JP7576259B2 - Structure of rubber structure and method of using the rubber structure - Google Patents

Description

The present invention relates to a structure of a rubber structure and a method of using the rubber structure, and more specifically to a structure of a highly versatile rubber structure that can improve the dynamic friction force against a target surface without unnecessarily scratching the target surface with which it comes into contact during the initial period of use, and a method of using the rubber structure.

Rubber structures such as tires are used in contact with a target surface such as a road. For such rubber structures, the magnitude of kinetic frictional force against the target surface is one indicator of performance. For example, there are known tires that add hard particles such as seed shells to the tread rubber to increase kinetic frictional force against a target surface such as ice and snow, thereby improving frictional force through a scratching effect. However, structures in which such hard particles are exposed on the tread surface have the disadvantage of excessively scratching and damaging the road surface.

Alternatively, in order to improve the frictional force of tires against wet road surfaces, various compounding agents and additives to be compounded in rubber compositions have been devised (see, for example, Patent Document 1). That is, special rubber compositions have been developed to improve frictional force. In other words, in various rubber structures, not limited to tires, it is difficult to improve the dynamic frictional force against the target surface when a general-purpose vulcanized rubber or the like is used on the contact surface. Therefore, there is room for improvement in realizing a versatile rubber structure that improves the dynamic frictional force against the target surface without causing unnecessary scratches on the contacting target surface.

JP 2001-335664 A

The object of the present invention is to provide a highly versatile rubber structure that can improve the dynamic frictional force against a target surface without unnecessarily scratching the target surface with which it comes into contact during the initial period of use, and a method for using the rubber structure.

In order to achieve the above-mentioned object, the rubber structure of the present invention is a rubber structure comprising vulcanized rubber and a rigid body embedded in the vulcanized rubber, and having a contact surface that comes into contact with a target surface during use, wherein the rigid bodies are scattered in a region near the contact surface at a predetermined depth from the contact surface made of the vulcanized rubber in which the rigid bodies are embedded , without being exposed from the contact surface, and the Young's modulus of the rigid bodies is 50% or less or 200% or more of the Young's modulus of the vulcanized rubber.

Another rubber structure structure of the present invention is a rubber structure structure comprising vulcanized rubber and a rigid body embedded in the vulcanized rubber, and having a contact surface that comes into contact with a target surface during use, characterized in that the rigid bodies are scattered in a region near the contact surface at a predetermined depth from the contact surface made of the vulcanized rubber in which the rigid bodies are embedded, without being exposed from the contact surface, and the density of the rigid bodies is 70% or less or 130% or more of the density of the vulcanized rubber.

The method of using a rubber structure of the present invention is a method of using a rubber structure having the structure of the rubber structure described above, characterized in that the diameter equivalent dimension of the rigid body is 30% or more of the arithmetic mean height Sa of the target surface, the predetermined depth is less than 1 mm, and the rubber structure is moved relative to the target surface so as to slide the contact surface against the target surface.

In the structure of the rubber structure of the present invention, the rigid bodies embedded in the vulcanized rubber are scattered in a region near the contact surface at a predetermined depth from the contact surface without being exposed from the contact surface, and the Young's modulus or density of the rigid bodies is significantly changed with respect to the vulcanized rubber. In this way, by making the rigidity (Young's modulus) and density in the region near the contact surface in the rubber structure significantly different from the surrounding vulcanized rubber, when the contact surface is slid against the target surface, the hysteresis loss of the rubber structure is larger than when the rigid bodies are not embedded. As a result, the dynamic friction force with respect to the target surface is improved even if general-purpose vulcanized rubber is used for the contact surface. In addition, since the rigid bodies are not exposed to the contact surface, the rigid bodies do not cause unnecessary scratches on the target surface in the early stages of use of the rubber structure.

In the method for using the rubber structure of the present invention, the diameter equivalent dimension of the rigid body is set to 30% or more of the arithmetic mean height Sa of the target surface, and the predetermined depth is set to less than 1 mm. Under these conditions, the rubber structure is moved relative to the target surface so that the contact surface slides against the target surface, thereby more effectively improving the dynamic friction force against the target surface.

