JP2009113759A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of fitting a distortion sensor at a correct position without any trouble attributable to vulcanization heat and vulcanization pressure, and suppressing degradation of the detection accuracy and the reliability caused by the effect of adhesive. <P>SOLUTION: A distortion sensor 21 is inserted in a fitting manner in a sensor fitting hole 20 of a tire body 10 with the sensor fitting hole 20 for fitting the distortion sensor being recessed in an outer surface Gs of a side wall rubber 3G. The distortion sensor 21 has a block shape with a magnet 11 and a magnetic sensor element 12 opposing the magnet 11 being embedded in a rubber base body 13. A peripheral wall surface 25 of the distortion sensor 21 and a peripheral wall surface 23 of the sensor fitting hole 20 are press-fitted to each other without any space by the fitting. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire used in a detection method for detecting a force acting on a tire based on strain measured by a strain sensor attached to a sidewall portion.

  In recent years, various vehicle control systems such as ABS (anti-lock brake system), TCS (traction control system), and VSC (vehicle stability control) have been developed in order to ensure the stability and safety of a running vehicle. Yes. In order to control these systems, it is necessary to accurately grasp the rolling state of the running tire.

Therefore, in the following Patent Document 1, the present applicant attaches three or more strain sensors to the sidewall portion, and simultaneously measures the strain of the sidewall portion at predetermined three positions. A technique for estimating three forces, namely, a longitudinal force Fx, a lateral force Fy, and a vertical load Fz acting on the tire, is proposed. And in this patent document 1, as the attachment method of the said strain sensor,
(1) Before the tire is vulcanized, the strain sensor is embedded in the sidewall portion or attached to the inner surface or the outer surface of the sidewall portion, and attached by vulcanization adhesion by subsequent vulcanization, or (2) It is disclosed that a strain sensor is attached to an inner surface or an outer surface of a sidewall portion after vulcanization by adhesion with an adhesive.

Japanese Patent Laid-Open No. 2005-126008

  However, in the former case, the vulcanization heat and the vulcanization pressure may cause a failure of the strain sensor, and it is difficult to obtain an accurate mounting position such as the mounting position fluctuating due to rubber flow during vulcanization. There is a problem that the detection accuracy is impaired. On the other hand, in the latter case, there is a problem that the elastic modulus of the adhesive greatly affects the measurement value of the strain, and the accuracy and reliability of the force detection are lowered.

  In any case, since the strain sensor is integrally fixed to the tire, even if one of the plurality of strain sensors fails, there is a problem that it is necessary to replace the entire tire, which impairs the economy. is there.

  Therefore, the present invention can attach the strain sensor to an accurate position without causing a failure due to vulcanization heat or vulcanization pressure, and can suppress a decrease in detection accuracy and reliability due to the influence of the adhesive. At the same time, it is an object to provide a pneumatic tire capable of replacing the strain sensor and improving economy.

In order to achieve the above-mentioned object, the invention of claim 1 of the present application is a pneumatic tire comprising a strain sensor used for detecting a force acting on the tire by outputting a strain output obtained by measuring the strain of the sidewall portion. There,
It has at least a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a sidewall rubber disposed on the outside of the carcass and having an outer surface forming a sidewall surface, and on the outer surface of the sidewall rubber. , Tire body with a bottomed sensor mounting hole for strain sensor mounting,
And a block-shaped strain sensor in which a magnet and a magnetic sensor element facing the magnet are embedded in a rubber base made of a rubber elastic material,
The strain sensor is characterized in that the peripheral wall surface of the strain sensor and the peripheral wall surface of the sensor mounting hole are in pressure contact with each other by being fitted into the sensor mounting hole by fitting.

  In the invention of claim 2, the strain sensor is characterized in that the Young's modulus E1 of the rubber base is set to be equal to or less than the Young's modulus E2 of the sidewall rubber.

  In the invention of claim 3, the strain sensor is a rectangular parallelepiped, and the strain sensor is attached by inclining the width center line of the rectangular parallelepiped at an angle of 30 to 60 ° with respect to the tire radial direction line. It is said.

  According to a fourth aspect of the present invention, the strain sensor is characterized in that a gain maximum line at which the gain becomes maximum coincides with a width center line of the rectangular parallelepiped.

  The invention of claim 5 is characterized in that the magnetic sensor element is a Hall element.

  The Young's modulus means an elastic modulus at 300% elongation measured in accordance with a test method described in JIS K6251 “Vulcanized rubber and thermoplastic rubber—How to obtain tensile properties”.

  As described above, the present invention uses a block-shaped sensor in which a magnet and a magnetic sensor element facing the magnet are embedded in a rubber base made of a rubber elastic material as a strain sensor. In the sensor mounting hole recessed in the outer surface of the rubber, it is fitted with a fit.

