JP2007256080A - Sensor mounting structure and tire state detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor mounting structure capable of detecting stain or the like in a compression or extension state and capable of appropriately transmitting a stress required for the detection to an elemental device, and to provide a tire condition detecting apparatus having the sensor mounting structure. <P>SOLUTION: The sensor mounting structure comprises: a pair of leg parts 15 each having one end 15a adhering to a tire; and a surface acoustic device 11 which is disposed between the leg parts 15 so as to be sandwiched thereby and varies its response signal to an input signal in accordance with the strain due to a bending force. The other end 15b of each of the leg parts 15 is supported as a fixed end in relation to the surface acoustic device 11 or its supporting body 16. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sensor attachment structure for attaching a surface acoustic wave element (SAW) sensor to a tire, and a tire condition detection device that has the sensor attachment structure and detects tire distortion, stress, and the like.

  Tire handling stability is a very important characteristic, but in general, it is often evaluated as a test driver with a specialized education. For this reason, a method for evaluating steering stability more objectively and with good reproducibility is desired, and in the evaluation method, measurement of strain and stress of the tread and the sidewall is important.

  Conventionally, there has also been a method of transmitting a detection signal wirelessly using an acceleration sensor, but the acceleration sensor can only obtain indirect information, and the so-called transmitter or power source greatly affects steering stability. Since the unsprung weight increases, it is difficult to say that substantial evaluation has been made.

  On the other hand, a surface acoustic wave element (SAW) sensor, which is a passive element (passive), has the advantage of being compact and lightweight without the need for a power source. If the distortion and stress of the tread and sidewall are directly detected, Steering stability can be evaluated. For this reason, as an application of the SAW sensor to a tire, detection of a ground contact state of the tire (for example, see Patent Document 1), an example of use as a part of the sensor (for example, see Patent Document 2), and the like have been proposed.

  However, the former detects the ground contact state and is insufficient as information for evaluating the steering stability. The latter is not suitable for evaluation of steering stability because the sensor device itself is large and has a large mass.

  Further, as a similar sensor, there is a sensor of an internal pressure alarm device, and as an example of embedding in a tire, there is a patent for embedding in a bead portion or a sidewall portion with relatively little movement (for example, see Patent Documents 3 to 4). ). In addition, since it is embed | buried in a site | part with few distortions, the adhesive force is not considered.

  Furthermore, a transponder comprising a SAW sensor, a matching circuit, and an antenna is attached to the tire, and a transmitter / receiver that transmits a drive signal to the transponder and receives a signal from the transponder is installed in the vehicle. A tire information detection device for detecting tire information is known (see, for example, Patent Document 5). In this device, as a sensor structure for detecting tire air pressure and the like, the SAW sensor element is combined with a diaphragm to form a closed space, and the other side of the sensor element is communicated with the inside of the tire, thereby A sensor structure in which a sensor element bends and deforms according to an internal pressure is disclosed.

  However, this Patent Document 5 does not specifically disclose a method for measuring strain using a SAW sensor. For this reason, for example, when a SAW sensor is bonded to the tire surface and the distortion of the tread or sidewall is measured directly, the tire has complicated irregularities such as tread pattern, side design, and air vent groove on the inner surface. Therefore, it is difficult to accurately measure originally generated distortion due to locally complicated distortion.

  Also, the SAW sensor element (elastic modulus: about 200 GPa) is small and extremely hard compared to rubber (elastic modulus: about 10 MPa). Since the stress necessary for detection is not sufficiently transmitted to the entire element, there is a problem that the detection capability of the sensor becomes extremely small.

  Further, when the deformation mode of the tire is bending as in the sidewall portion, the bending strain can be detected by the SAW sensor as it is. However, when the deformation mode is compression or expansion, the strain detection by the SAW sensor is possible. There was a problem that it was difficult to do directly.

Special Table 2003-526560 JP 2003-285612 A JP 2004-58997 A JP 2004-82775 A JP 2004-203165 A

  Accordingly, an object of the present invention is to detect a strain or the like at the time of compression or expansion, and to appropriately transmit stress necessary for the detection to the element, and to detect a tire condition having the sensor mounting structure. To provide an apparatus.

