JP7413230B2 - pulley structure - Google Patents

Description

The present invention relates to a pulley structure equipped with a coil spring.

In an auxiliary drive unit that drives auxiliary equipment such as an alternator using the power of an automobile engine, a belt runs across a pulley connected to the drive shaft of the auxiliary equipment such as the alternator and a pulley connected to the engine crankshaft. engine torque is transmitted to the auxiliary equipment via this belt. In particular, the pulley structures of Patent Documents 1 to 3, which can absorb rotational fluctuations of the crankshaft, are used for the pulley connected to the drive shaft of the alternator, which has a larger inertia than other auxiliary machines.

The pulley structures of Patent Documents 1 to 3 include an outer rotating body and an inner rotating body that is provided inside the outer rotating body and is rotatable relative to the outer rotating body, and is wound around the outer rotating body. From the viewpoint of preventing belt slippage, etc., a one-way clutch is provided between the outer rotating body and the inner rotating body to transmit or interrupt torque in one direction. A one-way clutch allows the outer rotating body (connected to a drive shaft such as a crankshaft via a belt) and the inner rotating body (connected to a driven body such as an auxiliary machine via a shaft) to rotate relative to each other. Absorbs the difference in rotational speed between the body and the internal rotator. For example, in Patent Documents 1 and 2, a coil spring type clutch including a torsion coil spring is provided as a one-way clutch. In Patent Document 3, a roller type clutch including rollers is provided as a one-way clutch.

Furthermore, in order to prevent overload on the one-way clutch, the pulley structures of Patent Documents 1 to 3 prevent the one-way clutch from being overloaded when excessive torque is input to the outer rotating body during a cold start of the engine. is in a state of strong frictional engagement with the outer rotating body (locked state), and has a mechanism (hereinafter referred to as a locking mechanism) in which the two rotating bodies rotate integrally together with the one-way clutch. For example, in Patent Documents 1 and 2, when the free portion (outer circumferential surface) of the coil spring is strongly frictionally engaged with the outer rotating body, a locked state is achieved. In Patent Document 3, when the cylindrical surface (outer peripheral surface) of the roller is strongly frictionally engaged with the outer rotating body (cam surface of the outer ring), a locked state is achieved.

JP2017-201210A Patent No. 5057997 Japanese Patent Application Publication No. 11-287311

In the conventional pulley structure (Patent Document 1), as shown in FIG. 17, when an engine is cold started, excessive torque is input to the outer rotating body, and the free portion of the coil spring expands in diameter, causing the coil to collapse. When the free part (outer circumferential surface) of the spring comes into contact with the inner circumferential surface (annular surface) of the outer rotating body, the locking mechanism is activated instantaneously, preventing further torsional deformation of the coil spring in the radial expansion direction. (block, stop).

Therefore, when the locking mechanism is activated, the damping by the coil spring is suddenly lost, and an impact load (excessive rotational braking force) is applied from the outer rotating body to the belt on the torque input side, resulting in an excessive increase in belt tension. . For example, in the pulley structure of an automobile engine's accessory drive belt system, if the locking mechanism is activated and the belt tension is excessively increased, the durability of the belt system decreases and the belt breaks (at the center). damage to the bearings of each auxiliary equipment, or damage to the fitting part due to tightening of the fitting (hinged) part between the drive shaft of the alternator and the internal rotating body. There is a risk of it getting lost.

The present invention provides a pulley structure having a locking mechanism that restricts torsional deformation in the diametrical direction of a coil spring, which has a relatively simple configuration and can suppress an excessive increase in belt tension when the locking mechanism operates. The purpose is to provide the body.

The pulley structure of the present invention includes a cylindrical outer rotating body around which a belt is wound, and a pulley structure that is provided inside the outer rotating body in the radial direction and rotates with respect to the outer rotating body in the same manner as the outer rotating body. An inner rotating body that is relatively rotatable about an axis, and a coil spring disposed between the outer rotating body and the inner rotating body, and the coil spring is configured to rotate when torsionally deformed in a diametrical direction. , transmitting torque between the outer rotating body and the inner rotating body, and interrupting torque transmission between the outer rotating body and the inner rotating body when the body is torsionally deformed in a diametrical direction; Further, when the free portion of the coil spring is excessively torsionally deformed in the diametrically expanding direction due to the diameter expansion of the coil spring, further torsional deformation of the coil spring in the diametrically expanding direction is restricted, and the outer rotating body and a pulley structure having a locking mechanism in which the inner rotating body rotates integrally with the coil spring, further comprising an elastic sleeve provided between the outer rotating body and the coil spring, and the elastic sleeve is configured to expand the coil spring. When the free portion of the coil spring comes into contact with the outer rotating body via the elastic sleeve and the locking mechanism is actuated, the elastic sleeve is compressively elastically deformed in the radial direction. shall be.

According to the above configuration, the locking mechanism operates in a state where the elastic sleeve is compressively and elastically deformed in the thickness direction. Therefore, when the locking mechanism operates, the damping by the coil spring is not suddenly lost, and the impact load (excessive rotational braking force) acting on the belt on the torque input side from the outer rotating body is alleviated. Accordingly, it is possible to suppress the belt tension from increasing excessively when the lock mechanism is activated. In addition, the relatively simple structure of adding an elastic sleeve to the conventional basic structure of the pulley structure reduces the impact load that acts on the belt when the locking mechanism is activated, and suppresses belt tension from increasing excessively. can.

Here, in this specification, "belt tension" refers to belt tension during belt running, and refers to so-called "dynamic belt tension." Dynamic belt tension can be obtained, for example, as follows. In other words, using an engine bench tester in which a touch pulley equipped with a sensor (strain gauge, etc.) for measuring dynamic belt tension was temporarily installed between the belt spans on the tension side of the belt system, the belt tension (dynamic Continuously measure belt tension. Through this measurement, a graph showing a time-series change in belt tension (dynamic belt tension) while the belt is running is obtained. The dynamic belt tension can be read from this obtained graph. As described above, "belt tension" in this specification is distinguished from mere belt tension measured when the belt is stopped.