  Here, the rubber has a Poisson's ratio of about 0.49 and has a characteristic that hardly shows a volume change with respect to strain. Accordingly, when the side wall portion is deformed and the sensor mounting hole is subjected to, for example, extension deformation by pulling in one direction, the sensor mounting hole causes compressive deformation in the other direction orthogonal to the one direction. . At this time, since the strain sensor inserted into the sensor mounting hole is formed using a rubber elastic material, the strain sensor is biased by the compression deformation of the sensor mounting hole and causes the compression deformation in the other direction. Along with this, extension deformation occurs in the one direction. That is, even if the strain sensor is not bonded to the peripheral wall surface of the sensor mounting hole, the strain sensor can be freely deformed following the expansion and compression deformation of the sensor mounting hole. Can be measured with high accuracy without being affected by the adhesive.

  Further, since the sensor mounting hole can be formed by a vulcanization mold when the tire is vulcanized, the strain sensor can be mounted at an accurate position. In addition, since the strain sensor is attached after the tire is vulcanized, failure of the strain sensor due to vulcanization heat or vulcanization pressure can be prevented. In addition, since the strain sensor is fitted into the sensor mounting hole, it is possible to replace a faulty strain sensor, and it is economical because the strain sensor can be removed from a pneumatic tire that has reached the end of its wear life and reused. Can be increased.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a pneumatic tire according to the present invention.

  In FIG. 1, a pneumatic tire 1 includes a tire body 10 having a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a sidewall surface of the tire body 10. And a strain sensor 21 that is fitted into a sensor mounting hole 20 provided in the sensor.

  The tire body 10 is a vulcanized tire that has been vulcanized by a vulcanization mold, and a sidewall rubber 3G having an outer surface Gs forming a sidewall surface is disposed outside the carcass 6.

  The carcass 6 is formed by one or more carcass plies 6A in this example, in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction. The carcass ply 6 </ b> A includes a series of ply folding portions 6 b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 on both sides of the ply main body portion 6 a that extends between the bead cores 5 and 5. Further, a bead apex rubber 8 for bead reinforcement having a triangular cross section extending outward from the bead core 5 in the tire radial direction is disposed between the ply main body portion 6a and the ply turn-up portion 6b.

  A tread reinforcing belt layer 7 is wound in the tire circumferential direction inside the tread portion 2 and outside the carcass 6 in the radial direction. The belt layer 7 is formed from two or more belt plies 7A and 7B in which belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction, and each belt cord is between plies. By crossing each other, the belt rigidity is enhanced, and the substantially entire width of the tread portion 2 is firmly reinforced with a tagging effect. In this example, a band layer 9 in which band cords are arranged at an angle of 5 degrees or less with respect to the circumferential direction is provided on the outer side in the radial direction of the belt layer 7 for the purpose of improving high-speed running performance and high-speed durability. Provided.

  Next, the sidewall rubber 3G is made of a soft rubber having a rubber hardness Hs (durometer A hardness) of, for example, 48 to 53, and covers and protects the carcass 6 from an injury. The outer surface Gs of the sidewall rubber 3G has at least one sensor mounting hole 20 for mounting the strain sensor 21, preferably three or more, more preferably six or more recessed. In the case where a plurality of sensor mounting holes 20 are formed, as shown in FIG. 2, it is convenient to arrange them at equal intervals on the same circumferential line i centered on the tire axis. From the viewpoint of properties and the like. In the figure, a case where eight sensor mounting holes 20 are formed on the same circumferential line i at equal intervals is illustrated.

  Here, as shown in an enlarged view in FIG. 3, the sensor mounting hole 20 includes a bottom surface 22 parallel to the outer surface Gs and a peripheral wall surface 23 surrounding the bottom surface 22. The case where the wall surface 23 consists of the four wall surface parts 23a, and each wall surface part 23a and the bottom face 22 are formed in the rectangular parallelepiped shape which makes a rectangle is illustrated. By forming the sensor mounting hole 20 in a rectangular parallelepiped shape in this way, the strain sensor 21 can be stably mounted in an accurate posture, and the deformation of the sensor mounting hole 20 is accurately transmitted to the strain sensor 21. Therefore, distortion measurement accuracy can be further improved.

  Further, as conceptually shown in FIG. 4, the sensor mounting hole 20 has a rectangular parallelepiped width center line c1 of 30 to 60 °, more preferably 40 to 50 °, and still more preferably, with respect to the tire radial direction line. It is formed at an angle θ of 45 °.

