Intelligent tire flexible strain sensor and preparation method thereof

Abstract

The application discloses a kind of intelligent tire flexible strain sensors and preparation method thereof, belong to sensor manufacturing technical field.The lower substrate layer of the flexible strain sensor of the intelligent tire of the present application is tire inner tread, when preparing tire inner tread, the embedded recess of the flexible strain sensor of the intelligent tire is imprinted by mould, then resistance layer, electrode and packaging layer are prepared, finally vulcanization is carried out to obtain integrally formed intelligent tire flexible strain sensor.The flexible strain sensor of the intelligent tire of the present application is a recess embedded sensor, which is the same as the tire as a whole, without the external pasting protruding structure of ordinary sensor, there is no bonding interface, which does not affect the appearance and safety of the tire inner tread, and can be stretched, bent and twisted, with better stability and longer service life.

Description

Technical Field

[0001] This invention relates to the field of sensor manufacturing technology, and in particular to an intelligent tire flexible strain sensor and its preparation method. Background Technology

[0002] With the development of the autonomous vehicle industry, the requirements for related automotive components are also increasing. Among them, intelligent tires are a crucial aspect of ensuring driving safety. Intelligent tires collect data on tire stress and deformation by integrating various sensors within the tire. This data is then processed to derive key factors for the autonomous driving control center, such as road conditions, load, and friction coefficient. Tire strain testing involves flexible strain, and the strain conditions are complex and variable, requiring flexible strain sensors with a large range for measurement. Flexible strain sensors possess properties such as flexibility, bendability, and strain tolerance, allowing for application in many complex scenarios within the tire. Common intelligent tire strain sensors include strain gauges (metal electrode plates) and attached flexible strain sensors, both of which are external sensors and cannot be integrated with the tire as a single strain gauge. Strain gauges generally have a small range and require amplification circuits for measurement. The strain gauge substrate is typically non-stretchable and must be attached to the surface of the object being measured. While attached strain sensors can meet the range requirements, the attached structure is prone to damage and detachment during the high-frequency movement of the tire, leading to uneven stress distribution. To improve the overall strain measurement integrity between the sensor and the tire, existing methods use flexible adhesives with stronger bonding strength. However, the following problems still exist: 1. The strain gauge substrate lacks tensile strength and relies on bending forces within the tire, making it prone to damage. 2. The need for adhesives results in poor adhesion between the strain gauge substrate and the tire inner tread, weakening the test results. 3. The bonded strain sensor to the tire inner tread is not tight, and the intermediate adhesive is prone to detachment. 4. The strain sensor lacks overall integrity with the tire, leading to distorted strain measurements. 5. The complex operating environment of tires limits the long-term usability of the strain sensor bonding structure. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an integrally molded intelligent tire flexible strain sensor and its preparation method.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides a method for fabricating an intelligent tire flexible strain sensor, comprising the following steps:

[0006] S1: Preparation of the lower base layer: The raw rubber is pre-vulcanized and imprinted under a mold to obtain a semi-vulcanized lower base layer with grooves;

[0007] S2: Preparation of resistive layer: The conductive filler slurry is coated or sprayed onto the groove surface of the semi-vulcanized substrate obtained in S1 to obtain a resistive layer, and electrodes are added to the surface of the resistive layer according to the direction required for testing to obtain a composite material with electrodes.

[0008] S3: Preparation of encapsulation layer: Raw rubber is filled into the groove and then vulcanized to obtain an integrally formed intelligent tire flexible strain sensor;

[0009] The raw rubber in step S1 is the same as the raw rubber in step S3. In order for the encapsulation layer to completely fill the groove, the size of the raw rubber in step S3 should be slightly larger than the size of the groove, with a size range of 0.05-0.1 mm.

