JPH085146B2 - Rubber crawler manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a rubber crawler mounted around the undercarriage of a mobile agricultural machine, a construction machine, or the like.

(Prior Art) FIGS. 1A, 1B and 1C show an example of a conventional rubber crawler. FIG. 1A is a plan view, and FIGS. 1B and 1C are sectional views taken along line XX and Y- in FIG. 1 is a rubber crawler main body, 12 is a core bar, 12a, 12b and 12c are blades, engaging portions and protrusions of the core bar 12, 13 is a steel cord, and 14 is a steel cord.
Is a grounding lug, 15 is an engaging hole, s is a distance between the blade portion 12a and the steel cord 13, and f ₁ and f ₂ are reinforcing cloths. Many cores 12
Is embedded, and a large number of steel cords 13 are arranged in the circumferential direction in close proximity to the grounding side of the wing portion 12a and embedded, and between the wing portion 12a and the steel cord 13 and the grounding of the steel cord 13. Reinforcing cloths f ₁ and f ₂ are buried in the respective sides, engaging holes 15 are provided in the front and rear of the engaging portion 12b, and a ground lug 14 is provided on the ground side surface.

In the above structure, the blade portion 12a and the steel cord 13 are firmly adhered to each other through the small space s, so that the driving force transmitted from the drive wheel to the engaging portion 12b is immediately and smoothly applied to the steel cord 13. Is transmitted to the entire circumference of the rubber crawler main body 11.

Further, since the rubber crawler main body 11 is formed of a vulcanized rubber of a general-purpose rubber compound such as natural rubber and SBR, the unvulcanized rubber of the compound has a large fluidity, and therefore, it is press-vulcanized. It is possible to fill every corner inside the mold when the mold is clamped during molding.
The unvulcanized rubber in the portion between 12a and the steel cord 13 flows out to the other portion, and the small space s becomes insufficient (If the small space s becomes insufficient, the steel cord 13 is wound at the winding portion with the drive wheel. The steel cord 13 is abraded and the blade portion 12a comes into contact with the blade portion 12a), and in order to prevent this, a flow of the reinforcing cloth f ₁ is made to intervene in the unvulcanized rubber in the portion with the small interval s. The property is suppressed to secure a space and to reinforce the rubber layer having a small space s. On the other hand, the reinforcing cloth f ₂ is buried on the grounding side of the steel cord 13, and the growth of cut scratches and the like from the grounding surface is prevented by the reinforcing cloth f ₂ layer so as not to reach the deep part. It prevents the steel cord from corroding due to water intruding from the side. Furthermore,
In order to prevent the unvulcanized rubber in the portion where the steel cords 13 are embedded from flowing during the mold clamping and disturbing the arrangement of the steel cords significantly, the entire circumference of the embedded unvulcanized rubber is arranged in advance. It may be wrapped in a reinforcing cloth and embedded in the rubber crawler body. In this case, the reinforcing cloth f ₁ and
f ₂ is used as a piece of cloth.

Reinforcement cloths f ₁ and f ₂ are made of nylon fiber, such as chafer sail cloth or blind woven cloth, which has a large weave, and the reason is that it is difficult to peel off the portion where the reinforcing cloth is interposed. This is because it is necessary to connect the rubber material through the weave and to integrate the rubber material on both sides of the reinforcing cloth.

In addition, the core metal, steel cord, and reinforcing cloth must be firmly adhered to the rubber material. Therefore, the core metal is surface-polished and treated with an adhesive, the steel cord is brass-plated, and the nylon reinforcing cloth is RFL. Known pretreatment such as coating with unvulcanized rubber after the treatment is performed.

2A and 2B are cross-sectional views showing an example of a conventional press vulcanization molding method for a rubber crawler, 16a and 16b are upper and lower molds of a long mold, and 17 is a general rubber compound. The unvulcanized rubber has thicknesses and dimensions suitable for the respective places, 17a is a composite in which the steel cords 13 are aligned and embedded in the unvulcanized rubber 17, and 17T is a composite. A composite body in which an unvulcanized rubber 17 is entirely covered in advance with a reinforcing cloth f ₁ all around the body 17a, and 18a and 18b are an upper heating plate and a lower heating plate of a vulcanizing press, respectively. After placing the core metal 12, the composite 17T and the unvulcanized rubber 17 at a predetermined position of the lower die 16b as shown in, the lower die 16b is placed on the lower heating plate 18b of the vulcanizing press (in this case, The upper mold 16a is the upper heating plate 18a in advance.
The upper and lower heating plates are preheated to the vulcanization temperature), and then the lower heating plate 18b is raised by hydraulic power, and subsequently, as shown in FIG. The lower die 16b is united and clamped. At this time, the unvulcanized rubber 17 flows by pressurization and heating, and most of it is formed inside the united upper die 16a and lower die 16b. The space is filled to form the rubber crawler body 11, and a part of the rubber crawler body flows out of the mold to form a burr. In this state, heating and pressurization are continued for a predetermined time to make the unvulcanized rubber a vulcanized rubber. After that, the molded rubber crawler is molded.