In the pulley structure of the present invention, the elastic sleeve is arranged in the radial direction between the free portion of the coil spring on the inner peripheral surface of the outer rotor and the inner rotor when the outer rotor and the inner rotor are not rotating. It may be in contact with the part facing the. Here, when the elastic sleeve is not in contact with the portion of the inner peripheral surface of the outer rotor that is radially opposed to the free portion of the coil spring when the outer rotor and the inner rotor are not rotating, During the operation of the pulley structure, the coil spring is deformed to expand its diameter excessively, and each time the locking mechanism is activated, the positional relationship of the elastic sleeve in the radial direction of the outer rotating body changes. The expansion and contraction deformations of the sleeve are repeated. On the other hand, according to the above configuration, the positional relationship of the elastic sleeve in the radial direction with respect to the outer rotating body is maintained in a manner that does not change throughout the operation of the pulley structure. Therefore, the expansion and contraction deformations of the elastic sleeve are not repeated every time the locking mechanism is activated. As a result, it becomes easier to ensure the quality of the elastic sleeve.

In the pulley structure of the present invention, a convex portion may be provided on the outer circumferential surface of the elastic sleeve, and a concave portion capable of engaging with the convex portion may be provided on the inner circumferential surface of the outer rotating body. According to the above configuration, the elastic sleeve is mounted on the inner circumferential surface of the outer rotating body radially facing the free portion of the coil spring so as to be able to fit in the concave and convex portions. Therefore, compared to the case where the elastic sleeve has a simple cylindrical shape, the elastic sleeve can be positioned more reliably in the direction of the rotation axis. Accordingly, it becomes easier to ensure the quality of the elastic sleeve.

In the pulley structure of the present invention, when the outer rotating body and the inner rotating body are not rotating, the elastic sleeve is applied to the outer circumferential surface of the free portion of the coil spring by self-elastic restoring force in the diametrical direction. May be in contact. According to the above configuration, the elastic sleeve is mounted so as to extend in the radial direction and come into contact with the outer peripheral surface of the free portion of the coil spring. For this reason, the elastic sleeve after being installed is kept in contact with the outer circumferential surface of the free portion of the coil spring from beginning to end, and the portion facing the gap between the axially adjacent spring wires is in contact with the axially adjacent spring wire. It is held in a manner that it slightly bites into the gap between the matching spring wires. Therefore, there is no need to perform processing on the pulley structure for positioning the elastic sleeve with respect to the rotation axis direction, and the pulley structure can be made simpler accordingly.

In the pulley structure of the present invention, the elastic sleeve may be made of synthetic rubber. According to the above configuration, the elastic sleeve has excellent heat resistance, oil resistance, etc. As a result, it can be suitably used as a pulley structure provided in a belt system for driving auxiliary equipment of an automobile engine.

FIG. 1 is a sectional view of the pulley structure of the first embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a cross-sectional view taken along line III--III in FIG. 1. FIG. 4 is a side view of the elastic sleeve shown in FIG. 1. FIG. 5 is a front view of the elastic sleeve shown in FIG. 1. FIG. 6 is a graph showing the relationship between the torsion angle and torsion torque of the torsion coil spring of the pulley structure shown in FIG. FIG. 7 is a partial sectional view showing an enlarged diameter of the free portion of the torsion coil spring of the pulley structure shown in FIG. FIG. 8 is a partial sectional view showing an enlarged diameter of the free portion of the torsion coil spring of the pulley structure shown in FIG. FIG. 9 is a sectional view of the pulley structure of the second embodiment. FIG. 10 is a side view of the elastic sleeve shown in FIG. 9. FIG. 11 is a front view of the elastic sleeve shown in FIG. 9. FIG. 12 is a schematic diagram of the engine bench test machine. FIG. 13 is a schematic configuration diagram of an engine bench testing machine. FIG. 14 is a graph showing a time-series change in dynamic belt tension of the pulley structure of Example 1 during engine cold start. FIG. 15 is a graph showing a time-series change in dynamic belt tension of the pulley structure of Example 2 during engine cold start. FIG. 16 is a graph showing a time-series change in dynamic belt tension of the pulley structure of Comparative Example 1 during engine cold start. FIG. 17 is a sectional view of a conventional pulley structure.

(First embodiment)
Hereinafter, a pulley structure 1 according to a first embodiment of the present invention will be described.
The pulley structure 1 is installed on the drive shaft of an alternator in an automobile accessory drive system (not shown). Note that the pulley structure of the present invention may be installed on the drive shaft of an auxiliary device other than the alternator.

As shown in FIGS. 1 to 3, the pulley structure 1 includes an outer rotating body 2, an inner rotating body 3, a coil spring 4 (hereinafter simply referred to as "spring 4"), an end cap 5, and an elastic sleeve 6. . In the following description, the left side in FIG. 1 is referred to as the front, and the right side is referred to as the rear. The end cap 5 is arranged at the front end of the outer rotating body 2 and the inner rotating body 3.

Both the outer rotating body 2 and the inner rotating body 3 have a substantially cylindrical shape and have the same rotation axis. The rotation axes of the outer rotor 2 and the inner rotor 3 are the rotation axes of the pulley structure 1, and are hereinafter simply referred to as "rotation axes." Furthermore, the direction of the rotation axis is simply referred to as the "axial direction." The inner rotating body 3 is provided inside the outer rotating body 2 in the radial direction, and is rotatable relative to the outer rotating body 2. A belt B is wound around the outer peripheral surface of the outer rotating body 2.

The inner rotating body 3 has a cylinder main body 3a and an outer cylinder part 3b arranged outside the front end of the cylinder main body 3a. A drive shaft S such as an alternator is fitted into the cylinder body 3a. A support groove 3c is formed between the outer cylinder part 3b and the cylinder main body 3a. The inner peripheral surface of the outer cylinder part 3b and the outer peripheral surface of the cylinder main body 3a are connected via the groove bottom surface 3d of the support groove part 3c.

A rolling bearing 7 is interposed between the inner peripheral surface of the rear end of the outer rotating body 2 and the outer peripheral surface of the cylinder body 3a. A sliding bearing 8 is interposed between the inner circumferential surface of the front end of the outer rotating body 2 and the outer circumferential surface of the outer cylinder portion 3b. The outer rotary body 2 and the inner rotary body 3 are coupled by bearings 7 and 8 such that they can rotate relative to each other.

A space 9 is formed between the outer rotating body 2 and the inner rotating body 3 and in front of the rolling bearing 7. A spring 4 is housed in the space 9. The space 9 is formed between the inner circumferential surface of the outer rotating body 2, the inner circumferential surface of the outer cylinder portion 3b, and the outer circumferential surface of the cylinder body 3a.

