JP7160766B2 - pulley structure - Google Patents

Description

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

In an auxiliary machine drive unit that drives auxiliary machines such as an alternator by the power of an automobile engine, a belt is stretched over a pulley connected to the drive shaft of the auxiliary machine such as the alternator and a pulley connected to the crankshaft of the engine. The torque of the engine is transmitted to the auxiliary machine via this belt. In particular, the pulley connected to the drive shaft of the alternator, which has a larger inertia than other accessories, has a pulley structure capable of absorbing rotational fluctuations of the crankshaft, as described in Patent Document 1, for example. Used.

The pulley structure described in Patent Document 1 includes an outer rotating body, an inner rotating body provided inside the outer rotating body and rotatable relative to the outer rotating body, a torsion coil spring (hereinafter simply referred to as "spring"). ), and torque is transmitted or interrupted between the outer rotor and the inner rotor by expanding or contracting deformation of the spring. The spring of this pulley structure is a one-way clutch (coil spring) that transmits or blocks torque in one direction between the outer rotor and the inner rotor in order to prevent the belt wound around the outer rotor from slipping. function as a clutch).

In a pulley structure having a coil spring type clutch as described in Patent Document 1, when the outer rotating body rotates relative to the inner rotating body in the positive direction, the springs are applied to the outer rotating body and the inner rotating body, respectively. is engaged with and is in an engaged state, and torque is transmitted between the outer rotor and the inner rotor. On the other hand, when the outer rotating body rotates in the opposite direction relative to the inner rotating body, the spring slides (slips) in the circumferential direction with respect to the outer rotating body or the inner rotating body to disengage the outer rotating body. Do not transmit torque between the rotating body and the inner rotating body.

In the pulley structure described in Patent Document 1, in a state where no external force is applied to the pulley structure, the region of the spring on the one end side in the axial direction along the rotation axis of the outer rotor or the inner rotor The pressure contact surface, which is in contact with the outer peripheral surface of the spring due to the self-elastic restoring force of the spring in the diameter expanding direction, serves as a clutch engaging portion that slides in the circumferential direction with the spring of the outer rotating body or the inner rotating body. Therefore, the spring is housed between the outer rotating body and the inner rotating body by reducing the diameter of the one end side region of the spring by an appropriate amount in advance.

JP 2014-114947 A

Here, in the pulley structure as described in Patent Document 1, when the spring is accommodated between the outer rotating body and the inner rotating body, the amount of diameter reduction of the region on the one end side of the spring (clutch engagement surface The outer rotating body rotates in the opposite direction relative to the inner rotating body, and the spring (clutch) twists and deforms in the radially contracting direction is disengaged (sliding It is considered to set the torsional torque (hereinafter, also referred to as "slip torque") of the spring when it is in the state) to be as small as possible (for example, about 1 N·m). If the slip torque is reduced, the frequency of sliding (slipping) between the pressure contact surface (clutch engagement portion) and the spring will increase, and the ability to absorb tension fluctuations in the belt will improve accordingly. The slippage of the belt that is applied is suppressed, and the life of the belt is extended.

However, when the spring is accommodated between the outer rotating body and the inner rotating body in order to reduce the slip torque, if the amount of diameter reduction of the region on the one end side of the spring is reduced, the pressure contact surface (clutch engagement portion ) is also reduced.

When the pressure contact force of the spring against the pressure contact surface (clutch engaging portion) also decreases, the outer rotating body rotates relative to the inner rotating body in the positive direction, and the spring is torsionally deformed in the radially expanding direction, resulting in the outer rotating body and the inner rotating body. When engaging with each of the inner rotating bodies and transmitting torque between the outer rotating body and the inner rotating body, the engagement force (grip force) between the spring and the pressure contact surface becomes insufficient, and the spring and the pressure contact occur. Slippage (idling) occurs between the surfaces. As a result, torque transmission becomes unstable between the outer rotating body and the inner rotating body, and there is a risk that the torque of the engine will not be smoothly transmitted to the accessories.

An object of the present invention is to extend the service life of the belt by reducing the slip torque, while maintaining the contact surface between the torsion coil spring and the torsion coil spring of the outer rotating body or the inner rotating body when the clutch is engaged. To provide a pulley structure capable of suppressing instability of torque transmission between an outer rotating body and an inner rotating body due to slippage between the outer rotating body and the inner rotating body.