The above object can be achieved by the present invention as described below.
That is, the sensor mounting structure according to the present invention includes a pair of leg portions bonded at one end to a tire, and a surface acoustic wave element that is straddled between the leg portions and changes a response signal to an input signal by distortion caused by a bending force. The other end of the leg portion is fixedly supported by the surface acoustic wave element or its support. Here, the fixed end support refers to support of an end portion that restrains displacement and rotation.

  According to the sensor mounting structure of the present invention, when a compressive strain or an extension strain is generated in a tire, a pair of leg portions bonded at one end to the tire are closed or opened, and the leg portions are surface acoustic wave elements or a support thereof. Since it is supported by the body at the fixed end, bending deformation occurs in the surface acoustic wave element, so that the distortion during compression or expansion can be detected by the surface acoustic wave element. At that time, since the displacement and the stress on the element can be adjusted by adjusting the height of the leg portion, the stress necessary for detection can be suitably transmitted to the element.

  In the above, the height of the leg is 0.5 to 3 times the interval between the other ends of the leg, and the width of the other end of the leg is 0.5 to 3 of the width of the surface acoustic wave element. It is preferable that it is double. When the height and width of the leg are within this range, stress necessary for detection can be more suitably transmitted to the element.

  Preferably, the surface acoustic wave element is integrated with the support, and an antenna connected to the surface acoustic wave element is provided on the support. This eliminates the need for antenna wiring and prevents detection noise from being generated by the input of external force through the wiring.

  On the other hand, the tire state detection device of the present invention includes a surface acoustic wave element and a responder having an antenna connected thereto and installed on the tire side, and transmits a drive signal to the responder and responds In the tire state detection device comprising a transmission / reception means installed on the vehicle body side for receiving a response signal from the vehicle body and processing the signal, the surface acoustic wave element transmits a response signal to the input signal due to distortion caused by a bending force. The surface acoustic wave element is attached to a tire by the sensor attachment structure of the present invention.

  In the tire condition detection apparatus of the present invention, when a drive signal is transmitted from a transmission / reception means to a responder having a surface acoustic wave element that changes a response signal to an input signal due to distortion caused by a bending force, the input signal from the antenna On the other hand, the response signal changes due to the strain caused by the bending force, and this is received by the transmission / reception means to process the signal, whereby the strain generated in the surface acoustic wave element can be detected. At that time, since the surface acoustic wave element is attached to the tire by the sensor attachment structure of the present invention, the pair of legs, one end of which is bonded to the tire, is closed when the tire is compressed or stretched. Alternatively, the legs are opened, and the legs are fixedly supported by the surface acoustic wave element or its support, so that bending deformation occurs in the surface acoustic wave element, so that the distortion during compression or extension is caused by the surface acoustic wave element. Can be detected. At that time, since the displacement and the stress on the element can be adjusted by adjusting the height of the leg portion, the stress necessary for detection can be suitably transmitted to the element. Therefore, the tire state detection device can detect strain at the time of compression or expansion and can suitably transmit stress necessary for the detection to the element.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of a sensor mounting structure of the present invention, FIG. 2 is a schematic configuration diagram showing an example of a tire condition detecting device of the present invention, and (a) is a cross section in the tire meridian direction. FIG. 2B is a cross-sectional view in the tire equator direction. Moreover, FIG. 3 is explanatory drawing which shows the effect | action of the sensor attachment structure of this invention.

  First, the tire condition detection apparatus of the present invention will be described. As shown in FIG. 2 (a), the tire condition detection device of the present invention has a surface acoustic wave element 11 and an antenna 12 connected thereto, a responder 10 installed on the tire side, and its responder. 10 is provided with transmission / reception means 20 installed on the vehicle body side for transmitting a drive signal to 10 and receiving a response signal from the responder 10 and processing the signal.

  The responder 10 may be provided with a matching circuit unit 13 for impedance matching between the surface acoustic wave element 11 and the antenna 12. As will be described later, the surface acoustic wave element 11 is a part that detects strain and stress generated in the tire as a change in propagation characteristics of the surface acoustic wave, and the antenna 12 is a part that transmits and receives radio signals.

  Further, the matching circuit unit is composed of elements such as a resistor, a capacitor, and a coil in order to achieve impedance matching. However, when the impedance matching is taken, this matching circuit unit is unnecessary.