FIG. 1 is an explanatory diagram illustrating a cross-sectional view of a rubber structure in which a structure of the present invention is adopted. FIG. 2 is a view taken along the arrow A in FIG. FIG. 2 is an explanatory diagram illustrating, in an enlarged scale, a state in which the contact surface of the rubber structure in FIG. 1 is in contact with a target surface. FIG. 2 is an explanatory diagram illustrating the right half of a tire, which is a rubber structure, in a width direction cross-sectional view. FIG. 4 is an explanatory diagram illustrating a schematic example of a state in which the rubber structure in FIG. 3 is moved relatively to a target surface. FIG. 2 is a graph illustrating the relationship between the dynamic friction force of a rubber structure against a target surface and Young's modulus of a rigid body. FIG. 2 is a graph illustrating the relationship between the dynamic friction force of a rubber structure against a target surface and the density of a rigid body. FIG. 4 is a graph illustrating the relationship between the kinetic friction force of a rubber structure against a target surface and a depth position from a contact surface of a rigid body. FIG. 11 is a graph illustrating the relationship between the dynamic friction force of a rubber structure against a target surface and the diameter of a rigid body.

The structure of the rubber structure of the present invention and the method of using the rubber structure will be explained based on the embodiment shown in the figure.

The rubber structure 1 of the embodiment illustrated in Figures 1 to 3 employs the structure of the present invention, has a contact surface 2 that contacts a target surface 5 during use, and is characterized by a large dynamic friction force against the target surface 5. In other words, by employing the structure of this rubber structure 1, it is possible to increase the dynamic friction coefficient. This dynamic friction coefficient can be measured in accordance with the test method specified in JIS K7125.

The rubber structure 1 comprises vulcanized rubber 3 and rigid bodies 4 embedded in the vulcanized rubber 3. In a region R near the contact surface 2 at a predetermined depth h from the contact surface 2, the rigid bodies 4 are scattered without being exposed from the contact surface 2. The region R near the contact surface 2 where the rigid bodies 4 are embedded is a region where the predetermined depth h (shortest distance between the rigid bodies 4 and the contact surface 2) is, for example, in a range of 0.05 mm or more and less than 1 mm from the contact surface 2. Note that an appropriate predetermined depth h may differ depending on the size of the rigid bodies 4 and the roughness of the target surface 5, and is generally in the range of 10 mm or less.

The rigid bodies 4 may be embedded in a region deeper than the nearby region R, but even if the rigid bodies 4 are embedded in a region deeper than the nearby region R, the improvement in the dynamic friction force of the rubber structure 1 cannot be expected to be significant. Therefore, in this embodiment, the rigid bodies 4 are embedded only in the nearby region R. Also, in this embodiment, a large number of rigid bodies 4 are scattered in two layers, one above the other, but they may be scattered in multiple layers or in a single layer.

In the first embodiment, the Young's modulus of the rigid body 4 is set to 50% or less or 200% or more of the Young's modulus of the vulcanized rubber 3. The Young's modulus of the vulcanized rubber 3 is generally in the range of 0.9 MPa or more and 1.1 MPa or less. The vulcanized rubber 3 can be formed from a general-purpose rubber composition.

Therefore, in the first embodiment, the rubber structure 1 has a structure in which the region R near the contact surface 2 has a stiffness distribution with a significantly different Young's modulus from the surrounding area. The region R near the contact surface 2 can be structured to have a stiffness distribution with a significantly smaller Young's modulus than the surrounding area, or a stiffness distribution with a significantly larger Young's modulus.

Examples of the rigid body 4 include metal particles, resin particles, and inorganic filler particles. Specifically, the metal particles can be steel balls or aluminum balls that are harder than the vulcanized rubber 3. The resin particles can be hard resin balls that are harder than the vulcanized rubber 3, or soft resin balls that are softer than the vulcanized rubber 3. The inorganic filler particles can be silica that is harder than the vulcanized rubber 3.

