Stiffness-adjustable device

Abstract

To provide a better stiffness-adjustable device.SOLUTION: A stiffness-adjustable device 10 comprises: a stiffness-adjustable member 24 that is removably provided in a tire inner cavity 33 of a tire 30 having a tread portion 40 with a tread surface 41; and a control unit 18 that controls the stiffness of the stiffness-adjustable member 24 by providing a power source 16 to the stiffness-adjustable member 24. The control unit 18 changes the stiffness of the tread portion 40 by varying the stiffness of the stiffness-adjustable member 24.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a variable stiffness device. [Background technology]

[0002] Tires mounted on vehicles are required to have steering stability and ride comfort during driving. These two performance characteristics are mutually contradictory. In other words, increasing tire stiffness improves steering stability, but increasing tire stiffness reduces ride comfort. For example, Patent Document 1 discloses a tire stiffness varying device that includes a stiffness variable member and a control unit that changes the stiffness of the stiffness variable member. The stiffness variable member is made of a magnetic elastomer and is disposed between an outer layer having a tread contact surface and an inner layer located radially inward of the outer layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-165076 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a superior variable stiffness device. [Means for solving the problem]

[0005] One embodiment of the stiffness varying device of the present invention comprises a stiffness varying member that is removably provided on a tire inner cavity surface of a tire having a tread portion having a tread surface, and a control unit that controls the stiffness of the stiffness varying member by supplying a power source to the stiffness varying member, wherein the control unit is a stiffness varying device that changes the stiffness of a portion of the tread portion in the tire circumferential direction by changing the stiffness of the stiffness varying member. Effect of the Invention

[0006] The stiffness varying device of the present invention is superior to the conventional devices in that it is capable of varying the stiffness of a portion of the tread portion in the tire circumferential direction. [Brief description of the drawings]

[0007] [Figure 1] 1 is a block diagram showing a stiffness varying device according to an embodiment of the present invention; [Diagram 2] 1 is a meridian cross-sectional view illustrating a tire equipped with a stiffness varying device according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a plan view showing a schematic diagram of the stiffness variable member according to the present embodiment. [Figure 4A] FIG. 1 is a schematic diagram (1) for explaining the operation of the stiffness varying device according to the present embodiment. [Figure 4B] FIG. 4 is a schematic diagram (2) for explaining the operation of the stiffness varying device according to the present embodiment. [Diagram 5] FIG. 4 is a schematic diagram (3) for explaining the operation of the stiffness varying device according to the present embodiment. [Figure 6A] FIG. 4 is a schematic diagram (4) for explaining the operation of the stiffness varying device according to the present embodiment. [Figure 6B] FIG. 5 is a schematic diagram (5) for explaining the operation of the stiffness varying device according to the present embodiment. [Figure 6C] FIG. 6 is a schematic diagram (6) for explaining the operation of the stiffness varying device according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The embodiments of the present invention relate to the following aspects.

[0009] [Aspect 1] A variable stiffness member that is removably provided on a tire cavity surface of a tire having a tread portion having a tread surface; a control unit that controls the stiffness of the stiffness variable member by supplying a power source to the stiffness variable member, The control unit changes the rigidity of the rigidity variable member, thereby changing the rigidity of a portion of the tread portion in the tire circumferential direction. [Aspect 2] 2. The stiffness varying device according to aspect 1, wherein the control unit increases stiffness of a portion of the tread portion that comes into contact with a road surface in the tire for a drive wheel when a vehicle equipped with the tire is accelerating. [Aspect 3] 3. The stiffness varying device according to aspect 1 or 2, wherein the control unit increases stiffness of a portion of the tread portion that comes into contact with a road surface in the tire for a front wheel when braking a vehicle equipped with the tire. [Aspect 4] The rigidity varying device according to any one of aspects 1 to 3, wherein the control unit uses the outer edge of the tire circumferential side of the contact surface of the tire that contacts the road surface as a boundary, and makes the rigidity of the tread portion on a side away from the contact surface from the boundary higher than the rigidity of the tread portion of the contact surface. [Aspect 5] 5. The stiffness varying device according to any one of aspects 1 to 4, wherein the control unit varies the stiffness of the stiffness variable member based on predetermined sensor output information. [Aspect 6] The rigidity variable member has a width direction member that is in contact with a tire cavity surface exposed to the tire cavity surface and extends in a tire width direction, 6. The rigidity varying device according to any one of aspects 1 to 5, wherein a plurality of the width direction members are arranged at predetermined intervals in the tire circumferential direction. [Aspect 7] A tire in which the stiffness varying device according to any one of the first to sixth aspects is used.

