[0001]The present invention relates to a pulley structure with a coil spring.
BACKGROUND
[0002]In the accessory drive unit by the power of the engine of an automobile or the like for driving the auxiliary machine of the alternator or the like, a pulley connected to auxiliary drive shaft, such as an alternator, a belt over pulley multiplied passed to be connected to the crankshaft of the engine is, the torque of the engine through the belt is transferred to the auxiliary machine. In particular, the pulley connected to the alternator drive shaft having a large inertia than that of other auxiliary devices, can absorb rotational fluctuation of the crankshaft, for example, a pulley structure of Patent Documents 1 to 3 is used.
[0003]
　Pulley structure described in Patent Documents 1 to 3, the outer rotation body, a pulley structure consisting of an inner rotary body and a coil spring which can rotate relative to the and the outer rotary member is provided inside the outer rotary member , so that the torque between the outer rotor and the inner rotary member is transmitted or blocked by enlarged or shrink deformation of the coil spring. These pulleys structures to prevent damage due to diameter expansion deformation of the coil spring, when the outer peripheral surface of the free portion of the coil spring is in contact with the outer rotation body, more expanded deformation of the coil spring is restricted is, has a mechanism of two rotating bodies rotate integrally with the coil spring (hereinafter, referred to as locking mechanism.). Further, the coil spring of the pulleys structures, to prevent slippage of the belt wound around the outer rotary member, for transmitting or interrupting torque in one direction between the outer rotor and the inner rotation body in one direction functions as a clutch (coil spring clutch).
[0004]
　In the pulley structure described in Patent Documents 1 to 3, the cross-sectional shape of the spring wire of the coil spring (hereinafter, the spring cross section) Focusing on, from each of the illustrated, Patent Document 1 square shape, in Patent Documents 2 and 3 embodiments seen a trapezoidal shape. In Patent Documents 2 and 3, as the cross-sectional shape of a coil spring, albeit references to rectangular (square) shape, references to trapezoidal shape (adoption Reason-basis) is not found.
CITATION
Patent Document
[0005]
Patent Document 1: Japanese Patent 2014-114947 JP
Patent Document 2: Japanese Kohyo 2013-527401 JP
Patent Document 3: U.S. Patent Application Publication No. 2013/0237351 Pat
Summary of the Invention
Problems that the Invention is to Solve
[0006]
　In a pulley structure for transmitting or interrupting torque between the outer rotary member and the inner rotary member by enlarged or reduced in diameter of the coil spring, the coil spring, diameter direction of the torsional deformation (hereinafter, enlarged deformation) and maximizing the (corresponding torsion angle locking mechanism works) is excessively repeated, the bending stress generated in the surface of the coil spring (particularly the inner peripheral surface) tensile force is applied, the surface of the coil spring (particularly an inner peripheral surface) there is a risk that such cracks and fractures occur in. Therefore, as compared with the case where expanded deformation of the coil spring is not repeated excessively, resistance to torsion of the coil spring (diameter direction and diameter direction of the torsional deformation) is reduced. In particular, when the pulley structure of the alternator pulley is torsion torque is high frequency of the maximum is input to the pulley. Thus, in particular, in the case pulley structure of the alternator pulley when the operating conditions enlarged deformation and maximize coil spring is excessively repeated, the durability is most lowered against torsion coil spring tends . The torsional torque is input to the alternator pulley, specifically, the torsional torque caused by the rotational fluctuation of the engine, and the torsional torque accompanying the power generation load of the alternator, further, generated during starting and rapid acceleration or deceleration of the engine it is considered to be instantaneous torsional torque or the like. Most reduced likely operating conditions resistance to torsion of the coil spring is a time of starting the engine. In other words, the most lowered likely operating conditions resistance to torsion of the coil spring is a operating condition starting and stopping of the engine is repeated.
[0007]
　By increasing the number of turns and wire diameter of the coil spring, although the durability of the coil spring is increased, the pulley structure is increased in size, difficult to arrange in a limited space in the engine accessory drive system to become. Therefore, the pulley structure, frequently torsional torque is maximum is applied to a high alternator pulley is input, diameter variations and maximize coil spring excessive by operating conditions starting and stopping of the engine is repeated be repeated also, without increasing the size of the pulley structure, it is required that can ensure the durability against torsion coil spring.
[0008]
　The one-way clutch (coil spring) when the inner rotation body rotates relatively in the forward direction relative to the outer rotary member, engages the respective outer rotating body and the inner rotation body, an outer rotor and an inner rotary body while transmitting torque between, when the inner rotation body rotates relatively in the opposite direction to the outer rotary member, become disengaged, sliding relative to the outer rotary member and / or inner rotation body (slip) and it does not transmit torque between the outer rotor and inner rotor. By the sliding, in particular, the portion which slides a clutch (coil spring) in the outer rotating member and / or inner rotating body is worn. Further, by the slide, it can be worn portion slides on the outer rotating body and / or the inner rotating member in the clutch (coil spring). When the portion that slides the clutch (coil spring) in the outer rotating member and / or inner rotary member is worn, when the clutch is in the engaged state, the contact surface pressure between the clutch and the outer rotary member and / or inner rotary body by decreasing the torque value to be transmitted is reduced.
[0009]
　The present invention has been made in view of the above problems, also enlarged deformation and maximize coil spring is excessively repeated, without increasing the size of at least the rotation axis direction to the pulley structure, it is possible to secure durability against torsion coil spring, the wear of the coil spring and the sliding portion can be suppressed in the outer rotating member and / or inner rotating member, it is to provide a pulley structure.
Means for Solving the Problems
[0010]
　Pulley structure of the present invention, the center and the outer rotary member cylindrical belt is wound, is provided inside the outer rotary member, the same rotation axis and said outer rotary member relative to the outer rotary member as an inner rotary member rotatable relative, a coil spring provided between the inner rotor and the outer rotary member, a pulley structure provided with, of the coil spring by the enlarged diameter of the coil spring when the outer peripheral surface of the free portion is in contact with the outer rotation body, the torsional deformation of more diameter direction of the coil spring is regulated, integrally the outer rotary member and the inner rotary member and the coil spring has a locking mechanism that rotates, the coil spring, when the inner rotary body is relatively rotated in the forward direction relative to the outer rotary member, by deformed torsion diameter direction, said outer rotary member and said It engages the respective inner rotary member, the outer rotor and the front To transmit torque between the inner rotating body, when the inner rotation body rotates relatively in the opposite direction relative to the outer rotary member, by twisting the diameter direction deformation, rotation the outer rotating body and in the slides with respect to at least one of the body functions as a one-way clutch which does not transmit torque between the inner rotor and the outer rotating member, the spring wire of said coil spring, and through the rotary shaft said rotary shaft section along the direction parallel a trapezoidal rotary axis direction length of the cross-section definitive inner diameter side portion Ti [mm] is the rotation axial length of the radially outer portion in the cross to [mm] longer than, the number of turns of the coil spring when the N, satisfies the following formula (1).