[0010] The lower base layer of the intelligent tire flexible strain sensor of this invention is the tire inner tread. During the preparation of the tire inner tread, the embedded groove of the intelligent tire flexible strain sensor is imprinted using a mold. Then, a resistive layer, electrodes, and an encapsulation layer are prepared, and finally, vulcanization is performed to obtain a one-piece intelligent tire flexible strain sensor. The intelligent tire flexible strain sensor of this invention has no bonding interface and can be integrally formed with the tire, eliminating the external adhesive protrusion structure of ordinary sensors. It does not affect the morphology and safety of the tire inner tread, and can be stretched, bent, and twisted, resulting in more stable performance and a longer service life. The lower base layer and encapsulation layer of the intelligent tire flexible strain sensor of this invention use the same raw rubber as raw materials, having the same or similar elastic modulus, which can improve the accuracy of intelligent tire strain testing.

[0011] The groove in step S1 of this invention can be of any shape, such as a square, rectangle, hexagon, irregular shape, etc., which can be prepared by those skilled in the art according to actual needs; the position of the groove is also arbitrary, such as the center of the tire crown, the tire sidewall, or the tire shoulder, which can be set by those skilled in the art according to actual needs.

[0012] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, in step S1, the depth of the groove is 0.5-1.5 mm.

[0013] In this invention, the depth of the groove is one of the factors affecting the performance of the intelligent tire flexible strain sensor. If the groove is too deep, it will affect the air tightness inside the tire, causing the data collected after the tire becomes unbalanced to be distorted. If the groove is too shallow, the upper encapsulation layer of the intelligent tire flexible strain sensor will become thinner, the encapsulation sealing will be weakened, and the influence of the tire environment on the stable strain of the resistive layer will be increased, resulting in a weakening of the stability of data acquisition.

[0014] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, in step S1, the pre-vulcanization temperature is 90-110℃, the pre-vulcanization time is 10-15min, and the pre-vulcanization pressure is 3-5MPa.

[0015] The temperature, time, and pressure of pre-curing affect the performance of the substrate layer. If the pre-curing temperature is too high and / or the time is too long, the substrate layer will be over-cured, resulting in poor adhesion to the resistive layer and the upper encapsulation layer. If the pre-curing temperature is too low and / or the time is too short, the substrate layer will not be sufficiently imprinted, and the imprinted shape will be difficult to fix. The present invention preferably uses a pre-curing temperature of 90-110℃, a pre-curing time of 10-15min, and a pre-curing pressure of 3-5MPa to obtain a substrate layer with better performance.

[0016] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, in step S3, the vulcanization temperature is 120-145℃, the vulcanization time is 30-90min, and the vulcanization pressure is 3-5MPa.

[0017] The temperature, time, and pressure of vulcanization affect the performance of intelligent tire flexible strain sensors. Specifically, if the vulcanization temperature is too high, the time is too long, or the pressure is too high, the resistive layer of the intelligent tire flexible strain sensor is prone to cracking and breakage due to the flowability of rubber during hot vulcanization. If the vulcanization temperature is too low, the time is too short, or the pressure is too low, the imprint shape and adhesion of the intelligent tire flexible strain sensor will be reduced.

[0018] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, the raw rubber in step S1 and the raw rubber in step S3 are one of natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, silicone rubber, chloroprene rubber, butyl rubber, nitrile rubber, ethylene propylene rubber, and fluororubber.

[0019] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, in step S2, the conductive filler slurry is one of carbon-based filler slurry, metal filler slurry, elastomer / carbon-based composite filler slurry, and elastomer / metal composite filler slurry.

[0020] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, the carbon-based filler slurry is at least one of carbon nanotube slurry, graphene slurry, graphite slurry, and carbon black slurry.

[0021] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, the metal filler slurry is at least one of nickel slurry, silver slurry, copper slurry, aluminum slurry, and liquid metal ink.

[0022] As a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, the method for preparing the elastomer / carbon composite filler slurry is as follows: the elastomer and the carbon filler slurry are mixed evenly to obtain the elastomer; the elastomer is rubber, polyurethane, or styrene-ethylene-butene-styrene block copolymer.