At the time of mold clamping in the above process, the unvulcanized rubber between the blade portion 12a and the steel cord 13 is in a thin gap above and below the reinforcing cloth f ₁ and fluidity is suppressed, so that a small gap s is secured. On the other hand, since the entire circumference of the unvulcanized rubber in which the steel cords 13 are aligned and embedded is wrapped with the reinforcing cloth f ₁ , the arrangement of the steel cords is not disturbed. (Note that this is omitted because it requires a step of connecting both ends in the longitudinal direction to form a bandless rubber crawler after that.) (Problem to be solved by the invention) As described above, the conventional rubber crawler is reinforced. Although it is necessary to embed the cloth, the cost of using the reinforcing cloth increases, and if the reinforcing cloth is present inside the vulcanized rubber, the reinforcing cloth is reinforced in the compression and shear directions. , The embedding part of the reinforcing cloth becomes a weak point against the external force in the pulling and peeling direction, and the strength decreases,
Since the reinforcing cloth has a large weave, the reinforcing cloth embedded on the grounding side of the steel cord may partially cut the weaving yarn when it receives an impact from the grounding side. The present invention is intended to solve such a problem because there is a problem that a cut flaw reaches a steel cord.

By the way, the gist of the contents relating to the rubber layer 4 in Japanese Patent Publication No. 57-43470 is as follows: "Between the mandrel 3 and the tension holding cord 2 in the rubber material of the crawler main body 1, the rubber hardness is 70 °.
Since the rubber thin film 4 of JIS or higher hardness is intervened,
Lateral flow of rubber is reduced during vulcanization molding. Therefore, turbulence of the tension-holding cord 2 due to rubber flow is prevented, and contact between the mandrel 3 and the tension-holding cord 2 is completely prevented, so that the desired distance is accurately maintained. I was able to show up. ''
However, this content is incorrect for the following reasons. The high hardness of vulcanized rubber is not directly related to the low rubber flow (mold flow) during vulcanization molding, and the viscosity (or plasticity) of unvulcanized rubber is related to mold flow. To do. With respect to the viscosity of the unvulcanized rubber and the rubber hardness after vulcanization, it can be set in a fairly wide range, for example, the unvulcanized rubber has a low viscosity and good mold flow,
In addition, it is a routine practice to mix vulcanized rubber with a rubber having a high hardness.

The gist of the description about the intermediate rubber B in Japanese Patent Publication No. 58-55944 is "High hardness rubber B (70 ° to 95 ° JIS.
A) effectively prevents the disorder of the arrangement of the strips 12 at the time of molding and vulcanization, "which is the same as that in the above-mentioned publication and is not correct.

(Means for Solving the Problems) A feature of the present invention is that a press-molding is performed by appropriately disposing unvulcanized rubber of a general-purpose rubber compound, steel cord, core metal, etc. inside the upper and lower molds of a long mold. By the vulcanization molding method, a large number of cored bars are embedded transversely in the circumferential direction in a rubber crawler body made of a vulcanized rubber of a general-purpose rubber compound, and a small interval is provided on the ground side of the wing part of the cored bar In a method for manufacturing a rubber crawler in which a large number of steel cords are arranged in the circumferential direction so as to be embedded in the rubber crawler, the steel cord-embedded rubber is compatible with general-purpose rubber and is heat-vulcanizable with sulfur. It is formed by a "thermoplastic rubber blend compound" in which a plastic rubber is blended with a general-purpose rubber.

In this case, general-purpose rubber means NR (natural rubber), SBR
(Styrene butadiene rubber), BR (polybutadiene rubber), IR (polyisoprene rubber), etc., and thermoplastic rubbers that are compatible with general-purpose rubbers and can be co-vulcanized with sulfur are syndiotactic 1,2- Polybutadiene (for example, trade name; JSR-RB, manufacturer: Japan Synthetic Rubber Co., Ltd.), S
A block copolymer represented by -BS (S is styrene, B is butadiene) (for example, trade name; Califlex TR,
Manufacturer; Shell Petroleum Co., Ltd.) and the like.