A pulley structure according to a first aspect of the present invention includes a cylindrical outer rotating body around which a belt is wound, and a pulley structure provided inside the outer rotating body in a radial direction and centering on the same rotation axis as the outer rotating body. a torsion coil spring provided between the outer rotating body and the inner rotating body and compressed in an axial direction along the rotating shaft; wherein one of the outer rotating body and the inner rotating body is a portion located on one end side in the axial direction, and an external force is applied to the pulley structure. The region on the one end side of the torsion coil spring has a clutch engagement portion that is in contact with the torsion coil spring by self-elastic restoring force with respect to diameter expansion or diameter contraction of the torsion coil spring in a state in which the torsion coil spring is By being torsionally deformed in a radially expanding or contracting direction, it becomes an engaged state in which it engages with the outer rotating body and the inner rotating body, and transmits torque between the outer rotating body and the inner rotating body. , torsional deformation in a direction opposite to that during torque transmission results in an engagement disengagement state in which the clutch engagement portion of the one rotor slides, and the gap between the outer rotor and the inner rotor is disengaged. A groove is formed in the circumferential surface forming the clutch engaging portion of the one rotating body, and the groove extends obliquely with respect to the axial direction. and is spaced apart from and faces the one end region in the radial direction when no external force is applied to the pulley structure, and torque is transmitted between the outer rotating body and the inner rotating body. a bottom portion in contact with the peripheral surface of the one end side region of the torsion coil spring that is torsionally deformed in a diameter-expanding or diameter-reducing direction when the spring is pressed;
A portion that connects a portion of the bottom portion that is most distant in the radial direction from the region on the one end side when no external force is applied to the pulley structure, and the clutch engagement portion, the portion connecting the outer rotating body. and the inner rotating body, the corner portion of the torsion coil spring, which is torsionally deformed in the radially expanding or radially contracting direction, in contact with the corner portion of the cross section of the spring wire in the one end region and has.

In the present invention, when torque is transmitted between the outer rotating body and the inner rotating body, the torsion coil spring that is torsionally deformed in the direction of diameter expansion or diameter reduction is formed on the bottom part of the peripheral surface of the region on the one end side. In addition to touching, it touches corners at corners. Therefore, in order to prolong the service life of the belt, the torsion torque (slip torque) of the spring in the clutch disengaged state is set to be small, while the spring and the one rotating body are set in the clutch engaged state. It is possible to sufficiently secure the grip force between. Thereby, it is possible to suppress the occurrence of slippage (idling) between the spring and the one rotating body. As a result, torque is stably transmitted between the outer rotating body and the inner rotating body.

A pulley structure according to a second aspect of the present invention is the pulley structure according to the first aspect, in which an external force is applied to the pulley structure toward the other end side in the axial direction. It extends obliquely with respect to the axial direction so as to be spaced apart from the one end region in the radial direction when it is not closed, and the groove extends parallel to a plane perpendicular to the rotation axis.

When the clutch engaged state in which torque is transmitted between the outer rotating body and the inner rotating body, first, of the outer peripheral surface of the spring wire, one end in the axial direction is the portion closest to the bottom spring ( hereinafter referred to as the top), and then the spring wire falls along the bottom with the top as a fulcrum. In the present invention, the bottom portion is inclined with respect to the axial direction so as to radially separate from the region on the one end side in a state where no external force is applied to the pulley structure toward the other end side in the axial direction. . Therefore, when the spring wire falls down as described above, the fallen spring wire approaches the spring wire located on the other end side in the axial direction. The tilt angle becomes smaller (approaching a direction parallel to this plane).

On the other hand, in the present invention, the groove extends along the circumferential direction of one of the rotors and parallel to the plane perpendicular to the rotation axis. Therefore, in the clutch engaged state, the region on the one end side of the spring that is torsionally deformed in the radially expanding or contracting direction fits into the groove so that the peripheral surface contacts the bottom and the corner contacts the corner. Cheap. Therefore, the above effects can be obtained more reliably.