　　N × (Ti-To) / 2 <1 ··· (1)
[0011]
　Spring wire of the coil spring is a trapezoidal wire in cross section a trapezoidal shape, the rotation axis direction length Ti of the inner diameter side portion enlarged deformation (diameter direction of the torsional deformation) at a tensile force acts, diameter variations sometimes longer than the rotational axial length to of the outer diameter side portion compressive force is exerted. Thereby, the spring wire cross-sectional area present invention equal round wire (cross section circular spring wire) or cross-sectional area and radial length of the present invention with equal angular line (cross section square or rectangular as compared with the case where a spring wire), the cross section of the spring wire, tension also neutral axis that does not undergo compression, can be close to the inner circumferential surface of the coil spring tension acts upon diameter variations. Bending stress is proportional to the distance from the neutral axis, that closer to the inner peripheral surface of the coil spring tension acts a neutral axis when expanded deformation, the inner peripheral surface of the coil spring tension acts upon diameter variations It can reduce the maximum value of the bending stress occurring.
　Further, by the spring wire is trapezoidal wire cross-sectional area is equal round wire or cross-sectional area and radial length as compared with the same rectangular wire, can be increased section modulus. The larger section modulus, bending stress is reduced. Therefore, as compared with the case where the cross-sectional area of the spring wire is equal round wire or cross-sectional area and radial length is equal rectangular wire, the bending stress generated in the inner peripheral surface of the coil spring tension acts upon diameter variations the maximum value can be further reduced.
　Thus, the operating conditions starting and stopping of the engine is repeated, compared to the case diameter variations and maximize coil spring is excessively repeated, the spring wire cross-sectional area which is equal round wire or a rectangular wire , it can be suppressed maximum value of bending stress generated in the surface of the coil spring (particularly the inner peripheral surface) of tensile force acts upon diameter variations. Thereby, the instantaneous torsional strength for the torque and strength (flexural rigidity) increases occur starting or the like, it is possible to increase the limit value of the twist angle of the enlarged diameter direction of the coil spring. Hence, it is possible to ensure the durability against torsion coil spring.
[0012]
　Spring wire of trapezoidal wire cross-sectional area and radial length as compared with the same axial length are different rectangular wire, the length of the rotation axis direction is longer by (Ti-To) / 2. Therefore, as compared with the case where the cross-sectional area and radial length of the spring wire are equal axial length is different from rectangular wire, the natural length of the rotation axis direction of the coil spring, ΔL (ΔL = N × ( Ti-To ) / 2) only becomes long.
　However, in the present invention, increase [Delta] L of the natural length in the rotation axis direction of the coil spring (ΔL = N × (Ti- To) / 2) is smaller and less than 1 mm. Therefore, when incorporating the coil spring on the pulley structure, adjusting the amount of compression in the axial direction of the coil spring (i.e., the gap between the spring wire adjacent to the rotation axis direction adjustment) is to be, the cross-sectional area of the spring wire and as compared with the case where the radial length equal axial length and different rectangular wire, it is not necessary to enlarge the pulley structure in the rotation axis direction.
　Therefore, the pulley structure of the present invention also expanded deformation and maximize coil spring is excessively repeated, without increasing the size of at least the rotation axis direction to the pulley structure, durability against torsion coil spring sex can be ensured.
[0013]
　Coil spring is formed by winding (coiling) the spring wire helically. After coiling, the outer diameter side portion in the cross section of the spring wire (surface on the outer diameter side) is slightly with respect to the central axis parallel to the outer diameter reference line of the coil spring (e.g. 1 °) an inclined surface inclined phenomenon ( below, the strands fall that.) may occur. Falling strands of the coil spring becomes higher oblateness of the spring wire of the coil spring (radial length W of the axial length T / spring wire of the spring wire) is less large. Therefore, by the spring wire and trapezoidal wire cross-sectional area and radial length equal axial length different angular lines as compared with the case of the spring wire, the maximum length in the rotation axis direction in the cross section of the spring wire is is long, it is possible to suppress the fallen wires.
　Further, by the rotation axial length Ti of the inner diameter side portion is longer than the axial direction length To of the outer diameter side portion, in the cross section of the spring wire, the tensile stress is not generated even compressive stress neutral axis, radially the center, close to the long inner diameter side portion of the rotational axial length. As a result, it is possible to further suppress the fallen wires.
　By suppressing the falling strands, during disengagement of the one-way clutch, the surface pressure acting on the coil spring and the sliding part of the outer rotating member and / or inner rotating body is reduced. Therefore, it is possible to suppress the wear of the coil spring and the sliding part of the outer rotating member and / or inner rotor.
[0014]
　By the above, also enlarged deformation and maximize coil spring is excessively repeated, without increasing the size of at least the rotation axis direction to the pulley structure, it is possible to secure durability against torsion coil spring, the outer the wear of the coil spring and the sliding portion can be suppressed in the rotating body and / or the inner rotating body, it can be realized pulley structure.
[0015]
　In the present invention, the cross section of the spring wire is to be a trapezoidal shape, the four corners in the cross section of the spring wire comprises a case which is chamfered (C plane or R plane).
[0016]
　In the pulley structure of the present invention, the spring wire of said coil spring, it radial length of the cross section is longer than the rotation axis direction length Ti of the inner diameter side portion in the cross-section is preferred.
[0017]
　According to this configuration, the cross-sectional shape of the spring wire rod, the radial length W is compared with the case trapezoidal equal short or equal and cross-sectional area than Ti rotational axial length of the inner diameter side portion is section modulus growing. Therefore, bending from the relationship between the stress and the section modulus (bending stress sigma = bending moment M / section modulus Z), further reduce the maximum value of the bending stress generated in the inner peripheral surface of the coil spring tension acts upon diameter variations it can. As a result, the easier to ensure durability against torsion coil spring.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
[1] Figure 1 is a cross-sectional view of a pulley structure of an embodiment of the present invention.
FIG. 2 is a sectional view taken along line II-II of Figure 1.
FIG. 3 is a sectional view taken along line III-III in FIG.
