WO2018003746A1 - 補機駆動ベルトシステムに備わるオートテンショナ - Google Patents
補機駆動ベルトシステムに備わるオートテンショナ Download PDFInfo
- Publication number
- WO2018003746A1 WO2018003746A1 PCT/JP2017/023412 JP2017023412W WO2018003746A1 WO 2018003746 A1 WO2018003746 A1 WO 2018003746A1 JP 2017023412 W JP2017023412 W JP 2017023412W WO 2018003746 A1 WO2018003746 A1 WO 2018003746A1
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- WIPO (PCT)
- Prior art keywords
- arm
- friction member
- belt
- inner peripheral
- base
- Prior art date
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F7/00—Vibration-dampers; Shock-absorbers
- F16F7/02—Vibration-dampers; Shock-absorbers with relatively-rotatable friction surfaces that are pressed together
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
- F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
- F16F15/04—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using elastic means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H7/00—Gearings for conveying rotary motion by endless flexible members
- F16H7/08—Means for varying tension of belts, ropes, or chains
- F16H7/10—Means for varying tension of belts, ropes, or chains by adjusting the axis of a pulley
- F16H7/12—Means for varying tension of belts, ropes, or chains by adjusting the axis of a pulley of an idle pulley
Definitions
- the present invention relates to an auto tensioner provided in an accessory drive belt system for driving an accessory of an automobile engine.
- an auto tensioner In the belt that drives the auxiliary equipment of an automobile engine, the belt tension fluctuates due to rotational fluctuation caused by engine combustion. Belt slip occurs due to fluctuations in belt tension, causing problems such as slip noise and wear. In order to solve this problem, an auto tensioner has been conventionally employed as a mechanism for automatically maintaining an appropriate belt tension even when the belt tension fluctuates and suppressing the occurrence of belt slip.
- An auto tensioner provided in an auxiliary drive belt system for an automobile engine has a movable member (hereinafter referred to as an arm) that is rotatably supported with respect to a fixed member (hereinafter referred to as a base) particularly when the belt tension increases.
- a damping mechanism (damping mechanism) is provided in order to sufficiently dampen the swinging motion.
- the damping mechanism for example, many so-called dry damping mechanisms disclosed in Patent Documents 1 and 2 are employed.
- the dry damping mechanism has a structure in which a friction member as a damping generating member is provided between the base and the arm and is locked to the arm, and the frictional action is exerted on the sliding surface between the friction member and the base. As a result, the swing of the arm is attenuated.
- the friction member of Patent Document 1 is locked to the arm and sandwiched in the radial direction between the base and the arm.
- the friction member is formed in a substantially fan shape when viewed in the direction of the swing axis of the arm.
- the sliding surface of the friction member of Patent Document 1 is an arc surface that can be slidably contacted with the inner peripheral surface of the outer cylindrical portion of the base.
- the friction member disclosed in Patent Document 2 is pressed against a base (specifically, a friction member mounting plate fixed to the base) by a coil spring that is locked to the arm and compressed in the direction of the swing axis of the arm.
- the friction member is formed in an annular shape when viewed in the axial direction.
- the sliding surface of the friction member of Patent Document 2 is an annular surface that can slide in contact with the base (friction member mounting plate).
- the arm swings violently as the belt tension changes.
- the friction member which is a damping generating member, is gradually worn and worn by the frictional action that repeatedly occurs on the sliding surface. If at least a part of the sliding surface of the friction member is worn at an early stage, it becomes difficult to ensure the effect of damping the swinging of the arm, and the auto tensioner may reach the end of its life early.
- the bearing of the swinging shaft also receives uneven load on the sliding surface (wear surface) side of the friction member when viewed in the axial direction, causing uneven wear.
- the arm tilts in that direction.
- misalignment that occurs in the accessory drive belt system becomes significant.
- the belt receives a large lateral pressure from the tensioner pulley, and in the worst case, the belt is detached from the tensioner pulley, and there is a possibility that the auto tensioner may reach the end of its life early.
- an aqueous medium such as muddy water may be applied to the auto tensioner provided in the auxiliary drive belt system of the automobile engine.
- an aqueous medium such as muddy water may infiltrate from an annular gap formed between the front end portion) and the arm. For this reason, in some cases, foreign matter contained in an aqueous medium such as muddy water is interposed between the sliding surface of the friction member and the base.
- the auto tensioners disclosed in Patent Documents 3 and 4 can solve the problem that foreign matter is interposed between the sliding surface of the friction member and the base, while the arm swinging while ensuring durability against the seal member.
- a dedicated design for materials and shapes that give sufficient consideration not to give as much resistance as possible to the dynamic motion is required, which increases the manufacturing cost of the auto tensioner.
- an object of the present invention is to prevent foreign matter from intervening on the sliding surface between the friction member and the mating surface even without a seal member.
- An object of the present invention is to provide an auto tensioner provided in an accessory drive belt system that can prevent the sliding surface of a friction member from being worn at an early stage and can ensure the durability of the auto tensioner.
- the auto tensioner provided in the accessory drive belt system of the present invention has the following characteristics. That is, the auto tensioner provided in the accessory drive belt system of the present invention includes a base having a cylindrical portion, and an arm supported to be rotatable about the central axis of the inner peripheral surface of the cylindrical portion with respect to the base.
- the arm is rotatably provided on the arm and is sandwiched in the radial direction of the cylindrical portion between the tensioner pulley around which the belt is wound, the inner peripheral surface of the cylindrical portion and the arm, and is locked to the arm.
- a friction member having an arc surface slidable with respect to the inner peripheral surface of the cylindrical portion, and a coil spring that urges the arm to rotate in one direction with respect to the base.
- the arm swings by generating a frictional force between the arc surface and the inner peripheral surface of the cylindrical portion.
- the arc surface passes through the central axis. It is provided so that it may remain at the above height.
- the friction member which is a damping generating member locked to the arm, is a friction member when sliding with respect to the mating surface (the inner peripheral surface of the cylindrical portion of the base) as the arm swings.
- the arc surface (sliding surface) is provided so as to remain at a height equal to or higher than a horizontal plane passing through the central axis of the inner peripheral surface of the cylindrical portion of the base.
- the arcuate surface (sliding surface) of the friction member is provided so as to remain at a height higher than the horizontal plane passing through the central axis of the inner peripheral surface of the cylindrical portion of the base. is there.
- the base of the auto tensioner is fixed to a surface along the substantially vertical direction such as an engine block.
- the foreign matter contained in the muddy water or other aqueous medium that has entered from the gap between the cylindrical portion of the base and the arm It is not deposited in a portion above the horizontal plane passing through the central axis, but is deposited in a portion below the horizontal plane passing through the central axis. Therefore, foreign matter can be prevented from intervening between the arc surface (sliding surface) of the friction member and the inner peripheral surface of the cylindrical portion of the base. As a result, even if no seal member is provided, the arc surface (sliding surface) of the friction member can be prevented from being worn at an early stage, and the durability of the auto tensioner can be ensured.
- the friction member has a center angle of the arc surface of less than 150 ° when viewed in the central axis direction, and a predetermined initial tension is applied to the belt.
- the position of the uppermost portion on the inner peripheral surface of the cylindrical portion is provided so as to be in contact with the central portion of the circular arc surface and a central angle of 10 °. It is preferable.
- the belt tension decreases from the moment when the initial tension is applied, and then stabilizes.
- the initial tension is set on the assumption that the belt has a reference dimension.
- the belt length varies within an allowable value when the belt is manufactured. The shorter the belt length is than the reference dimension, the higher the initial tension and the higher the subsequent stable tension.
- the position of the friction member in a state where the belt tension is stable even when there is a decrease in belt tension and variations in belt length after the initial tension is applied, is the point when the predetermined initial tension is applied to the belt of the reference dimension.