[0023] As a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, the method for preparing the elastomer / carbon composite filler slurry is as follows: the elastomer and the metal filler slurry are mixed evenly to obtain the elastomer; the elastomer is rubber, polyurethane, or styrene-ethylene-butene-styrene block copolymer.

[0024] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, the size of the conductive filler in the conductive filler slurry is at the nanometer or micrometer level; the micrometer-level conductive filler is of any one of the following types: fibrous, sheet-like, or spherical.

[0025] In a preferred embodiment of the method for preparing the intelligent tire flexible strain sensor of the present invention, in step S2, the electrode is one of the following: metal electrode terminal, metal wire, metal gasket, screen-printed conductive film, and metal-plated woven fabric.

[0026] Secondly, the present invention also provides an intelligent tire flexible strain sensor, which is prepared by the above-described method for preparing an intelligent tire flexible strain sensor.

[0027] As a preferred embodiment of the intelligent tire flexible strain sensor of the present invention, the intelligent tire flexible strain sensor is an integrally molded structure, including: a tire inner tread with grooves; a resistive layer coated on the surface of the grooves; a pair of electrodes located at both ends of the resistive layer surface in the test direction; and an encapsulation layer formed of rubber covering the surface of the resistive layer, wherein the tire inner tread and the encapsulation layer are made of the same type of rubber.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The intelligent tire flexible strain sensor of the present invention has a lower base layer and an encapsulation layer made of the same tire rubber material, with the same or similar elastic modulus, which can improve the authenticity of intelligent tire strain testing; at the same time, the intelligent tire flexible strain sensor can be stretched, bent and twisted, with better stability and longer service life.

[0030] (2) The intelligent tire flexible strain sensor of the present invention is an embedded sensor in the embossed groove, which is the same as the tire. It does not have the external adhesive protrusion structure of ordinary sensors, and there is no bonding interface. It does not affect the morphology and safety of the tire inner tread.

[0031] (3) The intelligent tire flexible strain sensor of the present invention has a large strain range and can be subjected to shear deformation and shear bending, and can be applied to the tire sidewall strain test of complex road surface and tire steering. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the fabrication process of the intelligent tire flexible strain sensor of the present invention.

[0033] Figure 2 This is a schematic diagram of the structure of the intelligent tire flexible strain sensor of the present invention, including a lower base layer 4, a resistive layer 3, an electrode 2, and an encapsulation layer 1;

[0034] Figure 3 The strain detection diagram is shown in Example 1 for the intelligent tire flexible strain sensor.

[0035] Figure 4 This is a top view of the U-shaped resistive layer obtained in Example 2;

[0036] Figure 5 This is a schematic diagram of the intelligent tire triaxial strain sensor obtained in Example 4;

[0037] Figure 6 The image shows the test results of the intelligent tire triaxial strain sensor obtained in Example 4, which tested the triaxial deformation of the tire.

[0038] Figure 7 The initial resistance diagram of the fatigue test of the intelligent tire flexible strain sensor obtained in Example 5;

[0039] Figure 8 The resistance diagram of the intelligent tire flexible strain sensor obtained in Example 5 after 200,000 fatigue tests.

[0040] Figure 9 Example 6: 1 / 1000 strain cycle test diagram of the intelligent tire flexible strain sensor;

[0041] Figure 10 This is a diagram of the tensile and bending cycle test of the intelligent tire flexible strain sensor in Example 7.

[0042] Figure 11 This is a test distribution diagram of the intelligent tire flexible strain sensor on the tire bench in Example 8.

