JP4321119B2 - Block element with optimized arc groove for stress concentration relaxation - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a block element of an endless block belt, and relates 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 are 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-type pulley pairs. It is known that a continuously variable transmission is constructed by interposing it, and the basic configuration of such an endless block belt is disclosed in, for example, Patent Document 1 below. In the invention described in this patent document, the tensile stress of the metal belt in such an endless block belt is made uniform in the width direction of the belt so as to extend the life against the fatigue.
[Patent Document 1]
JP 2002-54689 A
[0003]
Such an endless block belt generally has a structure as shown in FIG. FIG. 5 is a diagram 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 is composed of a block element 10 and a pair of endless belts 12 arranged in order so that a large number form an annular shape. 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, and a pair of endless belts 12 are carried on the pair of saddle portions, and the saddle portion 18 spans two V-shaped pulley pairs at both ends 20. A portion of the conical belt engaging surface of one of the two V-shaped pulley pairs is shown as 22.
[0004]
In this structure, when rotational power is transmitted between the two V-shaped pulley pairs, 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. A bending moment acts to reduce the angle between the two at the boundary. In this case, if the boundary between the neck portion and the saddle portion is a sharply cut corner, high stress concentration occurs there, so an arc groove 24 for stress concentration relaxation is provided at the boundary between the neck portion and the saddle portion. Has been 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]
This invention makes it a subject to obtain | require the optimal shape from a viewpoint of the improvement of durability of a block element about the circular arc groove for stress concentration relaxation of this block element.
[0006]
[Means for Solving the Problems]
In order to solve such a problem, the present invention has a neck portion and a pair of saddle portions extending on both sides thereof, and a pair of endless belts are carried on the pair of saddle portions to constitute an endless block belt. As a block element, the ratio of the depth to the saddle top surface of the arc groove for stress concentration relaxation formed at the boundary between the neck and the saddle portion and the radius of the arc 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, further, the stress at the bottom of the arc groove with respect to the ratio is lowered by locally projecting the lower edge contour of the block element at a portion corresponding to the bottom of the arc groove, and the saddle top surface When the stress at the corresponding position and the stress at the bottom of the arc groove are substantially equal to each other, the value of the stress may be lowered.
[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]
[Action and effect of the invention]
A load is applied to the saddle part of the block element seated on the conical surface of the pulley pair at both ends of the pair of saddle parts from the endless bell, and this causes a moment in the direction of reducing the angle between the neck part and the saddle part. In order to avoid high stress concentration at the boundary between the neck portion and the saddle portion when acting, an arc groove 24 is also formed for stress concentration relaxation at this boundary. It is noted that there are two places where the stress is high when looking at the stress in the case. One of them is a portion corresponding to the saddle top surface indicated by 26 in FIG. The stress due to the moment concentrates on this portion, but at the same time, the end of the endless block belt may come into contact with the portion, and special attention is required for strength. The other is the bottom 28 of the arc groove 24. The stress due to the moment is also concentrated here. Further, the stress at the saddle top surface corresponding position 26 of the arc groove and the stress at the bottom portion 28 of the arc groove are increased or decreased with respect to the ratio of the depth and the radius with respect to the saddle top surface of the arc groove. It is noted that are mutually opposite.
[0010]
That is, regarding the stress at the position 26 corresponding to the saddle top surface of the arc groove, the value increases as the depth D with respect to the saddle top surface of the arc groove decreases and the radius R increases. The stress at this point generally increases with decreasing ratio D / R of depth D to radius R. In contrast, the stress at the bottom 28 of the arc groove increases as the depth D increases and the radius R decreases, and therefore the stress at the bottom 28 of the arc groove increases as the ratio D / R increases. .
[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 of the stress concentration alleviating arc groove can be reduced. It is considered that the stress concentration relaxation effect at the boundary can be maximized. FIG. 2 shows the result of an experiment conducted by the inventors based on this idea.
[0012]