- the friction member remains within a range of approximately ⁇ 5 ° around the central axis from the position of the friction member. Further, the swinging width of the arm is approximately 10 ° or less.
- the friction member according to the present invention has a base cylinder with a center angle of an arc surface of less than 150 ° when viewed in the central axis direction, and when viewed in the central axis direction when a predetermined initial tension is applied to the belt.
- the uppermost position on the inner peripheral surface of the portion is provided so as to be in contact with a region having a central angle of 10 ° at the center of the arc surface.
- the arc surface of the friction member stays at a height equal to or higher than a horizontal plane passing through the central axis when the arm swings. Even if the belt tension decreases and the belt length varies after the initial tension is applied, when the arm swings, the middle position of the arc surface of the friction member as viewed in the central axis direction is The position can be close to the top of the inner peripheral surface. Compared with the case where the arc lengths of the arc surfaces are the same, the lower end of the arc surface is higher as the intermediate position of the arc surface is closer to the uppermost position of the inner peripheral surface of the cylindrical portion.
- FIG. 1 is a configuration diagram of an accessory drive belt system according to an embodiment of the present invention.
- 2 is a cross-sectional view taken along line AA in FIG.
- FIG. 3 is a diagram in which the sectional view taken along the line BB of FIG. 2 is combined with FIG. 1 and shows a state in which the belt tension is stable.
- FIG. 4 is a diagram in which the sectional view taken along the line BB of FIG. 2 is combined with FIG. 1 and shows a state where an initial tension is applied.
- FIG. 5A shows the force acting on the friction member when the belt tension increases
- FIG. 5B shows the force acting on the friction member when the belt tension decreases.
- FIG. FIG. 6 is a configuration diagram of the test belt system.
- FIG. 6 is a configuration diagram of the test belt system.
- FIG. 7A is a diagram showing a state in which the belt tension is increased and the friction member is slid in the first belt system
- FIG. 7B is a diagram in which the belt tension is decreased and friction is caused in the first belt system
- FIG. 7C is a diagram showing a state in which the friction member is slid due to an increase in belt tension in the second belt system
- FIG. It is a figure which shows the state which the belt tension decreased and the friction member slid in the 2nd belt system.
- FIG. 8 is a diagram for explaining a method of calculating the arm inclination amount.
- FIG. 9 is a graph showing the relationship between the amount of arm inclination and the test time in Example 2 and Comparative Example 1.
- FIG. 1 is an example of an auxiliary drive belt system for an automobile engine to which the present invention is applied.
- the accessory drive belt system 100 includes a crank pulley 101 fixed to a crankshaft, an ALT pulley 102 connected to an alternator (ALT), a WP pulley 103 connected to a water pump (WP), an air conditioner compressor ( AC pulley 104 connected to AC) and the auto tensioner 1.
- the engine output is transmitted from the crank pulley 101 to the ALT pulley 102, the WP pulley 103, and the AC pulley 104 via a single belt 105, respectively, and each auxiliary machine (alternator, water pump, air conditioner) is transmitted. ⁇
- the compressor is driven.
- the auto tensioner 1 is provided between the belt spans of the crank pulley 101 and the ALT pulley 102 so that the tensioner pulley 4 of the auto tensioner 1 contacts.
- the belt 105 is a transmission belt such as a V-ribbed belt, a V-belt, a toothed belt, or a flat belt.
- the auto tensioner 1 is provided with a base 2, an arm 3 supported so as to be rotatable about an axis R (center axis) with respect to the base 2, and a rotatable structure on the arm 3.
- the tensioner pulley 4, the coil spring 5, and the friction member 6 are provided.
- the auto tensioner 1 has a dry damping mechanism that attenuates the swing of the arm 3, and the damping mechanism includes a friction member 6 as a damping generation member that attenuates the swing of the arm 3.
- the right direction in FIG. 2 is defined as the forward direction, and the left direction in FIG. 2 is defined as the rear direction.
- a radial direction centered on the axis R is simply defined as a radial direction
- a circumferential direction centered on the axis R is simply defined as a circumferential direction.
- the base 2 includes an annular pedestal portion 20 fixed to the engine block 106, an outer cylindrical portion (cylindrical portion) 21 extending forward from the outer edge portion of the pedestal portion 20, and an inner cylinder extending forward from the center portion of the pedestal portion 20. Part 22.
- the base 2 is made of a metal such as an aluminum alloy casting.
- the pedestal portion 20 is fixed to the engine block 106 via bolts and pins.
- the surface to which the pedestal portion 20 of the engine block 106 is fixed is a substantially vertical surface.
- a swing shaft 8 extending in the front-rear direction is inserted through the bearing 7 through the inner cylinder portion 22 so as to be rotatable.
- the axis R is the central axis of the swing shaft 8. The axis R passes through the center of the inner peripheral surface of the outer cylinder portion 21.
- a spring accommodating chamber 9 is formed between the inner cylinder part 22 and a projecting part 31 to be described later of the arm 3 and the outer cylinder part 21.
- a coil spring 5 is disposed in the spring accommodating chamber 9. The coil spring 5 is spirally wound in the X direction from the rear end portion toward the front end portion. The rear end portion of the coil spring 5 is held by the base 2.
- the arm 3 is formed to protrude from a disk part 30 disposed in front of the outer cylinder part 21 of the base 2, a protruding part 31 extending rearward from the center part of the disk part 30, and a part of the outer edge of the disk part 30.
- Pulley support portion 32 The arm 3 is also formed of a metal such as an aluminum alloy casting, as with the base 2 described above.
- a hole extending in the front-rear direction is formed in the center part of the disk part 30 and the protruding part 31, and the swing shaft 8 is inserted in this hole so as not to be relatively rotatable. Therefore, the arm 3 is rotatably supported by the base 2 via the swing shaft 8.
- the tensioner pulley 4 is rotatably attached to the pulley support portion 32.
- a belt 105 is wound around the tensioner pulley 4. As the tension of the belt 105 increases or decreases, the tensioner pulley 4 (and the arm 3) swings about the axis R. In FIG. 2, the internal structure of the tensioner pulley 4 is not shown.
- An annular gap 30 a is formed between the vicinity of the outer edge of the rear surface of the disk part 30 and the front end part of the outer cylinder part 21 of the base 2.
- the annular gap 30 a is formed by accommodating the front end portion of the outer cylindrical portion 21 of the base 2 in an annular groove formed in the vicinity of the outer edge of the rear surface of the disk portion 30.
- a part of the annular gap 30a is along a direction orthogonal to the axis R.
- a portion radially outside the protrusion 31 and radially inside the annular gap 30 a is formed in a flat shape perpendicular to the axis R.
- the protrusion 31 is formed in a substantially cylindrical shape. As shown in FIG. 3, a fan-shaped notch is formed in the front portion of the protrusion 31. Both sides in the circumferential direction of the notch are constituted by a locking surface 31a and a contact surface 31b.
- FIG. 3 is a combination of FIG. 1 and the cross-sectional view taken along the line BB shown in FIG. When viewed in the direction of the axis R, the locking surface 31a intersects a straight line passing through an arbitrary point on the locking surface 31a and the axis R. That is, the locking surface 31a is inclined with respect to the radial direction.
- the locking surface 31a is inclined with respect to the radial direction so as to go in the X direction as it goes outward in the radial direction.
- the contact surface 31b is inclined with respect to the radial direction so as to go in the opposite direction to the X direction as going outward in the radial direction.
- the friction member 6 is sandwiched in the radial direction between the inner peripheral surface of the outer cylindrical portion 21 of the base 2 and the protruding portion 31 of the arm 3.
- the longitudinal length of the friction member 6 is substantially the same as the longitudinal length of the locking surface 31a and the contact surface 31b.
- the longitudinal length of the friction member 6 is preferably about 1.2 to 3 times the wire diameter of the coil spring 5.
