JP2004353755A - Block element with optimized circular arc groove for reducing stress concentration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate an optimal shape of a circular arc groove in a block element for a no-end block belt which has a neck portion and a pair of saddle portions placed in both sides of the neck portion and in which a circular arc groove for reducing stress concentration is formed in a boundary between the neck portion and the saddle portion in terms of improving the durability of the block element. <P>SOLUTION: The ratio of the depth from the position corresponding to a saddle top face and the radius of a circular arc of the circular arc groove for reducing stress concentration formed in the boundary between the neck portion and the saddle portion is set to such a value as to substantially equalize the stress at the position corresponding to the saddle top face and the stress at the bottom of the circular arc. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a block element of an endless block belt, and to an improvement of the block element against stress concentration in an arc groove provided at a boundary between a neck portion and a saddle portion.
[0002]
[Prior art]
A pair of endless belts is carried on the pair of saddle portions of the block element having a neck portion and a pair of saddle portions extending on both sides thereof to form an endless block belt, and the endless block belt is connected to two V-shaped pulley pairs. It is known to form a continuously variable transmission by bridging between the belts. A basic configuration of such an endless block belt is disclosed in, for example, Patent Document 1 below. The invention described in this patent document aims to make the tensile stress of the metal belt in such an endless block belt uniform in the width direction of the belt, thereby extending the life of the belt against fatigue.
[Patent Document 1]
JP-A-2002-54689
[0003]
An endless block belt of this type generally has a structure as shown in FIG. FIG. 5 is a view showing an example of an endless block belt in a state where the endless belt is cut between two adjacent block elements. The endless block belt includes a block element 10 and a pair of endless belts 12 arranged in order so that a large number forms a ring. In the illustrated example, each endless belt 12 has a two-layer structure. Each block element 10 has a head portion 14, a neck portion 16, and a pair of saddle portions 18 extending on both sides thereof. A pair of endless belts 12 are carried on the pair of saddle portions, and the saddle portion At both ends 20 of 18, it is stretched between two V-shaped pulley pairs. A portion of the conical belt engaging surface of one pulley of the two V-shaped pulley pairs is shown as 22.
[0004]
When rotational power is transmitted between the two V-shaped pulley pairs in such a structure, a load from the endless belt is applied to the saddle portion of the block element engaged with the pulley, whereby the neck portion and the saddle portion are A bending moment acts to reduce the angle between the two. In this case, if the boundary between the neck portion and the saddle portion forms a sharply cut corner, high stress concentration occurs there. Therefore, it is necessary to provide an arc groove 24 for reducing stress concentration at the boundary between the neck portion and the saddle portion. Is being done. Such an arc groove is also provided in the block element in Patent Document 1 described above.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to determine the optimum shape of the arc groove for reducing stress concentration of the block element from the viewpoint of improving the durability of the block element.
[0006]
[Means for Solving the Problems]
In order to solve this problem, the present invention comprises a neck portion and a pair of saddle portions extending on both sides thereof, and a pair of endless belts is carried on the pair of saddle portions to constitute an endless block belt. As a block element, the ratio of the depth of the arc groove for stress concentration formed at the boundary between the neck portion and the saddle portion to the saddle top surface and the arc radius is the stress at the position corresponding to the saddle top surface of the arc groove. The present invention proposes a block element characterized in that the stress at the bottom of the arc groove is made substantially equal.
[0007]
In this case, the stress at the bottom of the arc groove with respect to the ratio is further reduced by locally projecting the lower edge contour of the block element at a position corresponding to the bottom of the arc groove, and the saddle top surface When the stress at the corresponding location and the stress at the bottom of the arc groove are substantially equal to each other, the value of the stress may be reduced.
[0008]
In particular, the ratio may be in the range of 0.3 to 0.75, and the radius of the arc groove may be in the range of 0.5 to 1.5 mm.
