JP2004345563A - Elastic crawler and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elastic crawler and its manufacturing method capable of reducing manufacturing cost by shortening curing time without causing a secondary harmful effect such as strength reduction of the elastic crawler or vibration increase during travel. <P>SOLUTION: The elastic crawler is formed of a rubber elastic body like an endless belt. The rubber elastic body comprises a crawler body having a plurality of driving protrusions arranged circumferentially at a predetermined interval on its inner peripheral surface and a lug group formed integrally on the outer peripheral surface of the crawler body in a predetermined lug pattern. A porous structure formed of many hollow particles is formed in the rubber elastic body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an elastic crawler used for various crawler traveling devices and a method for manufacturing the same.
[0002]
[Prior art]
The elastic crawler traveling device is now widely used for agricultural machines such as combine harvesters and construction work machines such as backhoes. These agricultural machines and the like are equipped with an elastic crawler made of an endless rubber belt or the like.The elastic crawler includes a crawler body formed in an endless belt shape, and a plurality of driving protrusions formed on an inner peripheral surface of the crawler body. A lug group formed on the outer peripheral surface with a predetermined lug pattern is used.
Conventionally, a tension member embedded in the crawler body along the circumferential direction or a core having a core bar embedded at a position corresponding to the lug in the crawler body has been used. In high-speed crawler vehicles such as trucks and half-tracks, the traveling speed is relatively high, so it is necessary to employ an elastic crawler having flexibility and light weight capable of high-speed rotation.
[0003]
As such an elastic crawler having both flexibility and light weight, a core-less type in which a core is not buried in a crawler body is widely used.
In the case of such a coreless crawler, instead of not using the core, a plurality of drive protrusions and the like arranged at regular intervals on the inner peripheral surface of the elastic crawler increase the rubber thickness of the rubber elastic body to obtain rigidity. . In molding such a coreless elastic crawler, an unvulcanized material is heated and vulcanized and molded by a heated mold to obtain a rubber elastic body.
[0004]
However, in the case of a coreless elastic crawler, the rubber gauge is generally thickened in order to secure the rigidity of the drive projection, and the vulcanization time due to heating is relatively long. was there. Further, even with an elastic crawler containing a cored bar, there is also a problem that the vulcanization time is similarly increased depending on the thickness of the rubber gauge of the crawler body.
This is remarkable not only in the drive protrusion but also in a lug integrally formed on the outer peripheral surface of the elastic crawler in a predetermined lug pattern.
Therefore, in order to solve the above problem, a recess is formed in the thick part of the rubber gauge to reduce the gap between the two mold surfaces, to make the unvulcanized product as thin and uniform as possible, and to reduce the difference in the thermal conductivity of each part. There is known one that is eliminated (see Patent Document 1).
[0005]
As another means for solving the above problems, it is also known to mix a filler such as a pipe-shaped filler or a metal piece into an unvulcanized product.
[Patent Document 1]
JP-A-6-305460 [Problems to be solved by the invention]
However, when a depression is formed in the rubber elastic body, the thickness around the depression is reduced, so that the strength may be reduced. Further, when a filler such as a pipe or a metal piece is mixed into the rubber elastic body, a secondary adverse effect that the rubber elastic body and the filler are separated due to poor adhesion at an interface between the filler and the rubber material. Could cause.
[0006]
In addition, if a filler such as a pipe or a metal piece is mixed in, the vibration of the elastic crawler during traveling increases, and in the case of mixing a metal piece, the weight of the elastic crawler increases. Had occurred.
In view of such circumstances, the present invention provides an elastic crawler capable of shortening the vulcanization time and suppressing the manufacturing cost without causing secondary harm such as a decrease in the strength of the elastic crawler and an increase in vibration during traveling. And a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has taken the following technical measures.
That is, the present invention relates to a crawler body in which a plurality of drive projections arranged at regular intervals in the circumferential direction are formed on an inner peripheral surface, and a lug group integrally formed on the outer peripheral surface of the crawler body in a predetermined lug pattern. , An elastic crawler formed in an endless belt shape from a rubber elastic body, wherein the rubber elastic body has a porous structure formed by a large number of hollow particles.