The rigid body 4 is not limited to being granular (spherical), but may also be rod-shaped. The cross-sectional shape of the rigid body 4 may be circular, elliptical, or of various other polygonal shapes such as triangles and rectangles, but it is preferable that the surface has as few corners (especially acute corners) as possible. This is because corners on the surface of the rigid body 4 can easily become the starting point for scratches in the vulcanized rubber 3.

The diameter d (equivalent diameter dimension d) of the rigid body 4 is, for example, 0.1 mm or more and 2.0 mm or less. The equivalent diameter dimension d for a rigid body 4 having a cross section other than a circular cross section is 80% of the diameter of the circumscribing circle of the cross section.

All rigid bodies 4 can be of the same specifications, for example made of the same material and with the same cross-sectional shape and equivalent diameter. Alternatively, rigid bodies 4 of different specifications can be mixed. For example, rigid bodies 4 made of the same material but with different equivalent diameter dimensions d in the range of 0.1 mm to 2.0 mm can be mixed.

The rigid bodies 4 are preferably scattered such that the distance m between adjacent rigid bodies 4 is about 50% to 200% of the equivalent diameter d of the rigid body 4 (the smaller equivalent diameter d of the adjacent rigid bodies 4). This is because if the density of the rigid bodies 4 is too high or too low, it becomes difficult to improve the frictional force of the rubber structure 1.

The shape of the rubber structure 1 is not limited to a block-like body, and may be a circular tire 1A as shown in FIG. 4. The dashed line CL in FIG. 4 indicates the tire width direction center. In the tire 1A, the contact surface 2 is the tread surface 2A. The target surface 5 in the case of the tire 1A is an asphalt road surface on which the tread surface 2A comes into contact. Other examples of the rubber structure 1 include brake pads and sealing materials (packing).

As a second embodiment of the structure of the rubber structure 1, instead of the structure in which the Young's modulus of the rigid body 4 in the first embodiment is specified, a structure in which the density of the rigid body 4 is specified can also be used.

In the second embodiment, the rigid bodies 4 are scattered in a region R near the contact surface 2 at a predetermined depth h from the contact surface 2 without being exposed from the contact surface 2, and the density of the rigid bodies 4 is set to 70% or less or 130% or more of the density of the vulcanized rubber 3. The upper limit of the density of the rigid bodies 4 is, for example, about 2500% of the density of the vulcanized rubber 3. The density of the vulcanized rubber 3 is generally in the range of 900 kg/m3 or ^more and 1500 kg/m3 ^{or less} .

Therefore, in the second embodiment, the rubber structure 1 has a structure in which the region R near the contact surface 2 has a density distribution that is significantly different from the surrounding area. The region near the contact surface 2 can have a density distribution that is significantly lower than the surrounding area, or a density distribution that is significantly higher than the surrounding area. As for the other configurations of the rubber structure 1, the same arrangements as those described in the first embodiment can be applied to the second embodiment as well.

The method of using the rubber structure 1 in each of the above-mentioned embodiments is as follows.

The target surface 5 is an uneven surface with various recesses 6a and protrusions 6b on the surface. The conditions for using the rubber structure 1 are that the diameter equivalent dimension d of the rigid body 4 is 30% or more of the arithmetic mean height Sa of the target surface 5, and that the predetermined depth h at which the rigid body 4 is embedded is 0.05 mm or more and less than 1 mm. By making the target surface 5 have recesses and protrusions that satisfy this condition, the dynamic friction force of the rubber structure 1 can be more effectively improved.

Then, the rubber structure 1, with the contact surface 2 in contact with the target surface 5 as illustrated in FIG. 3, is pressed toward the target surface 5 with a predetermined pressure as illustrated in FIG. 5. The pressing force at this time is a pressure according to the usage conditions of the rubber structure 1. As a result, the contact surface 2 is pressed into the target surface 5. More specifically, the contact surface 2 is pressed into the convex portion 6b of the target surface 5 (the convex portion 6b is biting into the contact surface 2). The degree of deformation of the nearby region R varies depending on the unevenness of the target surface 5, the pressing force applied to the rubber structure 1, etc.