(Function) (1) The unvulcanized rubber of the "thermoplastic rubber blend compound" shows a property similar to that of the vulcanized rubber at around room temperature and hardly flows, while the unvulcanized rubber during press vulcanization molding Since the temperature around the steel cord-embedded rubber placed almost in the middle of the mold is almost room temperature, the unvulcanized rubber of the "thermoplastic rubber blend compound" with the steel cord embedded hardly flows. Therefore, a small space can be secured without interposing a reinforcing cloth between the wing portion of the core metal and the steel cord, and since the arrangement of the steel cords is not disturbed, the portion where the steel cord is embedded is reinforced cloth. No need to wrap it in.

(2) The "thermoplastic rubber blend compound" has a high compatibility with a general-purpose rubber compound and is a sulfur vulcanizing compound, so that the interface between the two is integrated and adhered in cooperation. Moreover, it becomes a vulcanized rubber that adheres strongly to the steel cord and has a large physical strength.

(3) Since the vulcanized rubber of the "thermoplastic rubber blend compound" has relatively high hardness and excellent elasticity and tear resistance, the vulcanized rubber grows even if it has grown with cut scratches on the ground contact surface. Prevents scratches from reaching the steel cord layer at the rubber interface.

(Example) Table 1 shows the physical properties of the general-purpose rubber compound and the "thermoplastic rubber blend compound", and the "thermoplastic rubber blend compound" has the following characteristics as compared with the general-purpose rubber compound. Is shown.

The unvulcanized rubber has a large tensile stress at room temperature,
It exhibits properties almost similar to vulcanized rubber, and it hardly flows near room temperature. (This is a property related to the flow of unvulcanized rubber inside the mold during mold clamping during press vulcanization molding of rubber crawlers. That is, unvulcanized rubber flows inside the mold immediately after mold clamping. Since the steel cord embedding part is almost in the middle of the upper mold and the lower mold, the unvulcanized rubber in this vicinity is at about room temperature during this period, so that it hardly flows and therefore does not deform. The adhesive strength between vulcanized rubber and steel cord is large.

The hardness of vulcanized rubber is high.

FIG. 3 is a cross-sectional view of an embodiment of the present invention, in which 1 is a rubber crawler, 1a is a rubber crawler body made of vulcanized rubber of a general-purpose rubber compound, and 2 is a cored bar. 2a, 2b and 2c are wings, engaging portions and protrusions of the cored bar 2 respectively, 3 is a steel cord, and 3a is a steel cord-embedded rubber, which is formed of a "thermoplastic rubber blend compound". , The rubber crawler body as shown in the figure
The construction is the same as that of the conventional rubber crawler except that the steel cord-embedded rubber 3a inside 1a is a "thermoplastic rubber blend compound" and no reinforcing cloth is used. (4 is a grounding lug, 5 is an engaging hole) FIG. 4 shows a steel cord-embedded rubber 3a, in which the steel cords 3 are arranged in an unvulcanized rubber sheet of "thermoplastic rubber blend compound". It is then buried and is molded by an extrusion molding machine or the like.

FIG. 5 is a cross-sectional view showing one example of the press vulcanization molding process of this embodiment, 6a and 6b are the upper and lower molds of the long mold, and 7 is a general rubber compound The vulcanized rubber has thicknesses and dimensions suitable for the respective locations, and 7s is an unvulcanized rubber sheet of a general-purpose rubber compound and is a core metal in the rubber crawler body after press vulcanization molding. This is for adjusting the distance between the wing and the steel cord.As shown in the figure, after placing the core metal 2, the steel cord-embedded rubber 3a, etc. at predetermined positions of the lower mold 6b, the conventional rubber The mold clamping and press vulcanization are performed in the same manner as the crawler press vulcanization molding method. In this case, the steel cord-embedded rubber 3a can be made slightly thicker and the unvulcanized rubber sheet 7s can be omitted.

When clamping the mold, unvulcanized rubber of general-purpose rubber compound 7,7,
..., the fluidity increases due to the mold clamping pressure and heat transfer from the upper die 6a and the lower die 6b, so that the die rapidly fills, whereas the steel cord embedded rubber 3a almost flows. It is fixed in the middle position of the mold without performing the vulcanization of each rubber of the general-purpose rubber compound and the "thermoplastic rubber blend compound" in a pressurized state inside the mold and both of them. As the co-vulcanization of the interface progresses, the vulcanization adhesion of the rubber to the core metal and steel cord also progresses to the completion.

