JP2007107640A - Auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an auto tensioner which more effectively absorbs fluctuation of belt tension. <P>SOLUTION: This auto tensioner 1 includes a swinging arm provided with a base end part 3 having an outer raceway surface 31 formed on the inner periphery and with an arm extending from the base end part 3 and having a rotatably fixed pulley around which a belt is wound; a support member 2 having an inside raceway surface 21 in the outer peripheral side and supporting the swinging arm so as to freely swings it by relatively rotatably supporting the base end part 3; and cylindrical rollers 4 interposed between the outside raceway surface 31 and the inside raceway surface 21 so as to be freely rolled. On the inside raceway surface 21 and the outside raceway surface 31, respective raceway surfaces 2k, 3k of different shapes are formed to gradually narrow nipping intervals of the cylindrical rollers 4 while rolling the cylindrical rollers 4 along with the relative rotation of the base end part 3 and the support member 2 and apply rotation energizing force in a direction canceling a phase difference between the base end part 3 and the support member 2 generated by the relative rotation between the base end part 3 and support member 2. Due to this rotation energizing force, the swinging arm is energized in a predetermined swinging direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an auto tensioner that applies tension to a belt wound around a pulley.

A belt is generally used as means for transmitting power from an engine to an auxiliary machine such as an alternator. The belt tension is kept constant by the auto tensioner. The auto tensioner has a pulley around which the belt is wound around the tip of a swing arm which can swing around a support portion fixed to an engine or the like. It can be elastically swung by an elastic force generated by a torsion coil spring attached between the arm and the support (see, for example, Patent Document 1).
Such an auto tensioner applies a certain tension to the belt by urging the pulley in a predetermined swinging direction. At the same time, fluctuations in belt tension caused by fluctuations in engine rotation speed, etc. are absorbed by the elastic swing of the swing arm, preventing belt vibration and abnormal noise to ensure the original life of the belt. can do. Further, it is possible to absorb an attachment error of the auxiliary machine, a dimensional change due to a temperature change, a belt length variation, and the like.

Japanese Patent Laid-Open No. 7-4481 (FIG. 1)

According to the conventional auto tensioner, the fluctuation absorption characteristic of the belt tension of the swing arm depends on the torsion coil spring, and the torsion coil spring is large enough to be incorporated in the auto tensioner. Therefore, the wire diameter, the free length, the number of windings, and the like are limited, and the characteristics of the elastic force of the torsion coil spring cannot be set freely. For this reason, the degree of freedom in setting the fluctuation absorption characteristic of the belt tension as an auto tensioner is limited, and the fluctuation of the belt tension may not be sufficiently absorbed.
The present invention has been made in view of such circumstances, and an object thereof is to provide an auto tensioner capable of more effectively absorbing fluctuations in belt tension.

  The auto tensioner of the present invention has a cylindrical base end portion having an outer raceway surface formed on the inner periphery, and a swing having an arm that is rotatably fixed to a pulley that extends from the base end portion and on which a belt is wound. An arm, a support member having an inner raceway surface facing the outer raceway surface on an outer peripheral side and supporting the base end part so as to be relatively rotatable, and the outer raceway, A rolling element interposed between the inner raceway surface and the inner raceway surface such that at least one of the inner raceway surface and the outer raceway surface rolls with relative rotation between the base end portion and the support member. The rolling biasing force in a direction to eliminate the phase difference between the base end portion and the support member generated by the relative rotation by gradually narrowing the holding interval of the rolling body while rolling the moving body. Variant applied between the end and the support member Has at least a portion the road surface, by the turn biasing force, it is characterized by biasing the swing arm in a predetermined oscillation direction.

  According to the auto tensioner configured as described above, a rotation biasing function (torsion spring property) is imparted between the base end portion and the support member with a simple configuration without using a torsion coil spring or the like. Can do. In other words, this torsion spring property makes it possible to elastically swing the swing arm and to bias the swing arm in a predetermined swing direction. As a result, tension can be applied to the belt wound around the pulley. In addition, the torsion spring property obtained by the above configuration can be changed in various ways by changing the shape of the irregular raceway surface, the outer diameter of the rolling element, etc., and the degree of freedom of setting becomes extremely high. Therefore, the elastic force characteristics when the swing arm swings can be suitably set according to the characteristics and specifications of the engine.