The inner diameter of the outer rotating body 2 decreases in two steps toward the rear. The inner circumferential surface of the outer rotating body 2 at the smallest inner diameter portion is referred to as a pressure contact surface 2a, and the inner circumferential surface of the outer rotating body 2 at the second smallest inner diameter portion is referred to as an annular surface 2b. The inner diameter of the outer rotating body 2 at the pressure contact surface 2a is smaller than the inner diameter of the outer cylinder portion 3b. The inner diameter of the outer rotating body 2 at the annular surface 2b is the same as or larger than the inner diameter of the outer cylinder portion 3b.

The annular surface 2b of the outer rotating body 2 is formed with one groove 2b1 (corresponding to a "recess") extending all the way around the circumferential direction of the rotating shaft. The concave groove 2b1 can be engaged with a protrusion 6a (corresponding to a "protrusion") of the elastic sleeve 6, which will be described later.

The cylinder main body 3a has a larger outer diameter at the front end. The outer circumferential surface of the inner rotating body 3 at this portion is referred to as a contact surface 3e.

The spring 4 is a torsion coil spring formed by spirally winding (coiling) a spring wire (spring wire). The spring 4 is left-handed (counterclockwise from the front end to the rear end). The number of turns N of the spring 4 is, for example, 5 to 9 turns. The spring wire of the spring 4 is a trapezoidal wire having a trapezoidal cross-sectional shape (cross-sectional shape along a direction passing through the rotational axis and parallel to the rotational axis). The four corners in the cross section of the spring wire have a chamfered shape (for example, an R surface or a C surface with a radius of curvature of about 0.3 mm).

The spring 4 has a constant diameter over its entire length when it is not receiving any external force. The outer diameter of the spring 4 in a state where no external force is applied is larger than the inner diameter of the outer rotating body 2 at the pressure contact surface 2a. The spring 4 is housed in the space 9 with the rear end region 4c having a reduced diameter. The outer circumferential surface of the rear end side region 4c of the spring 4 is pressed against the pressure contact surface 2a by the self-elastic restoring force of the spring 4 in the diametrically expanding direction. The rear end side region 4c is a region extending one or more turns from the rear end of the spring 4 (more than 360 degrees around the rotation axis).

Further, in a state where the pulley structure 1 is stopped and the outer peripheral surface of the rear end side region 4c of the spring 4 is pressed against the pressure contact surface 2a by the self-elastic restoring force in the radially expanding direction of the spring 4, the front end of the spring 4 The side region 4b is in contact with the contact surface 3e in a slightly enlarged state. That is, when the pulley structure 1 is at rest, the inner peripheral surface of the front end side region 4b of the spring 4 is pressed against the contact surface 3e. The front end side region 4b is a region extending one or more turns from the front end of the spring 4 (more than 360° around the rotation axis). When no external force is acting on the pulley structure 1, the spring 4 has a substantially constant diameter over its entire length.

The spring 4 is compressed in the axial direction when no external force is acting on the pulley structure 1 (that is, when the pulley structure 1 is stopped), and the axial end surface of the front end side region 4b of the spring 4 is compressed. A circumferential portion (half a circumference or more from the front end) contacts the groove bottom surface 3d of the inner rotating body 3, and a circumferential portion (half a circumference or more from the rear end) of the axial end surface of the rear end side region 4c of the spring 4 contacts the outer rotation. It is in contact with the front surface of the annular plate portion 2c of the body 2. The axial compression ratio of the coil spring 4 may be, for example, about 20%. The axial compression ratio of the spring 4 is 100×( It is calculated as L0-L1)/L0. In addition, the spring 4 has a gap (for example, 0.6 mm) between the axially adjacent spring lines when the spring 4 is compressed in the axial direction.

When the spring 4 is compressed in the axial direction, the axial end surface of the rear end region 4c contacts the annular plate portion 2c of the outer rotary body 2, and the axial end surface of the front end region 4b contacts the inner rotary body 3. It comes into contact with the annular plate portion (groove bottom surface 3d). A groove bottom surface 3d of the support groove portion 3c is formed in a spiral shape. As a result, substantially the entire circumferential area of the axial end surface of the front end side region 4b of the spring 4 comes into contact with the groove bottom surface 3d.

As shown in FIG. 2, in the front end side region 4b, a portion near a position 90 degrees away from the front end of the spring 4 around the rotation axis is a second region 4b2, and a portion closer to the front end than the second region 4b2 is a first region 4b1. , the remaining portion is referred to as a third region 4b3. Further, as shown in FIG. 1, the area between the front end side area 4b and the rear end side area 4c of the spring 4, that is, the area that does not contact either the pressure contact surface 2a or the contact surface 3e, is defined as a free portion 4d. .

As shown in FIG. 2, a contact surface 3f facing the front end surface 4a of the spring 4 is formed at the front end portion of the inner rotating body 3. Furthermore, a protrusion 3g is provided on the inner peripheral surface of the outer cylinder part 3b, protruding inward in the radial direction of the outer cylinder part 3b and facing the outer peripheral surface of the front end side region 4b. The protrusion 3g faces the second region 4b2.

As shown in FIG. 1, FIG. 4, and FIG. It is a cylindrical elastic member made of a rubber composition containing

The elastic sleeve 6 is provided between the outer rotating body 2 and the spring 4, as shown in FIG. The elastic sleeve 6 also has a spring 4 on the inner peripheral surface of the outer rotor 2 when the outer rotor 2 and the inner rotor 3 are not rotating (that is, when the pulley structure 1 is stopped). It is in contact with the annular surface 2b that is radially opposed to the free portion 4d.

The outer peripheral surface of the elastic sleeve 6 is provided with one protrusion 6a that extends all the way in the circumferential direction. The diameter of the portion 6b of the elastic sleeve 6 other than the ridges 6a is constant over the entire length along the axial direction in a state where no external force is applied. The protruding strip 6a can fit into a concave groove 2b1 formed on the inner circumferential surface (annular surface 2b) of the outer rotating body 2. When the elastic sleeve 6 is mounted so that the protrusions 6a and the grooves 2b1 are fitted into the grooves 2b1, the elastic sleeve 6 is in a state in which no gap is created between it and the inner circumferential surface (annular surface 2b) of the outer rotating body 2 (i.e., in a contact state). ), the outer diameter of the portion 6b other than the protruding strip 6a is approximately equal to the inner diameter of the inner circumferential surface (annular surface 2b) of the outer rotating body 2. Note that when the outer rotating body 2 starts to rotate, centrifugal force acts on the elastic sleeve 6, so the contact interface between the elastic sleeve 6 and the outer rotating body 2 is reduced compared to when the pulley structure 1 is stopped. The intensity increases, and the two become closer together.