[0010] 1. Overall structure Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings. In the following description, the tire radial direction refers to a direction perpendicular to the tire rotation axis, the tire radial inner side refers to a side toward the tire rotation axis in the tire radial direction, and the tire radial outer side refers to a side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to a direction around the tire rotation axis as a central axis. Furthermore, the tire width direction refers to a direction parallel to the tire rotation axis, the tire width inner side refers to a side toward the tire equatorial plane (tire equatorial line) in the tire width direction, and the tire width outer side refers to a side away from the tire equatorial plane in the tire width direction. The tire equatorial plane CL refers to a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width of the tire. "Along" a certain reference includes following a direction within a range of less than ±15° with respect to a certain reference. Furthermore, turning includes a case where a user driving a vehicle changes direction by steering. Furthermore, turning is not limited to changing direction so that the vehicle draws a circle, but also includes lane changing.

[0011] Similarly, in the following description, a regular rim refers to an "applicable rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by ETRTO.

[0012] Similarly, in the following explanation, normal internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value specified in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO. Also, normal load refers to the "maximum load capacity" specified by JATMA, the maximum value specified in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO.

[0013] A stiffness varying device according to an embodiment is applied to a tire mounted on a vehicle. As shown in FIG. 1, the stiffness varying device 10 includes a sensor unit 12, an input unit 14, a power source 16, a control unit 18, a power transmission unit 20, a power receiving unit 22, and a stiffness variable member 24. In the stiffness varying device 10, the power receiving unit 22 and the stiffness variable member 24 are provided on the tire 30, and the input unit 14, the power source 16, the control unit 18, and the power transmission unit 20 are provided on the vehicle body 31 side. In the stiffness varying device 10, the input unit 14, the power source 16, and the power transmission unit 20 are connected to the control unit 18 via a bus. The power receiving unit 22 is connected to the control unit 18 via a communication network such as wireless LAN or Bluetooth (registered trademark). Although an example in which the sensor unit 12 is installed on the vehicle body 31 via a bus is shown in FIG. 1, the present invention is not limited to this, and includes a case in which the sensor unit 12 is installed on the tire 30. When the sensor unit 12 is installed on the tire 30, it is connected to the control unit 18 via the above-mentioned communication network.

[0014] The sensor unit 12 may use, for example, an air pressure sensor, an acceleration sensor, and an image sensor. The air pressure sensor may be provided on the tire 30 to which the rigidity variable member 24 is applied, or on a rim (not shown) attached to the tire 30. The air pressure sensor detects the air pressure of the tire 30 when the rim is attached, and the detected air pressure information is used as sensor output information. The acceleration sensor is provided on the tire 30 to which the rigidity variable member 24 is applied, and detects acceleration acting on the tire 30 in the travel direction, left and right directions, and up and down directions perpendicular to the travel direction and left and right directions, and the obtained acceleration information is used as sensor output information. The image sensor is provided on the vehicle body 31 to which the tire 30 to which the rigidity variable member 24 is applied is mounted. The image sensor may use, for example, a visible light camera, a LiDAR, a radar, and a sonic sensor. The image sensor captures an image of a space including a road surface in front of the vehicle, and uses the obtained image data as sensor output information. The sensor unit 12 outputs the detected sensor output information to the control unit 18.

[0015] The input unit 14 is a device with which the user selects and inputs a setting mode for the stiffness variable member 24, and includes, for example, an operation switch or an operation panel. The setting modes may include, for example, a normal mode, a high-speed mode, and an automatic mode. The normal mode is a driving mode that prioritizes the ride comfort of the user in the vehicle. The high-speed mode is a driving mode that is set to improve driving performance and is suitable for, for example, circuit driving. The automatic mode is a driving mode in which the stiffness variable device 10 performs control intermediate between the high-speed mode and the normal mode depending on the driving conditions. The input unit 14 outputs input information based on the result of the user's operation to the control unit 18.

[0016] The power source 16 is, for example, a battery mounted on a vehicle body 31 on which a tire 30 to which the stiffness variable device 10 is applied is mounted.

[0017] The control unit 18 is composed of a microcomputer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc., and controls the operation of the stiffness varying device 10. In particular, the control unit 18 realizes various functions related to the stiffness varying device 10 by reading out a predetermined program stored in a storage unit (not shown). That is, information processing by software stored in the storage unit is specifically realized by the control unit 18, which is an example of hardware, thereby executing each mechanism described below. The control unit 18 is not limited to being single, and may be multiple for each function.