A pulley structure according to a third aspect of the present invention is the pulley structure according to the first aspect, wherein the groove is spirally formed such that the pitch in the axial direction is equal to the pitch in the axial direction of the spring wire. It is

In the present invention, since the groove portion is formed in a helical shape with an axial pitch equal to the axial pitch of the spring wire, in a clutch engaged state in which torque is transmitted between the outer rotating body and the inner rotating body, , By the time the outer rotor rotates one round relative to the inner rotor, the area on the one end side of the spring that is torsionally deformed in the direction of diameter expansion or diameter contraction is in contact with the bottom, and the corner is in contact with the bottom. fit into the groove so as to come into contact with the Therefore, the above effects can be made more reliable.

A pulley structure according to a fourth aspect of the present invention is the pulley structure according to the first to third aspects, wherein the contour shape of the corner is the same as the contour shape of the corner.

According to the present invention, when the torsion coil spring contacts the corners at the corners, the adhesion between the corners becomes high, and the grip force between the spring and one of the rotating bodies is sufficiently secured. can do.

A fifth aspect of the present invention is the pulley structure according to the first to fourth aspects, wherein the torsion coil spring has a torsion torque of 1 N·m or less in the disengaged state.

When the torsion torque of the torsion coil spring in the disengaged state is as small as 1 N·m or less, the spring presses against the clutch engaging portion in the clutch engaged state. A slip (idling) occurs between the spring and the surface to which the spring is pressed. Therefore, in such a case, a groove portion having a bottom portion and a corner portion is provided in the clutch engagement portion, and the region on the one end side of the spring that is torsionally deformed in the radially expanding or radially contracting direction in the clutch engaged state is formed on the peripheral surface. It is of great significance to secure a gripping force between the spring and the clutch engaging portion by fitting into the groove so that the spring contacts the bottom and the corner contacts the corner.

According to the present invention, while the torsion torque (slip torque) of the spring in the clutch disengaged state is set to be small, in the clutch engaged state, slippage (idling) occurs between the spring and the one rotating body. ) can be suppressed. As a result, torque is stably transmitted between the outer rotating body and the inner rotating body.

FIG. 1 is a cross-sectional view of the pulley structure of the first embodiment. FIG. 2 is a cross-sectional view taken along line II--II of FIG. FIG. 3 is a cross-sectional view taken along line III--III in FIG. 4(a) is an enlarged view of the IVA portion of FIG. 1, and FIG. 4(b) is a view corresponding to FIG. 4(a) when the clutch is in the engaged state. FIG. 5 is a diagram corresponding to FIG. 1 of the second embodiment. 6(a) is an enlarged view of the VIA portion of FIG. 5, and FIG. 6(b) is a view corresponding to FIG. 6(a) when the clutch is in the engaged state. FIG. 7 is a diagram corresponding to FIG. 1 of the third embodiment. FIG. 8(a) is an enlarged view of the VIIIA portion of FIG. 7, and FIG. 8(b) is a view corresponding to FIG. 8(a) when the clutch is in the engaged state. FIG. 9 is a diagram corresponding to FIG. 1 of the fourth embodiment. 10(a) is an enlarged view of the XA portion of FIG. 9, and FIG. 10(b) is a view corresponding to FIG. 10(a) when the clutch is in the engaged state. FIG. 11 is a schematic configuration diagram of a wear resistance test device. FIG. 12(a) is a diagram showing the relationship between the torsion angle of the spring and the torsion torque in Examples 1 to 4, and FIG. 12(b) is a diagram showing the relationship between the torsion angle of the spring and the torsion torque in the comparative example. FIG. 12(c) is a diagram showing the relationship between the torsion angle of the spring and the torsion torque in the reference example.

[First embodiment]
A first preferred embodiment of the present invention will be described below.

The pulley structure 1 of the first embodiment is installed, for example, on the drive shaft of an alternator in an automobile accessory drive system (not shown). It should be noted that the pulley structure of the present invention may be installed on the drive shaft of an accessory 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 sometimes simply referred to as "spring 4"), and an end cap 5. As shown in FIGS. Hereinafter, the left-right direction in FIG. 1 is defined as the front-rear direction, the left direction in FIG. 1 is defined as the front, and the right direction is defined as the rear. The end caps 5 are arranged at the front ends of the outer rotor 2 and the inner rotor 3 .

