JP2007198402A - Pulley - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce weight and cost of a pulley main body by optimizing its wall thickness. <P>SOLUTION: The pulley has the pulley main body 10 integrally provided with an inner cylinder 1, a belt winding part 2 in a cylinder shape, a flange part 3 in a ring shape and a bearing 20 fit and held by inside of the inner cylinder part 1. Standard wall thickness of the inner cylinder part 1, the belt winding part 2 and the flange part 3 of the pulley main body 10 is determined so that maximum main stress by tension of a belt becomes smaller than a fatigue limit value and then the wall thickness of a position where a maximum value of the maximum main stress is applied is increased. The position where the maximum value of the maximum main stress is applied is regarded as a corner part 4 formed by the inner cylinder part 1 and the flange part 3 of the pulley main body 10 and wall thickness of the corner part 4 is increased. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pulley, and more particularly to a pulley in which measures against fatigue destruction are taken against a pulley body holding a bearing.

  A pulley main body integrally including an inner cylindrical portion, a cylindrical belt winding portion, and an annular flange portion having one end thereof connected to each other, and fitted and held inside the inner cylindrical portion of the pulley main body. A pulley having a bearing is used for an idler pulley used in an automobile engine room. In addition, various proposals related to pulleys having this structure have also been made conventionally (see, for example, Patent Document 1 and Patent Document 2). Among them, Patent Document 2 describes that in order to improve the strength of the pulley body, It describes that a nitride layer is formed on the surface portion of the belt guide portion corresponding to the belt winding portion.

  On the other hand, in the above-structured pulley manufactured by pressing a sheet metal, it is common to appropriately determine the thickness of the pulley body as a means of imparting strength and durability that can withstand belt tension and preventing fatigue failure, etc. Has been done.

  Conventionally, when the strength and durability required for the pulley body are to be secured by appropriately determining the wall thickness, there is a possibility that the maximum main stress applied to the pulley body, that is, the belt tension may be applied to the pulley body. After investigating or assuming the distribution of the maximum value of a certain stress over the entire pulley body, press the sheet metal material with the required thickness at the location where the maximum value of the maximum principal stress is applied to press the pulley body. The method of manufacturing, in other words, the method of applying the wall thickness required for the place where the maximum value of the maximum principal stress is applied over the entire pulley body has been adopted.

JP 2000-74189 A JP 11-63173 A

  However, when the thickness of the pulley body is determined by the above-described conventional method, the thickness of the portion to which the maximum value of the maximum principal stress is applied is optimized, but the thickness is increased more than necessary at the other portions. It was found that the weight of the main body was hindered and the cost was adversely affected.

  The present invention has been made in view of the above problems, and the thickness is optimized not only at the portion where the maximum value of the maximum principal stress is applied, but also at other portions, thereby reducing weight and cost. An object of the present invention is to provide a pulley that can be easily lowered.

  In the pulley according to the present invention, the inner cylinder part, the cylindrical belt winding part arranged concentrically outside the inner cylinder part, and one end of the inner cylinder part and the belt winding part are connected to each other. In a pulley having a pulley body integrally provided with an annular flange portion and a bearing fitted and held inside the inner cylinder portion of the pulley body, the inner cylinder portion and belt winding forming the pulley body The reference wall thickness of the hook and flange is determined so that the maximum principal stress due to belt tension is smaller than the fatigue limit value, and the part where the maximum value of the maximum principal stress is applied is increased. The wall thickness is gradually decreased until the reference wall thickness is reached as the thickness increases away from both sides.

  According to the pulley of this configuration, the maximum principal stress applied to the pulley body is smaller than the fatigue limit value due to the reference thickness applied to the inner cylinder part, the belt winding part and the flange part forming the pulley body. Since the belt tension during use is kept at the normal tension, the pulley body strength is insufficient even when the belt tension reaches the maximum tension for some reason. Does not happen. In addition, by adopting a configuration in which the thickness where the maximum value of the maximum principal stress is applied is increased and the thickness is gradually reduced to the reference thickness as it moves away from both sides of the increased thickness, the maximum main stress is adopted. There is an effect that fatigue failure is less likely to occur at a location where the maximum value of stress is applied or in the vicinity thereof.

