JP2007022304A - Driving protrusion structure for crawler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To resist a force received from a sprocket or a truck roller by constituting high-hardness rubber as an inner layer and low-hardness rubber as an outer covering, thus improving durability as a protrusion. <P>SOLUTION: This driving protrusion structure for a crawler includes a driving protrusion formed on the inner periphery side of core metalless roller at regular intervals. The driving protrusion has the high-hardness rubber A (Hardness: 70 to 90 degrees) as an inner layer and the low-hardness rubber B having lower hardness than the inner layer rubber as its surface layer, and has 20 degrees or less in a harness difference between them. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in durability of a drive protrusion structure of a coreless crawler.

  The mandrel-less crawler forms a (drive) protrusion at a constant pitch on the inner peripheral side, hangs this on a sprocket and an idler, and engages the protrusion with the sprocket to transmit a driving force. Such a protrusion is subjected to a large shearing force from the front and rear or from the left and right from, for example, a sprocket and a track roller, so that the rubber material constituting the crawler base is extremely low in durability. Accordingly, in order to withstand this, the entire protrusion is made of rubber having a rigidity higher than that of the rubber of the crawler base, that is, a hard rubber.

  Such protrusions are formed by previously fitting an unvulcanized rubber block for protrusions into a depression of a molding mold and vulcanizing and bonding the uncured rubber constituting the crawler base body integrally. The protrusions achieve a certain purpose, but if the rubber is cracked, the rubber is inferior in elongation resistance. Therefore, once the rubber is cracked, the rubber tends to be largely chipped. Such protrusions are no exception.

  For this reason, a structure in which a resin rod is embedded in a rubber protrusion has been proposed (Patent Document 1). However, since a member different from rubber is embedded, there is a concern about peeling from the rubber, and there is also a concern about trouble due to forgetting to embed the resin rod in the molding process.

Japanese Patent Laid-Open No. 10-053171

  The present invention has been made in view of the prior art as described above, and an object thereof is to provide a protrusion structure that can cope with various requirements applied to the protrusion.

  The gist of the present invention is that, in the driving projection formed at a constant pitch on the inner peripheral side of the cored bar crawler, the high hardness rubber A is the inner layer and the rubber B having a lower hardness than the inner layer rubber A is the surface layer. The present invention relates to a driving projection structure of a crawler characterized by the above.

  The hardness of the high hardness rubber A is 70 to 90 degrees (JIS A), the hardness of the low hardness rubber B is 60 to 80 degrees (JIS A), and the high hardness rubber A and the low hardness rubber B This is a crawler drive projection structure in which the difference in hardness is 20 degrees (JIS A) or less.

  As a specific example of the drive projection structure, a rubber A having a high hardness of 70 to 90 degrees (JIS A) is used as an inner layer, and the hardness is 60 to 80, which is slightly lower in rigidity than the rubber A and excellent in extensibility. This is a crawler driving projection structure characterized in that the rubber B of degree (JIS A) is a surface layer and the difference in hardness between the rubber A and the rubber B is 20 degrees or less.

  As a more preferable driving protrusion structure, the driving protrusion includes a low friction member having a bulging portion at both ends and connecting the bulging portion with a narrower bridging portion. The present invention relates to a drive protrusion structure of a crawler exposed on the lateral side surface of the protrusion.

  In the present invention, the drive projection structure is improved as described above, and a high hardness rubber is used as an inner layer and a low hardness rubber is used as an outer cover. In other words, the projection is constructed with a highly rigid rubber inside and a rubber with excellent extensibility on the outside, which resists the force received from the sprocket and track roller and significantly improves the durability as a projection. It is.

  The present invention has been made on the basis of knowledge obtained by scrutinizing the state of resisting the external force of a conventional protrusion, and is the same in that the rigidity of the entire protrusion is improved. Is not directly brought into contact with a sprocket or the like, but has a structure in which a low-hardness rubber having low rigidity, that is, excellent extensibility, is covered with this, thereby eliminating the drawbacks of the conventional protrusions.

  That is, as a jacket rubber, the present invention is based on the knowledge that a rubber having a low crack growth property (that is, a low notch sensitivity) is suitable, and is a high hardness rubber generally used as a protrusion. This has led to the present invention because the crack growth property is higher and the low hardness rubber tends to have a lower crack growth property.

  In some cases, the low-hardness rubber may be a rubber having the same composition as that of the rubber constituting the crawler base. In this case, the structure is excellent in adhesion and integration between the protrusion and the crawler base.

  The hardness of the high hardness rubber A having high rigidity is 70 to 90 degrees (JIS A), and the hardness of the extensible low hardness rubber B is 60 to 80 degrees (JIS A). This is a crawler drive projection structure in which the difference in hardness between the rubber B and the low hardness rubber B is 20 degrees (JIS A) or less. As an effect of making the hardness difference 20 degrees or less, there is an effect that the hardness difference between the rubber A and the rubber B can be reduced to reduce the stress concentration at the contact interface between the two rubbers.

  Specifically, in the driving protrusion formed at a constant pitch on the inner peripheral side of the coreless crawler, the high hardness rubber A having high rigidity is used as the inner layer, and the rubber B having slightly low rigidity and excellent extensibility. Is a surface layer, and the hardness difference between the rubber A and the rubber B is 20 degrees or less.