[0043] Figure 12 This is a test result diagram of the tire test bench for the intelligent tire flexible strain sensor in Example 8;

[0044] Figure 13 This is an enlarged view of the test results of the intelligent tire flexible strain sensor tire test bench in Example 8. Detailed Implementation

[0045] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0046] Example 1

[0047] In this embodiment, a smart tire flexible strain sensor is fabricated using brominated butyl rubber as the lower substrate layer and encapsulation layer, and carbon nanotubes and graphite as conductive layers. The specific process is as follows:

[0048] S1: Preparation of the lower substrate layer 4: The brominated butyl rubber is pre-vulcanized and imprinted in a 5mm×10mm square mold. The pre-vulcanization temperature is 100℃ and the pre-vulcanization time is 20min to obtain a semi-vulcanized lower substrate layer 4 with grooves. The depth of the grooves is 1mm.

[0049] S2: Preparation of resistive layer 3: A slurry of carbon nanotubes and graphite is sprayed onto the surface of the groove obtained in step S1 to obtain resistive layer 3, and an electrode is added to each end of the resistive layer surface to obtain a composite material carrying electrode 2.

[0050] S3: Preparation of encapsulation layer 1: 5.1mm×10.1mm×1mm brominated butyl rubber is filled into the groove with a resistive layer on the surface obtained in S2, and then vulcanized at 120℃ and 4MPa for 1h to obtain an integrally formed intelligent tire flexible strain sensor.

[0051] The fabrication process of the intelligent tire flexible strain sensor in this embodiment is as follows: Figure 1 As shown in the figure, the structural diagram of the intelligent tire flexible strain sensor obtained in this embodiment is as follows. Figure 1 As shown.

[0052] The intelligent tire flexible strain sensor prepared in this embodiment was used to fabricate an uninflated tire. The tire was manually rolled back and forth at a speed of 3 km / h, and resistance was monitored using a multimeter. The results are as follows. Figure 3 As shown, from Figure 3 As can be seen, the strain resistance of the tire changes significantly, with high repeatability and a stable resistance baseline, indicating that the intelligent tire flexible strain sensor prepared by this invention has excellent strain response performance.

[0053] Example 2

[0054] In this embodiment, a smart tire flexible strain sensor is fabricated using brominated butyl rubber as the lower substrate layer and encapsulation layer, and carbon nanotubes and graphite as conductive layers. The specific process is as follows:

[0055] S1: Preparation of the lower substrate layer 4: The brominated butyl rubber is pre-vulcanized and imprinted in a 3mm×10mm square mold. The pre-vulcanization temperature is 100℃ and the pre-vulcanization time is 20min to obtain a semi-vulcanized lower substrate layer 4 with grooves. The depth of the grooves is 1mm.

[0056] S2: Preparation of resistive layer 3: A slurry of carbon nanotubes and graphite is sprayed onto the surface of the groove obtained in step S1 to obtain resistive layer 3. Then, U-shaped etching is performed under a laser etching machine to obtain a U-shaped resistive layer (e.g., Figure 4 As shown), an electrode is added to each end of the resistive layer to obtain a composite material carrying electrode 2.

[0057] S3: Preparation of encapsulation layer 1: 3.1mm×10.1mm×1mm brominated butyl rubber is filled into the groove with a resistive layer on the surface obtained in S2, and then vulcanized at 120℃ and MPa for 1h to obtain an integrally formed intelligent tire flexible strain sensor.

[0058] Example 3

[0059] This embodiment uses ethylene propylene rubber as the lower substrate layer and encapsulation layer, and carbon nanotubes and graphite as conductive layers to fabricate a smart tire flexible strain sensor. The specific process is as follows:

[0060] S1: Preparation of the lower base layer 4: Ethylene propylene rubber is pre-vulcanized and imprinted in a 4mm×4mm square mold. The pre-vulcanization temperature is 100℃ and the pre-vulcanization time is 20min to obtain a semi-vulcanized lower base layer 4 with grooves. The groove depth is 0.5mm.

[0061] S2: Preparation of resistive layer 3: A slurry of carbon nanotubes and graphite is sprayed onto the surface of the groove obtained in step S1 to obtain resistive layer 3. Then, U-shaped etching is performed under a laser etching machine to obtain a U-shaped resistive layer (e.g., Figure 4 As shown), an electrode is added to each end of the resistive layer to obtain a composite material carrying electrode 2.