  In the present invention, it is possible to adopt a configuration in which the corner portion is thickened as a corner portion formed by the inner cylinder portion and the flange portion of the pulley body where the maximum value of the maximum principal stress is applied. .

  Further, it is desirable that the reference thickness is determined so that the maximum principal stress is 50 to 95% with respect to the fatigue limit value. According to this, it is avoided that the belt winding part of the pulley main body becomes thicker than necessary, and the strength of the pulley main body is ensured without excess or deficiency, and it is easy to achieve weight reduction and cost reduction.

  In the present invention, it is desirable that the maximum thickness of the corner is set to 1.2 to 2.0 times the reference thickness. According to this, the pulley main body which is hard to produce fatigue failure is obtained.

  In the present invention, it is desirable that the corner portion is thickened by increasing the thickness of the corner portion formed by the inner cylinder portion and the flange portion of the pulley body. This eliminates the need to change the shape of the bearing fitting space of the pulley body.

  As described above, according to the present invention, the thickness is optimized not only at the portion where the maximum value of the maximum principal stress is applied, but also at other portions, and it is easy to reduce weight and reduce costs. Become. Therefore, although the manufacturing cost is reduced, the effect that the durability is improved is achieved.

  FIG. 1 is a sectional view of a pulley according to an embodiment of the present invention. As shown in the figure, this pulley includes an inner cylinder portion 1, a cylindrical belt winding portion 2 concentrically disposed outside the inner cylinder portion 1, and the inner cylinder portion 1 and the belt winding portion 2. It has a pulley body 10 that is integrally provided with an annular flange portion 3 that is connected at one end, and a bearing 20 that is fitted and held inside the inner cylinder portion 1 of the pulley body 10. Further, among the corners 4 formed by the inner cylinder part 1 and the flange part 3 of the pulley body 10, the corners 4 are thickened by increasing the thickness of the corners 41, and the thickened parts are increased. The wall thickness is gradually reduced until it becomes the same thickness as other parts as it moves away from both sides.

  FIG. 2 is a cross-sectional view of a conventional pulley manufactured by pressing a sheet metal material as a comparative example. When the pulley of FIG. 1 is compared with the pulley of FIG. 2, since the pulley of FIG. 2 is manufactured by press-molding a sheet metal material having a thickness t, the inner cylinder portion 1, the cylindrical belt winding portion 2 and While the thickness of the annular flange portion 3 and the thickness of the corner portion 4 and the like are all equal to the thickness t of the sheet metal material, in the pulley of FIG. The only difference is that the corner 4 is thickened by this, and that the thickness is gradually reduced until it reaches the thickness t as it goes away from the thickened portion of the corner 4 to both sides. . In FIG. 1, the outline of the corner 41 of the corner 4 that is not thickened is indicated by a virtual line.

  In the pulley configured as shown in FIG. 1, the thickness t of the portion having the thickness t of the pulley body 10 is determined so that the maximum principal stress due to the belt tension is smaller than the fatigue limit value. In other words, the pulley body 10 does not have a portion thinner than the wall thickness t, so that the maximum principal stress applied to the pulley body 10 is suppressed to a value smaller than the fatigue limit value. Therefore, not only when the belt tension during use is kept at the normal tension, but also when the belt tension reaches the maximum tension for some reason, the situation where the strength of the pulley body 10 is insufficient does not occur. . On the other hand, since the thickness T of the corner 4 is thicker than other portions, even when the largest load is applied to the corner 4, the maximum principal stress of the corner 4 is larger than that of the other portions. Since it is large, fatigue failure is less likely to occur in the corner 4 and the thickness gradually decreasing regions on both sides thereof. Here, the maximum principal stress is a stress that acts on the pulley body 10 when the belt tension reaches the maximum value that allows for a safety factor.