Both the outer rotating body 2 and the inner rotating body 3 are substantially cylindrical and have the same rotating shaft parallel to the front-rear direction. The rotation shafts of the outer rotor 2 and the inner rotor 3 are the rotation shafts of the pulley structure 1 (hereinafter simply referred to as "rotation shafts"). Also, 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 and is rotatable relative to the outer rotating body 2 . A belt B is wound around the outer peripheral surface of the outer rotor 2 .

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

A rolling bearing 6 is interposed between the inner peripheral surface of the rear end of the outer rotor 2 and the outer peripheral surface of the tubular body 3a. A sliding bearing 7 is interposed between the inner peripheral surface of the front end of the outer rotor 2 and the outer peripheral surface of the outer cylindrical portion 3b. The outer rotating body 2 and the inner rotating body 3 are connected by bearings 6 and 7 so as to be relatively rotatable.

A space 9 is formed between the outer rotor 2 and the inner rotor 3 and in front of the rolling bearing 6 . More specifically, the space 9 is formed between the inner peripheral surface of the outer rotating body 2 and the inner peripheral surface of the outer cylinder portion 3b, and the outer peripheral surface of the cylinder main body 3a. A spring 4 is accommodated in the space 9 . A protruding portion 2c that protrudes radially inward is provided at a portion of the outer rotating body 2 located between the rolling bearing 6 and the space 9. As shown in FIG.

The inner diameter of the outer rotating body 2 is reduced in two stages toward the rear. The inner peripheral surface of the outer rotating body 2 at the smallest inner diameter portion is called a pressure contact surface 2a, and the inner peripheral surface of the outer rotating body 2 at the second smallest inner diameter portion is called 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 cylindrical 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 cylindrical portion 3b. Further, the annular surface 2b extends to the vicinity of the outer cylindrical portion 3b on the other end side in the axial direction, and the gap between the portion forming the annular surface 2b of the outer rotating body 2 and the outer cylindrical portion 3b. The length is sufficiently short relative to the length of the spring wire of spring 4 in the axial direction.

The tube main body 3a has a large outer diameter at the front end. The outer peripheral surface of the inner rotor 3 at this portion is called 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 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 means the cross-section or cross-sectional shape on a plane passing through the rotation axis and parallel to the rotation axis. The spring wire of the spring 4 is a trapezoidal wire having a trapezoidal cross-sectional shape. Four corners 4g in the cross section of the spring wire are chamfered (for example, rounded surfaces with a radius of curvature of about 0.3 mm). The inner diameter side axial length is longer than the outer diameter side axial length.

The spring 4 has a constant diameter over its entire length when not receiving an external force. The outer diameter of the spring 4 in the state of not receiving external force is larger than the inner diameter of the outer rotor 2 at the pressure contact surface 2a. The spring 4 is accommodated in the space 9 with a rear end region 4c (“one end region” of the present invention) being reduced in diameter. The outer peripheral surface of the rear end 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 radially expanding direction. The rear end region 4c is a region extending from the rear end of the spring 4 by one turn or more (360° or more around the rotation axis). For example, when the number of turns of the spring 4 is 7, the rear end region 4c is a region whose upper limit is about two turns from the rear end of the spring 4 .

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 of the spring 4 in the diameter expanding direction, the front end of the spring 4 The side region 4b is in contact with the contact surface 3e while being slightly enlarged in diameter. That is, when the pulley structure 1 is stopped, the inner peripheral surface of the front end region 4b of the spring 4 is pressed against the contact surface 3e. The front end region 4b is a region extending from the front end 4a of the spring 4 by one turn or more (360° or more around the rotation axis). For example, when the number of turns of the spring 4 is 7, the front end region 4b is a region whose upper limit is about two turns from the front end 4a of the spring 4. As shown in FIG.

In this manner, the outer peripheral surface of the rear end region 4c of the spring 4 is pressed against the pressure contact surface 2a, and the inner peripheral surface of the front end region 4b of the spring 4 is pressed against the contact surface 3e. It is possible to stabilize the posture of the spring 4 in a state of being compressed in the direction.