[0008]
In this case, the presence of a large number of voids formed by the hollow particles substantially reduces the heat transfer distance toward the inside of the unvulcanized product, and facilitates the transfer of heat from the mold. The degree of vulcanization inside the sulphate reaches a predetermined state, and the vulcanization time can be reduced. At the same time, since the internal temperature of the unvulcanized material rises early, the difference between the degree of vulcanization in the surface layer and the inside can be reduced. Is excessive and the surface layer portion can be prevented from being overcured.
[0009]
In addition, by forming a porous structure, heat is easily transmitted to the inside of the unvulcanized material during vulcanization, so that the thickness of the rubber elastic body does not have to be reduced, and the adhesion between the filler and the rubber is not required. There is no problem of failure. Therefore, the strength of the elastic crawler does not decrease. Further, due to the presence of the voids constituting the porous structure, vibrations of the elastic crawler during traveling can be suppressed.
In the present invention, a large number of voids can be uniformly formed in the rubber elastic body by expanding and molding the hollow particles into fine particles containing a low boiling point hydrocarbon in a thermoplastic resin.
[0010]
In addition, in the present invention, since a large number of pores constituting the porous structure form closed cells, a decrease in rigidity can be suppressed. Furthermore, it is preferable that the diameter of the closed cell is 40 μm to 120 μm. Thereby, a high heat transfer speed can be obtained without greatly reducing the physical properties of the rubber elastic body.
In the case where the hollow particles are uniformly dispersed throughout the rubber elastic body, not only the thick portion and the thin portion during vulcanization, but also the heat transmission becomes high and uniform, and the vulcanization molding time can be shortened.
Further, the hollow particles may be buried only in a portion where the rubber gauge of the rubber elastic body is thickened, and in this case, heat is easily transmitted to the inside of the portion, so that vulcanization can be performed efficiently. In addition, the amount of hollow particles used can be reduced. The portion in which the hollow particles are buried can be included at a predetermined distance from the surface layer portion to have a two-layer structure of a normal rubber layer and a containing layer having a porous structure.
[0011]
In the above present invention, an elastic crawler provided with a core metal buried at a constant interval along a circumferential direction in a crawler body, wherein the hollow particles include the lug and / or the core metal and the crawler body inner periphery. By burying only in a portion sandwiched between the surfaces, heat is easily transmitted in such a portion, and rubber properties can be set to appropriate values.
Further, the present invention is a method for producing an elastic crawler comprising a rubber elastic body formed by heating an unvulcanized product, wherein the unvulcanized product is made to contain fine particles which can be expanded by heating in advance, and vulcanized. The volume of the fine particles is increased by heating at the time of sulfur molding to form a porous structure in the rubber elastic body.
[0012]
In this case, what is kneaded with the unvulcanized product is fine particles, and since the fine particles have a small particle size, they are easily dispersed, and the physical property values of the formed elastic crawler do not become uneven.
Further, in the present invention, a content layer in which the fine particles are dispersed in a rubber made of an unvulcanized material is prepared in advance, and this content layer is laminated or embedded in a part of the rubber layer made of an unvulcanized material. If vulcanization molding is performed later, the porous structure can be formed at a desired position.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a coreless elastic crawler 1 according to a first embodiment of the present invention, and FIG. 2 shows a side view of a main part of a crawler traveling device 2 using the elastic crawler 1. As shown in FIG. 2, the crawler traveling device 2 of the present embodiment includes a sprocket 3 which is a driving wheel disposed at a predetermined position, an idler not shown, and a plurality of rows arranged between the idler and the sprocket 3. And the elastic crawler 1 is wound around the outer periphery thereof.
[0014]
As shown in FIG. 1, the elastic crawler 1 of the present embodiment has a metal core in which a plurality of drive projections 4 arranged at regular intervals in a circumferential direction (arrow X direction in FIG. 2) are integrally provided from an inner peripheral surface. Crawler body 5, a lug group including a large number of lugs 6 formed on the outer peripheral surface of the crawler body 5 in a predetermined lug pattern, and a tensile strength embedded in the crawler body 5 along the circumferential direction. The crawler body 5 includes a bias cord 8 embedded inside the crawler body 5 on the outer peripheral side of the tension member 7.