  The inventor of the present application conducted an intensive investigation on an appropriate range of the wall thickness t, an appropriate range of the wall thickness T at the thickened portion, a thickened portion, and the like for the pulley having the configuration shown in FIG. This investigation will be described below.

(1) Location of generation of maximum principal stress Pressing the sample pulley with inner diameter d = 40mm and outer diameter D = 75mm shown in FIG. After the molding was performed and the bearing 20 was fitted and held in the inner cylinder portion 1, the magnitude of distortion of a required portion of the pulley body 10 was compared for each pulley. The strain was measured by attaching strain gauges at four locations A, B, C, and D shown in FIG. In addition, A is an entrance corner formed by the inner tube portion 1 and the flange portion 3, B is an exit corner portion formed by the flange portion 3, and C is formed by the outer tube portion 2 and the flange portion 3. A corner portion D is an inner peripheral portion of the end edge of the outer cylinder portion 4.
From this investigation, it has been found that the place where the maximum principal stress occurs is the corner portion 4 formed by the inner corner portion 1 and the flange portion 3 in FIG.
Therefore, as one condition for optimizing the wall thickness, it is effective to make the wall thickness of the corner 4 formed by the inner tube portion 1 and the flange portion 3 thicker than other portions. It turned out that.

(2) Change in maximum principal stress due to pulley plate thickness Wrap a belt around the above three types of sample pulleys with different thicknesses, and clarify the relationship between the maximum principal stress of each sample pulley and the fatigue limit value. The results are shown in FIG. The belt tension was a normal tension, a maximum tension, and a tension when the safety factor was 1.3.
According to FIG. 4, since the maximum principal stress is smaller than the fatigue limit value for any of the thicknesses of the sample pulley, even if the belt tension allows for a safety factor, the pulley body is required from this result. It can be seen that the strength and durability are satisfied at any thickness. However, the maximum principal stresses of the sample pulleys of 2.6 mm and 3.2 mm are significantly smaller than the fatigue limit values, 44% and 24%, respectively. It can be seen that it has great strength. Therefore, it can be said that the sample pulleys having the plate thicknesses of 2.6 mm and 3.2 mm are wasteful in terms of cost and weight reduction. On the other hand, the maximum principal stress of the sample pulley with a plate thickness of 2.0 mm is 76% of the fatigue limit value, and even if the safety factor is anticipated, material waste is lost in terms of cost and weight reduction It can be said that less is advantageous. From the viewpoint of cost and weight reduction, if the ratio (%) of the maximum principal stress to the fatigue limit value is 50 to 95%, it is advantageous that material waste is reduced.

  Considering the investigation results of (1) and (2) above, like the pulley described with reference to FIG. 1, the reference wall thickness of the pulley body 10, that is, the inner cylinder portion 1, the belt winding portion 2 and the flange portion. The thickness t of 3 is set to 2 mm as a reference thickness, for example, the corner 4 formed by the inner tube portion 1 and the flange portion 3 is defined as the weakest portion, and the corner 4 is increased to the thickness T. By adopting a configuration in which the thickness is gradually reduced until it reaches the same thickness as the other locations as it increases away from both sides of the thickened location, only the thickness at the location where the maximum value of the maximum principal stress is applied In addition, the thickness is optimized at other locations to reduce material waste and reduce the weight and cost of the pulley, but the durability is improved and fatigue at the corner 4 is reduced. It turns out that it becomes difficult to cause destruction.