  On the other hand, the transmission / reception means 20 of the present embodiment includes a transmission / reception circuit, an arithmetic circuit, and the like, and an antenna 21. The transmission / reception circuit is a part that transmits the generated drive signal to the responder 10 and receives from the responder 10. The arithmetic circuit or the like is a part that performs a calculation for determining a tire state by processing a response signal from the responder 10.

  Transmission / reception of signals between the responder 10 and the transmission / reception means 20 is performed by wireless communication between the antennas 12 and 21. The transmission / reception means 20 is provided at a position where signals on the vehicle body side can be transmitted / received. For example, the transmission / reception means 20 can be provided near the fender or the brake disc. In particular, when detecting strain or the like in the ground contact state of the tire, it is preferable to provide the transmission / reception means 20 at a position closest to the ground in the fender.

  The surface acoustic wave element 11 includes a piezoelectric substrate 11b and a comb-shaped electrode 11a and a reflector 11c formed on the surface of the piezoelectric substrate 11b. The comb-shaped electrode 11a is connected to an antenna 12 or a matching circuit. The comb-shaped electrode 11a and the reflector 11c are patterned at regular intervals. Thereby, the surface acoustic wave reflected by each reflector 11c can be converted into a signal by the comb-shaped electrode 11a.

  As the piezoelectric material used as the piezoelectric substrate 11b, a material having a predetermined physical property coefficient according to the state change of the measurement target is applied. For example, in the case of a strain sensor, for example, a lithium niobate single crystal 128 ° rotated Y-cut substrate, crystal, lithium tantalate, lithium tetraborate, langasite, or the like can be used.

  As a constituent material of the comb-shaped electrode 11a and the reflector 11c constituting the surface acoustic wave element 11, aluminum is a preferable example because it has a small electric resistance, is lightweight, and can be easily patterned. However, copper, titanium, chromium, gold or the like may be applied, and these metals may be mixed together, various metals may be added, or a laminated structure may be used.

  It is preferable that the material, width, and thickness of the thin film electrode 11a and the reflector 11c are adjusted so that inductance, capacitance, and the like according to design can be obtained. As a thin film forming method, a sputtering method, a vacuum thin film forming technique such as vapor deposition, a plating method, a paste printing method, or the like can be applied.

  Next, the principle of detecting tire distortion and the like by the surface acoustic wave element 11 will be described. When the piezoelectric substrate of the surface acoustic wave element 11 receives a change in the external environment, propagation characteristics such as the phase velocity and frequency of the surface acoustic wave propagating on the surface change. By comparing, for example, the phases of these signals, information on the external environment can be obtained.

  In the present embodiment, distortion or the like can be detected from the phase difference of the reflected waves. In this example, a method of detecting by phase comparison is used. However, in addition to this, a method of comparing delay times of reflected waves, a method of comparing deviation from a reference frequency, and the like can be applied.

  When detection is performed using a plurality of surface acoustic wave elements 11, it is necessary to determine each element 11. In this case, normally, the case where there is reflection is identified as 1 and the case where there is no reflection is identified as 0. Therefore, in order to insert N bits of information, it is possible to arrange a maximum of 2 N power reflectors.

  Next, the operation of the present embodiment configured as described above will be described. The transmission / reception means 20 transmits the pulsed drive signal generated by the transmission / reception circuit to the responder 10 via the antenna 21. This drive signal is supplied to the surface acoustic wave element 11 via the antenna 12 (and the matching circuit unit) of the responder 10. The surface acoustic wave element 11 generates a surface acoustic wave (SAW) having a wavelength corresponding to the pattern interval of the comb-shaped electrode 11a when a drive signal is input to the comb-shaped electrode 11a serving as a transmission / reception electrode. The surface acoustic wave generated at the center of the piezoelectric substrate 11b propagates to one end side of the piezoelectric substrate 11b, is reflected by the reflector 11c, and returns to the transmitting and receiving electrodes. The transmission / reception electrode detects the surface acoustic wave reflected by the reflector and converts it into an electric signal, and the converted electric signal is sent back to the transmission / reception means 20 via the antenna 12 as a response signal. The transmission / reception means 20 supplies the received response signal to the arithmetic circuit unit, and the arithmetic circuit unit calculates information such as the magnitude of distortion from the phase difference of the response signal.