Among them, the crawler body 5 is formed in an endless band shape having a substantially constant thickness by a rubber elastic body, and is located at the center of the inner peripheral surface of the crawler body 5 in the width direction (the left-right direction in FIG. 1A). The drive projection 4 made of a rubber elastic body made of the same material as the crawler body 5 is protruded. The driving projections 4 are provided at regular intervals in the circumferential direction over the entire circumference of the crawler body 5. By engaging the sprockets 3 with the driving projections 4, the elastic crawler 1 is moved in the circumferential direction. It can be driven along.
[0015]
The sprocket 3 is formed by connecting a pair of left and right circular drive plates 15 with a plurality of drive pins (not shown) arranged at equal intervals in the circumferential direction. The elastic crawler 1 has a function of feeding the elastic crawler 1 forward and backward by rotating forward and backward while being hooked on the hook 4.
The tensile member 7 is configured by juxtaposing tensile cords such as steel cords extending in the circumferential direction. On the other hand, the bias cord 8 is configured by arranging tensile strength cords such as steel cords in a direction inclined with respect to the circumferential direction. The bias cord 8 may be provided on the inner peripheral side of the tension member 7 or on both the inner peripheral side and the outer peripheral side.
[0016]
As shown in FIG. 1, the driving projections 4 and the lugs 6 have a thicker rubber gauge than other parts. In this part, a normal rubber layer 9 and hollow particles 12 are contained and are included in the rubber layer 9. And the containing layer 10 formed. As shown in the enlarged schematic diagram of FIG. 1 showing a part of the containing layer 10, the hollow particles 12 constitute closed cells, and voids 13 are formed therein. Around the hollow particles 12, there is a rubber 11 of the same material as the rubber layer 9, and the rubber 11 and the void 13 constitute a porous structure.
[0017]
The content layer 10 forming the porous structure is provided at a predetermined distance from the surface layer of the driving protrusion 4 or the lug 6, and the substantial thickness of the content layer 10 is reduced by the presence of the void 13, The heat transfer at the time of vulcanization is higher than that of the normal rubber layer 9.
The hollow particles 12 are formed by expansion of minute particles 16 described later. Resin spheres containing low-boiling hydrocarbons are used as the fine particles 16. The most common foaming agents are organic blowing agents, ie substances that undergo a chemical decomposition reaction under the influence of heat and release gas. However, since the organic foaming agent explosively releases gas, the foaming state and the bubble state are significantly affected by temperature conditions. For example, when foaming is formed, the distribution of the received heat differs at each part, causing variations in the foaming state and the like, resulting in a problem that the required performance is not satisfied.
[0018]
Therefore, in the present invention, such a problem is solved by using the fine particles 16 in order to make the foaming state and the like uniform. The fine particles 16 are formed by enclosing an encapsulant in an outer shell of a thermoplastic resin having gas barrier properties. Examples of the thermoplastic resin include copolymers such as vinylidene chloride and acrylonitrile, phenolic resins, and the like, and acrylonitrile-based resins are preferred from the viewpoint of a high melting point. As the encapsulating agent, a compound having a low boiling point is used, and examples thereof include isobutane and isopentane. Isopentane is particularly preferred.
The average particle diameter of the fine particles 16 is 10 μm to 20 μm. When the fine particles 16 are completely expanded to become hollow particles 12, the volume becomes about 40 times or more, and the specific gravity decreases dramatically. The expansion temperature of the fine particles used here is 80 ° C to 190 ° C.
[0019]
As described above, by providing the containing layer 10 containing the hollow particles 12 at a thick portion of the rubber gauge such as the driving protrusion 4 or the lug 6, the heat of the mold can be easily transferred from the surface layer portion to the inside during heat molding, Since the temperature gradient from the surface portion to the inside can be made gentle, the temperature inside the thick portion can be quickly raised. Therefore, the degree of vulcanization at a portion away from the mold can be reached to a predetermined state without taking a long time, and the vulcanization time can be shortened. For this reason, power consumption and the like can be reduced and production costs can be reduced.