  Next, in order to optimize the overall wall thickness of the pulley body 10, the above-mentioned reference wall thickness (the belt tension is applied to the thickened portion, that is, the maximum thickness of the corner portion 4, other than the thickened portion is adopted. It has been confirmed that it is appropriate to set the maximum principal stress to 1.2 to 2.0 times the wall thickness at which the maximum principal stress is smaller than the fatigue limit value. When the maximum wall thickness is thinner than 1.2 times the reference wall thickness, it is difficult to obtain a sufficient effect for making it difficult to cause fatigue failure because the increase width of the maximum main stress at the thickened portion is too small. On the other hand, if the maximum wall thickness is larger than 2.0 times the reference wall thickness, the thickened portion becomes unnecessarily thick, resulting in an increase in weight and cost. And when the maximum thickness is 1.2 to 2.0 times the reference thickness, a sufficient increase width of the maximum principal stress at the thickened portion is secured, and fatigue failure is less likely to occur. It is suppressed that the portion becomes unnecessarily thick and causes weight increase and cost increase. More preferably, if the maximum thickness is 1.4 times or less of the reference thickness, the effect of weight reduction and cost reduction is great.

  Next, as the means for increasing the thickness of the corner 4 shown in FIG. That is, after the pulley body 10 having the shape shown in FIG. 2 and having a reference thickness applied is manufactured by pressing from a sheet metal material, the thickness is increased by building up the corners of the corners 4. It becomes possible. As the means for overlaying, it is possible to employ, for example, a means for stacking and joining different plate materials, a means for rolling, a means for welding overlay, and the like. Further, as another means for increasing the thickness of the corner 4 from the reference thickness, after the pulley body 10 having a thickness required for the corner 4 is press-molded, the portions other than the increased thickness are set to the reference thickness. It is also possible to adopt a means of cutting until it becomes. Furthermore, it is also possible to employ a method of performing sheet metal processing on the pulley body 10 without using press molding or a method of rolling a sheet metal material.

  In the above-described embodiment, although the portion where the maximum value of the maximum principal stress is applied is the corner portion 4 formed by the inner cylinder portion 1 and the flange portion 3 of the pulley body 10, the corner portion is thickened. When a location other than the corner 4 is a location where the maximum value of the maximum principal stress is applied, the thickness is increased. For example, as shown in FIG. 5, the corners formed between the outer cylinder portion 2 and the flange portion 3 of the pulley body 10 may be thickened.

It is sectional drawing of the pulley which concerns on embodiment of this invention. It is sectional drawing of the conventional pulley as a comparative example. It is explanatory drawing which showed the sticking location of the strain gauge at the time of investigating the stress change by a belt winding angle. It is a figure which shows the ratio of the largest principal stress with respect to the plate | board thickness and fatigue limit value of a sample pulley. It is sectional drawing of the pulley which concerns on the modification of embodiment of this invention, Comprising: It is a figure which shows the state which thickened the corner part formed between an outer cylinder part and a flange part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner cylinder part 2 Belt winding part 3 Flange part 4 Corner part 10 Pulley main body 20 Bearing 41 Corner part

Claims (5)

An inner cylinder part, a cylindrical belt winding part concentrically arranged on the outer side of the inner cylinder part, and an annular flange part continuously connecting one end of the inner cylinder part and the belt winding part are integrated. In a pulley having a pulley body and a bearing fitted and held inside the inner cylindrical portion of the pulley body,
After determining the reference wall thickness of the inner cylinder part, belt winding part and flange part forming the pulley body so that the maximum principal stress due to the belt tension is smaller than the fatigue limit value, A pulley characterized in that the portion to which the maximum value of the maximum principal stress is applied is increased in thickness, and the thickness is gradually reduced until the reference thickness is reached as the thickness increases away from both sides. 2. The pulley according to claim 1, wherein the portion to which the maximum value of the maximum principal stress is applied is a corner portion formed by the inner cylinder portion and the flange portion of the pulley body, and the corner portion is thickened. The pulley according to claim 1 or 2, wherein the reference wall thickness is determined so that the maximum principal stress is 50 to 95% with respect to the fatigue limit value. The pulley according to any one of claims 2 and 3, wherein the maximum thickness of the corner is set to 1.2 to 2.0 times the reference thickness. The pulley according to any one of claims 2 to 4, wherein the corner portion is thickened by increasing the thickness of the corner portion formed by the inner cylinder portion and the flange portion of the pulley body.

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