JP3916074B2 - Auto tensioner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an auto tensioner that applies appropriate tension to a belt and attenuates vibration generated in the belt.
[0002]
[Prior art]
The auto tensioner has a configuration in which a pulley is attached to the tip of a rotating member that is rotatably supported by a swing shaft, and abuts against the pulley by changing the relative position of the pulley as the rotating member rotates. Appropriate tension is applied to the belt. The rotation axis of the pulley is parallel to the swing axis and separated by a predetermined distance. Although the distance between the two axes is reduced with the demand for miniaturization of the auto tensioner, in order for the pulley or belt to rotate without interfering with the rotating member, it is provided at a position different from the rotating member in the axial direction. There must be.
[0003]
[Problems to be solved by the invention]
However, since the pulley is pressed in one direction when the belt is tensioned, a moment load that tilts about the swing shaft acts on the rotating member. This moment load increases as the position in the axial direction increases with respect to the rotating member, so that the rotating member tends to tilt.
[0004]
The present invention has been made in view of such a point, and an object of the present invention is to obtain a small auto tensioner in which the inclination of the rotating member is reduced.
[0005]
[Means for Solving the Problems]
An auto tensioner according to the present invention includes a base having a fixed portion for fixing a swing shaft, a cup portion that opens toward the base, and whose opening end extends to the height of the fixed portion in the swing shaft center direction, and a cup A bearing part that extends from the bottom surface of the part toward the base and is rotatably supported by a swing shaft, and an arm part that extends from the outer peripheral surface of the cup part and that has a pulley attached to the tip thereof, is attached to be rotatable. And a rotating member fixed to the base and frictionally slid along the inner peripheral surface near the opening end of the cup portion, and spirally wound around the swinging shaft and the damping member that supports the opening end. A torsion coil spring having both ends rotated to the bottom of the cup portion and the base, and the diameter of the swing shaft fitted into the bearing portion is the diameter of the swing shaft fixed to the base portion. Relatively larger than Ri end to be locked to the base side of the coil spring is characterized in that it is formed in the pigtail end shape to avoid interference with the damping member. Thereby, with a small and simple configuration, it is possible to reduce the load burden on the bearing portion and prevent the tilting of the rotating member, and obtain a uniform and stable damping force.
[0006]
Specifically, the damping member may be a cylindrical member having an oscillation axis as an axis, and a cup-shaped spring provided on the inner side of the damping member with a substantially uniform force in the circumferential direction. It may be urged toward the inner peripheral surface.
[0007]
The torsion coil spring formed in the pigtail end shape avoids interference with not only the damping member but also the ring-shaped spring, and makes space utilization in the cup portion more efficient.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an auto tensioner according to the present invention will be described below with reference to the accompanying drawings.
[0009]
In FIG. 1, the auto tensioner 10 is shown together with the belt 20. The belt 20 is an endless belt hung on a driving pulley attached to an output shaft of an engine (not shown) or a driven pulley attached to various auxiliary machine shafts such as an air conditioner and an alternator. Transmit to the driven pulley.
[0010]
The auto tensioner 10 includes a base 30 fixed by three bolts 12 at a predetermined position of an engine block (not shown), and a swing shaft 40 is integrally fixed to the base 30. The rotating member 50 is rotatable within a predetermined angle range θ about the axis C1 of the swing shaft 40, and a pulley 60 is rotatably attached to the tip thereof. The rotation axis C2 of the pulley 60 is parallel to the swing axis C1. The three attachment portions 38 to which the bolts 12 are attached are arranged at substantially equal intervals around the swing axis C1, and the base 30 is fixed with a substantially uniform force in the circumferential direction.
[0011]
The pulley 60 is rotated around the rotation axis C2 by the rotation drive of the belt 20, and is indicated by a first position and a one-dot chain line indicated by a broken line along with a rotation operation around the swing axis C1 of the rotation member 50. The relative position between the second position and the second position is changed, and the belt 20 in contact with the outer peripheral surface of the pulley 60 is tensioned or relaxed. The rotating member 50 is urged by a predetermined force in the clockwise direction in the drawing around the swing axis C1, and the belt 20 is moderately tensioned.