The spring 4 is axially compressed in a state in which no external force is applied to the pulley structure 1 (that is, a state in which the pulley structure 1 is stopped), and the axial end face ( hereinafter referred to as "front end surface 4e") is in contact with the groove bottom surface 3d of the inner rotating body 3, and the axial direction of the rear end region 4c of the spring 4 is in contact with the groove bottom surface 3d of the inner rotor 3. A part of the end face (hereinafter referred to as “rear end face 4f”) in the circumferential direction (a range of about 1/4 circumference from the rear end) is in contact with the front surface 2c1 of the projecting portion 2c of the outer rotating body 2. As shown in FIG. The axial compression ratio of the spring 4 is, for example, about 20%. The compression rate of the spring 4 in the axial direction is the difference between the natural length of the spring 4 and the axial length of the spring 4 when no external force is applied to the pulley structure 1, and the natural length of the spring 4. is the ratio of

A front end surface 4e and a rear end surface 4f of the spring 4 are formed with a ground surface. The ground surface is a plane that is perpendicular to the axial direction of the spring 4 and is formed by grinding. The ground surfaces of the front end surface 4e and the rear end surface 4f are each formed in a range of about 1/4 turn (90°) from the end of the spring 4 in the circumferential direction. By forming the ground surface on the front end surface 4e and the rear end surface 4f of the spring 4 in this manner, the posture of the spring 4 that is compressed in the axial direction can be stabilized.

The bottom surface 3d of the groove is spirally formed so as to be in contact with the front end surface 4e of the spring 4. As shown in FIG. The groove bottom surface 3d of the support groove portion 3c and the front end surface 4e of the spring 4 are apparently in contact with each other in the entire circumferential direction. Sometimes. Aiming to make the gap zero by combining actual finished dimensions within the machining tolerance of the part, the gap is a dimension (nominal dimension) that takes into account the machining tolerance of the part (for example, the aim of the axial clearance value 0.35 mm). By making the gap as close to zero as possible, the spring 4 can be torsionally deformed stably. By forming the groove bottom surface 3d into a spiral surface, the posture of the spring 4 axially compressed between the outer rotor 2 and the inner rotor 3 can be stabilized. Furthermore, by forming the groove bottom surface 3d into a spiral surface, the central axis of the spring 4 becomes eccentric or inclined with respect to the rotation axes of both rotating bodies due to external factors such as vibration, and the attitude of the spring 4 becomes unstable. can be suppressed.

On the other hand, the front surface 2c1 of the protruding portion 2c slides on the rear end surface 4f of the spring 4 as will be described later, so it does not have a spiral surface but a flat surface.

A groove portion 2d is formed in the pressure contact surface 2a that contacts the outer peripheral surface of the rear end region 4c of the spring 4. As shown in FIG. The groove portion 2d extends parallel to a plane orthogonal to the front-rear direction over the entire circumferential direction of the pressure contact surface 2a. As shown in FIGS. 4A and 4B, the groove portion 2d has a bottom portion 11 and corner portions 12. As shown in FIGS.

The bottom portion 11 is inclined with respect to the front-rear direction so that the diameter increases toward the front, and the rear end thereof is connected to the pressure contact surface 2a. The inclination angle of the bottom portion 11 with respect to the front-rear direction is, for example, about 0.5°. In addition, in the radial direction of the outer rotor 2, the portion of the bottom portion 11 farthest from the pressure contact surface 2a (the left end in FIG. 4A) is about 40 μm away from the pressure contact surface 2a. That is, the maximum depth of the groove portion 2d is about 40 μm.

In a state where no external force is applied to the pulley structure 1, as shown in FIG. (hereinafter referred to as the top portion 13 ), and is separated from the portion of the bottom portion 11 located forward of the top portion 13 . Further, at this time, the farther the portion of the bottom portion 11 from the top portion 13 (the left portion in FIG. 4A), the greater the separation distance from the outer peripheral surface of the rear end side region 4c of the spring 4. As shown in FIG.

The corner portion 12 is a portion that connects the front end of the bottom portion 11, which is the portion with the largest diameter, and the pressure contact surface 2a. The contour shape of the corner portion 12 is the same shape as the contour of the corner portion 4g of the spring wire of the spring 4 (for example, a curved surface with a radius of curvature of about 0.3 mm).