- the front surface of the friction member 6 is flat, and the entire surface or a part thereof contacts the rear surface of the disk portion 30 of the arm 3.
- the friction member 6 is made of, for example, a material having high lubricity obtained by blending fibers, fillers, solid lubricants, and the like with synthetic resin.
- the synthetic resin constituting the friction member 6 include thermoplastic resins such as polyamide resin, polyacetal resin, polytetrafluoroethylene resin, polyphenylene sulfide resin, and ultrahigh molecular weight polyethylene resin, or thermosetting resins such as phenol resin. Resin is used.
- the friction member 6 may include a material other than the above as long as the front surface and a circular arc surface 60 described later are formed of the above-described materials.
- the friction member 6 has a substantially fan-shaped cross section perpendicular to the axis R, and includes an arcuate surface 60, an engaging surface 61 that opposes the arcuate surface 60, and two side surfaces 62 and 63 that oppose each other in the circumferential direction.
- the locking surface 61 contacts the locking surface 31 a of the protruding portion 31 of the arm 3.
- the radially inner end portion of the side surface 63 opposite to the X direction contacts the contact surface 31 b of the protruding portion 31 of the arm 3.
- the friction member 6 is locked to the arm 3 by a locking surface 61 and a side surface 63.
- the center of the arc of the arc surface 60 coincides with the axis R, and the arc surface 60 is formed with substantially the same curvature as the inner peripheral surface of the outer cylinder portion 21.
- the arc surface 60 is slidable along the inner peripheral surface of the outer cylinder part 21.
- the arm 3 rotates in the arrow X direction shown in FIG.
- the angle obtained by combining the angle that swings when the tension of the belt 105 increases and the angle that swings when the tension of the belt 105 decreases is referred to as the swing width of the arm 3.
- the angle at which the friction member 6 slides about the axis R (hereinafter referred to as the sliding width) is equal to the swinging width of the arm 3.
- the swing width of the arm 3 is approximately 10 ° or less. Note that even in an auto tensioner of an auxiliary drive belt system for a general automobile engine, the swinging width of the arm is approximately 10 ° or less.
- the friction member 6 attenuates the swing of the arm 3 by generating a frictional action on the sliding surface between the arc surface 60 and the inner peripheral surface of the outer cylinder portion 21.
- the central angle ⁇ of the arc surface 60 when viewed in the direction of the axis R is preferably less than 170 °.
- the central angle ⁇ of the arc surface 60 when viewed in the direction of the axis R is more preferably less than 150 °.
- a lower limit value regarding the central angle ⁇ of the arc surface 60 viewed in the direction of the axis R can be considered.
- a preferable lower limit value regarding the central angle ⁇ of the arc surface 60 viewed in the direction of the axis R varies depending on the material of the portion constituting the arc surface 60 of the friction member 6.
- the lower limit value of the central angle ⁇ of the arc surface 60 viewed in the direction of the axis R may be set to about 30 °. .
- the central angle ⁇ of the arcuate surface 60 is 43 °.
- the belt 105 When the belt 105 is a V-ribbed belt, the belt 105 further sinks slightly toward the bottom of the circumferential grooves of the pulleys 101, 102, and 104 with which the rib crests are engaged from the moment when a predetermined initial tension (for example, 330 N) is applied. It will be deformed. In this process, the belt tension slightly decreases. Thereafter, at a stage where the engagement state between the belt 105 and each pulley is familiar (for example, at the end of running-in), the belt 105 is stabilized with a substantially constant tension. Similarly, when the belt 105 is a transmission belt other than a flat belt such as a V-belt and a toothed belt, the belt tension is lowered after a predetermined initial tension is applied, and then stabilized.
- a predetermined initial tension for example, 330 N
- FIG. 4 shows a state in which a predetermined initial tension is applied to the belt 105.
- FIG. 3 shows a state in which the running-in after the initial tension is applied ends and the belt tension is stabilized. After the initial tension is applied, when the belt tension decreases, the arm 3 and the friction member 6 rotate in the arrow X direction.
- This embodiment is an example in which the belt length of the belt 105 is a reference dimension.
- the belt length varies within the allowable range at the manufacturing stage.
- the allowable value is the reference dimension ⁇ 8 mm.
- the predetermined initial tension is set on the assumption that the belt length is the reference dimension. Therefore, when the belt length is longer than the reference dimension, the initial tension is lower than that when the belt length is the reference dimension, and the stable tension after running-in is also reduced. On the other hand, when the belt length is shorter than the reference dimension, the initial tension is higher and the stable tension after running-in is higher than when the belt length is the reference dimension.
- the positions of the arm 3 and the friction member 6 when the belt tension is stabilized are the positions of the arm 3 and the friction member 6 when the belt tension is stable when the belt length is the reference dimension.
- the position is shifted in the arrow X direction with respect to the position.
- the position of the arm 3 and the friction member 6 when the belt tension is stabilized when the belt length is the maximum within the allowable value is the position of the arm 3 and the friction when the initial tension is applied when the belt length is the reference dimension.
- the position of the member 6 is shifted within 5 ° in the arrow X direction.
- the positions of the arm 3 and the friction member 6 when the belt tension is stabilized are the positions of the arm 3 and the friction member 6 when the belt tension is stabilized when the belt length is the reference dimension.
- the position is shifted in the direction opposite to the arrow X direction with respect to the position.
- the position of the arm 3 and the friction member 6 when the belt tension is stabilized when the belt length is the maximum within the allowable value is the position of the arm 3 and the friction when the initial tension is applied when the belt length is the reference dimension.
- the position of the member 6 may be shifted in the direction opposite to the arrow X direction. This angle is less than 5 ° at the maximum.
- a region that is the central portion of the arc surface 60 and has a central angle of 10 ° when viewed in the direction of the axis R is defined as a central region 60c.
- the friction member 6 is seen in the direction of the axis R when the predetermined initial tension is applied to the belt 105, so
- the uppermost position 21t on the circumferential surface is preferably provided so as to contact the central region 60c of the circular arc surface 60.
- the friction member 6 is provided so that the uppermost position 21 t on the inner peripheral surface of the outer cylinder portion 21 is in contact with the middle position of the arc surface 60 when viewed in the axis R direction.
- the position of 6 is not limited to this.
- an accessory driving belt There are the following two specific operations performed when determining the layout of the system 100.
- the positions of the locking surface 31a and the contact surface 31b of the protrusion 31 and the position of the front end portion of the coil spring 5 are adjusted, and the above-described configuration
- the friction member 6 is arranged so that When the fixed position of the base 2 is not determined, the base 2 is moved so that the friction member 6 has the above-described configuration by moving the position of the axis R in the circumferential direction around the axis of the rotation shaft of the tensioner pulley 4. Is fixed to the engine block 106.
- the locking surface 61 of the friction member 6 is located on the X direction side with respect to the circumferential direction from the arc surface 60. Further, the locking surface 61 is inclined with respect to the radial direction so as to go to the X direction side as going outward in the radial direction.
- the two side surfaces 62 and 63 are inclined with respect to the radial direction so as to go to the opposite side to the X direction as going outward in the radial direction. Of the side surfaces 62 and 63, the side surface 62 on the X direction side is substantially orthogonal to the locking surface 61.
- the length in the direction perpendicular to the locking surface 61 from the locking surface 61 to the circular arc surface 60 is from the locking surface 31 a of the arm 3 to the outer cylinder portion of the base 2. It is slightly larger than the interval in the direction orthogonal to the locking surface 31a up to the inner peripheral surface of 21. Therefore, the friction member 6 is disposed between the protruding portion 31 of the arm 3 and the outer cylinder portion 21 of the base 2 in a state where the friction member 6 is slightly compressed in a direction substantially orthogonal to the locking surface 61.
- a holding groove 64 that holds the front end of the coil spring 5 is formed on the rear surface of the friction member 6.