In this state, the rubber structure 1 is moved relative to the target surface 5 so that the contact surface 2 slides against the target surface 5. The direction of relative movement is along the surface of the target surface 5, as shown by the arrow in FIG. 5. The target surface 5 may be fixed and the rubber structure 1 moved, or the rubber structure 1 may be fixed and the target surface 5 moved. The rubber structure 1 moves relative to the target surface 5 while deforming the nearby region R, and a kinetic friction force is generated as a resistance force during this movement.

When the rubber structure 1 is a tire 1A, the contact surface 2 is the tread surface 2A. Then, the tire 1A is rolled with the tread surface 2A pressed against a target surface 5 such as a road surface. In other words, the tread surface 2A is moved in a tangential direction along the target surface 5 to cause the tire 1A to slide against the target surface 5.

In the first embodiment, the rigidity of the vicinity region R of the contact surface 2 is significantly different from that of the surrounding vulcanized rubber 3, so when the contact surface 2 is slid against the target surface 5, the hysteresis loss of the rubber structure 1 (vicinity region R) becomes larger than when the rigid body 4 is not embedded. As a result, heat generation is promoted around the contact surface 2, and the dynamic friction force against the target surface 5 is improved even if general-purpose vulcanized rubber 3 is used for the rubber structure 1.

In the second embodiment, the density of the area near the contact surface 2 is significantly different from that of the surrounding vulcanized rubber 3, so when the contact surface 2 is slid against the target surface 5, the hysteresis loss of the rubber structure 1 (nearby area R) becomes larger than when the rigid body 4 is not embedded. As a result, heat generation is promoted around the contact surface 2, and the dynamic friction force against the target surface 5 is improved even if general-purpose vulcanized rubber 3 is used for the rubber structure 1.

In addition, in each embodiment, the rigid body 4 is not exposed to the contact surface 2. Therefore, during the period until the vulcanized rubber 3 covering each rigid body 4 wears down and the rigid body 4 becomes exposed, that is, at least in the initial period of use of the rubber structure 1, the rigid body 4 does not unnecessarily scratch the target surface 5.

Therefore, when the rubber structure 1 is a tire 1A, at least in the early stages of use, the tire 1A exhibits excellent grip without causing unnecessary damage to the road surface. When the rubber structure 1 is a brake pad or a sealing material, at least in the early stages of use, the tire 1A exhibits excellent braking performance and excellent sealing performance without causing unnecessary damage to the target surface 5.

In each embodiment, the relative movement speed is generally in the range of 0.1 m/s or more. The upper limit of the relative movement speed is the speed that the rubber structure 1 can withstand in practical use. As the relative movement speed increases, the kinetic friction force tends to increase.

The influence (general tendency) of the Young's modulus of the rigid body 4 on the dynamic friction force of the first embodiment will be described with reference to FIG. 6. The data shown in FIG. 6 is calculated by calculating the dynamic friction force generated when the rubber structure 1 is moved relatively along the target surface 5 so that the contact surface 2 slides against the target surface 5 under common conditions, with only the Young's modulus of the spherical rigid body 4 embedded in the rubber structure 1 being different. The arithmetic mean height Sa of the target surface 5 is set to 1.0 mm, and the contact surface 2 is set to be pressed about 0.2 mm against the target surface 5. The vertical axis shows the magnitude of the dynamic friction force as an index, and the larger the value (in the direction of the arrow), the larger the dynamic friction force. The Young's modulus of the vulcanized rubber 3 is 1 MPa, and the data when the rigid body 4 is not embedded in the rubber structure 1 is shown by △. That is, the magnitude of the dynamic friction force shown by the dashed line in FIG. 6 is the dynamic friction force in the rubber structure 1 without the rigid body 4 embedded. As shown in FIG. 6, by embedding the rigid body 4, which has a significantly different Young's modulus from the vulcanized rubber 3, in the nearby region R, the dynamic friction force is improved compared to when the rigid body 4 is not embedded. However, even if the Young's modulus of the rigid body 4 is excessively large, the dynamic friction force does not increase significantly.