[0062] S3: Preparation of encapsulation layer 1: 4.1mm×4.1mm×0.5mm ethylene propylene rubber is filled into the groove with a resistive layer obtained in S2, and then vulcanized at 120℃ and 4MPa for 1h to obtain an integrally formed intelligent tire flexible strain sensor.

[0063] Example 4

[0064] In this embodiment, a smart tire flexible strain sensor is fabricated using brominated butyl rubber as the lower substrate layer and encapsulation layer, and carbon nanotubes and graphite as conductive layers. The specific process is as follows:

[0065] S1: Preparation of the lower base layer 4: Brominated butyl rubber is pre-vulcanized and imprinted in a 5mm×10mm square mold. The pre-vulcanization temperature is 100℃ and the pre-vulcanization time is 20min, resulting in a semi-vulcanized lower base layer 4 with grooves. The grooves are parallel to the tire rolling direction, perpendicular to the tire rolling direction, and at a 45° angle to the tire rolling direction, respectively. The groove depth is 1mm.

[0066] S2: Preparation of resistive layer 3: A slurry of carbon nanotubes and graphite is sprayed onto the surface of the groove obtained in step S1 to obtain resistive layer 3. Then, U-shaped imprinting is performed under a laser imprinter to obtain a U-shaped resistive layer. An electrode is added to each end of the resistive layer surface to obtain a composite material carrying electrode 2. The electrodes of each directional sensor are located at the same end. The three-directional sensors work independently, but are subjected to cascading strain on the same substrate.

[0067] An electrode is added to each end of the resistive layer to obtain a composite material carrying electrode 2.

[0068] S3: Preparation of encapsulation layer 1: 5.1mm×10.1mm×1mm brominated butyl rubber is filled into the groove with a resistive layer on the surface obtained in S2, and then vulcanized at 120℃ and 4MPa for 1h to obtain an integrally formed intelligent tire flexible strain sensor.

[0069] The fabrication process of the intelligent tire flexible strain sensor in this embodiment is as follows: Figure 1 As shown in the figure, the structural diagram of the intelligent tire flexible strain sensor obtained in this embodiment is as follows. Figure 5 As shown.

[0070] The intelligent tire flexible strain sensor prepared in this embodiment was used to fabricate an uninflated tire. The tire was manually rolled back and forth at a speed of 3 km / h, and resistance was monitored using a multimeter. The results are as follows. Figure 6 As shown, from Figure 6 As can be seen, the strain resistance changes significantly in the tire rolling direction, while the strain is smaller in the vertical and 45° angle directions, which is consistent with the test of tire triaxial force, indicating that the sensor has excellent tire triaxial force strain response performance.

[0071] Example 5

[0072] This embodiment tests the fatigue resistance of an intelligent tire flexible strain sensor. The intelligent tire flexible strain sensor prepared in Example 2 was fixed on an electromagnetic fatigue testing machine and subjected to tensile and recovery stresses at a rate of 50 mm / min, with a tensile strain of 5%. The resistance value was monitored using a multimeter during the test. The test results are as follows: Figure 7 and Figure 8 As shown, Figure 7 The figure shows the initial cyclic resistance. Figure 8The resistance after 200,000 stretching cycles shows that the sensor has good fatigue resistance and can be used for a long time.

[0073] Example 6

[0074] The intelligent tire flexible strain sensor prepared in Example 2 was subjected to sensitivity testing. The test measured a minute deformation signal of one-thousandth, and the resistance value was monitored using a multimeter. Figure 9 As shown, this sensor can sensitively detect deformations as small as one-thousandth.