Furthermore, the outer circumferential surface of the elastic sleeve 6 and the inner circumferential surface (annular surface 2b) of the outer rotating body 2 may be partially or entirely bonded. The standard thickness t of the elastic sleeve 6 (thickness of the portion other than the protrusions), the protruding height and width of the protrusions 6a, the number of protrusions 6a, etc. are determined by determining the maximum dynamic belt tension in, for example, an engine starting test to be described later. The decision may be made after confirming the reduction effect. The hardness is preferably in the range of 50 to 90, more preferably 60 to 80 in durometer A hardness (according to JIS K6253:2012). If it is less than 50, the elastic sleeve 6 will bottom out early, and it will be difficult to ensure the effect of suppressing the belt tension from increasing excessively when the locking mechanism 10 (described later) operates. If it exceeds 90, it becomes difficult for the elastic sleeve 6 to undergo compressive elastic deformation in its thickness direction, and similarly, it becomes difficult to ensure the effect of suppressing an excessive increase in belt tension when the locking mechanism 10 operates.

Next, the operation of the pulley structure 1 will be explained.

First, a case where the rotational speed of the outer rotary body 2 becomes higher than the rotational speed of the inner rotary body 3 (that is, a case where the outer rotary body 2 accelerates) will be described.

In this case, the outer rotating body 2 rotates relative to the inner rotating body 3 in the positive direction (in the direction of the arrow in FIGS. 2 and 3). With the relative rotation of the outer rotating body 2, the rear end side region 4c of the spring 4 moves together with the pressure contact surface 2a, and rotates relative to the inner rotating body 3. As a result, the spring 4 is torsionally deformed in the diameter expanding direction (hereinafter simply referred to as diameter expanding deformation). The pressing force of the rear end side region 4c of the spring 4 against the pressing surface 2a increases as the twist angle of the spring 4 in the radially expanding direction increases. The second region 4b2 is most susceptible to torsional stress, and as the torsion angle in the diametrical direction of the spring 4 increases, it separates from the contact surface 3e. At this time, the first region 4b1 and the third region 4b3 are in pressure contact with the contact surface 3e. The outer circumferential surface of the second region 4b2 comes into contact with the protrusion 3g approximately at the same time as the second region 4b2 leaves the contact surface 3e, or when the twist angle of the spring 4 in the diametrical direction becomes even larger. By the outer circumferential surface of the second region 4b2 coming into contact with the protrusion 3g, the diameter expansion deformation of the front end side region 4b is restricted, and the torsional stress is dispersed to a portion of the spring 4 other than the front end side region 4b, and especially the rear end of the spring 4. The torsional stress acting on the end region 4c increases. As a result, the difference in torsional stress acting on each part of the spring 4 is reduced, and strain energy can be absorbed by the entire spring 4, so that local fatigue failure of the spring 4 can be prevented.

Further, the pressing force of the third region 4b3 against the contact surface 3e decreases as the twist angle of the spring 4 in the radially expanding direction increases. At the same time as the second region 4b2 comes into contact with the protrusion 3g, or when the twist angle of the spring 4 in the radially expanding direction becomes even larger, the pressing force of the third region 4b3 against the contact surface 3e becomes approximately zero. At this time, the twist angle of the spring 4 in the diameter expansion direction is set to θ1 (for example, θ1=3°). When the twist angle of the spring 4 in the diameter expansion direction exceeds θ1, the third region 4b3 is deformed to expand its diameter and moves away from the contact surface 3e. However, near the boundary between the third region 4b3 and the second region 4b2, the spring 4 does not curve (bend), and the front end side region 4b is maintained in an arc shape. In other words, the front end side region 4b is maintained in a shape that allows it to easily slide on the projection 3g. Therefore, when the torsion angle of the spring 4 in the radial expansion direction increases and the torsional stress acting on the front end side region 4b increases, the front end side region 4b increases the pressing force against the protrusion 3g of the second region 4b2 and the pressure of the first region 4b1. It slides in the circumferential direction of the outer rotating body 2 with respect to the protrusion 3g and the contact surface 3e against the pressure force applied to the contact surface 3e. By pressing the front end surface 4a against the contact surface 3f, torque can be reliably transmitted between the outer rotating body 2 and the inner rotating body 3.

Note that when the torsion angle in the diameter expansion direction of the spring 4 is θ1 or more and less than θ3 (for example, θ3=45°), the third region 4b3 is separated from the contact surface 3e and on the inner peripheral surface of the outer cylinder portion 3b. The second region 4b2 is not in contact with the projection 3g, but is in pressure contact with the projection 3g. Therefore, in this case, the effective number of turns of the spring 4 is larger and the spring constant (the slope of the straight line shown in FIG. 6) is smaller than when the twist angle in the diameter expansion direction of the spring 4 is less than θ1.

Further, as the torsion angle increases, the diameter of the free portion 4d of the spring 4 expands, and when the torsion angle in the diameter expansion direction of the spring 4 reaches θ2 (for example, θ2=35°), as shown in FIG. The outer circumferential surface of the free portion 4d of 4 abuts against the elastic sleeve 6.

When the torsion angle exceeds θ2, the free portion 4d of the spring 4 comes into contact with the inner circumferential surface (annular surface 2b) of the outer rotating body 2 via the elastic sleeve 6, so that the free portion 4d of the spring 4 The expansion deformation of the diameter begins to be restricted. As the torsion angle increases, while the compressive elastic deformation (thickness reduction) of the elastic sleeve 6 is progressing, the radial expansion deformation of the free portion 4d of the spring 4 is moderately regulated, and the damping by the coil spring rapidly increases. is not lost.

When the twist angle reaches an angle θ4 (for example, θ4=42°) close to a predetermined angle θ3 (for example, θ3=45°), the compressive elastic deformation of the elastic sleeve 6 reaches its limit, as shown in FIG. At this point, the free portion 4d of the spring 4 and the outer rotating body 2 are in a state of strong frictional engagement via the elastic sleeve 6 (locked state). Further, at this time, the twist angle of the front end side region 4b of the spring 4 in the diametrically expanding direction reaches a predetermined angle θ3 (for example, 45°), and comes into contact with the outer cylinder portion 3b of the inner rotating body 3. This restricts further diametric expansion deformation of the entire spring 4, the torsion angle of the spring 4 does not become larger than θ3, and the outer rotating body 2 and the inner rotating body 3 rotate together with the spring 4.