[0009]
Function and effect of the present invention
A load is applied to the saddle part of the block element seated on the conical surface of the pair of pulleys at both ends of the pair of saddle parts from the endless bell, and as a result, a moment in the direction of reducing the angle between the neck part and the saddle part is reduced. In order to avoid high stress concentration at the boundary between the neck portion and the saddle portion during operation, an arc groove 24 is also formed at this boundary to relieve stress concentration. It is noted that there are two places where the stress is high when looking at the stress at the point. One of them is a position corresponding to the top surface of the saddle indicated by reference numeral 26 in FIG. The stress due to the above moment concentrates in this portion, but at the same time, the end of the endless block belt may come into contact with the portion, so that special attention is required in terms of strength. The other is the bottom 28 of the arc groove 24. Here, the stress due to the above moment is concentrated. Further, the stress at the position 26 corresponding to the saddle top surface of the arc groove and the stress at the bottom portion 28 of the arc groove indicate the direction of increase / decrease with respect to the magnitude of the ratio of the depth to the radius of the arc groove relative to the top surface of the saddle. Are noted to be opposite to each other.
[0010]
That is, regarding the stress at the saddle top surface corresponding position 26 of the circular groove, the value becomes larger as the depth D of the circular groove with respect to the saddle top surface becomes smaller and the radius R becomes larger. The stress at the surface generally increases with decreasing ratio D / R of depth D to radius R. On the other hand, the stress at the bottom 28 of the arc groove increases as the depth D increases and the radius R decreases, so that the stress at the bottom 28 of the arc groove increases with an increase in the ratio D / R. .
[0011]
Therefore, if the relationship between the stress at the saddle top surface corresponding position 26 and the stress at the bottom 28 can be optimized by adjusting the ratio D / R, the neck and saddle portions are formed by the stress concentration relief arc grooves. It is considered that the effect of alleviating stress concentration at the boundary can be maximized. FIG. 2 shows the results of experiments performed by the present inventors based on this idea.
[0012]
The graph of FIG. 2 shows the stress at the saddle top surface corresponding position 26 and the stress at the bottom 28 with respect to the change in the ratio D / R in comparison with each other. The stress at the surface corresponding position 26 and the stress at the bottom 28 are indicated by black circles (•). Both values are the stress σ at the saddle top surface corresponding position 26 or the bottom 28 corresponding to each D / R value, and the stress value at the bottom 28 when D / R = 1. It is shown as a ratio for a certain σ _{D / R = 1} . As described above, the direction of the change in the stress at the saddle top surface corresponding position 26 and the direction of the change in the stress at the bottom 28 with respect to the change in the D / R are opposite to each other, and represent both changes. The curves intersect each other. This is because the stress at the saddle top surface corresponding position 26 decreases as the D / R increases and the stress at the bottom 28 increases as the D / R increases. Mean that there are D / R values that are equal to each other. From the results shown in the figure, it is understood that the value of D / R may be in the range of about 0.3 to 0.75, and it is particularly preferable that the value is around 0.5. Incidentally, the value of R is preferably 0.5 to 1.5 mm.
[0013]
Thus, the ratio D / R of the depth D to the radius R of the arc groove for stress concentration formed at the boundary between the neck portion and the saddle portion with respect to the saddle top surface and the ratio of the stress at the saddle top surface corresponding position 26 to the stress at the saddle top surface 26 are determined. If the stress at the bottom 28 is made substantially equal, two stresses at which stress is further concentrated in the arc groove for relieving stress concentration are equalized, and the stress is reduced at the boundary between the neck portion and the saddle portion. Thus, the effectiveness of the arc groove for reducing the stress concentration in the groove can be further enhanced.
[0014]
Furthermore, the stress at the bottom 28 of the arc groove can be reduced by increasing the thickness of the block element (dimension B in FIG. 5) at the location corresponding to the bottom of the arc groove. Therefore, if the lower edge contour of the block element is locally protruded at a portion corresponding to the bottom of the arc groove, the curve of the stress at the bottom of the arc groove in the graph of FIG. By changing the curve as shown by the broken line in the graph, the value of σ at the point where the curve for the saddle top surface corresponding position 26 and the curve for the bottom 28 intersect can be further reduced by Δσ.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 3 is a view showing one embodiment of a saddle section according to the present invention, following the conventional example shown in FIG. In FIG. 3, portions corresponding to those described as a conventional example in FIG. 5 are denoted by the same reference numerals as those in FIG. 5, and a renewed description of these portions will be described with reference to redundancy of the specification. Omitted to avoid. As shown in FIG. 3, according to the present invention, the arc groove 24 for relieving stress concentration has the above-mentioned ratio D / R substantially in order to exhibit the function and effect of the present invention described above with reference to FIG. It is formed to be 0.5.