[0018] The control unit 18 has an input processing unit 26 and a stiffness control unit 28. That is, the control unit 18 functions as the input processing unit 26 and the stiffness control unit 28 by executing various programs stored in the storage unit. The control unit 18 calculates a target control amount based on input information selected by a user and sensor output information obtained from the sensor unit 12. The control unit 18 also controls the stiffness of a predetermined stiffness variable member 24 based on the control amount obtained by the input processing.

[0019] The input processing unit 26 receives or acquires sensor output information and input information via a communication network. The input processing unit 26 calculates a predetermined control amount based on the sensor output information and input information. For example, the input processing unit 26 calculates a control amount that provides an appropriate stiffness for the stiffness variable member 24 based on information obtained from the tires 30 during running. The input processing unit 26 also reflects input information selected by the user in the control amount calculated from the sensor output information, and calculates a control amount that provides a target stiffness.

[0020] The stiffness control unit 28 controls the stiffness of a predetermined stiffness variable member 24 based on the control amount calculated by the input processing unit 26. That is, the stiffness control unit 28 controls a predetermined stiffness variable member 24 among the multiple stiffness variable members 24 so that it changes to a predetermined stiffness at a predetermined timing. First, the stiffness control unit 28 controls the on / off of the power supplied from the power source 16 to the power transmission unit 20.

[0021] Next, the rigidity control unit 28 controls the timing and amount of power supplied from the power transmitting unit 20 to the power receiving unit 22. That is, the rigidity control unit 28 controls the power transmitting unit 20 to supply a predetermined amount of power to the power receiving unit 22 at a predetermined timing based on the control amount.

[0022] Next, the rigidity control unit 28 controls the power supplied from the power receiving unit 22 to a predetermined rigidity variable member 24. That is, the rigidity control unit 28 controls the power receiving unit 22 to supply a predetermined amount of power to each rigidity variable member 24 at a predetermined timing.

[0023] In this way, the control unit 18 adjusts the magnitude and timing of the power supplied from the power source 16 to the stiffness variable members 24 via the power transmitting unit 20 and the power receiving unit 22. In this way, the control unit 18 changes the stiffness of a given stiffness variable member 24 in accordance with the magnitude of the power. In this case, the stiffness of the stiffness variable member 24 increases as the supplied power increases.

[0024] The power transmitting unit 20 forms a resonant circuit using a capacitor and a coil, and is attached to the vehicle side. The power transmitting unit 20 is configured to be able to supply power to the power receiving unit 22 in a non-contact manner. The power transmitting unit 20 supplies power to the power receiving unit 22 in a non-contact manner, for example, by induced electromotive force due to electromagnetic induction.

[0025] The power receiving unit 22 forms a resonant circuit using a capacitor and a coil, and is attached to the tire 30. The power receiving unit 22 is configured to be able to contactlessly receive the power supplied from the power transmitting unit 20. The power receiving unit 22 is electrically connected to the rigidity variable member 24 via a power line.

[0026] As shown in Fig. 2, the variable stiffness member 24 is provided on a stabilizer 32 attached to a tire 30. The tire 30 is preferably a so-called comfort tire that aims to provide a smooth ride by providing a high level of riding comfort, i.e., a high level of ability to absorb impacts from the road surface. The tire 30 has, from the inner side to the outer side in the tire radial direction, a bead portion 34, a sidewall portion 36, a shoulder portion 38, and a tread portion 40. Fig. 2 is a meridian cross-sectional view of the tire 30 with the stabilizer 32 attached. Note that Fig. 2 shows the tire portion on the contact surface side in a state where the tire is mounted on a rim and normal internal pressure is applied and a normal load is applied.

[0027] In Fig. 2, the cross-sectional structure of the tire 30 is omitted because it is similar to that of known tires, and will be briefly described below. The bead portion 34 is provided with a bead core and a bead filler. The tire 30 is provided with an inner liner exposed to the tire cavity surface 42 in the region from the bead portion 34 to the tread portion 40. The tire 30 is provided with a carcass extending along the inner liner on the opposite side of the inner liner from the tire cavity surface 42. The tire 30 is provided with a belt on the tire radial direction outer side of the carcass in the tread portion 40. The cross-sectional structure of the tire 30 can be a known one as described above, and therefore a description thereof will be omitted in this specification.