In this way, the pulley structure 1 prevents further torsional deformation of the spring 4 in the diameter expansion direction when the free portion 4d of the spring 4 is excessively torsionally deformed in the diameter expansion direction due to the diameter expansion of the spring 4. The outer rotating body 2 and the inner rotating body 3 have a locking mechanism 10 that rotates integrally with the spring 4. When the locking mechanism 10 is activated in the pulley structure 1, the spring 4 is prevented from being damaged due to excessive diameter expansion deformation, and the impact load (excessive rotation) that is applied from the outer rotating body 2 to the belt B on the torque input side braking force) is now relaxed.

Next, the relationship between the torsion angle of the spring 4 and the torsion torque acting on the spring 4 in the torsion angle range (0° to θ3) will be explained.

When the torsion angle of the spring 4 in the diameter expansion direction is in the range of 0° to θ1, the third region 4b3 of the front end side region 4b of the spring 4 is in contact with the contact surface 3e, and the effective number of turns of the spring 4 does not change. The spring constant (torsion torque/torsion angle), which is inversely proportional to the effective number of turns, is constant within the above range. That is, when the twist angle is in the range of 0° to θ1, the twist torque is proportional to the twist angle, and the graph is linear.

When the torsion angle in the radial expansion direction of the spring 4 is in the range θ1 to θ2, the third region 4b3 of the front end side region 4b of the spring 4 is away from the contact surface 3e, so compared to when the torsion angle is less than θ1, The effective number of turns of the spring 4 increases, and the spring constant of the spring 4 decreases. Note that even when the twist angle is in the range of θ1 to θ2, the effective number of turns does not change as described above, and the spring constant remains constant.

When the torsion angle in the radial expansion direction of the spring 4 is in the range θ2 to θ3, as the torsion angle increases, the frictional engagement between the free portion 4d of the spring 4 and the inner circumferential surface (annular surface 2b) of the outer rotating body 2 increases. , gradually and continuously increases. Therefore, as the twist angle increases, the spring constant of the spring gradually and continuously increases. Here, as described above, the value of the twist angle θ2 at which the outer circumferential surface of the free portion 4d of the spring 4 begins to contact the annular surface 2b via the elastic sleeve 6 is, for example, 35°. Further, the value of the maximum torsion angle (ie, θ3) at which the diameter expansion deformation of the entire spring 4 is restricted is, for example, 45°. That is, when the torsion angle of the spring 4 in the radial expansion direction becomes approximately 75% or more of the maximum torsion angle, the outer circumferential surface of the free portion 4d of the spring 4 comes into contact with the annular surface 2b via the elastic sleeve 6, The spring constant begins to change.

In addition, if the spring constant is constant even in the range of torsion angle θ2 to θ3 as in the conventional case (see the broken line in the graph of FIG. 6; the pulley structure shown in FIG. 17 has such characteristics), In comparison, the free portion 4d of the spring 4 of the pulley structure 1 of this embodiment is difficult to deform to expand in diameter. For example, in the pulley structure 1 of this embodiment, the torsion torque T that maximizes the radial expansion deformation of the spring of the conventional pulley structure (that is, the torsion angle in the radial expansion direction becomes θ3) is applied to the spring. 4, the twist angle of the free portion 4d of the spring 4 in the radially expanding direction remains at θ4, which is smaller than θ3, and the radially expanding deformation is not maximized.

Next, a case where the rotational speed of the outer rotary body 2 becomes smaller than the rotational speed of the inner rotary body 3 (that is, a case where the outer rotary body 2 decelerates) will be described.

In this case, the outer rotating body 2 rotates relative to the inner rotating body 3 in the opposite direction (the direction opposite to the arrow direction in FIGS. 2 and 3). With the relative rotation of the outer rotating body 2, the rear end side region 4c of the spring 4 moves together with the pressure contact surface 2a, and rotates relative to the inner rotating body 3. As a result, the spring 4 is torsionally deformed in the diameter-reducing direction (hereinafter simply referred to as diameter-reducing deformation). When the torsion angle in the diameter reduction direction of the spring 4 is less than θ5 (for example, θ5=4°), the pressing force of the rear end side region 4c against the pressing surface 2a is slightly lower than when the torsion angle is zero. , the rear end side region 4c is in pressure contact with the pressure contact surface 2a. Further, the pressing force of the front end side region 4b against the contact surface 3e increases slightly compared to the case where the twist angle is zero. When the torsion angle in the diameter reduction direction of the spring 4 is θ5 or more, the pressure contact force of the rear end side region 4c with respect to the pressure contact surface 2a becomes approximately zero, and the rear end side region 4c is slide in the direction. Therefore, no torque is transmitted between the outer rotating body 2 and the inner rotating body 3 (see FIG. 6).

In this way, the spring 4 is a coil spring type clutch, and functions as a one-way clutch that transmits or interrupts torque in one direction. When the inner rotating body 3 rotates relative to the outer rotating body 2 in the positive direction, the spring 4 engages with each of the outer rotating body 2 and the inner rotating body 3 to prevent the outer rotating body 2 and the inner rotating body 3 from rotating. While transmitting torque between them, when the inner rotating body 3 rotates relative to the outer rotating body 2 in the opposite direction, at least one of the outer rotating body 2 and the inner rotating body 3 (in this embodiment, the pressure contact surface 2a) The outer rotating body 2 and the inner rotating body 3 slide against each other and do not transmit torque.

According to the pulley structure 1 of the first embodiment described above, the lock mechanism 10 operates in a state where the elastic sleeve 6 is compressively and elastically deformed in its thickness direction. Therefore, when the lock mechanism 10 operates, the damping by the spring 4 is not suddenly lost, and the impact load (excessive rotational braking force) acting from the outer rotating body 2 on the belt B on the torque input side is alleviated. Accordingly, it is possible to suppress the belt tension from increasing excessively when the lock mechanism 10 is activated. As a result, the durability of the belt system can be improved. In addition, with a relatively simple configuration in which an elastic sleeve 6 is added to the conventional basic configuration of the pulley structure (see FIG. 17), an impact load (excessive rotational braking force) that acts on the belt B when the locking mechanism 10 is activated can be used. ) and suppress belt tension from increasing excessively.