[4] FIG. 4 is a graph showing the relationship between torsional torque and torsional angle of the torsion coil spring of the pulley structure shown in FIG.
FIG. 5 is a graph showing the relationship between torsional torque and the maximum principal stress.
FIG. 6 is a schematic configuration diagram of an engine bench test machine used in the test of Example.
DESCRIPTION OF THE INVENTION
[0019]
　The following describes the pulley structure 1 of an embodiment of the present invention.
　Pulley structure 1 of the present embodiment, an automobile accessory drive system (not shown) is installed in the alternator drive shaft. Incidentally, the pulley structure of the present invention may be installed in the auxiliary machine driving shaft other than the alternator.
[0020]
　As shown in FIGS. 1 to 3, the pulley structure 1, the outer rotary member 2, the inner rotary body 3, the coil spring 4 (hereinafter, simply referred to as. "Spring 4 ') and a end cap 5. Hereinafter, describing the left in FIG. 1 forward, rightward as the rear. The end cap 5 is disposed at the front end of the outer rotary member 2 and the inner rotor 3.
[0021]
　Outer rotary member 2 and the inner rotor 3 are both generally cylindrical, with the same rotation axis. The rotation axis of the outer rotating member 2 and the inner rotor 3 is a rotary shaft of the pulley structure 1, hereinafter, simply referred to as "rotation axis". Further, the rotation axis direction, simply referred to as "axial direction". The inner rotor 3 is provided inside the outer rotary member 2 is rotatable relative to the outer rotary member 2. The outer peripheral surface of the outer rotating body 2, the belt B is wound.
[0022]
　The inner rotary body 3 has cylindrical body 3a, and the outer cylindrical portion 3b located outside the front end of the cylindrical body 3a. A cylindrical body 3a, is fitted a drive shaft S such as an alternator. Between the outer tube portion 3b and the cylindrical body 3a, the support groove 3c is formed. The outer peripheral surface of the inner peripheral surface and the cylindrical body 3a of the outer tube portion 3b are connected through a groove bottom surface 3d of the support groove 3c.
[0023]
　And the inner surface of the rear end of the outer rotating body 2, between the outer peripheral surface of the cylindrical body 3a, the rolling bearing 6 is interposed. And the inner surface of the front end of the outer rotating body 2, between the outer peripheral surface of the outer tube portion 3b, the sliding bearing 7 is interposed. By bearings 6,7, the outer rotary member 2 and the inner rotor 3 is relatively rotatably coupled.
[0024]
　A space between the inner rotor 3 and the outer rotary member 2, in front of the rolling bearing 6, an annular thrust plate 8 is disposed. The thrust plate 8 is fixed to the inner rotary body 3 rotates the inner rotor 3 and integrally. When assembling the pulley structure 1, the thrust plate 8, the order of the rolling bearing 6 is fitted to the cylindrical body 3a.
[0025]
　A space between the inner rotor 3 and the outer rotary member 2, the forward of the thrust plate 8, a space 9 is formed. In the space 9, the spring 4 is accommodated. Space 9, the inner peripheral surface of the inner peripheral surface and the outer cylindrical portion 3b of the outer rotating body 2, is formed between the outer peripheral surface of the cylindrical body 3a.
[0026]
　Inner diameter of the outer rotary member 2 is smaller in two steps toward the rear. The inner peripheral surface of the outer rotating body 2 in the small inner diameter of the inner peripheral surface of the outer rotating body 2 to the pressure contact surface 2a, 2 th of the annular surface 2b of the smallest inner diameter. Inner diameter of the outer rotary member 2 in the contact face 2a is smaller than the inner diameter of the outer tube portion 3b. Inner diameter of the outer rotary member 2 in the annular surface 2b is equal to or greater than the inner diameter of the outer tube portion 3b.
[0027]
　Cylindrical body 3a has an outer diameter is greater at the front end. That the outer peripheral surface of the inner rotor 3 contact surface 3e in this portion.
[0028]
　The spring 4 is a torsion coil spring formed spring wire (spring wire) by winding (coiling) spirally. The spring 4 is a left-handed (counterclockwise toward the rear end from the front end). The number of turns N of the spring 4 is, for example, 5-9 turns. In the following description, the cross-section or cross-sectional shape of the spring wire, is that the cross section or cross-sectional shape along the street a rotation axis and parallel to the rotational axis direction. Spring wire of the spring 4, a trapezoidal line of cross section trapezoidal. Four corners in the cross section of the spring wire is chamfered shape (eg, R surface curvature radius of about 0.3 mm, or, C-plane) has become. The axial length of the section definitive inner diameter side portion of the spring wire, and the inner diameter side axial length Ti [mm]. The axial length of the section definitive radially outer portion of the spring wire, and the outer diameter side axial length To [mm]. The inner diameter side axial length Ti [mm] is longer than the outer diameter side axial length To [mm]. The number of turns N of the spring 4, the inner diameter side axial length Ti [mm], and the outer diameter side axial length the To [mm] satisfies the following formula (1).
　　N × (Ti-To) / 2 <1 ··· (1)
[0029]
　Spring 4, in a state where no external force is applied, a diameter over the entire length is constant. The outer diameter of the spring 4 in a state where no external force is applied is greater than the inner diameter of the outer rotary member 2 in the contact face 2a. Spring 4, with the rear end region 4c has a reduced diameter, is accommodated in the space 9. The outer peripheral surface of the rear end region 4c of the spring 4, by the self elastic restoring force of the enlarged diameter direction of the spring 4, is pressed against the contact face 2a. Rear end region 4c is an area of ​​more than one turn from the rear end of the spring 4 (360 ° or more around the rotation axis).
[0030]
　Further, a pulley structure 1 is stopped, in the state in which the outer peripheral surface of the rear end region 4c of the spring 4 is pressed against the contact face 2a by the self elastic restoring force of the enlarged diameter direction of the spring 4, the front end of the spring 4 side regions 4b is in a state of being slightly enlarged in contact with the contact surface 3e. That is, in a state where the pulley structure 1 is stopped, the inner peripheral surface of the front end side region 4b in the spring 4 is pressed against the contact surface 3e. Front end area 4b is an area of ​​more than one round from the front end of the spring 4 (360 ° or more around the rotation axis). In a state where external force to the pulley structure 1 is not acting, the spring 4, the diameter over the entire length is substantially constant.