[0016]
FIG. 4 further reduces the stress at the bottom of the arc groove relative to said ratio by locally extending the lower edge profile of the block element at a location corresponding to the bottom of the arc groove, ie, FIG. By shifting the line connecting the black circles as a broken line, the stress at the position corresponding to the top surface of the saddle and the stress at the bottom of the arc groove become substantially equal to each other to reduce the value of the stress. FIG. 4 is a view similar to FIG. 3, showing an embodiment according to the embodiment of FIG. In FIG. 4 as well, portions corresponding to the portions shown in FIG. 3 are denoted by the same reference numerals as in FIG. 3, and the description of these portions will not be repeated. In this case, if the stress at the position corresponding to the top surface of the saddle has a minimum value for a certain D / R value as in the example shown in FIG. In the area corresponding to the bottom of the arc groove, the lower edge contour of the block element is locally extended by ΔB so that the stress line corresponding to the cross section of the stress line at the top surface of the saddle just crosses the stress line at the minimum value. What is necessary is just to adjust the degree to make it.
[0017]
In the above, the present invention has been described in detail with respect to one embodiment and another embodiment by changing a part of the embodiment. However, various changes may be made to these embodiments within the scope of the present invention. Variations will be apparent to those skilled in the art.
[Brief description of the drawings]
FIG. 1 is a schematic cross-section around an arc groove showing a change in a relative relationship between a depth and an arc radius of a circular arc groove for stress concentration formed at a boundary between a neck portion and a saddle portion of a block element with respect to a saddle top surface corresponding position; FIG.
FIG. 2 shows a comparison between the stress (△) at the position corresponding to the saddle top surface of the arc groove for stress concentration relaxation and the stress (●) at the bottom of the arc groove, and the ratio of depth and radius to the position corresponding to the saddle top surface. 4 is a graph showing changes in D / R.
FIG. 3 shows an embodiment of a block element according to the invention, with the endless belt cut between two adjacent block elements of the endless block belt.
FIG. 4 is a view similar to FIG. 3 showing another embodiment of the block element according to the present invention in which a part of the block element shown in FIG. 3 is further modified;
FIG. 5 is a view showing a typical example of a conventional block element in a state where an endless belt is cut between two adjacent block elements of an endless block belt.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Block element, 12 ... Endless belt, 14 ... Head, 16 ... Neck, 18 ... Saddle part, 20 ... Both ends of saddle part, 22 ... Conical belt engagement surface of pulley, 24 ... Arc groove, 26 ... Saddle Top surface corresponding position, 28 ... Bottom of arc groove

Claims (4)

A neck element and a pair of saddle portions extending on both sides thereof, and a block element that carries a pair of endless belts on the pair of saddle portions to form an endless block belt, the neck portion and the saddle portion. The ratio of the depth to the saddle top surface of the arc groove for stress concentration formed at the boundary of the arc and the radius of the arc is substantially the stress at the position corresponding to the saddle top surface of the arc groove and the stress at the bottom of the arc groove. A block element characterized in that the value is set to be equal to each other. By locally projecting the lower edge contour of the block element at a position corresponding to the bottom of the arc groove, the stress at the bottom of the arc groove with respect to the ratio is reduced, and at the position corresponding to the saddle top surface. 2. The block element according to claim 1, wherein the value of the stress when the stress and the stress at the bottom of the arc groove are substantially equal to each other is reduced. The block element according to claim 1, wherein the ratio is a value in a range of 0.3 to 0.75. The block element according to any one of claims 1 to 3, wherein a radius of the arc groove is in a range of 0.5 to 1.5 mm.

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