Here, if the elastic sleeve is not in contact with the part of the inner peripheral surface of the outer rotor that is radially opposed to the free part of the spring when the outer rotor and the inner rotor are not rotating, During the operation of the pulley structure, the spring expands excessively and each time the locking mechanism operates, the positional relationship of the elastic sleeve in the radial direction of the outer rotating body changes, causing the expansion of the elastic sleeve along with the spring. Radial deformation and diameter reduction deformation will be repeated. However, according to the pulley structure 1 of the first embodiment, the elastic sleeve 6 is arranged so that the spring 4 on the inner circumferential surface of the outer rotor 2 is not rotated. It is in contact with a portion (annular surface 2b) radially opposed to the free portion 4d. Therefore, the expansion and contraction deformations of the elastic sleeve 6 are not repeated every time the locking mechanism 10 operates, and as a result, the quality of the elastic sleeve 6 can be more easily ensured.

Further, a protruding strip 6a is provided on the outer circumferential surface of the elastic sleeve 6, and a groove 2b1 that can fit into the protruding strip 6a is provided on the inner circumferential surface (annular surface 2b) of the outer rotating body 2. Therefore, the elastic sleeve 6 is mounted on the inner circumferential surface (annular surface 2b) of the outer rotary body 2 radially opposed to the free portion 4d of the spring 4 so as to be able to fit in the concave and convex portions. Therefore, the elastic sleeve 6 can be positioned more reliably in the axial direction than when the elastic sleeve has a simple cylindrical shape. Accordingly, it becomes easier to ensure the quality of the elastic sleeve 6.

Further, since the elastic sleeve 6 is made of synthetic rubber, the elastic sleeve 6 has excellent heat resistance, oil resistance, and the like. As a result, the pulley structure 1 can be suitably used in a belt system for driving auxiliary equipment of an automobile engine.

(Second embodiment)
Next, a pulley structure 101 according to a second embodiment will be described. The pulley structure 101 according to the second embodiment differs from the pulley structure 1 according to the first embodiment mainly in the configuration of the elastic sleeve. In the following, the same parts as in the first embodiment described above are given the same reference numerals, and the explanation thereof will be omitted as appropriate.

As shown in FIG. 9, unlike the first embodiment, no groove is formed on the annular surface 102b of the outer rotating body 102 of the pulley structure 101.

As shown in FIGS. 10 and 11, the elastic sleeve 106 is made of a rubber composition containing a rubber component such as synthetic rubber (for example, chloroprene rubber, urethane rubber, nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, silicone rubber, fluororubber, etc.). It is a cylindrical elastic member made of material.

The elastic sleeve 106 is provided between the outer rotating body 102 and the spring 4, as shown in FIG. In addition, when the outer rotating body 102 and the inner rotating body 3 are not rotating (that is, the pulley structure 1 is stopped), the elastic sleeve 106 is able to maintain the elasticity of the spring 4 due to its self-elastic restoring force in the diameter reduction direction. It is in contact with the outer peripheral surface of the free portion 4d.

As shown in FIGS. 10 and 11, the elastic sleeve 106 has a constant diameter over its entire length in the axial direction when it is not receiving external force, and the inner diameter of the elastic sleeve 106 at this time is It is smaller than the outer diameter of the spring 4 in the unsupported state. That is, the elastic sleeve 106 is stretched in the radial direction and is attached so as to contact the outer peripheral surface of the free portion 4d of the spring 4. For this reason, the elastic sleeve 106 is held in contact with the outer circumferential surface of the free portion 4d of the spring 4 from beginning to end after installation, and the portion facing the gap between the axially adjacent spring lines is It is held in a manner that it slightly bites into the gap between adjacent spring wires (see the partially enlarged view in the circle in FIG. 9).

The thickness etc. of the elastic sleeve 106 may be determined, for example, after confirming the effect of reducing the maximum tension of the dynamic belt in an engine starting test, which will be described later.

Next, the operation of the pulley structure 101 will be explained.

The operation of the pulley structure 101 is substantially the same as the operation of the pulley structure 1 of the first embodiment described above, except for the following points. That is, in the pulley structure 101, when the twist angle of the spring 4 in the radial expansion direction becomes θ2 (for example, θ2=35°), the elastic sleeve 106 that is in contact with the outer peripheral surface of the free portion 4d of the spring 4 is It comes into contact with the inner circumferential surface (annular surface 2b) of the rotating body 102. The other operations of the pulley structure 101 are substantially the same as those of the pulley structure 1.

According to the pulley structure 101 of the second embodiment described above, when the outer rotating body 102 and the inner rotating body 3 are not rotating, the elastic sleeve 106 is caused by the self-elastic restoring force in the diametrical direction to It is in contact with the outer peripheral surface of the free portion 4d. Therefore, the elastic sleeve 106 is mounted so as to extend in the radial direction and contact the outer peripheral surface of the free portion 4d of the spring 4. After installation, the elastic sleeve 106 is kept in contact with the outer peripheral surface of the free portion 4d of the spring 4 from beginning to end, and the portions facing the gap between the axially adjacent spring wires are axially adjacent to each other. It is held in a manner that it slightly bites into the gap between the spring wires. Therefore, there is no need to perform processing on the pulley structure 101 to position the elastic sleeve 106 in the axial direction, and the pulley structure 101 can have a simpler configuration.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims.

For example, in the first embodiment described above, the convex portion formed on the outer circumferential surface of the elastic sleeve is a convex strip that extends over the entire circumference in the circumferential direction, and the convex portion formed on the inner circumferential surface of the outer rotating body Although the recessed portion was a groove extending all the way around in the circumferential direction, it is not particularly limited to this. For example, multiple protrusions (equivalent to "protrusions") are arranged on the elastic sleeve all the way around the rotating shaft, and multiple grooves (equivalent to "recesses") are formed on the annular surface of the outer rotating body. The plurality of protrusions and the plurality of grooves may be fitted in a concave and convex manner. Furthermore, the protrusions may be formed only in a part of the circumferential direction of the elastic sleeve, and the grooves may be formed only in a part of the circumferential direction of the annular surface of the outer rotating body. Further, in the first embodiment, the elastic sleeve does not need to have the protrusions, and the annular surface of the outer rotating body does not need to have the grooves.

Further, in the first and second embodiments described above, the elastic sleeve is made of synthetic rubber, but is not particularly limited to this, and may be made of any elastic material.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.
Pulley structures according to Examples 1 and 2 and Comparative Example 1 were manufactured. Each pulley structure will be specifically explained below.