[0031]
　Spring 4, in a state in which the external force to the pulley structure 1 is not applied (i.e., a state where the pulley structure 1 is stopped), is compressed in the axial direction, the axial end face of the front end region 4b of the spring 4 circumferential portion (or half from the front end) is in contact with the groove bottom surface 3d of the inner rotary body 3, the circumferential portion of the axial end face of the rear end region 4c of the spring 4 (or half from the rear end) of the thrust plate It is in contact with the front of the 8. Axial compressibility of the coil spring 4, for example, may be about 20%. Note that the axial compressibility of the coil spring 4, the ratio of the axial length of the spring 4 in a state where an external force to the pulley structure 1 is not applied, the natural length of the spring 4.
[0032]
　Groove bottom surface 3d is formed in a spiral shape so as to be in contact with a portion of the axial end surface of the front end region 4b (or half from the front end). Further, the front face of the thrust plate 8 is formed in a spiral shape so as to be in contact with a portion of the axial end surface of the rear end region 4c (or half from the rear end).
　A groove bottom surface 3d of the support groove 3c, and the circumferential portion of the axial end face of the front end region 4b of the coil spring 4, apparently, but the whole circumferential direction is in contact, in practice, the machining tolerance of the parts , there is a generation of a gap in a part of the circumferential direction. Aim of the gap is zero, depending on the combination of the finished record size in the part tolerances, the gap is dimensioned in consideration of the machining tolerances of the parts (nominal dimensions) (e.g., target value of the axial clearance 0.35mm). Clearance is as close as possible that the zero, the spring 4 can be stably torsional deformation.
[0033]
　As shown in FIG. 2, of the front end region 4b, the front end second region 4b2 near position apart 90 ° around the rotation axis from the spring 4, the front end portion than the second region 4b2 first region 4b1 the remaining portion of the third region 4b3. The region between the front end region 4b and the rear end region 4c of the spring 4, i.e., a region that does not contact with any of the contact face 2a and the contact surface 3e, and the free portion 4d.
[0034]
　As shown in FIG. 2, the front end portion of the inner rotary body 3, contact surface 3f facing the front end surface 4a of the spring 4 is formed. The inner circumferential surface of the outer cylindrical portion 3b, the outer peripheral surface opposite to the protrusion 3g of the front end region 4b protrudes radially inward of the outer tube portion 3b is provided. Projections 3g is opposed to the second region 4b2.
[0035]
　Next, the operation of the pulley structure 1.
[0036]
　First, when the rotational speed of the outer rotating body 2 is greater than the rotational speed of the inner rotor 3 (i.e., when the outer rotary member 2 is accelerated) will be described.
[0037]
　In this case, the outer rotary body 2 is relatively rotated in the positive direction relative to the inner rotary body 3 (arrow direction in FIG. 2 and FIG. 3). With the relative rotation of the outer rotating body 2, the rear end region 4c of the spring 4 is moved together with the pressing surface 2a, it rotates relative to the inner rotor 3. Thus, the spring 4 is torsionally deformed in the diameter direction (hereinafter, simply referred to as enlarged deformation.) To. Pressing force against contact face 2a of the rear end region 4c of the spring 4 increases as the torsion angle of the enlarged diameter direction of the spring 4 is increased. The second region 4b2 is most likely to undergo torsional stress and torsional angle of the enlarged diameter direction of the spring 4 is increased, away from the contact surface 3e. The first region 4b1 and the third region 4b3 is pressed against the contact surface 3e. Substantially simultaneously with the second region 4b2 is separated from the contact surface 3e, or when the twist angle of the diameter expansion direction of the spring 4 is further increased, the outer circumferential surface of the second region 4b2 abuts against the protrusion 3g. By the outer circumferential surface of the second region 4b2 abuts against the protrusion 3g, is restricted diameter deformation of the front side region 4b, torsional stress is dispersed in a portion other than the front end side region 4b of the spring 4, particularly after the spring 4 torsional stress increases acts on the end side region 4c. Thus, the difference between the torsional stress acting on each portion of the spring 4 is reduced, since it is possible to absorb the strain energy throughout the spring 4, thereby preventing localized fatigue failure of the spring 4.
[0038]
　Also, pressure contact force against the contact surface 3e of the third region 4b3 decreases as the twist angle of the enlarged diameter direction of the spring 4 is increased. At the same time the second region 4b2 abuts against the protrusion 3g, or, when the twist angle of the diameter expansion direction of the spring 4 is further increased, the contact pressure to the contact surface 3e of the third region 4b3 becomes substantially zero. The twist angle of the diameter expansion direction of the spring 4 at this time .theta.1 (e.g., θ1 = 3 °) to. When twist angle of the enlarged diameter direction of the spring 4 exceeds .theta.1, third region 4b3, by expanding the diameter deformed, moving away from the contact surface 3e. However, in the vicinity of the boundary between the third region 4b3 and the second region 4b2, rather than the spring 4 is curved (bent), the front end side region 4b is maintained in a circular arc shape. In other words, the front end side region 4b is maintained easily shaped slide relative to the protrusion 3g. Therefore, when the twist angle of the enlarged diameter direction of the spring 4 is torsional stress increases acts on the front end side region 4b becomes large, the front-side region 4b is contact pressure and the first region 4b1 for projection 3g of the second region 4b2 against the pressure contact force against the contact surface 3e, slides in the circumferential direction of the outer rotary member 2 relative to the protrusion 3g and contact surfaces 3e. By the front end surface 4a presses the abutment surface 3f, can be reliably transmit torque between the inner rotor 3 and the outer rotary member 2.
[0039]
　Incidentally, twist angle θ1 or more and .theta.2 of the enlarged diameter direction of the spring 4 (e.g., θ2 = 45 °) of less than, the third region 4b3 is on the inner peripheral surface of spaced and the outer cylinder portion 3b from the contact surface 3e not in contact, the second region 4b2 is pressed against the protrusion 3g. Therefore, in this case, as compared with the case twist angle of the enlarged diameter direction of the spring 4 is less than .theta.1, increasing the effective number of turns of the spring 4, the spring constant (slope of a straight line shown in FIG. 4) is small. Further, when the twist angle of the enlarged diameter direction of the spring 4 is .theta.2, that the outer peripheral surface of the free portion 4d of the spring 4 abuts against the annular surface 2b, is restricted further expanded deformation of the spring 4, the outer rotary member 2 and the inner rotor 3 acts lock mechanism to rotate integrally. This can prevent damage due to diameter expansion deformation of the spring 4.
[0040]
　Then, when the rotational speed of the outer rotary member 2 is smaller than the rotational speed of the inner rotor 3 (i.e., when the outer rotary member 2 is decelerated) will be described.