[0020]
Furthermore, since the internal temperature of the unvulcanized product can be raised at an early stage, the heating state of the surface layer is close to that of the surface layer, and the difference in the degree of vulcanization between the inside and the surface layer can be reduced. Conventionally, the heating time was long to reach a predetermined degree of vulcanization inside, and the degree of vulcanization of the surface layer portion was excessive. In this case, if the degree of vulcanization is excessive due to overcure, the physical properties of the molded rubber elastic body cannot be set to the desired values, for example, causing a reduction in wear resistance and rigidity. Was.
On the other hand, in the present embodiment, the overall degree of vulcanization can be made substantially uniform, so that overcure of the surface layer can be prevented, and abrasion resistance and cut resistance are improved.
[0021]
On the other hand, regarding the weight of the rubber elastic body, since the gap 13 is formed in the rubber elastic body, the weight is reduced accordingly, and the driving efficiency of the elastic crawler 1 is increased. The gap 13 also has a function of reducing vibration of the elastic crawler 1 during traveling. Furthermore, since the voids 13 form closed cells, a decrease in rigidity is small. In addition, for example, as in the case where a pipe-shaped filler is mixed, poor adhesion between the filler and the rubber material surrounding the filler occurs. The secondary harm that occurs is eliminated.
In the present embodiment, the hollow particles 12 are contained only in the driving protrusions 4 and the lugs 6 having a thick rubber gauge. However, by uniformly dispersing the rubber particles throughout the rubber elastic body, the heat is not limited to the thick and thin portions, but is applied to the whole. May be made uniform and high. In this case, the vulcanization molding time is shortened, and only a single material need be molded, so that the production cost can be reduced.
[0022]
FIG. 5 schematically shows a partial cross section of the elastic crawler 1 before vulcanization molding (a) and after vulcanization molding (b). In the containing layer 10 before vulcanization molding, the fine particles 16 are contained in the rubber composed of the unvulcanized product 17, and the volume of the fine particles 16 increases due to heating during vulcanization molding. The hollow particles 12 in the rubber 11 constituting the matrix will be described later. As a result, in the containing layer 10 after vulcanization molding, a porous structure is formed by the existence of the voids 13 of the hollow particles 12. The vulcanization molding can be performed by a generally known method.
[0023]
Further, since the microparticles 16 are very small, when the unvulcanized product 17 is kneaded, it is easily dispersed in the unvulcanized product 17 and the kneading operation efficiency is good. For example, if a relatively large hollow filler is mixed before vulcanization molding, the difference in specific gravity between the unvulcanized product 17 and such a filler becomes large, and it becomes difficult to sufficiently disperse the filler. The adverse effect of biasing the physical properties of the elastic body occurs. In this regard, in the present invention, since the porous structure having the voids 13 uniformly dispersed in the rubber elastic body can be formed, the above problem can be solved.
[0024]
Further, the containing layer 10 in which the fine particles 16 are dispersed in the rubber composed of the unvulcanized product 17 is prepared in advance, and the containing layer 10 is laminated at a desired position such as another unvulcanized sheet. By embedding and then vulcanizing, a porous structure can be formed at a specific location, and a two-layer structure as shown in FIG. 5 can be efficiently formed.
Examples of the component of the rubber 11 include NBR, EPDM, acrylic rubber, epichlorohydrin rubber, urethane rubber, SBR, CR, and the like, and one or more kinds selected from these can be used. Further, a vulcanization accelerator, a vulcanization aid, a vulcanization retarder and the like are appropriately added.
[0025]
FIG. 3 shows an elastic crawler 1 according to a second embodiment of the present invention.
The different point of the elastic crawler 1 of the present embodiment from the case of the first embodiment is that the crawler main body 5 is provided with a metal core 14 which is long in the crawler width direction.
Here, the lug 6 is provided with the containing layer 10 containing the hollow particles 12 as in the first embodiment. The content layer 10 is provided in a portion extending in the width direction of the cored bar 14 and a portion sandwiched between the inner peripheral surface of the crawler body. By doing so, not only the molding time is shortened, but also the effect of reducing the running vibration of the crawler including the metal core 14 can be obtained. In the present embodiment, the hollow particles 12 may be uniformly contained over the entire rubber elastic body, instead of having the two-layer structure.