[0012]
FIG. 2 is a cross-sectional view of the auto tensioner 20. The rotating member 50 includes a cup portion 52 that opens toward the base 30, and a part of the opening side of the cup portion 52 is accommodated in a circular groove 36 formed in the base 30. The rotating member 50 includes a bearing portion 54 that is supported in the radial direction by the swing shaft 40, and the bearing portion 54 has a cylindrical shape that extends from the center of the cup bottom surface 52 a toward the base 30, and its axis is the swing shaft. It matches the heart C1. The shaft length of the bearing portion 54 is about half of the shaft length of the cup portion 52. Since the rotating member 50 and the base 30 are complicated in shape, they are made of a soft metal such as aluminum that can be easily processed. In the following description, the axial direction refers to a direction parallel to the swing axis C1.
[0013]
A cylindrical sliding bearing 70 formed of a synthetic resin material having excellent wear resistance and a relatively small friction coefficient is press-fitted into the bearing portion 54, and the upper half of the swing shaft 40 passes through the sliding bearing 70. Insert. The lower half of the swing shaft 40 is smaller in diameter than the upper half and is press-fitted and fixed to the cylindrical fixing portion 32 of the base 30. The head portion 42 of the swinging shaft 40 protruding from the cup portion 52 is formed in a disk shape having a diameter approximately twice the diameter of the swinging shaft 40, and the relative position in the axial direction of the cup portion 52 is determined by the flange portion. Be regulated. That is, the rotating member 50 is fixed so as to be rotatable around the swing axis C1. When the rotating member 50 is rotated, the sliding bearing 70 and the swing shaft 40 frictionally slide. A flange 72 is formed on the slide bearing 70, and the flange 72 is interposed between the flange portion of the head portion 42 and the cup portion 52 to prevent cracks and breakage due to interference between the two.
[0014]
The rotating member 50 includes an arm portion 56 that is integral with the cup portion 52, and the arm portion 56 extends radially outward from a part of the bottom surface side outer peripheral surface of the cup portion 52. A pulley 60 is attached to the tip of the arm portion 56 via a ball bearing 64, whereby the pulley 60 is rotatable about the rotation axis C <b> 2 with respect to the arm portion 56. The ball bearing 64 is fixed in the axial direction by a bolt 62 and a washer 66 to prevent the ball bearing 64 from dropping upward in the figure.
[0015]
Inside the cup portion 52, a torsion coil spring 80 spirally wound around the swing shaft 40 is housed in a moderately twisted state, and one end portion 82 of the torsion coil spring 80 is locked to the cup bottom surface 52a. The other end 84 is locked to the base 30. Due to the spring force of the torsion coil spring 80, the cup portion 52, that is, the rotation member 50 is always urged to rotate in a fixed rotation direction (clockwise direction in FIG. 1) with respect to the base 30. As a result, the belt 20 is moderately tensioned to prevent its bending, and the driving force of the engine is reliably transmitted to each auxiliary machine.
[0016]
The auto tensioner 10 has a damping mechanism for attenuating vibration generated in the belt 20 due to a change in the rotational speed of the engine, etc., and this damping mechanism is a synthetic resin that is fixed to the base 30 and frictionally slides on the rotating member 50. And a ring-shaped spring 92 that urges the damping member 90 toward the rotating member 50 with a constant pressing force. The damping mechanism imparts frictional resistance to the rotation of the rotation member 50, whereby the rotation member 50, that is, the pulley 60 is braked, and the vibration of the belt 20 is attenuated.
[0017]
The damping member 90 will be described in detail with reference to the cross-sectional view of FIG. 2 and the plan view of FIG. FIG. 3 shows a state in which the damping member 90 is attached to the base 30.