[0041]
　In this case, the outer rotary body 2 is relatively rotated in the reverse direction relative to the inner rotary body 3 (arrow direction opposite to the direction in FIGS. 2 and 3). With the relative rotation of the outer rotating body 2, the rear end region 4c of the spring 4 is moved together with the pressing surface 2a, it rotates relative to the inner rotor 3. Thus, the spring 4 is deformed torsion direction of reducing the diameter (hereinafter, simply referred to as shrink deformation). Diameter direction of the torsion angle of the spring 4 is .theta.3 (e.g., θ3 = 10 °) of less than, pressing force for pressing surface 2a of the rear end region 4c, although twist angle slightly lower than that of the zero , rear end region 4c is pressed against the contact face 2a. Also, pressure contact force against the contact surface 3e of the front end region 4b is twist angle slightly increased as compared with the case of zero. If twist angle of diameter reduction direction of the spring 4 is θ3 above, contact pressure against the contact face 2a of the rear end region 4c becomes substantially zero, periphery of the outer rotary member 2 at the rear side region 4c against contact face 2a slides in the direction. Therefore, no transmitted torque between the inner rotor 3 and the outer rotary member 2 (see FIG. 4).
[0042]
　Thus, the spring 4 is a coil spring clutch, which functions as a one-way clutch for transmitting or interrupting the torque in one direction. Spring 4, the inner rotary body 3 and the inner rotor 3 and the outer rotary member 2 engages the respective outer rotary member 2 and the inner rotor 3 when the relative rotation in the forward direction relative to the outer rotary member 2 while transmitting torque between, (in this embodiment, contact face 2a) at least one of the outer rotary member 2 and the inner rotor 3 when the inner rotor 3 rotate relative to the opposite direction with respect to the outer rotary member 2 to It does not transfer torque between the inner rotor 3 and the outer rotary member 2 slides against.
[0043]
　The thrust plate 8 is integrally rotated with the inner rotor 3. Therefore, during disengagement of the clutch, target slide of the spring 4 is merely contact face 2a, an axial end surface of the spring 4 does not slide relative to thrust plate 8. Patent Document 1 described above, during disengagement of the clutch, not only the pressure contact surface of the coil spring and the outer rotor and the (inner peripheral surface) slides, a spring seat axial end face of the outer rotating body of the coil spring to slide with respect to the surface. In this case, amount that is compressed in the coil Banegajiku direction, wear of the spring seat surface is progressed more than the degree of wear of the contact face and can lead to failure such as breakage of the spring seat surface. In contrast, the present embodiment, at the time of disengagement of the clutch, for the axial end surface of the spring 4 does not slide relative to thrust plate 8, as compared with the spring seat surface of the Patent Document 1, the wear of the thrust plate 8 the greatly suppressed, thereby suppressing failure due to wear.
　Also, thrust plate 8 does not spring 4 and the sliding during disengagement of the clutch, which is either a separate part which varies the inner rotor 3 and the outer rotary member 2. Therefore, the thrust plate 8, dare may not subjected to surface hardening treatment. Moreover, in the case of applying the surface hardening treatment to the thrust plate 8 is easily subjected to another part because surface hardening, the surface hardness of the thrust plate 8 reliably increased, thereby imparting wear resistance due to contact with the spring 4 be able to.
[0044]
　It will now be described cross section characteristics of the spring wire of the coil spring.
　When the coil spring is torsionally deformed in the cross section of the spring wire, tensile stress of the neutral axis position not subject to compressive stress. Neutral axis of trapezoidal wire is closer to the long side of the center of the height direction. Distance e round wire (cross section circular spring wire), a rectangular wire (cross section square or rectangular spring wire), and a trapezoidal wire neutral axis to the surface is expressed by the following equation.
[0045]
　Round wire: e = d / 2
　　　(where, d: diameter)
　square wire: e = h / 2
　　　(where, h: height)
　trapezoidal wire: e1 = (3b1 + 2b2) H / 3 (2b1 + b2), e2 = H- e1
　　　　(where, b1: short side length, b2: the difference between the long and short sides, H: height, e1> e2)
[0046]
　The distance from the neutral axis y, the bending moment M, the second moment and I, the bending stress σ generated in the coil spring, the formula: is proportional to the distance y from the neutral axis.
　　σ = M · y / I
　Therefore, the maximum principal stress which is durable indicator for torsion of the coil spring (the maximum value of the bending stress), the y occurs in the spring surface that acts becomes maximum tensile force.
[0047]
　The distance e from the neutral axis to the spring surface, round wire with the same cross-sectional area A, the rectangular wire, compared with trapezoidal wire. The cross-sectional area A = 100. For round wire, because the d = 11.284, a e = d / 2 = 5.642. For the rectangular wire, when h = 10, a e = h / 2 = 5.0. For trapezoidal wire, H = 10 (the same height as the rectangular wire), when b1 + b2 = 12, b1 = 8, b2 = 4 since, e1 = (3b1 + 2b2) H / 3 (2b1 + b2) = 5.33, e2 = the H-e1 = 4.67. Therefore, the distance e from the neutral axis to the spring surface, round wire having the same cross-sectional area A, the corner line, and among trapezoidal wire, the distance e2 from the neutral axis in the trapezoidal line to a long side surface, the smallest .
[0048]
　Therefore, if the axial length of the inner diameter side portion of the long trapezoidal wire than the axial length of the outer diameter side, as compared to round wire and rectangular wire, a neutral axis that does not occur even tensile stress and compressive stress, expanded deformation sometimes it is possible to approach the inner peripheral surface of the coil spring tensile force acts. As described above, bending stress is proportional to the distance from the neutral axis, that closer to the inner peripheral surface of the coil spring tension acts upon diameter variations among the coil spring tension acts upon diameter variations the maximum value of the bending stress generated in the periphery can be reduced.
[0049]
　Further, the bending stress σ generated in the coil spring, with a bending moment M and section modulus Z, is expressed by the following equation.
　　sigma = M / Z
　Thus, as the section modulus Z is large, the bending stress sigma is reduced. Incidentally, the section modulus, for example, when is under external force bent member, bending ease of members, a value representing the bending difficulty in the (rigid), determined only by the shape of the cross section. Section modulus Z is the distance y from the neutral axis and second moment I, is expressed by the following equation.
　　Z = I / y
　The cross-sectional secondary moment I of trapezoidal wire is expressed by the following equation.