[0026]
FIG. 4 shows an elastic crawler 1 according to a third embodiment of the present invention.
The difference between the elastic crawler 1 of the present embodiment and the second embodiment is that, as shown in FIG. 4B, the containing layer 10 is arranged not only at the position corresponding to the cored bar 14 but also long in the circumferential direction. Is a point. By doing so, it is possible to obtain an even higher running vibration reduction effect of the cored crawler. Moreover, since the continuous long containing layer 10 can be produced, the production efficiency is improved.
The present invention is not limited to the embodiments described above.
For example, in order to increase the strength of the elastic crawler 1 according to the first embodiment, a hard resin or metal reinforcing member may be embedded inside the drive projection 4. The shape of the lug 6 is not limited to the shape extending in the crawler width direction, but may be inclined in the crawler width direction.
[0027]
【The invention's effect】
As described above, according to the present invention, the vulcanization time can be shortened and the manufacturing cost can be reduced without causing secondary adverse effects such as a decrease in the strength of the elastic crawler and an increase in vibration during traveling.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view of an elastic crawler according to a first embodiment, and FIG. 1B is a vertical cross-sectional view of a central portion in a width direction of the crawler (a cross-sectional view taken along line AA in FIG. 1A). ).
FIG. 2 is a side view of a main part of the crawler type traveling device equipped with the elastic crawler of the first embodiment.
3A is a cross-sectional view of an elastic crawler according to a second embodiment, and FIG. 3B is a vertical cross-sectional view of a center portion in the width direction of the crawler (a cross-sectional view taken along line BB of FIG. 3A). ).
4A is a cross-sectional view of an elastic crawler according to a third embodiment, and FIG. 4B is a vertical cross-sectional view of a central portion in the width direction of the crawler (a cross-sectional view taken along line CC in FIG. 4A). ).
FIG. 5 (a) is a schematic partial cross-sectional view of an elastic crawler before vulcanization molding, and FIG. 5 (b) is a schematic partial cross-sectional view of the same crawler after vulcanization molding.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 elastic crawler 4 drive projection 5 crawler body 6 lug 9 rubber layer 10 containing layer 12 hollow particle 13 void 16 microparticle 17 unvulcanized material

Claims (9)

A rubber provided with a crawler body in which a plurality of drive protrusions arranged at regular intervals in the circumferential direction are formed on an inner circumferential surface, and a lug group integrally formed in a predetermined lug pattern on the outer circumferential surface of the crawler body. In an elastic crawler formed in an endless band shape from an elastic body,
An elastic crawler, wherein a porous structure of a large number of hollow particles is formed in the rubber elastic body. The elastic crawler according to claim 1, wherein the hollow particles are formed by increasing the volume of the microparticles that can be expanded by heating. 3. The elastic crawler according to claim 1, wherein each of the plurality of holes forming the porous structure forms a closed cell. The elastic crawler according to claim 3, wherein the closed cell has a diameter of 40 µm to 120 µm. The elastic crawler according to any one of claims 1 to 4, wherein the hollow particles are uniformly dispersed throughout the rubber elastic body. The elastic crawler according to any one of claims 1 to 4, wherein the hollow particles are embedded only in a portion of the rubber elastic body where the rubber gauge is thickened. An elastic crawler provided with a core metal embedded in the crawler body at a constant interval along a circumferential direction,
The elastic crawler according to any one of claims 1 to 4, wherein the hollow particles are embedded only in a portion between the lug and / or the core metal and the inner peripheral surface of the crawler body. A method for producing an elastic crawler comprising a rubber elastic body formed by heating an unvulcanized product,
An elastic crawler characterized in that the unvulcanized material contains microparticles expandable by heating in advance, and the volume of the microparticles is increased by heating during vulcanization molding to form a porous structure in a rubber elastic body. Manufacturing method. A vulcanization molding after preparing a containing layer in which the fine particles are dispersed in a rubber made of an unvulcanized product, and laminating or embedding this containing layer on a part of a rubber layer made of an unvulcanized product. 9. The method for producing an elastic crawler according to item 8.

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