- the front end portion of the coil spring 5 is bent in the vicinity of the distal end, like the rear end portion, and the portion on the distal end side extends linearly from the bent portion. This linear portion is held in the holding groove 64.
- the holding groove 64 is located on the outer side in the radial direction from the locking surface 61 and is positioned on the opposite side to the X direction from the locking surface 61 in the circumferential direction.
- the coil spring 5 is arranged in a compressed state in the direction of the axis R. Therefore, the coil spring 5 presses the friction member 6 against the rear surface of the disk portion 30 of the arm 3 by an elastic restoring force in the axis R direction.
- the coil spring 5 is arranged in a state twisted in the diameter increasing direction. Therefore, the coil spring 5 is rotated by the elastic restoring force in the circumferential direction in the direction of increasing the tension of the belt 105 by pressing the arm 3 in the X direction via the friction member 6, that is, pressing the tensioner pulley 4 against the belt 105. It is fast.
- the operation of the auto tensioner 1 will be described.
- the arm 3 rotates in the arrow A direction (opposite to the X direction) shown in FIG. 5A against the circumferential biasing force of the coil spring 5.
- the friction member 6 receives a force Fa from the locking surface 31 a of the arm 3 and rotates in the direction of arrow A, and the arc surface 60 of the friction member 6 slides with the inner peripheral surface of the outer cylinder portion 21 of the base 2.
- the circular arc surface 60 of the friction member 6 is located on the opposite side (arrow A direction side) to the X direction with respect to the circumferential direction with respect to the locking surface 61 of the friction member 6. Furthermore, in the present embodiment, the tangential direction of the circumference around the axis R at an arbitrary point of the locking surface 61 (hereinafter simply referred to as “tangential direction”) and the circular arc surface 60 intersect. Since the force Fa received by the locking surface 61 of the friction member 6 from the arm 3 is a tangential force on the locking surface 61, the arc surface 60 exists on a straight line in the direction of the force Fa from the locking surface 61. become. Therefore, the force Fa received by the locking surface 61 of the friction member 6 from the arm 3 can be used as a force for pressing the arc surface 60 of the friction member 6 against the inner peripheral surface of the outer cylinder portion 21 of the base 2.
- the friction member 6 receives an elastic restoring force (hereinafter referred to as “torsion restoring force”) Fs caused by torsionally deforming the coil spring 5 in the diameter expansion direction.
- the torsional restoring force Fs is a resultant force of the component force Fs1 in the X direction and the component force Fs2 in the reduced diameter direction.
- the resultant force Fr of the force Fa received from the arm 3 and the torsional restoring force Fs of the coil spring 5 acts on the friction member 6. Since the force Fa is greater than the torsional restoring force Fs, the resultant force Fr is a radially outward force, and the arc surface 60 of the friction member 6 is pressed against the inner peripheral surface of the outer cylindrical portion 21 of the base 2 by the resultant force Fr. Therefore, a large frictional force can be generated between the arcuate surface 60 of the friction member 6 and the inner peripheral surface of the outer cylindrical portion 21 of the base 2, and a large damping force that sufficiently attenuates the swing of the arm 3. Can be generated.
- the arm 3 rotates in the arrow B direction (the same direction as the X direction) shown in FIG. 5B by the torsional restoring force of the coil spring 5, and the tensioner The pulley 4 swings so as to recover the belt tension.
- the friction member 6 receives the torsional restoring force Fs from the coil spring 5 and rotates in the direction of arrow B, so that the arc surface 60 of the friction member 6 slides with the inner peripheral surface of the outer cylinder portion 21 of the base 2.
- the friction member 6 Since the friction member 6 is biased radially inward by the component force Fs2 in the diameter reduction direction of the torsional restoring force Fs, the friction member 6 is interposed between the arc surface 60 of the friction member 6 and the inner peripheral surface of the outer cylindrical portion 21 of the base 2. The resulting frictional force is small.
- the arc surface 60 of the friction member 6 is generated by the circumferential component force Fs1 of the torsional restoring force Fs of the coil spring 5.
- the arc surface 60 of the friction member 6 is opposite to the locking surface 61 of the friction member 6 in the direction opposite to the X direction. Therefore, the arc surface 60 of the friction member 6 is not pressed against the inner peripheral surface of the outer cylinder portion 21 by the circumferential component force Fs1 of the torsional restoring force Fs of the coil spring 5. An increase in frictional force between the arc surface 60 and the inner peripheral surface of the outer cylinder portion 21 can be prevented.
- the friction member 6, which is a damping generating member locked to the arm 3, slides on the mating surface (the inner peripheral surface of the outer cylindrical portion 21 of the base 2) as the arm 3 swings.
- the arc surface 60 (sliding surface) of the friction member 6 is provided so as to remain at a height equal to or higher than the horizontal plane HP passing through the central axis (axis R) of the inner peripheral surface of the outer cylindrical portion 21 of the base 2.
- the arm swings violently, but the swinging width of the arm itself is relatively small (approximately 10 ° at the maximum).
- the arc surface 60 (sliding surface) of the friction member 6 has a height equal to or higher than the horizontal plane HP passing through the central axis (axis R) of the inner peripheral surface of the outer cylindrical portion 21 of the base 2. It is feasible to be provided so as to remain at Generally, the base of the auto tensioner is fixed to a surface along the substantially vertical direction such as an engine block. Therefore, in an environment where an aqueous medium such as muddy water is applied to the auto tensioner 1, the foreign matter M contained in the aqueous medium such as muddy water that has entered from the annular gap 30 a formed between the outer cylindrical portion 21 of the base 2 and the arm 3.
- an aqueous medium such as muddy water
- the remaining foreign matter M is accumulated on the inner peripheral surface of the outer cylinder portion 21 of the base 2 (see FIG. 3).
- the foreign matter M is not deposited on the inner peripheral surface of the outer cylindrical portion 21 of the base 2 in a portion above the horizontal plane HP passing through the axis R, but is deposited in a portion below the horizontal plane HP passing through the axis R. Therefore, the arcuate surface 60 (sliding surface) of the friction member 6 does not come into contact with the portion where the foreign matter M is deposited on the inner peripheral surface of the outer cylinder portion 21 of the base 2.
- the belt tension decreases from the moment when the initial tension is applied and then becomes stable.
- the initial tension is set on the assumption that the belt 105 has a reference dimension.
- the belt length varies within an allowable value. The shorter the belt length is than the reference dimension, the higher the initial tension and the higher the subsequent stable tension. Even if the belt tension decreases and the belt length varies after the initial tension is applied, the position of the friction member 6 in a state where the belt tension is stable applies the predetermined initial tension to the belt 105 having the reference dimension.
- the friction member 6 has a central angle of the arc surface 60 less than 150 ° when viewed in the direction of the axis R, and when the belt 105 is applied with a predetermined initial tension, The uppermost position 21t on the inner peripheral surface of the cylindrical portion 21 is provided so as to be in contact with the region 60c that is the central portion of the circular arc surface 60 and has a central angle of 10 °.
- the base 2 is positioned in the middle of the arc surface 60 of the friction member 6 when the arm 3 is swung. It can be set as the position close
- the lower end of the arc surface 60 is higher as the intermediate position of the arc surface 60 is closer to the uppermost position 21t of the inner peripheral surface of the outer cylinder portion 21. In position. As the lowermost end of the arc surface 60 is higher, the foreign matter M is less likely to enter between the arc surface 60 and the inner peripheral surface of the outer cylindrical portion 21 of the base 2, and even if it enters, it is easily swept down. Therefore, it is possible to more reliably prevent the foreign matter M from being interposed between the arc surface 60 (sliding surface) of the friction member 6 and the inner peripheral surface of the outer cylinder portion 21 of the base 2.