As shown in FIG. 2, of the front end side region 4b, the vicinity of the position away from the front end 4a of the spring 4 by 90° around the rotation axis is the second region 4b2, and the portion closer to the front end than the second region 4b2 is the first region. 4b1, and the remaining portion is called a third region 4b3. A free portion 4d is defined as a region between the front end region 4b and the rear end region 4c of the spring 4, that is, a region that does not come into contact with either the pressure contact surface 2a or the contact surface 3e.

As shown in FIG. 2, the front end portion of the inner rotor 3 is formed with a contact surface 3f facing the front end 4a of the spring 4 in the circumferential direction of the inner rotor 3. As shown in FIG. A projection 3g is provided on the inner peripheral surface of the outer tubular portion 3b so as to protrude radially inward of the outer tubular portion 3b and face the outer peripheral surface of the front end region 4b. The protrusion 3g faces the second region 4b2.

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

First, the case where the rotation speed of the outer rotor 2 becomes higher than the rotation speed of the inner rotor 3 (that is, the case where the outer rotor 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 (the arrow direction in FIGS. 2 and 3). With the relative rotation of the outer rotor 2 , the rear end region 4 c of the spring 4 moves together with the pressure contact surface 2 a and rotates relative to the inner rotor 3 . As a result, the spring 4 is torsionally deformed in the diameter-expanding direction (hereinafter referred to as "diameter-expanding deformation"). The pressure contact force of the rear end region 4c of the spring 4 against the pressure contact surface 2a increases as the torsion angle of the spring 4 in the radial expansion direction increases. The second region 4b2 is most susceptible to torsional stress, and separates from the contact surface 3e as the torsion angle in the radially expanding direction of the spring 4 increases. At this time, the first region 4b1 and the third region 4b3 are in pressure contact with the contact surface 3e. Substantially at the same time when the second region 4b2 separates from the contact surface 3e, or when the torsion angle in the radial expansion direction of the spring 4 further increases, the outer peripheral surface of the second region 4b2 contacts the projection 3g. Since the outer peripheral surface of the second region 4b2 abuts against the protrusion 3g, the deformation of the front end region 4b is restricted, and the torsional stress is dispersed to the portions of the spring 4 other than the front end region 4b. 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 the strain energy can be absorbed by the entire spring 4, so that the spring 4 can be prevented from being locally fatigue-broken.

Further, the pressure contact force of the third region 4b3 against the contact surface 3e decreases as the torsion angle of the spring 4 in the diameter expanding direction increases. Substantially at the same time when the second region 4b2 comes into contact with the projection 3g, or when the torsion angle of the spring 4 in the diametrical expansion direction further increases, the pressing force of the third region 4b3 against the contact surface 3e becomes substantially zero. At this time, the torsion angle of the spring 4 in the radial expansion direction is θ1 (for example, θ1=3°). When the torsion angle of the spring 4 in the diametrical expansion direction exceeds θ1, the third region 4b3 undergoes diametrical expansion deformation and moves away from the contact surface 3e. However, the spring 4 does not bend (bend) near the boundary between the third region 4b3 and the second region 4b2, and the front end region 4b is maintained in an arc shape. In other words, the front end region 4b is maintained in a shape that facilitates sliding on the projection 3g. Therefore, when the torsion angle of the spring 4 in the radially expanding direction increases and the torsional stress acting on the front end side region 4b increases, the front end side region 4b exerts a pressing force against the projection 3g of the second region 4b2 and a pressure contact force of the first region 4b1. It slides in the circumferential direction of the outer rotor 2 against the projection 3g and the contact surface 3e against the pressure contact force on the contact surface 3e. Torque can be reliably transmitted between the outer rotor 2 and the inner rotor 3 by pressing the front end 4a of the spring 4 against the contact surface 3f.

When the torsion angle of the spring 4 in the radial expansion direction is θ1 or more and less than θ2 (for example, θ2=45°), the third region 4b3 is separated from the contact surface 3e and is located on the inner peripheral surface of the outer cylindrical portion 3b. There is no contact, and the second region 4b2 is pressed against the protrusion 3g. Therefore, in this case, the effective number of turns of the spring 4 is large and the spring constant is small compared to the case where the torsion angle of the spring 4 in the radially expanding direction is less than θ1. Further, when the torsion angle of the spring 4 in the diametrical expansion direction reaches θ2, the outer peripheral surface of the free portion 4d of the spring 4 comes into contact with the annular surface 2b, thereby restricting the deformation of the spring 4 to further diametrical expansion. A locking mechanism is activated in which the rotating body 2 and the inner rotating body 3 rotate integrally. As a result, it is possible to prevent the spring 4 from being damaged due to its diameter expansion deformation.