[0075] Example 7

[0076] This embodiment tests the tensile-compression cycle performance of the intelligent tire flexible strain sensor. The intelligent tire flexible strain sensor prepared in Example 2 was subjected to tensile and compressive stresses at a rate of 50 mm / min, with both tensile and compressive strains at 5%. Tensile stress was linear tension, and compression was bending compression. Resistance values ​​were monitored using a multimeter during the test. The test results are as follows: Figure 10 As shown, from Figure 10 As can be seen from the above, the intelligent tire flexible strain sensor of the present invention can continuously perform stretching and compression, and the stretching and compression states can be switched at will. It can also reflect the test state well and can be applied to complex working environments, such as environments where the rubber material in the tire is subjected to alternating stretching and compression.

[0077] Example 8

[0078] like Figure 11 The intelligent tire flexible strain sensor was prepared according to the method in Example 2, with the distribution points divided into the tread and sidewall portions. The obtained intelligent tire flexible strain sensor was placed on a tire test bench and tested under different load conditions: 30%, 50%, 80%, 100%, and 130% of the standard load (standard load is 5684 N). The test data are shown in the figure below. Figure 12 As shown in the enlarged image Figure 13 .from Figure 12 and Figure 13 As can be seen from the above, the intelligent tire flexible strain sensor of the present invention can not only test the tread data, but also test the sidewall data under complex working conditions. This shows that the intelligent tire flexible strain sensor of the present invention can be applied to large deformation strain scenarios, has a wide deformation range, and can withstand the shear strain of the sidewall.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for fabricating an intelligent tire flexible strain sensor, characterized in that, Includes the following steps: S1: Preparation of the lower base layer: The raw rubber is pre-vulcanized and imprinted under a mold to obtain a semi-vulcanized lower base layer with grooves; the lower base layer is the inner tread of the tire; S2: Preparation of resistive layer: The conductive filler slurry is coated on the groove surface of the semi-vulcanized substrate obtained in S1 to obtain a resistive layer, and electrodes are added to the surface of the resistive layer according to the direction required for testing to obtain a composite material with electrodes. S3: Preparation of the encapsulation layer: Raw rubber is filled into the groove and then vulcanized to obtain an integrally formed intelligent tire flexible strain sensor; the intelligent tire flexible strain sensor and the tire are the same whole; The raw rubber in step S1 is the same as the raw rubber in step S3; in step S1, the depth of the groove is 0.5-1.5mm.

2. The preparation method according to claim 1, characterized in that, In step S1, the pre-vulcanization temperature is 90-110℃, the pre-vulcanization time is 10-15 min, and the vulcanization pressure is 3-5 MPa.

3. The preparation method according to claim 1, characterized in that, In step S3, the vulcanization temperature is 120-145℃, the vulcanization time is 30-90 min, and the vulcanization pressure is 3-5 MPa.

4. The preparation method according to claim 1, characterized in that, The raw rubber in step S1 and step S3 is one of the following: natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, silicone rubber, chloroprene rubber, butyl rubber, nitrile rubber, ethylene propylene rubber, and fluororubber.

5. The preparation method according to claim 1, characterized in that, In step S2, the conductive filler slurry is one of the following: carbon-based filler slurry, metal filler slurry, elastomer / carbon-based composite filler slurry, and elastomer / metal composite filler slurry.

6. The preparation method according to claim 5, characterized in that, The conductive filler in the conductive filler slurry is of nanometer or micrometer size; the micrometer-sized conductive filler is of any of the following types: fibrous, sheet-like, or spherical.

7. The preparation method according to claim 1, characterized in that, In step S2, the electrode is one of a metal electrode terminal, a metal wire, or a metal pad.

8. A smart tire flexible strain sensor, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The intelligent tire flexible strain sensor as described in claim 8, characterized in that, The intelligent tire flexible strain sensor is an integrally molded structure, including: a tire inner tread with grooves; a resistive layer coated on the surface of the grooves; a pair of electrodes located at both ends of the resistive layer surface in the test direction; and an encapsulation layer formed of rubber covering the surface of the resistive layer, wherein the tire inner tread and the encapsulation layer are made of the same type of rubber.

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