- the arc surface of the friction member of the present invention is not limited to one surface that is slidably in contact with the inner peripheral surface of the cylindrical portion of the base continuously in the arc direction.
- the arc surface of the friction member may be formed of a plurality of arc surfaces that are discontinuously slid in the circumferential direction of the inner peripheral surface of the cylindrical portion of the base. Further, the friction member may be a single unit or may be a coupling body divided into a plurality of parts in the arc direction.
- the friction member may not be pressed against the arm in the axial direction.
- the auto tensioner provided in the accessory drive belt system of the present invention may be an auto tensioner having a symmetric damping characteristic.
- the target to which the base part of the auto tensioner provided in the accessory drive belt system of the present invention is fixed may not be the engine block.
- the auto tensioner of Example 1 used for this test had the same configuration as the auto tensioner 1 of the above embodiment.
- the material of the friction member (6) is polyamide resin (PA6T).
- the central angle ( ⁇ ) of the circular arc surface (60) viewed in the direction of the axis (R) of the swing shaft (8) is 43 °.
- the longitudinal length of the friction member 6 is about 1.4 times the wire diameter of the coil spring 5.
- the bearing (7) is a cylindrical metal bearing (so-called metal bearing).
- the inner peripheral surface of the bearing (7) in contact with the swing shaft (8) is made of a resin composition (low friction material) containing a polytetrafluoroethylene lubricant.
- the belt (105) is a V-ribbed belt (manufactured by Mitsuboshi Belting Co., Ltd.) with a belt designation of 6PK1555 (K-shaped rib, number of rib crests in the belt width direction, belt length (POC) of 1555mm, belt width of 21.4mm). A thing was used.
- the core wire embedded in the belt (105) is a twisted rope using a polyester cord.
- the auto tensioner of Example 1 was assembled to an auxiliary machine driving belt system having the same configuration as the auxiliary machine driving belt system 100 of FIG. 1, and a belt (105) was wound thereon.
- the initial tension of the belt (105) was 330N.
- the position of the friction member (6) in the state where the initial tension was applied was the position shown in FIG. That is, when viewed in the direction of the central axis (R) of the swing shaft (8), the intermediate position of the arc surface (60) of the friction member (6) is the inner circumference of the outer cylinder portion (21) of the base (2). It touches the top position on the surface.
- the position of the friction member (6) after running-in after the initial tension was applied was the position shown in FIG. Specifically, when viewed in the direction of the central axis (R) of the swing shaft (8), the intermediate position of the arc surface (60) of the friction member (6) is the outer cylinder portion (21) of the base (2). It was the position which shifted
- the swing width of the arm (3) is maximized when the engine is started. Therefore, an engine start test in which the engine is started and stopped alternately was performed, and the swinging width of the arm (3) during the engine start test was measured. After the running-in described above, the engine was started and stopped alternately under an atmospheric temperature of 95 ° C., and the test was terminated when the number of engine starts reached 50 times.
- the engine operating time time from start to stop was set to 10 seconds.
- the ambient temperature is a temperature that assumes the temperature in the thermostatic chamber surrounding the belt system in an actual vehicle.
- the number of rotations of the crankshaft at each engine start varied between 0 and 1800 rpm.
- the swing width of the arm (3) is determined by the amount of displacement by which the axis of the rotation shaft of the tensioner pulley (4) rotates about the axis (axis R) of the swing shaft (8) using a laser displacement meter. was obtained by measuring in time series.
- the swing width of the arm (3) during 50 engine start tests was approximately 10 ° (minimum 8.5 °, maximum 10 °, average value of 50 9.5 °).
- test belt system 200 is fixed to a single frame 220 extending vertically upward, and this frame 220 is fixed to a base 221 that is fixed to a floor or the like and extends in a substantially horizontal direction.
- the test belt system 200 has two belt systems (a first belt system 201 and a second belt system 202) that are simultaneously driven by one drive pulley 203.
- the two belt systems 201 and 202 share one drive motor having the drive shaft 204 and one drive pulley 203 connected to the drive shaft.
- the first belt system 201 includes an auto tensioner 205, a driven pulley 206, and a belt 207 according to the second embodiment.
- the second belt system 202 includes the auto tensioner 208 of the first comparative example, a driven pulley 209, and a belt 210.
- the positions of the three pulleys of the first belt system 201 and the positions of the three pulleys of the second belt system 202 are point-symmetric about the axis of the drive shaft 204.
- the drive shaft 204 was disposed in a direction orthogonal to the frame 220. No auxiliary machinery was connected to the driven pulleys 206 and 209. On the outer peripheral surface of the drive pulley 203, two circumferential grooves around which the belts 207 and 210 are wound in parallel are provided apart in the axial direction.
- the drive pulley 203 has a predetermined axis from the center of the drive pulley 203 as viewed in the axial direction of the drive shaft 204 so that the arms 3 of the auto tensioners 205 and 208 can be forcibly swung.
- a so-called eccentric pulley is formed at a position separated by an eccentric amount d.
- the eccentricity d was 4 mm so that the swinging width of the arm 3 (sliding width of the friction member) was 10 °.
- Belts 207 and 210 are V-ribbed belts (manufactured by Mitsuboshi Belting Co., Ltd.) and have a belt name of 6PK730 (K-shaped ribs, number of rib crests in belt width direction, belt length (POC) 730 mm, belt width 21.4 mm) A thing was used.
- the core wire embedded in the belts 207 and 210 is a twisted rope using a polyester cord.
- the auto tensioner 205 of Example 2 and the auto tensioner 208 of Comparative Example 1 those having the same structure as the auto tensioner of Example 1 were used.
- the same reference numerals as those in the above embodiment are used for the components of the auto tensioners 205 and 208.
- the auto tensioners 205 and 208 of Example 2 and Comparative Example 1 were attached to the frame 220 so that the positions of the arcuate surfaces 60 of the friction member 6 with respect to the horizontal plane HP passing through the axis R are different from each other.
- a position away from the horizontal plane HP by an angle X ° around the axis R is referred to as a horizontal plane HP + X ° position, and a position away from the horizontal plane HP around the axis R by an angle X °. This is referred to as the position of the horizontal plane HP-X °.
- the height of the arc surface 60 is equal to or higher than the horizontal plane HP passing through the axis R.
- the lowermost end of the arc surface 60 is kept between the horizontal plane HP and the position of the horizontal plane HP + 10 °. That is, as shown in FIG.
- the arcuate surface 60 has the axis R as viewed in the direction of the axis R. It was made to stay at the height below the horizontal plane HP which passes. Specifically, as shown in FIGS. 7 (c) and 7 (d), the uppermost end of the circular arc surface 60 is kept between the horizontal plane HP and the position of the horizontal plane HP-10 °. . That is, as shown in FIG.
- the muddy water dropping device has two muddy water dropping nozzles 211 and 212. Two muddy water dripping nozzles 211 and 212 are arranged above the annular gap 30a formed between the outer cylinder portion 21 and the arm 3 of the base 2 of the auto tensioners 205 and 208 of the second embodiment and the first comparative example, respectively. Thus, a substantially constant volume of muddy water per unit time can be infiltrated into the auto tensioners 205 and 208 (inside the outer cylinder portion 21).
- the method of dripping muddy water was a gravity drop type as in the drip device.
- As the muddy water a suspension in which a powder for testing (JIS 8 type: Kanto Loam baked product) defined in JIS Z 8901: 2006 was dispersed in water at a concentration of 5% by weight was used.
- the test was conducted at an ambient temperature of 95 ° C.
- the initial tension of the belts 207 and 210 was 330N.
- running-in about 10 seconds was performed to stop the drive pulley 203, and 500 cc of muddy water was dropped over 5 minutes.
- the drive pulley 203 was driven clockwise at a rotational speed of 1200 rpm for 25 minutes.
- the dripping of muddy water (5 minutes) and driving of the drive pulley 203 (25 minutes) were set as 1 cycle, and the cycle was repeated for a total of 7 cycles.