[0028] The stabilizer 32 is housed in the tire cavity 33. The stabilizer 32 is removable from the tire 30. The stabilizer 32 has a frame structure made of a plurality of elastically deformable members, for example, rubber, and at least some of the members are the stiffness variable members 24. Biometal Fiber (registered trademark) can be used for the stiffness variable member 24. For example, the stiffness variable member 24 can be a member in which the periphery of a material made of a strand obtained by impregnating a carbon fiber bundle of biometal fiber with an uncured epoxy resin composition is covered with rubber. The stabilizer 32 has a bead corresponding member 46, a width direction member 50, and a connecting member 52.

[0029] The bead corresponding members 46 are provided on the tire cavity surface 42 corresponding to the pair of bead portions 34 including the bead fillers. The bead corresponding members 46 are annular members.

[0030] A plurality of width direction members 50 are provided at positions in contact with the tire cavity surface 42 on the opposite side of the tread surface 41 in the tread portion 40. Each width direction member 50 is a band-shaped member extending in the tire width direction. Each width direction member 50 has a tread corresponding portion 54 extending in the tire width direction corresponding to the tread portion 40, and a side corresponding portion 56 corresponding to the sidewall portion 36 and the shoulder portion 38 extending in the tire radial direction on both sides of the tread corresponding portion 54 in the tire width direction, integrally formed. The width direction member 50 is a band-shaped member with the tire width direction of the tire cavity surface 42 as the longitudinal direction. The outer edges of both sides in the tire circumferential direction of the width direction member 50 extend in the direction along the tire width direction. Each width direction member 50 is arranged at a predetermined interval in the tire circumferential direction.

[0031] Fig. 3 is a partial plan view of the stabilizer 32 as viewed from the outside. The stabilizer 32 has N width direction members 50. As shown in Fig. 3, if a certain width direction member 50 is the first (hereinafter referred to as the "first width direction member"), a second width direction member 60, a third width direction member 62, ..., an (N)th width direction member 64 are arranged in this order in the tire circumferential direction with respect to the first width direction member 58. In the following description, when there is no distinction between the first width direction member 58, the second width direction member 60, ..., the (N)th width direction member 64, they will be collectively referred to as the width direction members 50.

[0032] A plurality of connecting members 52 are provided on the side of the width direction member 50 opposite to the side in contact with the tire cavity surface 42. The connecting members 52 are strip-shaped extending in the tire circumferential direction and arranged at predetermined intervals in the tire width direction. The connecting members 52 connect the width direction members 50 to each other. Each connecting member 52 has a length sufficient to connect a pair of adjacent width direction members 50 to each other. For example, the connecting member 52 arranged between the first width direction member 58 and the second width direction member 60 has one side in the tire circumferential direction joined to the first width direction member 58 and the other side in the tire circumferential direction joined to the second width direction member 60.

[0033] The bead corresponding member 46 on the left side in Fig. 3 is connected to the left end of the width direction member 50. Similarly, the bead corresponding member 46 on the right side in Fig. 3 is connected to the right end in the tire width direction of the width direction member 50. The width direction members 50 are connected to each other via connecting members 52 with gaps between them in the tire circumferential direction.

[0034] Each member is joined to another, that is, the bead corresponding member 46 and each width direction member 50, and each width direction member 50 and the connecting member 52. The members may be joined to another by adhesive, rivets, screws, or the like.

[0035] The width direction member 50 is formed of the rigidity variable member 24. The width direction member 50 is electrically connected to the power receiving unit 22 via a power line. That is, the first width direction member 58, the second width direction member 60, the third width direction member 62, ..., the (N)th width direction member 64 are each connected to the power receiving unit 22 via an independent power line. When the width direction member 50 is formed of the above-mentioned biometal fiber, it is formed so as to have a shape and size corresponding to the tire inner cavity surface 42 corresponding to the tread surface 41 when electricity is applied. That is, the tire width direction length of the width direction member 50 in a non-energized state is formed to be longer than the tire width direction length of the tire inner cavity surface 42 corresponding to the tread portion 40.

[0036] The stabilizer 32 has the lowest rigidity and can be folded when no power is supplied to the rigidity variable member 24 from the power receiving unit 22 electrically connected via a power line. On the other hand, when power is supplied from the power receiving unit 22 to the rigidity variable member 24, the rigidity of the stabilizer 32 increases according to the magnitude of the power, and the outer shape becomes a ring shape corresponding to the tire inner cavity surface 42.