  Next, as the strain sensor 21, as shown in FIGS. 5 to 7, a magnet 11 and a magnetic sensor element 12 facing the magnet 11 with a gap are embedded in a rubber base 13 made of a rubber elastic material. A block-shaped one is adopted. The strain sensor 21 needs to be fitted into the sensor mounting hole 20 by fitting. Accordingly, the strain sensor 21 has a sectional shape (sensor mounting larger than the sensor mounting hole 20 by a fitting margin). (Cross-sectional shape perpendicular to the depth direction of the hole 20). In this example, since the sensor mounting hole 20 is formed in a rectangular parallelepiped shape, the strain sensor 21 is also formed in a rectangular parallelepiped shape having a large cross section by a fitting allowance. Thereby, the strain sensor 21 is attached in a state where the peripheral wall surface 25 and the peripheral wall surface 23 of the sensor mounting hole 20 are in pressure contact with no gap. The fitting allowance is not particularly limited, but is preferably in the range of greater than 0% and less than 5% with respect to the dimension (length) of the sensor mounting hole 20, for example.

  As the magnetic sensor element 12 of the strain sensor 21, a Hall element, an MR element (magnetoresistance effect element), a TMF-MI element, a TMF-FG element, an amorphous sensor, etc. can be adopted, and particularly compactness, sensitivity, and easy handling. A Hall element can be suitably employed from the standpoints of height.

  As the strain sensor 21, as shown in FIGS. 5A and 5B, a 1-1 type formed by one magnet 11 and one magnetic sensor element 12, and as shown in FIGS. 6A and 6B. 1-n type formed by one magnet 11 and plural (n, for example, two) magnetic sensor elements 12, and plural (n, for example, two) as shown in FIGS. N-1 type formed by a magnet 11 and one magnetic sensor element 12). In the figure, reference numeral 12 s denotes a sensing surface 12 s of the magnetic sensor element 12, reference numeral 11 s denotes a magnetic pole face of the magnet 11, and reference numeral N denotes a gain maximum line at which the gain of the strain sensor 21 is maximum. In any case, it is preferable that the maximum gain line N coincides with the width center line c2 of the rectangular parallelepiped shape of the strain sensor 21, so that when the strain sensor 21 is mounted in the sensor mounting hole 20, the maximum gain is obtained. The line N can be inclined at the angle θ with respect to the tire radial line. Thereby, since the distortion of the sidewall portion 3 including the shear strain can be measured, the detection accuracy of the force acting on the tire can be increased.

  Each strain sensor 21 has a built-in transmission means (not shown) for transmitting a strain output of the measured strain to an electronic control unit (ECU) of a vehicle control system provided in the vehicle. This transmitting means is composed of a semiconductor in which a transmission / reception circuit, a control circuit, a memory, etc. are made into a chip, and an antenna. The distortion output data can be transmitted as response radio waves.

  Here, as exaggeratedly shown in FIG. 8 (A), when the sidewall portion 3 is deformed and the sensor mounting hole 20 is stretched and deformed in one direction by, for example, the tension f1, the sensor mounting hole 20 is In the other direction orthogonal to the one direction, compression deformation occurs. At this time, since the strain sensor 21 inserted into the sensor mounting hole 20 is formed using a rubber elastic material, the sensor mounting hole 20 is compressed in the other direction as shown exaggeratedly in FIG. It is urged by f2 to cause compressive deformation in the other direction, and along with this compressive deformation, it causes expansion deformation in the one direction. That is, even if the strain sensor 21 is not bonded to the peripheral wall surface 23 of the sensor mounting hole 20, the strain sensor 21 can be freely deformed following the expansion and compression of the sensor mounting hole 20, The distortion of the sidewall portion 3 can be measured with high accuracy without being affected by the adhesive.

  At this time, in order for the strain sensor 21 to deform following the sensor mounting hole 20, the Young's modulus E1 of the rubber base 13 needs to be equal to or less than the Young's modulus E2 of the sidewall rubber 3G. At> E2, the followability of the strain sensor 21 is reduced and the measurement accuracy is lowered. From such a viewpoint, it is more preferable that the upper limit of the Young's modulus E1 is smaller than 1.0 times the Young's modulus E2 and further 0.95 times or less. Further, the lower limit of the Young's modulus E1 is preferably 0.7 times or more of the Young's modulus E2 from the viewpoint of the strength of the strain sensor 21.