- the drive pulley 203 was continuously driven at a rotation speed of 1200 rpm for 12 hours. During this time, the aqueous medium contained in the muddy water gradually evaporates, and only foreign matter (solid content) accumulates in the outer cylinder portion 21 of the base 2.
- the auto tensioners 205 and 208 of Example 2 and Comparative Example 1 were removed from the frame 220, and three evaluation items described later were determined.
- the evaluation was performed without disassembling the auto tensioners 205 and 208.
- the time required for the evaluation was about 0.5 hours. That is, the total time from the first muddy water dripping to the evaluation is 16 hours.
- the above operation operation for a total of 16 hours
- the friction member 6 is calculated to slide back and forth about 20 million times.
- measurements on three evaluation items were performed, and initial values before the test were measured.
- the first evaluation item is the amount of arm inclination.
- the degree of wear of the arc surface 60 of the friction member 6 cannot be evaluated without disassembling the auto tensioner. Therefore, the amount of inclination of the arm 3 toward the arc surface 60 was measured as a substitute characteristic of the degree of wear of the arc surface 60 of the friction member 6.
- the inclination amount [°] of the arm 3 was calculated by measuring the following A dimension and B dimension. As shown in FIG. 8, the central axis of the swing shaft 8 before the arm 3 is tilted is referred to as an axis R0, and the central axis of the swing shaft 8 after the arm is tilted is referred to as an axis R1.
- the dimension A is the dimension of the base 2 along the axis R0 direction from the front outer edge of the arm 3 at a circumferential position that bisects the arc surface 60 of the friction member 6 in the arc direction when viewed in the axis R0 (or axis R1) direction.
- the height to the rear outer edge of the pedestal portion 20 was used.
- the B dimension is the rear surface of the base portion 20 of the base 2 along the axis R0 direction from the front outer edge of the arm 3 at a circumferential position 180 ° away from the measurement position of the A dimension when viewed in the axis R0 (or axis R1) direction.
- the height to the outer edge was taken.
- the “center axis of the cylindrical portion of the base” in the present invention is not limited to the axis R0, and may be the axis R1.
- the evaluation is A (pass), and when the arm tilt amount exceeds 1 °, the evaluation is C (fail).
- the evaluation is B (caution).
- the second evaluation item is damping torque.
- torque measurement was performed using a torque measuring device to obtain a torque curve (a diagram showing the relationship between arm rotation angle and damping torque). From the torque curve, the width [N ⁇ m] of the damping torque at the angle at which the arm 3 is rotated when the coil spring 5 is assembled (hereinafter referred to as the arm rotation angle, for example, 60 °) was read.
- the width [N ⁇ m] of the damping torque means the damping torque in the direction of tensioning the belt from the damping torque [N ⁇ m] in the direction of loosening the belt at an arbitrary arm rotation angle (for example, 60 °). The value obtained by subtracting [N ⁇ m].
- the evaluation is A (passed).
- the evaluation was C (failed).
- the evaluation is B (caution).
- the third evaluation item is spring torque.
- the arm rotation angle when the coil spring 5 is assembled (the twist angle of the coil spring 5)
- the torsional torque [N ⁇ m] of the coil spring 5 at 60 ° was calculated.
- the evaluation is A (pass), and when it is less than 20 N ⁇ m or more than 28 N ⁇ m, the evaluation is C (fail).
- FIG. 9 is a graph showing the relationship between the arm tilt amount [°] and the test time in Example 2 and Comparative Example 1.
- the test was continued not only for the target test time of 300 hours but also for 390 hours, but the arm inclination amount was approximately 0.4 ° to 0.5 ° with respect to the initial value before the test (over 0.3 °). It was stable throughout the range of °, and the evaluation result of evaluation A (pass) was obtained with a margin.
- the auto tensioner 205 is disassembled, and the state of wear of the arc surface 60 of the friction member 6 and the state of the inner peripheral surface of the outer cylindrical portion 21 of the base 2 facing the arc surface 60 are visually confirmed.
- the wear depth (maximum) of the arcuate surface 60 was only 0.15 mm, which was a satisfactory level. Further, no foreign matter was accumulated on the inner peripheral surface of the outer cylindrical portion 21 of the base 2 facing the arc surface 60.
- the arm inclination amount reached 0.6 ° in only 32 hours (sliding of the friction member 6: about 2 million reciprocations), from the initial value before testing (0.4 ° slightly more). Increase was recognized (evaluation B). Therefore, the test was terminated at this point.
- the auto tensioner 208 is disassembled, and the wear state of the arc surface 60 of the friction member 6 and the state of the inner peripheral surface of the outer cylinder portion 21 of the base 2 facing the arc surface 60 are visually observed.
- the wear depth (maximum) of the arc surface 60 reached 0.25 mm.
- the wear was conspicuous as compared with Example 2, and the level should be regarded as a problem.
- the level should be regarded as a problem.
- a considerable amount of foreign matter was found on the portion facing the arc surface 60.
- the test time for the arm inclination amount to reach 1 ° is estimated to be only 70 hours, and the wear depth (maximum) of the arc surface 60 of the friction member 6 at this time is estimated.
- the wear suppression effect on the arc surface 60 of the friction member 6 is more remarkable in Example 2 than in Comparative Example 1.
- the width of the damping torque of Example 2 is a stable value (approximately 5 to 7 N ⁇ m) during the test with respect to the initial value (10 N ⁇ m) before the test, and a torque curve measured during the test. No disturbance was observed (Evaluation A). On the other hand, in Comparative Example 1, there was no problem with the width of the damping torque as in Example 2, but disturbance was observed in the torque curve measured during the test (Evaluation B). This is presumably because foreign matter is present between the arc surface 60 of the friction member 6 and the inner peripheral surface of the outer cylindrical portion 21 of the base 2.