<Example 1>
The pulley structure of Example 1 corresponds to the pulley structure according to the first embodiment described above. The spring wire of the coil spring was an oil tempered spring wire (based on JIS G3560:1994). The spring wire was a trapezoidal wire, and had an inner axial length of 3.8 mm, an outer axial length of 3.6 mm, and a radial length of 5.0 mm. Note that the four corners in the cross section of the spring wire were chamfered (R surface with a radius of curvature of about 0.3 mm). The number of turns of the spring was 7, and the winding direction was left-handed. The compression ratio of the spring in the axial direction was approximately 20%. The gap between axially adjacent spring wires was 0.6 mm when the springs were compressed in the axial direction.

The elastic sleeve of the pulley structure of Example 1 was produced as follows. That is, first, a rubber composition containing hydrogenated nitrile rubber as a rubber component (with the formulation shown in Table 1 below) was kneaded using a Banbury mixer, and then formed into a rubber sheet using a rolling roll. The rubber sheet was put into the cavity of a mold assembly consisting of a core and a two-split outer mold, and the mold was clamped using a press molding machine and vulcanization molded by applying heat and pressure. This provides the elastic sleeve with excellent heat resistance, oil resistance, and the like. Although the elastic sleeve is formed by press molding, it may be formed by any method (for example, rubber injection molding, rubber transfer molding, rubber extrusion molding, etc.). The durometer A hardness (based on JIS K6253:2012) of the elastic sleeve after vulcanization molding was approximately 70.

The standard thickness t (thickness of the portion other than the protrusions) of the elastic sleeve is 1.5 mm. The outer diameter of the elastic sleeve (the outer diameter of the portion other than the protrusions) was made to match the inner diameter of the inner circumferential surface (annular surface) of the outer rotating body. The axial length of the elastic sleeve was made to match the surface length of the annular surface. The protrusions had a rectangular cross section, had a protrusion height of 1.5 mm, a width of 2.5 mm, and the number of protrusions was 1 (extending in the circumferential direction at the center in the axial direction). The grooves machined on the outer rotating body are formed to be able to fit into the grooves with the above-mentioned protrusions, and have a rectangular cross section, a groove depth of 1.5 mm, a groove width of 2.5 mm, and the number of grooves is 1 (in the axial direction). center). The elastic sleeve formed in this way is reduced in diameter (indented) at a portion of the circumferential direction of the protruding part by the protruding height of the protruding part, and then the outer circumferential surface of the elastic sleeve and the inner surface of the outer rotating body are It is inserted into the inner side of the outer rotating body (annular surface) from the front while making sliding contact with the circumferential surface (annular surface), and then the protrusions and grooves are fitted over the entire circumference, and the outer rotating body is inserted into the outer rotating body. I installed it. Note that no adhesive treatment was performed. The pulley structure of Example 1 was completed by sequentially assembling each member including the outer rotating body equipped with this elastic sleeve.

<Example 2>
The pulley structure of Example 2 corresponds to the pulley structure according to the second embodiment described above. The structure of the coil spring in the pulley structure of Example 2 is the same as that of the coil spring in the pulley structure of Example 1.

The method for manufacturing the elastic sleeve of the pulley structure of Example 2 is substantially the same as that of the elastic sleeve of Example 1. That is, first, a rubber composition (formulation shown in Table 1) containing hydrogenated nitrile rubber as a rubber component was kneaded using a Banbury mixer, and then formed into a rubber sheet using a rolling roll. The rubber sheet was put into the cavity of a mold assembly consisting of a core and a two-split outer mold, and the mold was clamped using a press molding machine and vulcanization molded by applying heat and pressure. The durometer A hardness (based on JIS K6253:2012) of the elastic sleeve after vulcanization molding was about 70.

The standard thickness t of the elastic sleeve is 1.5 mm. Further, the axial length of the elastic sleeve was made to match the surface length of the annular surface. This axial length is approximately equal to the axial length of the free portion of the spring (the axial length of three turns). The inner diameter of the elastic sleeve was approximately 5% smaller than the outer diameter of the spring (free portion) in the free state.

The elastic sleeve formed in this manner is stretched in the radial direction so that the outer circumferential surface of the region including the free portion of the spring is radially opposed to the inner circumferential surface (annular surface) of the outer rotating body in the pulley structure. Attached (covered) to the part. The pulley structure of Example 2 was completed by sequentially assembling each member including the spring fitted with this elastic sleeve.

<Comparative example 1>
The pulley structure of Comparative Example 1 is obtained by omitting the elastic sleeve from the pulley structure of Example 2 described above. Therefore, the configuration of the coil spring in the pulley structure of Comparative Example 1 is the same as the configuration of the coil spring in the pulley structures of Examples 1 and 2.

[Engine cold start test]
An engine cold start test was conducted on the pulley structures of Examples 1 and 2 and Comparative Example 1 using an engine bench tester 200 shown in FIGS. 12 and 13. This engine cold start test is an actual machine bench test in which excessive torque is input to the outer rotating body of the pulley structure through the belt, and engine rotational fluctuations can be maximized to ensure the locking mechanism operates. be done. Here, engine cold starting is a form of engine starting, and specifically refers to starting the engine when the engine is completely cold (for example, the engine cooling water temperature is 30°C or lower). Refers to starting. Therefore, starting the engine from a state where the engine is temporarily stopped (idling stop, etc.) while driving (after warming up) is excluded from this test condition.

The engine bench testing machine 200 is a testing device that includes an auxiliary drive system, including a crank pulley 201 attached to a crankshaft 211 of an engine 210, an AC pulley 202 connected to an air conditioner compressor (AC), and a water pump. (WP) and a WP pulley 203 connected to the WP pulley 203. The pulley structures 100 of Examples 1 and 2 and Comparative Example 1 are connected to a shaft 221 of an alternator (ALT) 220. Further, an auto tensioner (A/T) 204 is provided between the belt spans of the crank pulley 201 and the pulley structure 100. The engine output is transmitted clockwise from the crank pulley 201 to the pulley structure 100, WP pulley 203, and AC pulley 202 via one belt (V-ribbed belt) 250, and is transmitted to each auxiliary machine ( (alternator, water pump, air conditioner/compressor) are driven.

In addition, as shown in FIG. 13, a touch pulley 205 with a sensor (strain gauge) (not shown) for measuring dynamic belt tension attached to the mounting shaft is temporarily installed between the belt spans on the tension side of the belt system. ing. The sensor (strain gauge) is connected to a PC (personal computer) via a bridge box, strain amplifier, and data logger (not shown). By doing this, the belt tension (dynamic belt tension) while the belt 250 is running can be continuously measured, and the maximum dynamic belt tension (maximum value of dynamic belt tension) (N/belt) can be measured continuously. This can be read from the data of time-series changes in belt tension.