  Of course, the drive protrusion according to the present invention should be considered also for the rolling wheel contacting from the left and right width direction, and particularly, the sliding with respect to the rolling wheel is improved, and as a result, the abrasion of the protrusion, the rubber chipping, etc. are prevented. Things are desired. From this point, it is preferable to incorporate a low friction member in the projection and to expose both ends of the projection on the side surface of the projection.

  The present invention will be further described below with reference to examples. FIG. 1 is a first example of the protrusion A of the present invention, and is a cross-sectional view in the longitudinal direction of the crawler, and FIG. 2 is a cross-sectional view in the width direction. As shown in FIG. 1, the projection A has a substantially regular triangular frustum as a whole. In the figure, 1 is a high hardness rubber mainly composed of SBR having a hardness of 83 degrees (JIS A), and 2 is a layer made of NR rubber having a hardness of 67 degrees covering the outside of the high hardness rubber 1. 3 is a rubber lug, and 4 is a steel cord embedded in the longitudinal direction of the crawler.

  FIG. 3 is a cross-sectional view in the longitudinal direction of the crawler at the protrusion B which is the second example of the present invention, and FIG. 4 is a cross-sectional view in the width direction thereof. Reference numerals 1 to 4 are the same as in the previous example, but in this example, the rod 5 is further incorporated in the protrusion B. The rod 5 has bulging portions 5a and 5b at both ends thereof, and a bridging portion 5c that connects the two is thin. The side surfaces of the bulging portions 5a and 5b are exposed, and other portions are made of the high-hardness rubber 1. It has a structure covered with.

  FIG. 5 shows an example in which the high-hardness rubber 1 is exposed on the side surface of the protrusion C. In order to make the protrusion C into the high-hardness rubber 1, it is possible to mix a resin such as PP, thereby improving the slipperiness. Thus, there is an effect that the friction with the wheel can be reduced.

(test)
A model of the projection A having a height of 70 mm shown in FIGS. 1 and 2 is created, and a plate having a tip 30 mm from the base portion of the projection and having a rounded tip is subjected to forcible displacement back and forth and its durability. Tested. Specifically, a projection A was created on a rubber plate, and this plate was fixed on a table for testing. The rubber layer 2 had a thickness of 5 mm.

  In the case of a conventional protrusion in which the entire protrusion is formed of high-hardness rubber, cracks occurred when the above-mentioned forced displacement number was about 10 times, and a phenomenon of rubber chipping occurred shortly thereafter. On the other hand, in the projection A having the above structure according to the present invention, the forced displacement was repeated 500 times, but no crack was generated.

  As described above, the effect of the present invention is remarkable, and is particularly applicable to the drive protrusion of a coreless crawler used for relatively high speed running.

FIG. 1 is a cross-sectional view of the projection A of the present invention in the longitudinal direction of the crawler. 2 is a cross-sectional view of the protrusion A in FIG. 1 in the width direction of the crawler. FIG. 3 is a cross-sectional view of the protrusion B of the present invention in the longitudinal direction of the crawler. 4 is a cross-sectional view of the protrusion B in FIG. 1 in the width direction of the crawler. FIG. 5 is a cross-sectional view of the protrusion C in the width direction of the crawler.

Explanation of symbols

A, B, C ... projections of the present invention,
1. High hardness rubber layer,
2. Low hardness rubber layer
3. Rubber rug,
4. Steel cord,
5. Rod,
5a, 5b ... The bulging part of the rod.

Claims (8)

  A crawler drive characterized by having a high hardness rubber A as an inner layer and a rubber B having a lower hardness than the inner layer rubber as a surface layer in a drive projection formed at a constant pitch on the inner peripheral side of the coreless crawler. Protrusion structure.   The crawler driving projection structure according to claim 1, wherein the hardness of the high hardness rubber A is 70 to 90 degrees (JIS A).   The crawler drive protrusion structure according to claim 1, wherein the hardness of the low hardness rubber B is 60 to 80 degrees (JIS A).   The crawler driving protrusion structure according to any one of claims 1 to 3, wherein a difference in hardness between the high-hardness rubber A and the low-hardness rubber B is 20 degrees (JIS A) or less.   The crawler driving protrusion structure according to any one of claims 1 to 4, wherein the high hardness rubber A is a highly rigid rubber.   The crawler driving protrusion structure according to claim 1, wherein the low hardness rubber B is a rubber having excellent extensibility.   The drive protrusions formed at a constant pitch on the inner peripheral side of the coreless crawler have rubber A with a high rigidity of 70 to 90 degrees (JIS A) as the inner layer, and the rigidity is slightly lower than that of the rubber A. A crawler drive protrusion structure characterized in that rubber B having excellent extensibility in hardness of 60 to 80 degrees (JIS A) is used as a surface layer, and the difference in hardness between rubber A and rubber B is 20 degrees or less.   The drive projection includes a low friction member having a bulging portion at both ends and connecting the bulging portion with a narrower bridging portion, and the bulging portion is exposed on the lateral side surface of the projection. The drive projection structure of a crawler according to any one of claims 1 to 7.

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