  Next, although the strain sensor 21 is fitted into the sensor mounting hole 20, there is a possibility that the strain sensor 21 may come off from the sensor mounting hole 20 due to repeated deformation of the tire. Therefore, in this example, as illustrated in FIG. 3, a locking portion 26 that prevents the strain sensor 21 from coming off by engaging with the circumferential wall surface 25 of the strain sensor 21 and the circumferential wall surface 23 of the sensor mounting hole 20. Provided. In this example, the locking portion 26 is a rib-shaped (or groove-shaped) first locking portion 26A formed on the peripheral wall surface 25, and the first locking portion 26A formed on the peripheral wall surface 23. The case where it consists of the groove | channel-shaped (or rib-shaped) 2nd latching | locking part 26B to engage is illustrated. It is not necessary to form this latching | locking part 26 in all the wall surface parts 25a and 23a, for example, it can also form only in a pair of wall surface parts 25a and 23a which press-contact. Moreover, as the latching | locking part 26, it can also be set as multiple groove shape (or rib shape) other than 1 groove shape (or rib shape). Further, as shown in FIG. 9, it can be formed in a wedge shape in which the cross-sectional areas on the opening side of the strain sensor 21 and the sensor mounting hole 20 are reduced. Stop portions 26A and 26B are configured. Further, a rubber-based adhesive having rubber elasticity may be supplementarily used, and a part between the wall surface portions 25a and 23a may be bonded in a spot shape, for example.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  In order to confirm the effect of the present invention, a sensor mounting hole having a rectangular parallelepiped shape of 9.5 mm (vertical) × 6.5 mm (horizontal) × 5 mm (depth) is formed on the sidewall surface of the tire body of the tire size 245 / 40ZR18. A 9.7 mm (vertical) x 6.7 mm (horizontal) x 4.8 mm (height) rectangular parallelepiped strain sensor is inserted into this sensor mounting hole without using an adhesive. It was attached by inserting at (0.2 mm). The sensor mounting hole was formed at a position 5 mm away radially outward from the upper end of the rim flange with the width center line of the rectangular parallelepiped inclined at an angle of 45 ° with respect to the tire radial direction line. The strain sensor is formed by embedding a magnet and a hall element in a rubber base made of the same rubber as the sidewall rubber, and its maximum gain line coincides with the width center line of the rectangular parallelepiped.

  And this pneumatic tire with a strain sensor was run at a speed of 80 km / h with a drum tester, and the distortion of the sidewall portion was measured. FIG. 10 is a graph of the output value of the strain sensor when the tire makes one revolution. As shown in FIG. 10, it can be confirmed that the strain can be measured at the rotational position of the tire. In this experiment, it was also confirmed that the vehicle could travel 30,000 km while giving such an output value.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is a side view of the pneumatic tire which shows the arrangement state of a strain sensor schematically. It is a disassembled perspective view which shows a sensor attachment hole with a distortion sensor. It is a diagram which shows the attachment direction of a strain sensor. (A), (B) is the top view and perspective view which show one Example of a strain sensor. (A), (B) is the top view and perspective view which show the other Example of a strain sensor. (A), (B) is the top view and perspective view which show other Example of a strain sensor. (A), (B) is a top view explaining the effect of this invention. It is sectional drawing which shows the other example of a latching | locking part. It is a graph of the output value of the distortion sensor in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 3G Side wall rubber 4 Bead part 5 Bead core 6 Carcass 10 Tire main body 11 Magnet 12 Magnetic sensor element 13 Rubber base 20 Sensor mounting hole 21 Strain sensor 23, 25 Circumferential wall surface c1, c2 Width Center line Gs Outer surface N Gain maximum line

Claims (5)

A pneumatic tire comprising a strain sensor used for detecting a force acting on the tire by outputting a strain output obtained by measuring the strain of the sidewall portion,
It has at least a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a sidewall rubber disposed on the outside of the carcass and having an outer surface forming a sidewall surface, and on the outer surface of the sidewall rubber. , Tire body with a bottomed sensor mounting hole for strain sensor mounting,
And a block-shaped strain sensor in which a magnet and a magnetic sensor element facing the magnet are embedded in a rubber base made of a rubber elastic material,
The pneumatic tire according to claim 1, wherein the strain sensor is fitted into the sensor mounting hole by fitting so that the peripheral wall surface of the strain sensor and the peripheral wall surface of the sensor mounting hole are in pressure contact with each other without a gap.   The pneumatic tire according to claim 1, wherein the strain sensor has a Young's modulus E1 of the rubber base that is equal to or less than a Young's modulus E2 of the sidewall rubber.   3. The strain sensor according to claim 1, wherein the strain sensor is a rectangular parallelepiped, and the strain sensor is attached by inclining a width center line of the rectangular parallelepiped at an angle of 30 to 60 degrees with respect to a tire radial direction line. Pneumatic tires.   The pneumatic tire according to claim 3, wherein the strain sensor has a gain maximum line at which the gain is maximum matched with a width center line of the rectangular parallelepiped.   The pneumatic tire according to claim 1, wherein the magnetic sensor element is a Hall element.

Images