The effect (general tendency) of the density of the rigid body 4 on the dynamic friction force of the second embodiment will be described with reference to FIG. 7. The data shown in FIG. 7 is calculated by varying only the density of the spherical rigid body 4 embedded in the rubber structure 1, and calculating the dynamic friction force generated when the rubber structure 1 is moved relatively along the target surface 5 so that the contact surface 2 slides against the target surface 5 under common conditions. The arithmetic mean height Sa of the target surface 5 is set to 1.0 mm, and the contact surface 2 is pressed about 0.2 mm against the target surface 5. The density of the vulcanized rubber 3 is 1500 kg/m ³ , and the data in the case where the rigid body 4 is not embedded in the rubber structure 1 is indicated by △. That is, the magnitude of the dynamic friction force indicated by the dashed line in FIG. 7 is the dynamic friction force in the rubber structure 1 in which the rigid body 4 is not embedded. As shown in FIG. 7, the rigid body 4, whose density is significantly different from that of the vulcanized rubber 3, is embedded in the nearby region R, and the dynamic friction force is improved compared to the case where the rigid body 4 is not embedded. Incidentally, if the density of the rigid body 4 is made excessively large, the kinetic frictional force also increases accordingly up to a certain extent.

The influence of the depth position of the rigid body 4 on the dynamic friction force of each embodiment (general tendency) will be explained based on FIG. 8. This depth position is the shortest distance between the rigid body 4 and the contact surface 2. The data shown in FIG. 8 is calculated by calculating the dynamic friction force generated when the rubber structure 1 is moved relatively along the target surface 5 so that the contact surface 2 slides against the target surface 5 under common conditions, with only the depth position of the spherical rigid body 4 embedded in the rubber structure 1 being different. The arithmetic mean height Sa of the target surface 5 is set to 1.0 mm, and the contact surface 2 is set to be pressed about 0.2 mm against the target surface 5. The data when the rigid body 4 is not embedded in the rubber structure 1 is indicated by △. That is, the magnitude of the dynamic friction force indicated by the dashed line in FIG. 8 is the dynamic friction force in the rubber structure 1 without the rigid body 4 embedded. As shown in FIG. 8, the smaller the depth position, the higher the dynamic friction force is compared to when the rigid body 4 is not embedded. Note that when the depth position becomes large to a certain extent, the effect of improving the dynamic friction force disappears.

The effect (general tendency) of the size (diameter d) of the rigid body 4 on the dynamic friction force of each embodiment will be explained based on FIG. 9. The data shown in FIG. 9 is calculated by calculating the dynamic friction force generated when the rubber structure 1 is moved relatively along the target surface 5 so that the contact surface 2 slides against the target surface 5 under common conditions, with only the diameter of the spherical rigid body 4 embedded in the rubber structure 1 being different. . The arithmetic mean height Sa of the target surface 5 is set to 1.0 mm, and the contact surface 2 is set to be pressed about 0.2 mm against the target surface 5. The data when the rigid body 4 is not embedded in the rubber structure 1 is indicated by △. In other words, the magnitude of the dynamic friction force indicated by the dashed line in FIG. 9 is the dynamic friction force in the rubber structure 1 without the rigid body 4 embedded. As shown in FIG. 9, the larger the diameter d of the rigid body 4, the higher the dynamic friction force is compared to when the rigid body 4 is not embedded.

In a simulation model of a rubber structure in which spherical rigid bodies are embedded in a single layer in the vicinity of the contact surface of the rubber structure with the center of each rigid body being spaced 1 mm apart, the Young's modulus of the vulcanized rubber is 1 MPa, the arithmetic mean height Sa of the target surface is 0.5 mm (an uneven surface with continuous convex portions with a height of 0.5 mm), the indentation amount of the contact surface relative to the target surface is 0.2 mm, and the internal damping ratio of the rubber structure is 1×10 ⁻⁶ . The specifications of the rigid bodies are varied as shown in Table 1, and the kinetic frictional force of the rubber structure is calculated when the rubber structure is slid along the target surface at a relative movement speed of 10 m/s. The results are shown in Table 1. The kinetic frictional force in Table 1 is expressed as an index, with the kinetic frictional force of a conventional rubber structure in which no rigid bodies are embedded being taken as the reference, which is 100. The larger the index value, the larger the kinetic frictional force.