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Abstract
Description
特許文献2の摩擦部材は、アームに係止されて、アームの揺動軸方向に圧縮されたコイルばねによってベース(詳細にはベースに固定された摩擦部材取付板)に押し付けられている。この摩擦部材は、軸方向に見て、環状に形成されている。特許文献2の摩擦部材の摺動面は、ベース(摩擦部材取付板)に対して摺接可能な環状面である。
すなわち、本発明の補機駆動ベルトシステムに備わるオートテンショナは、円筒部を有するベースと、前記ベースに対して前記円筒部の内周面の中心軸を中心に回動自在に支持されたアームと、前記アームに回転自在に設けられるとともに、ベルトが巻き掛けられるテンショナプーリと、前記円筒部の内周面と前記アームとの間に前記円筒部の径方向に挟まれるとともに、前記アームに係止されて、前記円筒部の内周面に対して摺動可能な円弧面を有する摩擦部材と、前記アームを前記ベースに対して一方向に回動付勢するコイルばねと、を備え、前記テンショナプーリに巻き掛けられた前記ベルトの張力が変化して前記アームが揺動する際に、前記円弧面と前記円筒部の内周面との間に摩擦力を生じさせることで前記アームの揺動を減衰させる。
この補機駆動ベルトシステムに備わるオートテンショナにおいて、前記摩擦部材は、前記アームの揺動に伴い前記円筒部の内周面に対して摺動する際に、前記円弧面が前記中心軸を通る水平面以上の高さに留まるように、設けられている。
通常、補機駆動ベルトシステムに備わるオートテンショナにおいて、アームは激しく揺動するが、アームの揺動幅自体は比較的小さい(最大で概ね10°)。そのため、アームが揺動する際に、摩擦部材の円弧面(摺動面)がベースの円筒部の内周面の中心軸を通る水平面以上の高さに留まるように設けられることは実現可能である。
一般に、オートテンショナのベースは、エンジンブロック等の略鉛直方向に沿う面に固定されている。そのため、オートテンショナに泥水等の水媒体がかかる環境下で、ベースの円筒部とアームとの間の隙間から浸入した泥水等の水媒体に含まれる異物は、ベースの円筒部の内周面において、中心軸を通る水平面より上方の部分には堆積されず、中心軸を通る水平面より下方の部分に堆積される。
したがって、摩擦部材の円弧面(摺動面)とベースの円筒部の内周面との間に、異物が介在するのを防止できる。その結果、シール部材を備えていなくても、摩擦部材の円弧面(摺動面)が早期に摩耗するのを抑制して、オートテンショナの耐久性を確保することができる。
このような初期張力付与後のベルト張力の低下とベルト長さのばらつきがあっても、ベルト張力が安定した状態での摩擦部材の位置は、基準寸法のベルトに所定の初期張力を付与した時点の摩擦部材の位置から中心軸回りに概ね±5°の範囲内に留まる。さらに、アームの揺動幅は概ね10°以下である。
本発明の摩擦部材は、中心軸方向に見て円弧面の中心角が150°未満であって、かつ、ベルトに所定の初期張力が付与された時点で中心軸方向に見て、ベースの円筒部の内周面における最上部の位置が、円弧面の中央部であって中心角が10°の領域に接するように設けられている。そのため、アームの揺動時に、摩擦部材の円弧面が中心軸を通る水平面以上の高さに留まる構成を確実に実現できる。また、初期張力付与後のベルト張力の低下とベルト長さのばらつきがあっても、アームの揺動時に、中心軸方向に見て摩擦部材の円弧面の中間の位置を、ベースの円筒部の内周面の最上部に近い位置とすることができる。円弧面の円弧の長さが同じ場合で比べると、円弧面の中間の位置が円筒部の内周面の最上部の位置に近いほど、円弧面の最下端がより高い位置にある。円弧面の最下端がより高いほど、円弧面とベースの円筒部の内周面との間に異物が入り込みにくく、たとえ入り込んでも下方に掃き出されやすい。したがって、摩擦部材の円弧面(摺動面)とベースの円筒部の内周面との間に、異物が介在するのをより確実に防止できる。
ベルト長さが基準寸法より長い場合、ベルト張力が安定した時点のアーム3および摩擦部材6の位置は、ベルト長さが基準寸法の場合におけるベルト張力が安定した時点のアーム3および摩擦部材6の位置に対して、矢印X方向にずれた位置となる。ベルト長さが許容値内で最大の場合におけるベルト張力が安定した時点のアーム3および摩擦部材6の位置は、ベルト長さが基準寸法の場合における初期張力が付与された時点のアーム3および摩擦部材6の位置に対して、矢印X方向に5°以内ずれた位置となる。
ベルト長さが基準寸法より短い場合、ベルト張力が安定した時点のアーム3および摩擦部材6の位置は、ベルト長さが基準寸法の場合におけるベルト張力が安定した時点のアーム3および摩擦部材6の位置に対して、矢印X方向と反対方向にずれた位置となる。ベルト長さが許容値内で最大の場合におけるベルト張力が安定した時点のアーム3および摩擦部材6の位置は、ベルト長さが基準寸法の場合における初期張力が付与された時点のアーム3および摩擦部材6の位置に対して、矢印X方向と反対方向にずれる場合がある。この角度は、最大でも5°に満たない。
ベルト105の張力が増加した場合には、アーム3はコイルばね5の周方向の付勢力に抗して、図5の(a)に示す矢印A方向(X方向と逆方向)に回動する。摩擦部材6はアーム3の係止面31aから力Faを受けて矢印A方向に回動し、摩擦部材6の円弧面60がベース2の外筒部21の内周面と摺動する。
通常、補機駆動ベルトシステムに備わるオートテンショナにおいて、アームは激しく揺動するが、アームの揺動幅自体は比較的小さい(最大で概ね10°)。そのため、アーム3が揺動する際に、摩擦部材6の円弧面60(摺動面)がベース2の外筒部21の内周面の中心軸(軸R)を通る水平面HP以上の高さに留まるように設けられることは実現可能である。
一般に、オートテンショナのベースは、エンジンブロック等の略鉛直方向に沿う面に固定されている。そのため、オートテンショナ1に泥水等の水媒体がかかる環境下で、ベース2の外筒部21とアーム3との間に形成された環状隙間30aから浸入した泥水等の水媒体に含まれる異物Mは、その一部は下方の環状隙間30aから外部に抜けるものの、残りの異物Mは、ベース2の外筒部21の内周面に堆積されていく(図3参照)。異物Mは、ベース2の外筒部21の内周面において軸Rを通る水平面HPより上方の部分には堆積されず、軸Rを通る水平面HPより下方の部分に堆積される。
したがって、摩擦部材6の円弧面60(摺動面)は、ベース2の外筒部21の内周面において異物Mが堆積した部分と接触しない。また、たとえ摩擦部材6の円弧面60(摺動面)と相手面(ベース2の外筒部21の内周面)との間に異物Mが入り込んでも、異物Mは下方に掃き出されやすい。よって、摩擦部材6の円弧面60(摺動面)とベース2の外筒部21の内周面との間に、異物Mが介在するのを防止できる。その結果、シール部材を備えていなくても、摩擦部材6の円弧面60(摺動面)が早期に摩耗するのを抑制して、オートテンショナ1の耐久性を確保することができる。
このような初期張力付与後のベルト張力の低下とベルト長さのばらつきがあっても、ベルト張力が安定した状態での摩擦部材6の位置は、基準寸法のベルト105に所定の初期張力を付与した時点の摩擦部材6の位置から軸R回りに概ね±5°の範囲内に留まる。さらに、アーム3の揺動幅は概ね10°以下である。
摩擦部材6は、軸R方向に見て円弧面60の中心角が150°未満であり、かつ、ベルト105に所定の初期張力が付与された時点で軸R方向に見て、ベース2の外筒部21の内周面における最上部の位置21tが、円弧面60の中央部であって中心角が10°の領域60cに接するように設けられている。そのため、アーム3の揺動時に、摩擦部材6の円弧面60が軸Rを通る水平面HP以上の高さに留まる構成を確実に実現できる。また、初期張力付与後のベルト張力の低下とベルト長さのばらつきがあっても、アーム3の揺動時に、軸R方向に見て摩擦部材6の円弧面60の中間の位置を、ベース2の外筒部21の内周面の最上部に近い位置とすることができる。円弧面60の円弧の長さが同じ場合で比べると、円弧面60の中間の位置が外筒部21の内周面の最上部の位置21tに近いほど、円弧面60の最下端がより高い位置にある。円弧面60の最下端がより高いほど、円弧面60とベース2の外筒部21の内周面との間に異物Mが入り込みにくく、たとえ入り込んでも下方に掃き出されやすい。したがって、摩擦部材6の円弧面60(摺動面)とベース2の外筒部21の内周面との間に、異物Mが介在するのをより確実に防止できる。