  The tire condition detection device of the present invention employs the sensor mounting structure of the present invention in such a device. That is, as shown in FIG. 1, the sensor mounting structure of the present invention has a pair of leg portions 15 having one end 15a bonded to the tire T, and straddles between the leg portions 15 and is input by distortion caused by bending force. And a surface acoustic wave element 11 that changes a response signal to the signal, and a sensor mounting structure in which the other end 15b of the leg portion 15 is fixedly supported with respect to the surface acoustic wave element 11 or its support body 16. is there.

  In this embodiment, an example in which the surface acoustic wave element 11 is integrated with the support 16 and the antenna 12 connected to the surface acoustic wave element 11 is provided on the support 16 is shown. In this example, the bridge structure B is configured by supporting the other end 15b of the leg portion 15 with respect to the support body 16 at a fixed end.

  The surface acoustic wave element 11 is attached to the inner surface of the tire T, for example, in the direction shown in FIG. 2, and in this case, distortion at the time of compression or extension in the tire circumferential direction can be detected. Further, for example, when the surface acoustic wave element 11 is attached at an angle shifted by 90 ° with respect to the direction shown in FIG. 2, it is possible to detect a strain at the time of compression or expansion in the tire width direction. According to the present invention, it is possible to detect strain and stress at the time of compression or extension in any direction.

  More specifically, as shown in FIG. 3 (a), when compression distortion occurs in the tire, the pair of leg portions 15 having one end 15a bonded to the tire are closed, and the leg portions 15 are surface acoustic waves. Since the fixed end is supported by the support 16 of the element 11, the surface acoustic wave element 11 can be detected by the surface acoustic wave element 11 due to bending deformation in the surface acoustic wave element 11.

  Further, as shown in FIG. 3B, when an elongation strain occurs in the tire, a pair of leg portions 15 having one end 15 a bonded to the tire are opened, and the leg portions 15 are formed of the surface acoustic wave element 11. Since the support 16 is supported at the fixed end, bending deformation occurs in the surface acoustic wave element 11, so that the strain at the time of expansion and the like can be detected by the surface acoustic wave element 11.

  The leg portion 15 of the bridge structure B preferably has a higher bending rigidity than the surface acoustic wave element 11, and the material of the leg portion 15 may be metal, ceramics, glass, resin, or the like. Moreover, the same material as the piezoelectric substrate 11b of the surface acoustic wave element 11 may be used. The thickness of the leg portion 15 is preferably 1 to 3 mm although it depends on the material.

  The height of the leg 15 is preferably 0.5 to 3 times the interval between the other ends 15b of the leg 15. Specifically, the height of the leg portion 15 is preferably 3 to 18 mm. The width of the other end 15 b of the leg portion 15 is preferably 0.5 to 3 times the width of the surface acoustic wave element 11. Specifically, the width of the other end 15b of the leg portion 15 is preferably 1.5 to 9 mm.

  The support body 16 constituting the bridge structure B preferably has a bending rigidity comparable to that of the surface acoustic wave element 11, and the thickness of the support body 16 is preferably 0.5 to 2 mm. For this reason, as a material of the support body 16, a metal, ceramics, glass, etc. are preferable.

  Although the support body 16 and the leg part 15 which comprise the bridge structure B may be integrated by adhesion | attachment, joining, etc., it is preferable that it is integrally molded from the beginning. As a result, breakage and stress transmission loss at the boundary between the support 16 and the leg 15 can be effectively prevented.

  The surface acoustic wave element 11 and the support 16 can be integrated by adhesion, bonding, or the like. The adhesion can be performed using, for example, a thermosetting resin such as an epoxy resin or a phenol resin, or a solvent-type adhesive. Bonding can be performed using a ceramic sintering agent or the like.

  As a method for bonding the leg 15 to the tire T, a commercially available rubber adhesive can be used, and it is preferable to roughen or renew the bonding surface in advance by buffing, sanding or the like. Alternatively, the legs 15 may be partially embedded in the tire T and bonded and fixed.