[0037] The stabilizer 32 is assembled to the tire 30 in the following procedure. First, the stabilizer 32 is folded without supplying power from the power receiving unit 22 to the rigidity variable member 24. Next, the stabilizer 32 is placed in the tire cavity 33 while still in the folded state. Next, the power source 16 is turned on, and a reference power is supplied to the power transmitting unit 20. Furthermore, power is supplied to the power receiving unit 22 in a non-contact manner by induced electromotive force due to electromagnetic induction. The reference power is the minimum power required to maintain a shape that conforms to the tire cavity surface 42 so that the stabilizer 32 can roll integrally with the tire 30. In other words, by supplying the reference power, the stabilizer 32 including the rigidity variable member 24 imparts little or no additional rigidity to the tire 30.

[0038] When the power receiving unit 22 receives the reference power from the power transmitting unit 20, it supplies the reference power to the rigidity variable member 24, thereby forming the stabilizer 32 into a ring shape corresponding to the tire inner cavity surface. The tire 30 to which the stabilizer 32 is attached is assembled onto a rim in the same manner as an ordinary pneumatic tire, and a normal internal pressure is applied.

[0039] 2. Action and Effects The action and effect of the stiffness varying device 10 configured as above will be described. The tire 30, to which the stabilizer 32 having the stiffness varying member 24 is attached, is mounted on a vehicle body 31. When the vehicle accelerates, such as when starting off, the tire 30, which is a driving wheel, receives a larger load. While the vehicle is traveling, the tire 30 receives impacts from the road surface due to unevenness of the road surface. When the vehicle turns left or right, the tire 30 located on the outer side of the vehicle in the turning direction receives a larger load.

[0040] When the user selects the normal mode, that is, when the control unit 18 acquires input information corresponding to the normal mode, the control amount is zero, and in this case, the control unit 18 does not change the power supplied from the power receiving unit 22 to the rigidity variable member 24, and maintains the reference power. As a result, the stabilizer 32 maintains a shape along the tire cavity surface 42 and rolls integrally with the tire 30, but adds almost no additional rigidity to the tire 30. As a result, the tire 30 exerts rigidity due to the structure and air pressure of the tire itself, and behaves as, for example, a comfort tire. That is, the tire 30 absorbs vibrations caused by unevenness on the road surface and provides an excellent ride comfort.

[0041] When the user selects the high-speed mode, that is, when the control unit 18 acquires input information corresponding to the high-speed mode, the control unit 18 increases the power supplied from the power receiving unit 22 to the stiffness variable member 24. That is, the control unit 18 supplies power to the power receiving unit 22 in a non-contact manner by induced electromotive force from the power transmitting unit 20 due to electromagnetic induction. When the power receiving unit 22 receives power from the power transmitting unit 20, it supplies power to a predetermined stiffness variable member 24 electrically connected thereto. This increases the stiffness of the width direction member 50, which is the stiffness variable member 24, and the stabilizer 32 imparts additional stiffness to the tire 30. In this way, the stiffness variable member 24 changes the stiffness of the tire 30 to a stiffness suitable for high-speed driving conditions such as on an expressway, thereby improving steering stability during high-speed driving.

[0042] When the user selects the automatic mode, i.e., when the control unit 18 obtains input information corresponding to the automatic mode, the control unit 18 controls the rigidity of the rigidity variable member 24 so as to obtain a tread surface rigidity appropriate for the driving conditions.

[0043] First, the control unit 18 acquires sensor output information from the sensor unit 12. If the sensor output information obtained from the sensor unit 12 is equal to or less than the threshold value, the control unit 18 determines that stiffness control is unnecessary. In this case, the control unit 18 maintains the power supplied from the power receiving unit 22 to the stiffness variable member 24 at the reference power. As a result, the stabilizer 32 maintains a shape conforming to the tire cavity surface and rolls integrally with the tire 30, but does not add additional stiffness to the tire 30. As a result, the tire 30 exerts stiffness due to the structure and air pressure of the tire itself. In other words, the tire 30 absorbs vibrations caused by unevenness in the road surface and acts as a comfort tire with excellent ride comfort.

[0044] On the other hand, when the sensor unit 12 detects a load exceeding the threshold value, the control unit 18 determines that it is necessary to control the stiffness variable member 24. The control unit 18 then controls the stiffness of the predetermined stiffness variable member 24 to be the predetermined stiffness. For example, the air pressure sensor detects the load acting on the tire 30 as a change in the air pressure of the tire 30 as described above. The acceleration sensor detects the impact on the tire 30 due to unevenness in the road surface and the lateral load on the tire 30 during cornering as a change in acceleration. The sensor unit 12 outputs information detected by each of the above sensors as sensor output information to the control unit 18 via a communication network.