In the autotensioner, it is preferable that a rolling bearing that supports the base end portion and the support member so as to be relatively rotatable with each other is interposed between the base end portion and the support member.
In this case, since the radial load acting on the base end portion can be supported by the rolling bearing, the external load acting on the deformed raceway surface and the rolling element can be reduced. Therefore, the torsion spring property can be obtained more stably.

  As described above, according to the autotensioner according to the present invention, the elastic force characteristics when the swing arm swings can be suitably set, so that the belt tension fluctuation can be absorbed more effectively. it can.

  Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings. 1 and 2 are a cross-sectional view and a side view, respectively, of an auto tensioner according to an embodiment of the present invention. In FIG. 1, a swing arm 30 is a molded member in which a substantially cylindrical base end portion 3 and an arm 7 that extends from the base end portion 3 and on which a pulley 6 around which a belt 50 is wound are fixed. It is. The pulley 6 has a ball bearing 8 mounted at the center thereof. The inner ring of the ball bearing 8 is fitted on the distal end portion 7 a of the arm 7 and is fixed to the distal end portion 7 a by a bolt 9 and a nut 10. In this way, the pulley 6 is rotatably fixed to the distal end portion 7 a of the arm 7.

  On the other hand, the support member 2 that supports the swing arm 30 is a molded member having a shaft portion 25 formed in a hollow shaft shape and a fixing portion 26 for fixing to the engine to which the auto tensioner 1 is attached. The shaft portion 25 is coaxially disposed on the inner peripheral side of the base end portion 3, and the cylindrical roller 4 as a rolling element is interposed between the shaft portion 25 and the base end portion 3 so as to be able to roll. is doing. An outer raceway surface 31 on which the cylindrical roller 4 rolls is formed on the inner peripheral surface of the base end portion 3, and an inner raceway surface on which the cylindrical roller 4 rolls on the outer peripheral surface of the shaft portion 25. 21 is formed opposite to the outer raceway surface 31.

  Rolling bearings 51 and 52 are interposed between the base end portion 3 and the shaft portion 25 so as to be positioned on both sides of the cylindrical roller 4 in the axial direction, so that the base end portion 3 and the shaft portion 25 are relative to each other. While being able to rotate, the load of the radial direction which acts on the base end part 3 is supported. In addition, a pressing member 53 for press-fitting the cylindrical roller 4 and the rolling bearings 51 and 52 so as not to come out of the shaft portion 25 is press-fitted and fitted to the end portion of the shaft portion 25.

Next, the inner raceway surface 21 and the outer raceway surface 31 provided on the shaft portion 25 and the base end portion 3 will be described. FIG. 3 is an enlarged view of a cross section taken along line III-III in FIG. The inner raceway surface 21 of the shaft portion 25 continuously forms inner deformed raceway surfaces 2k as four deformed raceway surfaces different from the circumferential surface around the rotation axis X of the shaft portion 25 and the base end portion 3. It is comprised by doing. The outer raceway surface 31 is configured by continuously forming outer variant raceway surfaces 3k as four variant raceway surfaces.
Each inner deformed raceway surface 2k constituting the inner raceway surface 21 has the same shape, and each outer deformed raceway surface 3k constituting the outer raceway surface 31 has the same shape. The inner raceway surface 21 is equally divided into four in the circumferential direction (every 90 degrees), and each divided portion is an inner deformed raceway surface 2k. Similarly, the outer raceway surface 31 is also equally divided into four in the circumferential direction (every 90 degrees), and each divided portion is an outer deformed raceway surface 3k. One cylindrical roller 4 is disposed between each of the irregular raceway surfaces 2k and 3k.
Further, between the shaft portion 25 and the base end portion 3, there is a gradually reduced space portion (wedge-shaped space portion) in which the raceway surface interval gradually decreases in the circumferential direction due to the inner deformed raceway surface 2k and the outer deformed raceway surface 3k. The cylindrical roller 4 is compressed and elastically deformed by a so-called wedge effect with the relative rotation between the shaft portion 25 and the base end portion 3. As described above, the inner raceway surface 21 and the outer raceway surface 31 are formed by continuation of the modified raceway surfaces 2k and 3k, respectively, so that the inner raceway surface 21 and the outer raceway surface 31 are occupied only by the variant raceway surfaces 2k and 3k, respectively. ing. In addition, the deformed raceway surfaces 2k and 3k are equally arranged in the circumferential direction.