本発明の補機駆動ベルトシステムに備わるオートテンショナのアームの揺動幅の最大値を確認するための試験を行った。この試験に用いた実施例1のオートテンショナは、上記実施形態のオートテンショナ1と同じ構成とした。摩擦部材(6)の材質は、ポリアミド樹脂(PA6T)である。揺動軸(8)の軸心(R)方向に見た円弧面(60)の中心角(θ)は43°である。摩擦部材6の前後方向長さは、コイルばね5の線径の約1.4倍である。軸受(7)は、円筒状の金属製軸受(所謂メタル軸受)である。軸受(7)の揺動軸(8)と接触する内周面は、ポリ四フッ化エチレンの潤滑材を含有する樹脂組成物(低摩擦材)で構成される。ベルト(105)は、Vリブドベルト(三ツ星ベルト社製)で、ベルト呼称が6PK1555(K形リブ、ベルト幅方向のリブ山の数6、ベルト長さ(POC)1555mm、ベルト幅21.4mm)のものを用いた。ベルト(105)に埋設されている心線は、ポリエステルコードを用いた撚糸ロープである。
本発明の効果検証として、オ-トテンショナに泥水がかかる環境下でアームを強制的に揺動させる試験を行い、摩擦部材の摩耗に対する評価を実施した。この試験は、図6に示す試験用ベルトシステム200と泥水滴下装置(不図示)とを用いて行った。試験用ベルトシステム200は、鉛直上方に延びる1枚のフレーム220に固定されており、このフレーム220は、床等に固定されて略水平方向に延在する架台221に固定されている。試験用ベルトシステム200は、1つの駆動プーリ203によって同時に駆動される2つのベルトシステム(第1ベルトシステム201と第2ベルトシステム202)を有する。2つのベルトシステム201、202は、駆動軸204を有する1つの駆動モータと、駆動軸に接続された1つの駆動プーリ203とを共有する。第1ベルトシステム201は、実施例2のオートテンショナ205と、従動プーリ206と、ベルト207とを有する。第2ベルトシステム202は、比較例1のオートテンショナ208と、従動プーリ209と、ベルト210とを有する。第1ベルトシステム201の3つのプーリの位置と、第2ベルトシステム202の3つのプーリの位置は、駆動軸204の軸心を中心として点対称である。
1つ目の評価項目は、アームの傾き量である。摩擦部材6の円弧面60の摩耗度合いは、オートテンショナを分解しないと評価できない。そこで、摩擦部材6の円弧面60の摩耗度合いの代用特性として、アーム3の円弧面60側への傾き量を測定した。具体的には、以下のA寸法およびB寸法を測定することにより、アーム3の傾き量[°]を算出した。図8に示すように、アーム3が傾く前の揺動軸8の中心軸を軸R0とし、アームが傾いた後の揺動軸8の中心軸を軸R1とする。A寸法は、軸R0(または軸R1)方向に見て摩擦部材6の円弧面60を円弧方向に二等分する周方向位置における、アーム3の前面外縁から軸R0方向に沿ったベース2の台座部20の後面外縁までの高さ寸法とした。B寸法は、軸R0(または軸R1)方向に見てA寸法の測定位置から180°離れた周方向位置における、アーム3の前面外縁から軸R0方向に沿ったベース2の台座部20の後面外縁までの高さ寸法とした。なお、本発明における「ベースの円筒部の中心軸」は、軸R0に限らず、軸R1であってもよい。
2つ目の評価項目は、減衰トルクである。実施例2および比較例1のオートテンショナ205、208について、トルク測定装置を用いてトルク測定を行って、トルクカーブ(アーム回動角度と減衰トルクとの関係を示す線図)を得て、このトルクカーブから、コイルばね5の組み付け時にアーム3を回動させる角度(以下、アーム回動角度という、例えば60°)における減衰トルクの幅[N・m]を読み取った。ここで、減衰トルクの幅[N・m]とは、任意のアーム回動角度(例えば60°)における、ベルトを緩ませる方向の減衰トルク[N・m]から、ベルトを張る方向の減衰トルク[N・m]を差し引いた値を指す。
3つ目の評価項目は、スプリングトルクである。実施例2および比較例1のオートテンショナ205、208について、上記減衰トルクに関する評価で得られたトルクカーブを基に、コイルばね5の組み付け時のアーム回動角度(コイルばね5の捩じり角度、例えば60°)におけるコイルばね5の捩じりトルク[N・m]を演算で算出した。
図9は、実施例2と比較例1のアームの傾き量[°]と試験時間との関係を示すグラフである。実施例2は、目標試験時間300時間のみならず390時間まで試験を続行したが、アーム傾き量は、試験前の初期値(0.3°強)に対し概ね0.4°~0.5°の範囲内で終始安定しており、余裕をもって評価A(合格)の評価結果となった。
390時間での試験終了後、オートテンショナ205を分解し、摩擦部材6の円弧面60の摩耗状態、円弧面60と対向するベース2の外筒部21の内周面の状態等を目視で確認した。その結果、円弧面60の摩耗深さ(最大)は、僅か0.15mmと問題ないレベルであった。また、ベース2の外筒部21の内周面において円弧面60と対向する部分には、異物の堆積は認められなかった。
一方、比較例1は、僅か32時間(摩擦部材6の摺動:約200万回往復)で、アーム傾き量は0.6°に達し、試験前の初期値(0.4°強)からの増加が顕著と認められた(評価B)。そのため、この時点で試験を打ち切った。
32時間で試験を終了した後、オートテンショナ208を分解し、摩擦部材6の円弧面60の摩耗状態、円弧面60と対向するベース2の外筒部21の内周面の状態等を目視で確認した結果、円弧面60の摩耗深さ(最大)は、0.25mmに達し、試験時間を考慮すると実施例2に比べ摩耗が顕著で、問題視すべきレベルとなった。また、ベース2の外筒部21の内周面において円弧面60と対向する部分には、異物の堆積が相当量認められた。
なお、試験を打ち切らずにそのまま試験を続行した場合、アームの傾き量が1°に達する試験時間は僅か70時間と推定され、このときの摩擦部材6の円弧面60の摩耗深さ(最大)は0.40mmにも達すると推定された。
このように、実施例2は、比較例1に比べ、摩擦部材6の円弧面60に対する摩耗抑制効果が顕著であることが分かった。
実施例2の減衰トルクの幅は、試験前の初期値(10N・m)に対し、試験中は安定した値(概ね5~7N・m)で推移し、且つ、試験途中で測定したトルクカーブにも乱れが認められなかった(評価A)。
一方、比較例1では、減衰トルクの幅は、実施例2と同様に問題なかったが、試験途中で測定したトルクカーブに乱れが認められた(評価B)。これは、摩擦部材6の円弧面60とベース2の外筒部21の内周面との間に異物が介在したためと考えられる。
実施例2および比較例1ともに、スプリングトルクの値は、試験前の初期値(25N・m)に対し、試験中は安定した値(概ね22~23N・m)で推移していた(評価A)。
2 ベース
3 アーム
4 テンショナプーリ
5 コイルばね
6 摩擦部材
21 外筒部(円筒部)
60 円弧面
100 補機駆動ベルトシステム
105 ベルト
R 軸(中心軸)
HP 水平面
Claims (2)
- 円筒部を有するベースと、
前記ベースに対して前記円筒部の内周面の中心軸を中心に回動自在に支持されたアームと、
前記アームに回転自在に設けられるとともに、ベルトが巻き掛けられるテンショナプーリと、
前記円筒部の内周面と前記アームとの間に前記円筒部の径方向に挟まれるとともに、前記アームに係止されて、前記円筒部の内周面に対して摺動可能な円弧面を有する摩擦部材と、
前記アームを前記ベースに対して一方向に回動付勢するコイルばねと、を備え、
前記テンショナプーリに巻き掛けられた前記ベルトの張力が変化して前記アームが揺動する際に、前記円弧面と前記円筒部の内周面との間に摩擦力を生じさせることで前記アームの揺動を減衰させる、補機駆動ベルトシステムに備わるオートテンショナにおいて、
前記摩擦部材は、前記アームの揺動に伴い前記円筒部の内周面に対して摺動する際に、前記円弧面が前記中心軸を通る水平面以上の高さに留まるように、設けられている、補機駆動ベルトシステムに備わるオートテンショナ。 - 前記摩擦部材は、前記中心軸方向に見て前記円弧面の中心角が150°未満であり、かつ、前記ベルトに所定の初期張力が付与された時点で前記中心軸方向に見て、前記円筒部の内周面における最上部の位置が、前記円弧面の中央部であって中心角が10°の領域に接するように設けられている、請求項1に記載の補機駆動ベルトシステムに備わるオートテンショナ。
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