[0045] When the input processing unit 26 receives the sensor output information, it calculates a control amount necessary to improve the driving stability. The control amount includes the timing for changing the stiffness and a target stiffness value for each stiffness variable member 24 whose stiffness needs to be changed. The stiffness control unit 28 controls the amount of power supplied from the power transmitting unit 20 to the power receiving unit 22 and the timing of supply based on the calculated control amount. In this way, the power transmitting unit 20 supplies a predetermined amount of power to the power receiving unit 22 in a non-contact manner at a predetermined timing by induced electromotive force due to electromagnetic induction.

[0046] When the power receiving unit 22 receives the power transmitted from the power transmitting unit 20, it supplies a predetermined amount of power to a predetermined stiffness variable member 24 electrically connected thereto at a predetermined timing. The stiffness variable member 24 changes its stiffness in accordance with the supplied power. When the stiffness of the stiffness variable member 24 increases, the stiffness of the tire 30 can be increased through the stabilizer 32 in which the stiffness variable member 24 is provided. In this way, the stiffness varying device 10 can improve steering stability by changing the stiffness of the tire 30 to an appropriate magnitude at an appropriate timing.

[0047] The stiffness varying device 10 according to this embodiment can vary the stiffness of each of the multiple width direction members 50 individually. For example, as shown in FIG. 4A, a vehicle 65 equipped with a tire 30 will be described. The vehicle 65 is a rear-wheel drive vehicle. When the vehicle 65 accelerates, a large load acts on the rear tire 30R, which is a drive wheel. That is, a moment M about the tire rotation axis is generated in the rear tire 30R due to a frictional force generated between the contact surface and the road surface 66 during acceleration. In addition, a backward force F acts on the rear tire 30R due to the inertial force of the vehicle 65 during acceleration.

[0048] The above force increases as the weight of the vehicle 65 increases and as the acceleration of the vehicle 65 increases. In the case of a rear-wheel drive vehicle, the lower the rigidity of the rear tire 30R, the more likely it is that the vehicle 65 will tilt backward, reducing the ride comfort, and the more likely it is that torque cannot be appropriately transmitted to the road surface, causing slippage and reducing the driving stability.

[0049] The rigidity varying device 10 according to the present embodiment improves ride comfort and steering stability by appropriately controlling the rigidity of the tread portion 40, the shoulder portion 38, and the sidewall portion 36. Specifically, the control unit 18 controls the rigidity of the portion of the rear tire 30R corresponding to the ground contact surface in the tire circumferential direction so as to be higher. For example, in the case where the first width direction member 58 to the second width direction member 60 shown in FIG. 3 are the region corresponding to the ground contact surface, the rigidity of the region from the first width direction member 58 to the second width direction member 60 corresponding to the ground contact surface is made higher than the rigidity of the region from the third width direction member 62 to the (N)th width direction member 64, thereby making it possible to suppress the vehicle 65 from leaning backward and the occurrence of slipping.

[0050] As shown in FIG. 4B, a similar force acts when braking a vehicle 65 equipped with the tire 30. That is, when braking, a frictional force generated between the ground contact surface and the road surface generates a moment M about the tire rotation axis. In particular, a forward force F acts on the tire 30 due to the inertial force of the vehicle 65 when braking. During braking, the front tire 30F in particular is susceptible to the above force. The stiffness varying device 10 can suppress the vehicle 65 from tilting forward and the occurrence of slipping by increasing the stiffness of the region corresponding to the ground contact surface.

[0051] The stiffness varying device 10 can also recognize unevenness on the road surface 66 as image data, and determine whether or not it is necessary to control the stiffness of the tire 30 based on the magnitude of the unevenness. In this case, the control unit 18 first captures an image of the space including the road surface in front of the vehicle, and obtains the obtained image data as sensor output information. The control unit 18 measures the magnitude of the unevenness, particularly the elevation difference from the road surface, based on the obtained image data. If the elevation difference is greater than a threshold value, the control unit 18 determines that it is necessary to control the stiffness variable member 24.