Next, the contour shapes of the outer deformed raceway surface 3k and the inner deformed raceway surface 2k will be described in detail.
Each of the four outer deformed track surfaces 3k constituting the outer track surface 31 is a concave curved surface. Specifically, the outer deformed raceway surface 3k is located closer to the raceway surface (the outer deformed raceway surface 3k) than the rotation axis X (hereinafter also referred to as the shaft center X) of the shaft portion 25 and the base end portion 3. The circumferential surface is centered on the outer ring raceway curvature center Co. The curvature radius gro of the outer deformed raceway surface 3k is the maximum value of the distance between the outer raceway surface 31 and the axis center X, and is the outer track reference radius Ro that is the radius of a circle circumscribing the cross-sectional contour line of the outer raceway surface 31. Smaller than. Further, in a cross-sectional view, with respect to each of the three outer deformed raceway surfaces 3k, the outer raceway curvature center Co is a straight line including the outer track maximum radial position 3m and the shaft center X where the distance from the shaft center X is the maximum value. on p3.

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Each of the four inner deformed track surfaces 2k constituting the inner track surface 21 is a convex curved surface. Specifically, the inner deformed track surface 2k is a circumferential surface centered on the inner track curvature center Ci located on the side farther from the track surface (the inner deformed track surface 2k) than the axis center X. The curvature radius gri of the inner deformed raceway surface 2k is the minimum value of the distance between the inner raceway surface 21 and the axis center X and is the radius of a circle inscribed in the cross-sectional contour line of the inner raceway surface 21. Bigger than. Further, in a cross-sectional view, for each of the three inner deformed raceway surfaces 2k, the inner raceway curvature center Ci is a straight line including the inner raceway minimum diameter position 2m at which the distance from the shaft center X is the minimum and the shaft center X. on p2.

The shaft portion 25 and the base end portion 3 provided with both the raceway surfaces 21 and 31 having the above-described shape are rotated in a direction to eliminate a phase difference caused by the relative rotation when they are relatively rotated. It has a biasing function (torsion spring function). Hereinafter, this point will be described.
As described above, since the inner raceway surface 21 and the outer raceway surface 31 are not circumferential surfaces around the axis center X, a space (rolling space) between the inner raceway surface 21 and the outer raceway surface 31 is used. 3) changes depending on the relative phase relationship between the shaft portion 25 and the base end portion 3, but the state in FIG. 3 is the outer track maximum diameter position 3 m of the outer track surface 31 and the inner track minimum diameter position of the inner track surface 21. 2m is in the same phase. Hereinafter, this state is referred to as a reference state. In this reference state, each cylindrical roller 4 is arranged at a circumferential position in contact with the inner track minimum diameter position 2 m and the outer track maximum diameter position 3 m. This reference state is a state in which the holding interval of the cylindrical roller 4 between the outer deformed raceway surface 3k and the inner deformed raceway surface 2k (the track surface interval at the contact position of the cylindrical roller 4) is the widest. Therefore, in this reference state, the compressive force acting on the cylindrical roller 4 from both the raceway surfaces 2k and 3k becomes a minimum value (for example, 0).
Note that the radial distance between the inner track minimum diameter position 2 m and the outer track maximum diameter position 3 m in the reference state is substantially the same as the diameter of the cylindrical roller 4, but gives a slight radial gap (plus gap or minus gap). May be.

  Next, when the shaft portion 25 and the base end portion 3 are relatively rotated from this reference state, the cylindrical roller 4 rolls and the holding interval of the cylindrical roller 4 gradually decreases. Accordingly, with this relative rotation, the cylindrical roller 4 is compressed by the inner raceway surface 21 and the outer raceway surface 31 to be elastically compressed and deformed, and a rotational biasing force (elastic force; torsion) in a direction to eliminate the phase difference caused by this relative rotation. (Spring force) is applied between the shaft portion 25 and the base end portion 3.