　　I = (6b12 + 6b1b2 + b22 ) H3 / 36 (2b1 + b2)
[0050]
　As described above, the maximum principal stress which is durable indicator for torsion of the coil spring (the maximum value of the bending stress), the distance y from the neutral axis is generated in the spring surface that acts becomes maximum tensile force. That is, in the case of trapezoidal wire of the coil spring, the distance y from the neutral axis of the spring surface which maximum principal stress tensile force acts occurs, the distance e2 from the neutral axis to the long side surface. When the cross-sectional area A = 100, H = 10, b1 + b2 = 12 of trapezoidal wire, by b1 = 8, b2 = 4, e2 = 4.67, I = 822.2, and becomes a Z = 176.
[0051]
　Also, round wire, the section modulus Z of the rectangular wire is expressed by the following equation.
　Round wire: Z = Paidi3 / 32
　　　(where, d: diameter)
　square wire: Z = bh2 / 6
　　　(where, b: width, h: height)
　when the round wire, when the cross-sectional area A = 100, d = 11.284 next, the Z = 141, also in the case of rectangular wire, when the cross-sectional area a = 100, h = 10, b = 10, a Z = 167.
[0052]
　Thus, round wire, rectangular wire, equal cross-sectional area of ​​the trapezoidal line, and, if equal radial length of the rectangular wire and trapezoidal wire, round wire, rectangular wire, in the order of the trapezoidal line, section modulus Z is increased. As described above, as the section modulus Z is large, the bending stress σ is reduced. Thus, round wire, rectangular wire, equal cross-sectional area of ​​the trapezoidal line, and, if equal radial length of the rectangular wire and trapezoidal wire, round wire, rectangular wire, in the order of trapezoidal wire, tensile force at the time of enlarged deformation It can reduce the maximum value of the bending stress generated in the inner peripheral surface of the coil spring acting.
[0053]
　Pulley structure 1 of the present embodiment described above has the following characteristics.
　Spring wire of the coil spring 4 of the present embodiment, the outer cross section a trapezoidal wire of trapezoidal inner diameter side axial length Ti tensile force acts upon the enlarged diameter deformation, the compressive force acts upon diameter variations diameter axial longer than To. Therefore, the spring wire, as compared with the case of the equal angular lines are equal round wire or cross-sectional area and radial length sectional area, in the cross section of the spring wire, the neutral axis without tension nor receive compressed expanded deformation can sometimes closer to the tensile force is applied the inner peripheral surface of the spring 4. Bending stress is proportional to the distance from the neutral axis, that close to the inner circumferential surface of the spring 4 the tensile force acts to the neutral axis during diameter variations, the inner peripheral surface of the spring 4 the tensile force is exerted upon diameter variations It can reduce the maximum value of the bending stress occurring.
　Further, by the spring wire of the spring 4 is trapezoidal wire, as compared to the same rectangular wire is equal round wire or cross-sectional area and radial length sectional area, it can be increased section modulus. The larger section modulus, bending stress is reduced. Therefore, as compared with the case where the cross-sectional area of the spring wire is equal round wire or cross-sectional area and radial length is equal rectangular wire, the tensile force is exerted upon diameter variations of bending stress generated in the inner peripheral surface of the spring 4 the maximum value can be further reduced.
　Thus, the operating conditions starting and stopping of the engine is repeated, also enlarged deformation and maximize spring 4 are excessively repeated, as compared with the case of the spring wire cross-sectional area which is equal round wire or a rectangular wire , it is possible to reduce the bending maximum stress generated on the inner peripheral surface of the spring 4 the tensile force is exerted upon diameter variations. As a result, the instantaneous torsional strength for the torque and strength (flexural rigidity) increases occur starting or the like, it is possible to increase the limit value of the twist angle of the enlarged diameter direction of the spring 4. Hence, it is possible to ensure the durability against torsion spring 4.
[0054]
　Spring wire of trapezoidal wire, as compared to the cross-sectional area and radial length is equal axial length different rectangular wire, the length in the axial direction is longer by (Ti-To) / 2. Therefore, as compared with the case where the cross-sectional area and radial length of the spring wire are equal axial length is different from rectangular wire, natural length in the axial direction of the spring 4, ΔL (ΔL = N × ( Ti-To) / 2) only becomes long.
　However, in this embodiment, increase in the natural length in the axial direction of the spring 4 ΔL (ΔL = N × ( Ti-To) / 2) is smaller and less than 1 mm. Therefore, when incorporating the spring 4 to the pulley structure 1, adjusting the amount of compression in the axial direction of the spring 4 (i.e., the gap between the spring wire adjacent to the axial adjustment) by the cross sectional area of the spring wire and as compared with the case where the radial length equal axial length and different rectangular wire, it is not necessary to enlarge the pulley structure 1 in the axial direction.
　Therefore, the pulley structure 1 of the present embodiment, also enlarged deformation and maximize spring 4 are excessively repeated, without increasing the size of the pulley structure 1 at least in the axial direction, the torsion spring 4 the durability can be secured against.
[0055]
　The spring 4 is formed by winding (coiling) the spring wire helically. After coiling, the outer diameter side portion in the cross section of the spring wire (surface on the outer diameter side) is slightly with respect to the central axis outside diameter reference line parallel to the line of the spring 4 (e.g. 1 °) an inclined surface inclined phenomenon ( below, the strands fall that.) may occur. Wire spring 4 collapse becomes higher oblateness of the spring wire of the spring 4 (radial length W of the axial length T / spring wire of the spring wire) is less large. Therefore, by the spring wire and trapezoidal wire cross-sectional area and radial length equal axial length different angular lines as compared with the case of the spring wire, the maximum length in the axial direction in the cross section of the spring wire becomes longer, it is possible to suppress the fallen wires.
　Further, by the inner diameter side axial length Ti is greater than the outer diameter side axial length To, in the cross section of the spring wire, the neutral axis that does not occur even tensile stress and compressive stress, than the radial center, the axial close to a long inner diameter side portion of the length. As a result, it is possible to further suppress the fallen wires.
　By suppressing the falling strands, during disengagement of the one-way clutch (in the present embodiment, contact face 2a) spring 4 and the sliding parts in the outer rotary member 2 and / or the inner rotor 3 acting surface pressure is reduced. Therefore, it is possible to suppress the wear of the spring 4 and the sliding part of the outer rotary member 2 and / or the inner rotor 3.
[0056]
　By the above, also enlarged deformation and maximize spring 4 are excessively repeated, without increasing the size of the pulley structure 1 at least in the axial direction, it is possible to secure durability against torsion spring 4, the outer the wear of the spring 4 and the sliding portion can be suppressed in the rotating body 2 and / or the inner rotor 3, it can be realized pulley structure 1.