[0052] 5, a description will be given of the operation of the tire 30 when entering a recess 68 formed in a road surface 66 and when exiting the recess 68. Although not shown, the tire 30 shown in FIG. 5 is mounted on a regular rim 69 after the stabilizer 32 including the rigidity variable member 24 is attached, and is mounted on the vehicle body 31 in a state in which the regular internal pressure is applied.

[0053] The recess 68 is a depression formed in the road surface 66, and has a bottom surface 70 and an edge 72. The bottom surface 70 further includes an unevenness 71 that is smaller in height than the recess 68. The edge 72 is formed by the difference in height between the bottom surface 70, which is formed on the front side in the traveling direction (arrow in the figure) of the tire 30, and the road surface 66.

[0054] When the tire 30 enters the recess 68, the ground contact surface comes into contact with the bottom surface 70. That is, the tire 30 receives an impact from the unevenness 71 formed on the bottom surface 70, in addition to the impact when it falls from the road surface 66 to the bottom surface 70. The lower the rigidity of the tire 30, the easier it is to absorb the impact when the ground contacts the bottom surface 70. Therefore, the rigidity varying device 10 suppresses a decrease in ride comfort by maintaining low rigidity in an area AR1 in the tire circumferential direction corresponding to the ground contact surface that comes into contact with the bottom surface when the tire 30 enters the recess 68.

[0055] The tire 30, which has advanced further, receives an impact from the edge 72 in the process of coming into contact with the edge 72 and climbing over the edge 72 to get out of the recess 68. That is, as shown in Fig. 6A, the tire 30 comes into contact with the edge 72 in the tread portion 40 on the further leading-in side than the leading-in side outer edge of the ground contacting the bottom surface 70 of the recess 68. In the initial stage when the tire 30 comes into contact with the edge 72, the lower the rigidity of the tire 30, the more the tire 30 can absorb the impact from the edge 72. That is, the rigidity varying device 10 suppresses a deterioration in ride comfort by maintaining low the rigidity of the region AR2 in the tire circumferential direction corresponding to the portion in contact with the edge 72 in the initial stage.

[0056] Next, as shown in FIG. 6B, the tire 30 may be deformed by the edge 72 as it advances further. Therefore, in the middle stage when the tire 30 comes into contact with the edge 72, the higher the rigidity of the part in contact with the edge 72, the more likely it is that the tire 30 and the rim 69 will be damaged by the edge 72. That is, the rigidity variable member 24 keeps the rigidity of the tire circumferential area AR2 corresponding to the tread portion 40 on the further inward side than the outer edge of the inward side of the ground contact surface, which is the part in contact with the edge 72, high, thereby preventing excessive deformation of the tire 30 and preventing damage to the tire 30 and the rim 69. On the other hand, the rigidity variable device 10 keeps the rigidity of the tire circumferential area AR1 corresponding to the ground contact surface low in preparation for receiving an impact from the bottom surface 70 of the recess 68. The tire 30 receives a repulsive force from the edge 72 due to the increased rigidity of the tire 30 in the middle stage.

[0057] 6C, by further moving forward, the tire 30 rides up on the edge 72 while receiving a repulsive force from the edge 72. For this reason, in the final stage when the tire 30 comes into contact with the edge 72, a portion in contact with the edge 72 with a lower rigidity can smoothly ride up on the edge 72 while absorbing the repulsive force from the edge 72. That is, the rigidity varying device 10 suppresses a deterioration in ride comfort by maintaining low rigidity in the tire circumferential region AR2, which is the tread portion 40 on the further leading-in side than the outer edge of the leading-in side of the contact surface, corresponding to the portion in contact with the edge 72 in the final stage.

[0058] As described above, the stabilizer 32 having the variable rigidity member 24 according to this embodiment can achieve both improved steering stability and improved ride comfort by changing the rigidity of the tread surface.

[0059] The stabilizer 32 is removable from the tire 30, and can therefore be attached to a conventional tire 30. Furthermore, when the tire 30 to which the stabilizer 32 is attached deteriorates over time, the stabilizer 32 can be removed from the tire 30 and attached to a new tire 30, thereby making it possible to reuse the stabilizer 32.

[0060] The width direction member 50 is the rigidity variable member 24, and is integrally provided with the tread corresponding portion 54 and the side corresponding portion 56, so that the rigidity of the casing can be changed in addition to the rigidity of the tread surface. The rigidity variable device 10 can increase the rigidity of the casing in addition to the rigidity of the tread surface, so that the vehicle 65 can run even if the tire 30 is unexpectedly punctured, for example.