  The point at which the rotational biasing force (torsion spring force) is generated will be described in more detail. FIG. 4 is a cross-sectional view for explaining the rotational biasing force generated by the relative rotation between the shaft portion 25 and the base end portion 3, and the inner deformed track surface 2k and the outer deformed track surface 3k for easy understanding. Only the cross-sectional line of the cylindrical roller 4 is shown. FIG. 4 shows a balanced state in which the shaft portion 25 is fixed and the base end portion 3 is rotated counterclockwise by an angle θ to be stationary. In the reference state, the outer track maximum diameter position 3m is located at a position 3mi on the x axis in FIG. 4, and the inner track minimum diameter position 2m is also on the x axis. In this reference state, the center Pr of the cylindrical roller 4 is also on the x axis. When the base end 3 is rotated counterclockwise by an angle θ from such a reference state, the cylindrical roller 4 rolls counterclockwise to the position shown in FIG. The revolution angle of the cylindrical roller 4 due to this rolling is an angle φi with respect to the inner track curvature center Ci.

  At this time, if the center of the contact position between the inner deformed raceway surface 2k and the cylindrical roller 4 is Pi and the center of the contact position between the outer deformed track surface 3k and the cylindrical roller 4 is Po, the distance between Pi and Po is The distance between the minimum inner track diameter position 2m and the maximum outer track diameter position 3m in the reference state is narrower than the diameter 2Rr of the cylindrical roller 4 (twice the radius Rr of the cylindrical roller 4). It is narrower. Therefore, the cylindrical roller 4 receives the vertical force Qi from the inner raceway surface 21 and also receives the vertical force Qo from the outer raceway surface 31 and undergoes compression elastic deformation. In a balanced and stationary state, almost no tangential force acts on the cylindrical roller 4, and the points Ci, Co, Pi, Pr, Po are aligned on the straight line L1 as shown in FIG. The direction of the vector of the vertical force Qi and the vertical force Qo is the same as that of the straight line L1. Qo ′ is also in the same direction as the straight line L1. The normal force Qo ′ received by the base end portion 3 from the cylindrical roller 4 is different from the radial direction around the axial center X (the direction connecting the center Po of the contact position with the cylindrical roller 4 and the axial center X). Therefore, it has a clockwise component together with the radial component. In this way, the base end portion 3 receives a clockwise moment (hereinafter also referred to as a rotation biasing moment) that generates a rotation biasing force. The magnitude of the rotation urging moment is [(size of vector Qo ′) × (distance Ul from axis center X to straight line L1)].

  As described above, the inner deformed track surface 2k is a convex curved surface, and the outer deformed track surface 3k is a concave curved surface. In addition, the inner deformed raceway surface 2k and the outer deformed raceway surface 3k constitute a smoothly continuous curved surface. Only the boundary position 21b between the adjacent inner deformed raceway surfaces 2k is not a smoothly continuous curved surface in the inner raceway surface 21 (see FIG. 3), and the smoothly continuous curved surface in the outer raceway surface 31. Only the boundary position 31b between the adjacent outer deformed raceway surfaces 3k is not (see FIG. 3). Therefore, as long as the contact position between the cylindrical roller 4 and the raceway surface does not reach these boundary positions 21b and 31b, the raceway surface spacing at the cylindrical roller 4 contact position associated with the relative rotation between the shaft portion 25 and the base end portion 3 is gradually increased ( Will gradually change). Then, by the mechanism described with reference to FIG. 4, the rotational biasing force in a direction to eliminate the phase difference caused by the relative rotation between the shaft portion 25 and the base end portion 3 is generated between the shaft portion 25 and the base end portion 3. Granted in between.

  As described above, the shaft portion 25 supports the base end portion 3 so as to be relatively rotatable, and the swing arm 30 is swingable with respect to the support member 2. The auto tensioner 1 urges the swing arm 30 in the clockwise direction of FIG. 2 by the rotational urging force in a state where the belt 50 is wound around the pulley 6, and gives a constant tension to the belt 1. .

  According to the auto tensioner 1 configured as described above, the rotation urging function (torsion spring property) can be performed with the shaft portion 25 (the shaft support member 2) and the base with a simple configuration without using a torsion coil spring or the like. It can be applied between the end 3. That is, the torsion spring property allows the swing arm 30 to be elastically swung around the shaft portion 25, and tension can be applied to the belt 50. Further, the torsion spring characteristics obtained by the above configuration can be varied in various ways by changing the shapes of the two or two deformed raceway surfaces 2k and 3k, the outer diameter of the cylindrical roller 4, etc. Becomes extremely high. Therefore, the elastic force characteristic when the swing arm 30 swings can be suitably set according to the characteristics and specifications of the engine, and the tension variation of the belt 50 can be absorbed more effectively.