[0057]
　The coil spring of the spring 4 and the cross-sectional area and is equal square wire radial length of the present embodiment, when comparing the degree of collapse strands collapse wire of the coil spring of the rectangular wire is 1 ° greater (e.g. 1.2 °) if it was, it is possible to suppress the collapse wire in the spring 4 of the present embodiment 1 ° or less (e.g. 0.7 °).
[0058]
　Spring wire of the spring 4, the radial length W is longer than the inner diameter side axial length Ti. Thereby, the cross-sectional shape of the spring wire rod, the radial length W is compared with the case trapezoidal equal short or equal and cross-sectional area than the inner diameter side axial length Ti, the section modulus is increased. Therefore, bending from the relationship between the stress and the section modulus (bending stress sigma = bending moment M / section modulus Z), the maximum value of the tensile force is generated on the inner circumferential surface of the spring 4 acting bending stress further reduced when expanded deformation it can. As a result, the easier to ensure durability against torsion spring 4.
[0059]
　Having described the preferred embodiments of the present invention, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope recited in the claims.
[0060]
　Spring wire of the spring 4 of the above embodiments, the radial length W is longer than the inner diameter side axial length Ti. However, the spring wire of the spring 4, the radial length W may be shorter than or equal to the inner diameter side axial length Ti.
[0061]
　Front end region of the spring 4 above embodiments 4b is a region from the front end of one or more lap spring 4. That is, the spring 4, for more than one round from the front end of the spring 4, in contact with the contact surface 3e. However, the front end side region 4b of the spring 4 may be an area of ​​less than 1 round or half from the front end of the spring 4. That is, the spring 4, for less than one turn or more half from the front end of the spring 4 may contact the contact surface 3e.
[0062]
　The rear end region of the spring 4 above embodiments 4c is a region from the rear end of one or more lap spring 4. That is, the spring 4, for more than one round from the rear end of the spring 4, in contact with the contact face 2a. However, the rear end region 4c of the spring 4 may be an area of ​​less than 1 round or half from the rear end of the spring 4. That is, the spring 4 over one revolution or more to less than half from the rear end of the spring 4 may be in contact with the contact face 2a.
[0063]
　Pulley structure 1 of the above embodiment, the spring 4, by switching the state of state and sliding in pressure contact (engagement) with respect to the outer rotary member 2 (pressing surface 2a), the outer rotary member 2 and the inner It switched to a state of blocking the state of transmitting torque between the rotor 3. However, the coil spring, by switching the state of the state and the sliding engaging the inner rotary member, switches the state to block the state of transmitting torque between the outer rotor and the inner rotary body as such, the pulley structure may be configured. Further, a state a coil spring, by switching the state of the state and the sliding is engaged with both of the inner rotary member and the outer rotary member, for transmitting torque between the outer rotor and the inner rotary body to switch to a state of blocking, the pulley structure may be configured.
Example
[0064]
　Next, detailed embodiments of the present invention.
[0065]
　
　pulley structure of Example 1 has the same configuration as the pulley structure 1 of the above embodiment, the spring wire of the coil spring (4) is spring oil-tempered wire (JISG3560: 1994 It was compliant). Spring wire is a trapezoidal wire, the inner diameter side axial length Ti is set to 3.8 mm, the outer diameter side axial length To, and 3.6 mm, radial length W is a 5.0mm did. The number of turns N of the coil spring (4), and 7 wound, winding direction, and a left-handed. Axial compressibility of the coil spring (4) was about 20%. Gaps between the spring wire adjacent to each other in the axial direction was set to 0.3 mm. ΔL (ΔL = N × (Ti -To) / 2) was 0.7 mm. Note that a spring wire of the cross-sectional shape, even if the number of turns of the coil spring 9 wound (typically maximum) value of the ΔL becomes 0.9mm, and the less than 1 mm. Also, falling strands of the coil spring was 0.7 °. In other words, the outer diameter side portion in the cross section of the spring wire (surface on the outer diameter side) is, the outer diameter reference line parallel to the center axis of the cross-section coil springs of the spring wire, was 0.7 ° inclination.
[0066]
　Thrust plate (8) is made is a cold-rolled steel plate (SPCC), subjected to a surface hardening treatment by soft nitriding. To the surface hardness (Vickers hardness) HV180 surface pretreatment of the thrust plate (8), the surface hardness after surface treatment was about Hv 600. Outer rotating body (2) is a material of carbon steel (S45C), subjected to a surface hardening treatment by soft nitriding. To the surface hardness of the outer rotating body before the surface treatment is HV 200, the surface hardness after surface treatment was Hv 600.
[0067]
　
　pulley structure of Comparative Example 1, except a coil spring, and the same configuration as the pulley structure of Example 1. Spring wire of the coil spring of Comparative Example 1, the spring wire and radial length W and the cross-sectional area of trapezoidal wire of Example 1 is equal to the angular lines, otherwise, the same configuration as the coil spring of Example 1 did. Axial length T of the cross section of the spring wire was 3.7 mm. Also, falling strands of the coil spring was 1.2 °.
[0068]
　[Stress distribution simulation]
　For the coil spring of Example 1 and Comparative Example 1, the torsion in the diameter direction deformation (hereinafter, simply referred to as enlarged deformation) and the torsion torque inputted when the surface of the coil spring (inner peripheral surface the relationship between the maximum principal stress (maximum value of the bending stress) generated), was investigated by simulation by FEM (finite element method) analysis using a general-purpose structural analysis software. As the boundary conditions of the simulation, and set the following conditions.
　For 20% compression coil spring in the axial direction.
　- Both front and rear ends of the coil spring, torqued torsion in the direction in which the coil spring is expanded deformation.
[0069]
　Simulation results, Example 1, Comparative Example 1 together, the torsional torque when 20 N · m applied, in contact with the annular surface of the outer rotating member outer peripheral surface of the free portion of the coil spring (2) (2b), torsional deformation of more diameter direction of the coil spring has been found to be regulated. That is, when a 20 N · m imparting torsional torque to the coil spring, the torsional deformation of the enlarged diameter direction of the coil spring has been found to be a maximum. Twist angle of the diameter expansion direction of the coil spring when the torsional deformation of the enlarged diameter direction of the coil spring is maximum, was generally 70 °. Note that this result was consistent with the results of the measurement test of torsional torque (see FIG. 4).
[0070]
　Simulation result, the maximum principal stress occurring in the surface of the coil spring when expanded deformation (the maximum value of the bending stress) is in another site, the inner peripheral surface of the coil spring tensile force acts is the highest at the time of enlarged deformation I understood it.