[0018]
The damping member 90 includes a cylindrical portion 94 having the pivot axis C1 as an axis. The diameter of the outer peripheral surface 94a of the cylindrical portion 94 is substantially equal to the diameter of the inner peripheral surface (hereinafter abbreviated as the inner peripheral surface of the opening side) 52b in the vicinity of the opening of the cup portion 52, and about 2 of the cylindrical portion 94 in the axial direction. / 3 is inserted from the opening of the cup portion 52 to about ¼ of its axial length, and the cylindrical portion outer peripheral surface 94a and the opening side inner peripheral surface 52b are in close contact with each other over substantially the entire circumference. A flange 96 is formed on the outer peripheral surface 94a of the cylindrical portion, and this flange 96 is interposed between the opening of the cup portion 52 and the base 30 so as to be in close contact with each other to prevent interference between the two and into the cup portion 52. It serves to prevent the intrusion of dust, water, salt water, etc.
[0019]
The outer diameter of the flange 96 coincides with the outer diameter of the cup portion 52, and the outer diameter of the circular groove 36 for accommodating them is slightly larger than these. A circular groove 31 that is one step lower is formed concentrically inside the circular groove 36, and the cylindrical portion outer peripheral surface 94 a is in close contact with the side surface of the circular groove 31, and the base 30 of the cylindrical portion 94 is attached to the bottom surface of the circular groove 31. The side end surfaces are in close contact.
[0020]
The cylindrical portion 94 is partially open in the circumferential direction, and even if the outer peripheral surface 94a, which is a friction sliding surface, is worn, the opening portion 95 expands due to the urging force of the ring spring 92 outward in the radial direction. The outer peripheral surface 94a is always in close contact with the opening-side inner peripheral surface 52b. Thereby, uniform and stable frictional resistance is obtained in the circumferential direction, and uneven wear is prevented.
[0021]
Two arcuate mounting parts 98 are integrally provided inside the cylindrical part 94, and these arcuate mounting parts 98 extend from the end face on the base 30 side to the middle of the cylindrical part 94 in the axial direction. In order to allow displacement of the opening 95 in the circumferential direction, the two are provided in close proximity to each other at a position farthest from the opening 95. Each arcuate mounting portion 98 is formed with a pin hole 100 penetrating in the axial direction, and the pin 34 of the base 30 is inserted without a gap. The pin 34 extends from the bottom surface of the circular groove 31 toward the cup 52. Due to the engagement of the pin 34 and the pin hole 100, the damping member 90 is positioned in the circumferential direction on the base 30. Note that the flange 96 is sandwiched between the opening of the cup portion 52 and the circular groove 36 of the base 30, and the inner diameter of about 3/4 of the bottom surface side of the cup portion 52 is smaller than the diameter of the inner peripheral surface 52b of the opening side. By forming the inner peripheral surface of the cup portion 52 in a step shape, the damping member 90 is positioned in the axial direction.
[0022]
The damping member 90 is integrally formed of a synthetic resin material having excellent wear resistance in a high temperature environment. Suitable synthetic resins include polyamide resins, polyether sulfone resins, polyphenylene sulfide resins and the like.
[0023]
The damping member 90 has a function as a sliding bearing that supports a portion 52A in the vicinity of the opening of the cup 52 (for convenience, described as a cup opening) in the radial direction, and can function sufficiently as a sliding bearing. It has the rigidity of. When the tensioned belt 20 presses the side surface of the pulley 60 in one direction, the axial position of the load center W1 of the bearing portion 54 and the load center W2 of the pulley 60 is separated by a distance L. The moment load M (FIG. 2) rotating around the load center W1 acts, and the rotating member 50 is likely to be inclined. In order to reduce the lever L of the moment load M, that is, the axial distance L between the two load centers W1 and W2, the bearing portion 54 is brought closer to the pulley 60 side (cup bottom surface 52a side). When 50 is inclined, the displacement of the cup opening 52A farthest from the bearing load center W1 increases. In the present embodiment, the cup opening 52A is supported in the radial direction by the damping member 90, whereby the displacement of the cup opening 52A, that is, the inclination of the rotating member 50 can be effectively suppressed.
[0024]
Further, since the damping member 90 as a sliding bearing has a larger radius and a larger support area than the sliding bearing 70 of the bearing portion 54, the load on the sliding bearing 70 can be reduced, and early wear and early breakage can be prevented.
