio GR0 within the first projection area S0 in a new tire condition is in the range of 0.0%≦GR0<50.0%. The tire according to claim 1, characterized in that the functional part has a sensor element that detects tire information, the sensor element is disposed in the contact surface, and when a second projection area S is defined by projecting the sensor element onto the tread surface of the tread portion, the groove area ratio GR in the second projection area S in a new tire state is in the range of 0.0%≦GR<20.0%. The tire according to claim 1, characterized in that when a first three-dimensional region V0 is defined, which is formed by a path when the first projection region S0 is moved from the tread position of the tire in a new state toward the contact surface by the rubber thickness of the tread portion, the groove volume ratio GRV0 within the first three-dimensional region V0 is in the range of 0.0%≦GRV0<30.0%. The tire according to claim 2, characterized in that when a second three-dimensional region V is defined, which is formed by a path when the second projection region S is moved from the tread position of the tire in a new state toward the contact surface by the rubber thickness of the tread portion, the groove volume ratio GRV within the second three-dimensional region V is in the range of 0.0%≦GRV<20.0%. The tire described in claim 1, characterized in that the rate of change RGR0 of the groove area ratio GR0 in the first projection area S0 when the tread portion is in an 80% worn state relative to the groove area ratio GR0 in the first projection area S0 when the tire is new is within ±10%. The tire described in claim 2, characterized in that the rate of change RGR of the groove area ratio GR in the second projection area S when the tread portion is 80% worn relative to the groove area ratio GR in the second projection area S when the tire is new is within ±5%. The tire described in claim 2 is characterized in that the grooves formed in the tread portion have a repeating structure along the tire circumferential direction, and the second projection area S is disposed in a portion where a pitch larger than a middle pitch among multiple types of pitches is applied in a tire that employs pitch variation. The tire according to claim 2, characterized in that in a tire in which a belt layer is embedded in the tread portion, the second projected area S is located within the extension area of the belt layer. The tire described in claim 2 has an inscription in the tire side area that makes the position of the sensor element identifiable, and the inscription is positioned within a range of ±10° in the tire circumferential direction from the center position of the second projection area S around the tire rotation axis. A tire according to any one of claims 1 to 9, characterized in that a container for housing the functional parts is fixed to the back surface of the tread portion, and the functional parts are housed in the container. The tire according to claim 10, characterized in that the container is fixed to the back surface of the tread portion by adhesive. The tire according to claim 10, characterized in that the housing is made of vulcanized rubber. A tire according to any one of claims 1 to 9, characterized in that the functional part has a sensor function using a piezoelectric element as a sensor element.

Images