The results in Table 1 show that cases 5 to 13, in which the Young's modulus of the rigid body is significantly different from that of the vulcanized rubber and the rigid body is positioned at a depth of less than 1 mm and has a diameter of 0.2 mm or more, have improved dynamic frictional force compared to the conventional example (no rigid body embedded).

Furthermore, in a simulation model of a rubber structure in which spherical rigid bodies are embedded in a single layer in the vicinity of the contact surface of the rubber structure with the center of each rigid body being spaced 1 mm apart, the density of the vulcanized rubber is 1500 kg/m ³ , the arithmetic mean height Sa of the target surface is 0.5 mm (an uneven surface with continuous convex portions with a height of 0.5 mm), the indentation amount of the contact surface relative to the target surface is 0.2 mm, and the internal damping ratio of the rubber structure is 1×10 ^{−6 .} The specifications of the spherical rigid bodies embedded in the rubber structure are varied as shown in Table 2, and the kinetic frictional force of the rubber structure is calculated when the rubber structure is caused to slide along the target surface at a relative movement speed of 10 m/s. The results are shown in Table 2. The kinetic frictional force in Table 2 is expressed as an index, with the kinetic frictional force of a conventional rubber structure in which no rigid bodies are embedded being taken as the reference value of 100. The larger the index value, the larger the kinetic frictional force.

The results in Table 2 show that cases 1, 3-8, and 10-13, in which the density of the rigid body is significantly different from the density of the vulcanized rubber and the rigid body is positioned at a depth of less than 1 mm and has a diameter of 0.2 mm or more, have improved dynamic frictional force compared to the conventional example (no rigid body embedded).

Reference Signs List 1 Rubber structure 1A Tire 2 Contact surface 2A Tread surface 3 Vulcanized rubber 4 Rigid body 5 Target surface 6a Concave portion 6b Convex portion

Claims (6)

A rubber structure having a contact surface that contacts a target surface during use, the rubber structure comprising vulcanized rubber and a rigid body embedded in the vulcanized rubber, the contact surface comprising:
A rubber structure comprising: the rigid bodies are embedded in the vulcanized rubber and are scattered in a region adjacent to the contact surface at a predetermined depth from the contact surface, without being exposed from the contact surface; and the Young's modulus of the rigid bodies is 50% or less or 200% or more of the Young's modulus of the vulcanized rubber. A rubber structure having a contact surface that contacts a target surface during use, the rubber structure comprising vulcanized rubber and a rigid body embedded in the vulcanized rubber, the contact surface comprising:
A rubber structure comprising: the rigid bodies are embedded in the vulcanized rubber and are scattered in a region adjacent to the contact surface at a predetermined depth from the contact surface, without being exposed from the contact surface; and the density of the rigid bodies is 70% or less or 130% or more of the density of the vulcanized rubber. The rubber structure according to claim 1 or 2, wherein the predetermined depth is in the range of 0.05 mm or more and less than 1 mm from the contact surface. The rubber structure according to any one of claims 1 to 3, wherein the rigid bodies are any one of metal particles, resin particles, and inorganic filler particles (excluding those having a metal coating layer on the surface of each of the particles) . The rubber structure according to any one of claims 1 to 4, wherein the rubber structure is a tire and the contact surface is a tread surface. A method for using a rubber structure having the rubber structure according to any one of claims 1 to 5, comprising:
a diameter equivalent dimension of the rigid body is 30% or more of an arithmetic mean height Sa of the target surface, the predetermined depth is less than 1 mm, and the rubber structure is moved relatively to the target surface so as to slide the contact surface against the target surface.

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