[0071]
　5 were obtained by simulation is a graph showing the torsional torque is inputted to the coil spring, the relationship between the maximum principal stress of the coil spring (the maximum value of the bending stress). As is apparent from FIG. 5, the coil spring of Example 1 spring wire is trapezoidal wire, as compared to Comparative Example 1 the spring wire is square wire, when enlarged deformed, at any twist angle region also, (the maximum value of the bending stress) the maximum principal stress generated in the inner peripheral surface of the coil spring which is durable indicator for torsion coil springs were found to be reduced. In addition, Example 1 is compared with Comparative Example 1, the effect of reducing the maximum principal stress (maximum value of the bending stress) generated in the inner peripheral surface of the coil spring, torsion torque is maximum grant to the coil spring (20 N · m grant) became the largest at the time of the. Maximum principal stress torsional torque is generated in the inner peripheral surface of the coil spring at the maximum (the maximum value of the bending stress) in the case of Example 1 (799MPa), compared with the case of Comparative Example 1 (867MPa), It showed about 8% lower.
[0072]
　[Abrasion test]
　The pulley structure of Example 1 and Comparative Example 1, using the engine bench test machine 200 shown in FIG. 6 was subjected to abrasion resistance test. Engine bench test machine 200, a test device comprising a accessory drive system, a crank pulley 201 attached to the crankshaft 211 of the engine 210, AC pulley 202, a water pump connected to the air conditioning compressor (AC) and a WP pulley 203 connected to the (WP). Pulley structure 100 of Example 1 and Comparative Example 1 is connected to the shaft 221 of the alternator (ALT) 220. Further, between the belt span between the crank pulley 201 and the pulley structure 100, auto-tensioner (A / T) 204 is provided. The output of the engine through one of the belt (V-ribbed belt) 250, a crank pulley 201 in the clockwise direction, is transmitted respectively pulley structure 100, WP pulley 203, AC pulley 202, each accessory ( alternator, water pump, air conditioning compressor) is driven.
[0073]
　Atmospheric temperature 90 ° C., the belt tension 1500 N, repeatedly alternately start and stop the engine, the number of times the engine is started, when it reaches 500,000 times corresponding to the actual vehicle life, the test was terminated. Once per operating time of the engine (the time from start to stop) it was 10 seconds. Note that the ambient temperature is in the actual vehicle, the alternator, the pulley structure is a temperature assuming the temperature of the thermostatic bath surrounding the crank pulley. Further, the rotational speed of the crankshaft during each engine start was varied between 0 ~ 1800 rpm. By repeating the start and stop of the engine, the coil spring is pressed against surface of the outer rotating body (2) (2a) (hereinafter, the clutch referred engaging portion) are alternately repeated engagement and sliding against.
[0074]
　After the test, to decompose the pulley structure 100 were measured maximum wear depth of the clutch engaging portion (pressing surface). The results are shown in Table 1 below. Further, in Table 1, obtained by calculation, the maximum value of the contact pressure acting between the clutch engaging portion (contact face) and the coil springs were also displayed.
[0075]
　If the maximum wear depth of the clutch engaging portion (pressing surface) is more than 0.15 mm, it was evaluated × (the failure). If the maximum wear depth of the clutch engaging portion (pressing surface) is 0.15mm or less, a problem Naki level for practical use, was evaluated ○ (pass). Clutch engaging portion below the maximum wear depth of (pressing surface) is 0.075mm in the case of (half following acceptance judgment level 0.15 mm), a problem Naki level capable of withstanding with a sufficient margin for practical use, evaluation ◎ (pass) and the.
[0076]
[Table 1]

[0077]
　As shown in Table 1, the wear-suppressing effect for the clutch engaging portion (pressing surface) is better in Example 1 than in Comparative Example 1 was higher. The results, as the wire of the coil spring collapse is reduced, the surface pressure acting on the clutch engaging portion of the coil spring (pressing surface) is reduced, it can be seen that suppress the wear of the clutch engaging portion (pressing surface) . Incidentally, the wire of the coil spring collapse rating of the largest Comparative Example 1 does not become a × (fail) is not surface hardening treatment is performed with respect to the pulley including clutch engagement portion (pressing surface) It was considered for. Moreover, the wear of the spring seat surface of the thrust plate provided in Example 1 and Comparative Example 1 was minor, the fault associated with the progress of wear was observed.
[0078]
　This application, 2016 April 28 filed Japanese Patent Application 2016-090836, and is based on 2017 April 17 Japanese Patent Application date Application 2017-081321, the contents of which are incorporated herein by reference.
DESCRIPTION OF SYMBOLS
[0079]
　1 pulley structure
　2 outside the rotary body
　2a pressing surface
　3 within the rotary body
　4 coil spring
　4d free portion

WE CLAIM

An outer rotating body cylindrical belt is wound,
　the outer rotating member provided inside, the outside of the outer rotor and rotatable relative the inner rotating body about a same rotation axis with respect to the rotary body When,
　a coil spring provided between the inner rotor and the outer rotary member, a pulley structure comprising a
　outer circumferential surface the outer free portion of the coil spring by the enlarged diameter of the coil spring when in contact with the rotary member, the torsional deformation of more diameter direction of the coil spring is regulated, it has a locking mechanism for the outer rotary member and the inner rotary body is rotated integrally with the coil spring ,
　the coil spring, when the inner rotary body is relatively rotated in the forward direction relative to the outer rotary member, by deformed torsion diameter direction, respectively engage with the outer rotary member and the inner rotary body to the torque between the inner rotor and the outer rotary member Transmission and, when the inner rotation body rotates relatively in the opposite direction relative to the outer rotary member, by twisting the diameter direction deformation, sliding to at least one of the outer rotary member and the inner rotary body and functions as a one-way clutch which does not transmit torque between the inner rotor and the outer rotating member,
　the spring wire of said coil spring along said through an axis of rotation and a direction parallel to said rotation axis cross section is a trapezoid, the rotation axis direction length of the cross-section definitive inner diameter side portion Ti [mm] is longer than the rotational axial length of the radially outer portion the to [mm] in the cross section,
　the coil When the number of turns of the spring and N, satisfies the following formula (1), the pulley structure.
　　N × (Ti-To) / 2 <1 ··· (1)
[Requested item 2]
　Wherein the spring wire of the coil spring, the radial length of the cross section is greater than the rotation axis direction length Ti of the inner diameter side portion in the cross section, a pulley structure according to claim 1.