The graph of FIG. 2 shows the change in the stress at the saddle top surface corresponding position 26 and the change in the stress at the bottom 28 with respect to the change in the ratio D / R, with the white triangle (Δ) being the saddle top. The stress at the surface corresponding position 26 and the black circle (●) indicate the stress at the bottom 28. 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} . In this way, 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 are opposite to each other with respect to the change in D / R, and represent both changes. The curves intersect each other. This is because both the stress at the saddle top surface corresponding position 26 decreases as D / R increases, and the stress at the bottom 28 increases as D / R increases. Means that there exists a value of D / R that becomes equal to each other. From the results shown in the figure, it is sufficient that the D / R value is in the range of about 0.3 to 0.75, and it is found that the vicinity of 0.5 is most preferable. A suitable value for R is 0.5 to 1.5 mm.
[0013]
Therefore, the ratio D / R of the depth D to the radius R of the arc groove for stress concentration relaxation formed at the boundary between the neck portion and the saddle portion with respect to the saddle top surface is the stress at the saddle top surface corresponding position 26 and the arc groove. If the stress at the bottom 28 is made substantially equal, the stress at the two places where stress concentration further occurs in the stress concentration relaxation arc groove is equalized, and at the boundary between the neck and saddle. Therefore, the effectiveness of the arc groove for reducing the stress concentration can be further increased.
[0014]
Furthermore, the stress at the arc groove bottom 28 can be reduced by increasing the thickness of the blocking element (dimension B in FIG. 5) at the site corresponding to the arc groove bottom. Therefore, if the lower edge contour of the block element is locally projected at the part corresponding to the bottom of the arc groove, the stress curve at the bottom of the arc groove in the graph of FIG. By changing the graph as indicated by a broken line, 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 lowered by Δσ.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3 is a diagram showing an embodiment of the saddle portion according to the present invention, following the conventional example shown in FIG. In FIG. 3, the same reference numerals as those in FIG. 5 are attached to the portions corresponding to the portions described as the conventional example in FIG. 5, and the description of these portions is a redundant description. Omitted to avoid. As shown in FIG. 3, according to the present invention, the stress concentration alleviating arc groove 24 has the above ratio D / R substantially equal to that 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 the ratio by locally overhanging the lower edge contour of the block element at a location corresponding to the bottom of the arc groove, ie in FIG. By shifting the line connecting the black circles as indicated by the 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 are lowered when the stress is substantially equal to each other. FIG. 4 is a view similar to FIG. 3 showing the form following the embodiment of FIG. 3. Also in FIG. 4, parts corresponding to the parts shown in FIG. 3 are denoted by the same reference numerals as those in FIG. 3, and the description of these parts is omitted. In this case, when the stress at the position corresponding to the top surface of the saddle exhibits a minimum value with respect to a certain D / R value as in the example shown in FIG. The lower edge contour of the block element is locally projected by ΔB at the position corresponding to the bottom of the arc groove so that the stress line for the crosses the stress line at the position corresponding to the saddle top surface at the position of the minimum value. What is necessary is just to adjust the degree to make.
[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, these embodiments are not limited within the scope of the present invention. It will be apparent to those skilled in the art that changes are possible.
[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 with respect to a saddle top surface corresponding position of an arc groove for stress concentration relaxation formed at a boundary between a neck portion and a saddle portion of a block element; Figure.
Fig. 2 Comparison of stress (△) at the position corresponding to the saddle top surface of the arc groove for stress concentration relaxation and stress (●) at the bottom of the arc groove with respect to the position corresponding to the saddle top surface The graph shown with respect to the change of 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.
4 is a view similar to FIG. 3 showing another embodiment of a 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 diagram showing a typical example of a conventional block element in a state in which the endless belt is cut between two adjacent block elements of the endless block belt.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Block element, 12 ... Endless belt, 14 ... Head, 16 ... Neck part, 18 ... Saddle part, 20 ... Both ends of saddle part, 22 ... Conical belt engagement surface of a pulley, 24 ... Circular groove, 26 ... Saddle Top surface corresponding position, 28 ... bottom of arc groove

Claims (4)

A neck element and a pair of saddle parts extending on both sides thereof, and a pair of endless belts carried on the pair of saddle parts to form a block element constituting an endless block belt, the neck part and the saddle part; The ratio of the depth to the saddle top surface of the arc groove for stress concentration relaxation formed on the boundary of the arc and the radius of the arc substantially represents 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 values are equal. By locally projecting the lower edge contour of the block element at a portion 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 stress value 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 claim 1, wherein a radius of the arc groove is in a range of 0.5 to 1.5 mm.

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