[Other Embodiments]
(1) In the above-described embodiment, the example in which the surface acoustic wave element is integrated with the support is shown. However, in the present invention, as shown in FIG. The other end 15b of the leg portion 15 may be fixedly supported with respect to the wave element 11. According to this configuration, since the displacement of the leg portion 15 is directly transmitted to the surface acoustic wave element 11, detection sensitivity and detection accuracy can be further increased.

  In the above, the integration of the surface acoustic wave element 11 and the leg portion 15 can be performed by adhesion or bonding. The adhesion can be performed using, for example, a thermosetting resin such as an epoxy resin or a phenol resin, or a solvent-type adhesive. Bonding can be performed using a ceramic sintering agent or the like.

  When the support 16 is not used, the antenna 12 can be provided on the piezoelectric substrate 11 b of the surface acoustic wave element 11 or the leg portion 15.

  (2) In the above-described embodiment, an example in which the leg portion is bonded to the surface acoustic wave element or its support has been shown. However, in the present invention, the leg portion 15 is attached to the surface acoustic wave element 11 as shown in FIG. The leg portion 15 may be integrally formed with the support 16 of the surface acoustic wave element 11.

  In the above case, for example, when the piezoelectric substrate 11b of the surface acoustic wave element 11 is molded, the leg portion 15 is molded into a shape having the leg portion 15 or the intermediate portion of the thick piezoelectric substrate 11b is cut or the like. After forming the shape with 15 left, the comb-shaped electrode 11a and the reflector 11c may be formed by patterning or the like.

  (3) In the above-described embodiment, the example in which the electrode pattern forming surface of the surface acoustic wave element is disposed on the upper side is shown. However, in the present invention, the electrode pattern forming surface of the surface acoustic wave element is disposed on the lower side. It may be. This makes it easier to prevent trauma and dirt.

  (4) In the above-described embodiment, an example of a tire state detection device using only one surface acoustic wave element is shown, but in the present invention, a plurality of surface acoustic wave elements are bonded in a plurality of directions, You may make it detect simultaneously the distortion and stress of multiple directions.

  In that case, it becomes easy to distinguish each response signal by shifting the position of the antenna on the responder side in the tire circumferential direction. In addition, in order to identify the response signal from each surface acoustic wave element, identification information may be included in the response signal itself by changing the formation position or pattern of the reflector.

  (5) In the above-described embodiment, an example in which an antenna is provided in a block structure or a surface acoustic wave element has been shown. However, in the present invention, an antenna is provided separately from the antenna and wired via a matching circuit as necessary. Is also possible.

  In addition, the surface acoustic wave element can be attached to a sidewall portion or the like outside the tire.

The perspective view which shows an example of the sensor attachment structure of this invention BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows an example of the detection apparatus of the tire condition of this invention, (a) is sectional drawing of a tire meridian direction, (b) is sectional drawing of a tire equator direction Explanatory drawing which shows the effect | action of the sensor attachment structure of this invention The perspective view which shows the other example of the sensor attachment structure of this invention The perspective view which shows the other example of the sensor attachment structure of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Response machine 11 Surface acoustic wave element 12 Antenna 15 Leg part 15a One end of a leg part 15b The other end of a leg part 16 Support body 20 Transmission / reception means 21 Antenna T Tire

Claims (4)

  A pair of leg portions bonded at one end to a tire, and a surface acoustic wave element straddling between the leg parts and changing a response signal to an input signal by distortion caused by a bending force, the surface acoustic wave element or A sensor mounting structure in which the other end of the leg is fixedly supported with respect to the support.   The height of the leg is 0.5 to 3 times the distance between the other ends of the leg, and the width of the other end of the leg is 0.5 to 3 times the width of the surface acoustic wave element. The sensor mounting structure according to claim 1.   3. The sensor mounting structure according to claim 1, wherein the surface acoustic wave element is integrated with the support, and an antenna connected to the surface acoustic wave element is provided on the support. A surface acoustic wave element and a responder installed on the tire side having an antenna connected thereto, a drive signal is transmitted to the responder, and a response signal from the responder is received to process the signal. In a tire condition detection device comprising transmission / reception means installed on the vehicle body side to perform,
The surface acoustic wave element changes a response signal to an input signal due to distortion caused by a bending force, and the surface acoustic wave element is attached to a tire by the sensor mounting structure according to any one of claims 1 to 3. A tire condition detection device characterized by comprising:

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