In the engine cold start test, the dynamic belt maximum tension (N/belt), the presence or absence of failures in the pulley structure (in particular, abnormalities such as deformation or damage to the elastic sleeve, abnormalities in the mounting state of the elastic sleeve (lifting, slippage, etc.), The three evaluation items were the presence or absence of the locking mechanism (e.g.), and the level of impact noise when the locking mechanism was activated.

The engine cold start test was conducted using the following test method.
That is, the engine cold start was repeated five times every other day at an ambient temperature of about 0° C. (the test machine was installed in a low-temperature chamber) and a belt tension of 400 N. The reason for doing this every other day is to ensure that the engine is started when it is completely cold. The engine operation time (time from start to stop) per operation was 10 seconds. To confirm when the engine was started, the magnitude of the impact sound when the lock mechanism was activated was confirmed by human hearing (standing position: 1 m in front of the belt system).

The maximum dynamic belt tension (maximum value of dynamic belt tension) (N/belt) was read from the data on the time-series change in dynamic belt tension. FIGS. 14 to 16 show the time-series changes in dynamic belt tension of each of the pulley structures of Examples 1 and 2 and Comparative Example 1 at engine cold start.

Below, events in chronological order will be shown using the graph of FIG. 16 as an example.
・0 seconds: Engine start (switch ON)
・Beyond 0 seconds to 0.6 seconds before: Cranking ・0.6 seconds (engine ignition) to 0.625 seconds (at maximum belt tension): 1st explosion (first explosion) section, belt tension increases excessively (skyrocketing). Engine rotation fluctuations are maximized. During this time, the locking mechanism is activated and becomes locked.
・Over 0.625 seconds to 0.65 seconds: After the first explosion (initial detonation) is completed, the belt tension suddenly decreases. During this period, the lock state will be released.
・Over 0.65 seconds to 10 seconds (engine stopped) (switch OFF): Idle operation section. The engine rotational fluctuations converge and the locking mechanism does not operate.

As an example (guideline) of user requirements, based on past technology accumulation and empirical rules, the pulley structures of Examples 1 and 2 and Comparative Example 1 (number of rib grooves on the pulley: 6) should be used in the accessory drive belt system. When applied, the upper limit of the dynamic belt maximum tension (N/belt) is 2100N/belt (350N / rib × number of ribs 6). Therefore, when the dynamic belt maximum tension (N/belt) is 2100 N/belt or less, it is assumed that there is no risk of impairing the durability of the belt system, and the evaluation is ``○''. When the dynamic belt maximum tension (N/belt) exceeds 2100 N/belt, the durability of the belt system is likely to be impaired, and the evaluation is given as ×.

In addition, for each pulley structure 100, after the test is completed, the pulley structure is disassembled and visually inspected for failures in the pulley structure, such as the condition of the elastic sleeve (presence of abnormalities such as deformation, damage, lifting, and displacement). confirmed.

The results of the above three evaluation items are shown in Table 2 below.

As shown in Table 2, the maximum dynamic belt tension when applied to an actual engine (auxiliary drive belt system) is at the level of the conventional (Comparative Example 1) pulley structure without an elastic sleeve (6 ribs). The pulley structure of Examples 1 and 2 suppresses the pressure to a level that is approximately 25% smaller (approximately 1970N for a belt with 6 ribs) than that for a belt (2560N), and that level is lower than that at the initial stage of use. However, it can be seen that the level satisfies the user's requirements (2100N or less for a belt with 6 ribs). The difference in level between Example 1 and Example 2 (about 20 N/belt at the median) is because the spring is deformed to expand its diameter, and the free part of the spring is connected to the outer rotor through the elastic sleeve. This is thought to be due to the difference in whether or not the elastic sleeve slightly expands in the direction in which its thickness decreases until they come into contact with each other.

As described above, according to the configurations of Examples 1 and 2, the locking mechanism is relatively simple (the design can be easily changed without making any major changes to the basic configuration of the conventional (comparative example 1)). During operation, the belt tension (dynamic belt tension) can be prevented from increasing excessively to a level that does not pose a risk of impairing the durability of the belt system.

Further, as shown in Table 2, in both Examples 1 and 2 and Comparative Example 1, there was no failure of the pulley structure. The impact noise during the operation of the locking mechanism could not be confirmed in the pulley structures of Examples 1 and 2, but could be confirmed in Comparative Example 1, although it was slight. Therefore, it can be seen that the configurations of Examples 1 and 2 also have the effect of reducing impact noise when the lock mechanism is activated.

1 Pulley structure 2 Outer rotating body 2a Pressure contact surface 3 Inner rotating body 4 Coil spring 4d Free portion 6,106 Elastic sleeve 10 Lock mechanism

Claims (2)

a cylindrical outer rotating body around which the belt is wound;
an inner rotating body that is provided inside the outer rotating body in a radial direction and is rotatable relative to the outer rotating body about the same rotation axis as the outer rotating body;
a coil spring disposed between the outer rotating body and the inner rotating body,
The coil spring transmits torque between the outer rotating body and the inner rotating body when it is torsionally deformed in the direction of diameter expansion, and transmits torque between the outer rotating body and the inner rotating body when it is torsionally deformed in the direction of diameter contraction. Cutting off torque transmission between the rotating body and
Due to the expansion of the diameter of the coil spring, when the free portion of the coil spring is excessively torsionally deformed in the diametrically expanding direction, further torsional deformation of the coil spring in the diametrically expanding direction is restricted, and the outer rotating body and the In a pulley structure having a locking mechanism in which an inner rotating body rotates integrally with the coil spring,
further comprising an elastic sleeve provided between the outer rotating body and the coil spring,
Due to the diameter expansion of the coil spring, the free portion of the coil spring comes into contact with the outer rotating body via the elastic sleeve,
When the locking mechanism operates, the elastic sleeve is compressively elastically deformed in the radial direction, and
The elastic sleeve contacts a portion of the inner circumferential surface of the outer rotor that faces the free portion of the coil spring in the radial direction when the outer rotor and the inner rotor are not rotating;
A convex portion is provided on the outer peripheral surface of the elastic sleeve,
A pulley structure, characterized in that the inner circumferential surface of the outer rotating body is provided with a recess that can fit into the projection. The pulley structure according to claim 1 , wherein the elastic sleeve is made of synthetic rubber.

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