[0061] 3. Variations The present invention is not limited to the above embodiment, and can be modified as appropriate within the scope of the present invention. In the above embodiment, the rigidity variable member 24 is described as using a biometal fiber, but the present invention is not limited to this. The rigidity variable member 24 may be formed of a shape memory alloy. In this case, each member may be joined via an insulator. By joining each member via an insulator, the power supplied to each rigidity variable member 24 can be controlled.

[0062] The stiffness variable member 24 may be a tube-shaped member made of rubber, and may use a fluid such as air as a power source. The stiffness variable device 10 is preferably configured to control the fluid supplied to each member. In this case, the stiffness variable device 10 can change the stiffness of the tube-shaped member by feeding or discharging the fluid into or from the member.

[0063] In the above embodiment, the case where four connecting members are provided in the tire width direction has been described, but the present invention is not limited to this, and three, five or more connecting members may be provided in the tire width direction.

[0064] In the above embodiment, the width direction member 50 has the tread corresponding portion 54 and the side corresponding portion 56 integrally formed therein, but the present invention is not limited thereto. For example, the width direction member 50 may have the tread corresponding portion 54 and the side corresponding portion 56 as separate bodies, which are joined to each other via an insulator (not shown) to form an integral body. In this way, the rigidity varying device 10 can control the rigidity of the tread corresponding portion 54 and the rigidity of the side corresponding portion 56 independently of each other.

[0065] In the above embodiment, the connecting member 52 is a strip-shaped member extending in the tire circumferential direction and connects adjacent width direction members 50, but the present invention is not limited to this. For example, the connecting member 52 may be an annular member extending in the tire circumferential direction. In other words, the connecting member 52 can integrally connect the first width direction member 58 to the (N)th width direction member 64.

[0066] In the above embodiment, the width direction member 50 is described as being in a strip shape along the tire width direction, but the present invention is not limited to this. For example, the width direction member 50 may be in a strip shape extending in the tire width direction, having a shape that alternately and repeatedly meanders on one side and the other side in the tire circumferential direction. [Explanation of symbols]

[0067] 10 Variable stiffness device 12 Sensor section 14 Input section 16 Power source (power source) 18 Control Unit 20 Power Transmission Section 22 Power receiving section 24 Variable stiffness member 26 Input Processing Section 28 Rigidity control section 30 Tires 30R rear tire 30F front tire 31 Vehicle body 32 Stabilizer 34 Bead section 36 Sidewall 38 Shoulder section 40 Tread 41 Tread surface 42 Tire inner cavity surface 46 Bead compatible parts 48 Side corresponding parts 50 Width direction member 52 Connecting member 54 Tread corresponding part 56 Side Corresponding Part 58 First width direction member 60 Second width direction member 62 Third width direction member 64 (N)th width direction member 65 vehicles 66 Road surface 68 Recess 69 Rims 70 Bottom 71 Unevenness 72 Edge CL Tire Equatorial Plane

Claims

1. A variable stiffness member that is removably provided on a tire cavity surface of a tire having a tread portion having a tread surface; a control unit that controls the stiffness of the stiffness variable member by supplying a power source to the stiffness variable member, The control unit changes the rigidity of the rigidity variable member, thereby changing the rigidity of a portion of the tread portion in the tire circumferential direction.

2. 2. The stiffness varying device according to claim 1, wherein the control unit increases stiffness of a portion of the tread portion that comes into contact with a road surface in the tire for a drive wheel when a vehicle equipped with the tire is accelerating.

3. 2 . The rigidity varying device according to claim 1 , wherein the control unit increases the rigidity of a portion of the tread portion that comes into contact with a road surface in the tire for a front wheel when braking a vehicle equipped with the tire.

4. 2. The rigidity varying device according to claim 1, wherein the control unit sets a boundary at an outer edge of a leading side in a tire circumferential direction of the contact surface of the tire that contacts a road surface, and makes a rigidity of the tread portion on a side away from the contact surface from the boundary higher than a rigidity of the tread portion of the contact surface.

5. The stiffness varying device according to claim 1 , wherein the control unit varies the stiffness of the stiffness variable member based on predetermined sensor output information.

6. The rigidity variable member has a width direction member that is in contact with a tire cavity surface exposed to the tire cavity surface and extends in a tire width direction, The rigidity varying device according to claim 1 , wherein a plurality of the width direction members are arranged at predetermined intervals in the tire circumferential direction.

7. A tire in which the stiffness varying device according to any one of claims 1 to 6 is used.

Images