[0025]
Further, the damping member 90 is embedded in the circular grooves 36 and 31 of the base 30 in about 2/3 of its axial length, and the pin 34 is substantially in the center in the axial direction of the mounting portion 38 into which the bolt 12 is inserted. (Refer to FIG. 2). Thereby, the damping member 90 is fixed to the base 30 very firmly, and the displacement of the relative position is very small and stable. Therefore, the rotation member 50 supported by the damping member 90 is difficult to tilt. A part of the cup opening 52 </ b> A is accommodated in the circular groove 36, and the opening surface is located substantially on the same plane as the axial center of the mounting portion 38. Accordingly, excessive displacement of the cup opening 52A is prevented by supporting the side surfaces of the opposing circular grooves 36, that is, the mounting portions 38.
[0026]
In a conventional auto tensioner, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-119492, a base is formed in a cup shape and a rotating member is formed in a flat plate shape, and a damping member is fixed to a rotating member on the pulley side to fix the base. Friction sliding with the cup opening. In this case, since the damping member is located on the outer side in the radial direction of the bearing portion, it is necessary to set the cup diameter large in order to avoid interference with the torsion coil spring or to design the bearing portion to be relatively small, thereby reducing the size. The request could not be met. However, in the auto tensioner 10 of the present embodiment, the damping mechanism is positioned on the cup opening 52A side, and nothing is interposed between the torsion coil spring 80 and the bottom side inner peripheral surface of the cup portion 52. Therefore, the diameter of the upper half of the bearing part 54 and the rocking | fluctuation shaft 40 can be set largely compared with the past, with the cup part 52 remaining small. Therefore, the bearing area of the bearing portion 54 can be increased, the strength of the swing shaft 40 can be improved, and the tilt of the rotating member 50 can be further suppressed.
[0027]
As described above, the damping member 90 serves not only to impart a uniform and stable frictional resistance to the rotating member 50 but also to serve as a radial bearing that prevents the rotating member 50 from tilting.
[0028]
Next, the structure of the ring-shaped spring 92 and attachment to the damping member 90 will be described with reference to FIGS. 3 and 4. 4 is a cross-sectional view taken along the line IV-IV in FIG. 2, and shows a state in which a ring-shaped spring 92 and a torsion coil spring 80 are attached in addition to the damping member 90. FIG.
[0029]
The ring-shaped spring 92 is a C-type spring whose radial thickness gradually increases from the open end. Two ring-shaped springs 92 are attached in the axial center of the cylindrical portion inner peripheral surface 94b of the damping member 90 by being overlapped in the axial direction. . The ring-shaped spring 92 is attached in a state of being bent so as to contract in the radial direction, whereby the damping member 90 is applied to the radially outer side, that is, the opening-side inner peripheral surface 52b with a substantially uniform force in the circumferential direction. A certain frictional resistance is applied to the rotating member 50 by being pressed and urged. Note that the material, spring force, and number of the ring-shaped spring 92 are appropriately changed according to the required frictional resistance.
[0030]
A plurality of protrusions for positioning the ring-shaped spring 92 in the axial direction are formed on the inner circumferential surface 94 b of the damping member 90. Specifically, a trapezoidal pedestal 110 is provided at the two open ends of the cylindrical portion 94 by the same axial length as the arcuate mounting portion 98 from the end surface on the base 30 side, and the end surface on the pulley 60 side of each pedestal 110. Each is provided with one rectangular protrusion 112 for supporting the ring-shaped spring 92 from the base 30 side. Two circular protrusions 114 having the same height as the rectangular protrusions 112 are also provided on the pulley 60 side end surface of the arcuate mounting portion 98. An anti-rotation projection 116 for locking the open end of the ring-shaped spring 92 is formed on the open end edge of each pedestal 110. Between the arcuate mounting portion 98 and the pedestal 110, a band-shaped protrusion 118 that supports the ring-shaped spring 92 from the pulley 60 side is provided. With these configurations, the ring-shaped spring 92 is positioned in the radial direction and the axial direction with respect to the damping member 90.