  In the auto tensioner 1 of the above embodiment, when the rolling part between the cylindrical roller 4 and the inner raceway surface 21 and the outer raceway surface 31 is lubricated with a lubricant such as oil or grease, the cylindrical roller 4 Attenuation function can be imparted by rolling viscous resistance and agitation resistance of the lubricant when rolling, and it has torsion spring properties and also attenuates the external force acting and the rotational biasing force as the reaction force of the external force It can have a function. Thereby, the auto tensioner 1 of this embodiment can attenuate and relieve resonance and the like caused by the torsion spring property.

  In the auto tensioner 1, rolling bearings 51 and 52 are interposed between the shaft portion 25 and the base end portion 3, thereby acting between the shaft portion 25 and the base end portion 3. Supports radial load. As a result, the externally applied load acting on the deformed raceway surfaces 2k and 3k and the cylindrical roller 4 can be reduced. Therefore, the load necessary for generating the rotational biasing force can be reduced to the both deformed track surfaces 2k and 3k and The cylindrical roller 4 can be made to act stably. Therefore, the rotational urging force obtained by the auto tensioner 1 can be made more stable.

  In addition, compared with a conventional auto tensioner using a torsion coil spring, deterioration due to continuous use or change with time can be suppressed, and a longer life can be achieved. Furthermore, the peripheral structure can be simplified, the number of parts and assembly cost can be reduced, the reliability can be improved, and the auto tensioner can be reduced in size.

The auto tensioner of the present invention is not limited to the above embodiment. In the above embodiment, the rocking arm 30 is illustrated in which the base end portion 3 and the arm 7 are integrally formed. For example, the base end portion 3 and the arm 7 are formed as separate members, and these are − The swing arm may be configured by being fixed to the body.
In the above embodiment, a cylindrical roller is used as the rolling element. However, for example, a sphere or a tapered roller may be used. If the roller rolls with relative rotation between the shaft portion and the base end portion, the rolling roller may be used. The shape of the moving body is not particularly limited. In order to increase the degree of freedom in setting torsional rigidity, a hollow rolling element (for example, a hollow cylindrical roller or a hollow sphere) that is easily elastically compressed and deformed can be used. Further, the material of the rolling element is appropriately selected according to the performance required for the auto tensioner.

It is sectional drawing of the auto tensioner by one Embodiment of this invention. It is a side view of the auto tensioner by one Embodiment of this invention. FIG. 3 is an enlarged view of a cross section taken along line III-III in FIG. 1. It is sectional drawing for demonstrating the rotation energizing force which generate | occur | produces by the relative rotation of a shaft part (support member) and a base end part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Autotensioner 2 Support member 21 Inner raceway surface 2k Inner variant raceway surface 3 Base end part 30 Swing arm 31 Outer raceway surface 3k Outer variant raceway surface 4 Cylindrical roller (rolling element)
50 Belt 51, 52 Rolling bearing 6 Pulley 7 Arm

Claims (2)

A oscillating arm having a cylindrical base end portion having an outer raceway surface formed on the inner periphery, and an arm that extends from the base end portion and on which a pulley around which a belt is wound is rotatably fixed;
A support member that has an inner raceway surface that opposes the outer raceway surface on an outer peripheral side, and supports the swing arm in a swingable manner by supporting the base end portion in a relatively rotatable manner;
A rolling element interposed between the outer raceway surface and the inner raceway surface in a rollable manner;
At least one of the inner raceway surface and the outer raceway surface rolls the rolling element along with the relative rotation between the base end portion and the support member, gradually reducing the holding interval of the rolling element, and the relative rotation At least partly has a deformed raceway surface that imparts a rotation biasing force between the base end portion and the support member in a direction to eliminate the phase difference between the base end portion and the support member. An auto tensioner characterized in that the swinging arm biases the swing arm in a predetermined swing direction.   The auto tensioner according to claim 1, wherein a rolling bearing that supports the base end portion and the support member so as to be relatively rotatable with each other is interposed between the base end portion and the support member.

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