In the present invention, in order to make the "thermoplastic rubber blend compound" a preferable property, it is preferable that the blending ratio of the thermoplastic rubber in the rubber component of the compound is approximately 25% or more. Further, in order to prevent the growth of cutting scratches generated on the ground side of the rubber crawler body on the surface of the vulcanized rubber of the "thermoplastic rubber blend compound" in which the steel cord is embedded, the JIS hardness of the vulcanized rubber is grounded. It is preferable to be higher than the rubber quality of the side by about 5 degrees or more.

In order to confirm the effect of the present invention, the inventor conducted a comparative durability test on a rough terrain with a prototype according to the present invention and a conventional product of a rubber crawler for construction machinery, and as a result, the ground lug was worn out and the steel cord was It took much longer for the product of the present invention to be exposed to the ground side, and it was confirmed that the product of the present invention was superior in durability to the conventional product.

(Effects of the Invention) (1) According to the manufacturing method of the present invention, the steel cord-embedded rubber is set as a "thermoplastic rubber blend compound" so that it hardly flows during mold clamping in press vulcanization molding. The space between the parts and the steel cords can be secured without interposing a reinforcing cloth between them, so that there is no fear that they will come into contact with or close to each other, and the arrangement of the steel cords will not be disturbed. Since it is not necessary to wrap the steel cord embedded rubber with a reinforcing cloth, no reinforcing cloth is required, resulting in a significant cost reduction.

(2) The vulcanized rubber of the "thermoplastic rubber blend compound" has a relatively high hardness and is excellent in elasticity and tear resistance, so that even if a cut scratch occurs on the ground side and the vulcanized rubber grows. At the interface of the rubber crawler, it prevents the intrusion of scratches to reach the steel cord layer. Therefore, the moisture that has entered from the ground side does not reach the steel cord and corrode the steel cord. Durability has been greatly improved.

(3) The "thermoplastic rubber blend compound", which is a rubber embedded in steel cord, has great compatibility with general-purpose rubber compounds, and since it is a sulfur vulcanizing compound, the boundary surface with the surrounding rubber is strong. As a result, a vulcanized rubber having a high physical strength and a strong adhesion with a steel cord can be obtained. As a result, a rubber crawler having excellent durability can be obtained.

[Brief description of drawings]

FIG. 1A is a plan view of an example of a conventional rubber crawler, B and C of FIG. 1 are cross-sectional views taken along line XX and YY of FIG. A, and FIGS. 2A and 2B are conventional rubbers. FIG. 3 is a cross-sectional view showing a method for press vulcanizing and molding a crawler, showing states before and after mold clamping, respectively, FIG. 3 is a sectional view of a rubber crawler of the present invention, and FIG. 4 is used for the rubber crawler. FIG. 5 is a sectional view showing a state before mold clamping in the method for press vulcanization molding of a rubber crawler of the present invention, showing a rubber embedded in steel cords. 1 ... Rubber crawler, 1a ... Rubber crawler body, 2 ...
Core bar, 2a ... Wing part, 2b ... Engaging part, 3 ... Steel cord, 3a ... Steel cord embedded rubber, 6 ... Long mold,
6a …… upper mold, 6b …… lower mold, 7 …… unvulcanized rubber, 7s …… unvulcanized rubber sheet, 11 …… rubber crawler body (conventional product),
12 ...... metal core, 12a ...... wings, 12b ...... engaging portion 13 ...... steel cord, s ...... interval, f _1, f ₂ ...... reinforcing cloth, 16 ...... long mold, 16a ... … Upper mold, 16b …… Lower mold, 17 …… Unvulcanized rubber, 17a, 17T …… Composite, 18a …… Upper plate, 18b …… Lower plate

Claims (1)

[Claims] 1. A general-purpose rubber compound by a press vulcanization molding method in which an unvulcanized rubber of a general-purpose rubber compound, a steel cord, a core metal, etc. are appropriately placed inside the upper and lower molds of a long mold. A large number of metal cores are embedded in the rubber crawler main body made of vulcanized rubber transversely with respect to the circumferential direction, and a large number of steel cords are arranged at small intervals on the ground side of the wings of the metal cores. In a method for manufacturing a rubber crawler having a structure in which the steel cords are arranged in parallel with each other and embedded, a steel cord-embedded rubber is blended with a general-purpose rubber, a thermoplastic rubber compatible with a general-purpose rubber and co-vulcanizable with sulfur. "Thermoplastic rubber blend compound"
And a rubber crawler manufacturing method.