[0031]
As shown in FIGS. 2 and 4, the base 30 side of the torsion coil spring 80 is formed in a pigtail end shape, and in order to avoid interference with the damping member 90 and the ring-shaped spring 92, the diameter of the last turn gradually increases. It is getting smaller. The other end 84 of the torsion coil spring 80 is bent inward in the radial direction and extends linearly from the bent portion to the end. A first locking projection 33 is integrally formed on the outer peripheral surface of the cylindrical fixing portion 32 of the base 30 so as to support the other end portion 84 from the side. A second locking projection 35 that sandwiches the portion 84 is provided. As described above, one end of the torsion coil spring 80 is formed in a pigtail end shape, and the space inside the damping member 90 and the ring-shaped spring 92 is effectively used. Therefore, the cup portion 52 can be reduced in size.
[0032]
The torsion coil spring 80 extends in the counterclockwise direction from the other end portion 84, and the first winding passes above the two arcuate mounting portions 98. The torsion coil spring 80 is supported from the base 30 side by two support protrusions 37 and 39 (FIG. 4) provided in the vicinity of the arcuate mounting portion 98. In order to avoid contact between the torsion coil spring 80 and the arcuate mounting part 98, the support protrusion 39 sandwiched between the two arcuate mounting parts 98 is provided higher than the arcuate mounting part 98, and the right arcuate mounting part in the figure. The support protrusion 37 provided in front of 98 is set to a height substantially the same as or slightly lower than the arcuate mounting portion 98.
[0033]
In a belt system using a conventional auto tensioner in which a damping member and a ring-shaped spring are arranged on the pulley side, the endurance time until the tilt angle of the rotating member 50 reaches an allowable value of 0.5 degrees is about 250 hours. However, when the damping member 90 and the ring-shaped spring 92 are arranged on the base 30 side as in the auto tensioner 10 of the present embodiment, the durability time is extended to about 500 hours, and the durability is improved twice as much as the conventional one. .
[0034]
As described above, in the auto tensioner 10 of this embodiment, the damping member 90 not only brakes the rotating member 50 but also has a function as a bearing that supports the rotating member 50 in the radial direction. Tilt of the moving member 50 is prevented. Furthermore, since the damping member 90 is embedded in the circular grooves 31 and 36 of the base 30 by about 2/3, it is firmly supported.
[0035]
【The invention's effect】
According to the present invention, it is possible to obtain a small auto tensioner in which the inclination of the rotating member is reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an auto tensioner according to the present invention, and is a plan view shown with a belt.
FIG. 2 is a cross-sectional view of the auto tensioner shown in FIG.
FIG. 3 is a plan view showing a state in which a damping member is attached to a base.
4 is a cross-sectional view taken along line IV-IV of the auto tensioner shown in FIG.
[Explanation of symbols]
30 Base 40 Oscillating shaft 50 Rotating member 52 Cup portion 54 Bearing portion 56 Arm portion 60 Pulley 80 Torsion coil spring 90 Damping member 92 Ring-shaped spring

Claims (2)

A base having a fixing portion for fixing the swing shaft; a cup portion that opens toward the base and whose opening end extends to the height of the fixing portion in the swing shaft center direction; and a bottom surface of the cup portion. A bearing portion that extends toward the base and is rotatably supported by the swing shaft, and an arm portion that extends from the outer peripheral surface of the cup portion and has a pulley attached to the tip thereof, and is rotatable with respect to the base. A rotating member attached to the
A damping member that is fixed to the base and pressed against the inner peripheral surface in the vicinity of the opening end of the cup portion, frictionally slides along the inner peripheral surface, and supports the opening end;
The torsional coil is wound around the rocking shaft in a spiral shape, and both end portions thereof are provided with torsion coil springs respectively engaged with the bottom surface of the cup portion and the base, and the rocking shaft is inserted into the bearing portion. The diameter is relatively larger than the diameter of the oscillating shaft fixed to the base portion, and the end portion of the torsion coil spring that is locked to the base side has a pigtail end shape to avoid interference with the damping member. An auto tensioner characterized by being formed into.   The damping member is a cylindrical member having the pivot axis as an axis, and the ring-shaped spring provided inside the damping member is applied to the inner peripheral surface of the cup with a substantially uniform force in the circumferential direction. 2. The auto tensioner according to claim 1, wherein the auto tensioner is urged toward the front.

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