At this time, unlike the present embodiment, the length of the gap between the portion forming the annular surface 2b of the outer rotor 2 and the outer cylindrical portion 3b in the axial direction is equal to the length of the spring wire of the spring 4. If it is longer than the length, the outer peripheral surface of the second region 4b2 contacts the protrusion 3g, while the outer peripheral surface of the third region 4b3 contacts the outer cylindrical portion 3b, thereby restricting the expansion deformation of the front end region 4b. or when the outer peripheral surface of the free portion 4d abuts against the annular surface 2b and the radial expansion deformation of the free portion 4d is to be restricted, the spring wire of the spring 4 enters the gap and the front end side The expansion deformation of the region 4b and the free portion 4d may not be restricted. In this case, there is a risk that the spring 4 will be damaged due to deformation due to expansion. On the other hand, in the present embodiment, the length of the gap between the portion forming the annular surface 2b of the outer rotor 2 and the outer cylindrical portion 3b in the axial direction is the length of the spring wire of the spring 4. Short enough for length. Therefore, the spring wire of the spring 4 does not enter the gap, and the spring 4 can be reliably prevented from being damaged due to deformation due to diameter expansion.

Next, the case where the rotation speed of the outer rotor 2 becomes smaller than the rotation speed of the inner rotor 3 (that is, the case where the outer rotor 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 (direction opposite to the arrow direction in FIGS. 2 and 3). With the relative rotation of the outer rotor 2 , the rear end region 4 c of the spring 4 moves together with the pressure contact surface 2 a and rotates relative to the inner rotor 3 . As a result, the spring 4 is torsionally deformed in the diameter-reducing direction (hereinafter referred to as "diameter-reducing deformation"). When the torsion angle of the spring 4 in the radially contracting direction is less than θ3 (for example, θ3=approximately 4°), the pressure contact force of the rear end region 4c against the pressure contact surface 2a is slightly lower than when the torsion angle is zero. However, the rear end region 4c is in pressure contact with the pressure contact surface 2a. Also, the pressure contact force of the front end region 4b against the contact surface 3e is slightly increased compared to when the twist angle is zero. When the torsion angle of the spring 4 in the radially contracting direction is θ3 or more, the pressure contact force of the rear end region 4c against the pressure contact surface 2a becomes substantially zero, and the rear end region 4c is less than or equal to the pressure contact surface 2a. slide in the direction Therefore, no torque is transmitted between the outer rotor 2 and the inner rotor 3 (see FIG. 12(a)). That is, the clutch (spring 4) is disengaged.

Further, in the first embodiment, as described above, the torsional torque of the spring 4 when the spring 4 is torsionally deformed in the diameter contracting direction and the clutch (spring 4) is in the disengaged state (sliding state) (hereinafter referred to as , “slip torque Ts”) is set close to zero (for example, about 1 N·m).

<effect>
Here, unlike the first embodiment, consider a case in which the slip torque Ts is not set near zero, but is set to a torque that causes the spring 4 to undergo diameter-reducing deformation larger than the torsion angle θ3. Specifically, consider a case where the slip torque Ts is set to be 1 N·m or more and 10 N·m or less (for example, about 3 N·m). In this case, the disengagement of the clutch is performed only in a specific driving pattern (for example, when the engine is started) in which the spring 4 is greatly contracted in diameter. The sliding frequency of the contact surface 2a is reduced, and wear of the portion of the pressure contact surface 2a that slides on the spring 4 can be suppressed.

In contrast, when the slip torque Ts is made close to zero as in the first embodiment, disengagement of the clutch is not limited to the specific driving pattern (for example, when the engine is started). will be Therefore, the frequency of sliding (slipping) between the pressure contact surface 2a (clutch engaging portion) and the spring 4 increases. As a result, the function of absorbing fluctuations in belt tension is improved, slippage between the outer rotating member 2 and the belt B can be suppressed, and the life of the belt B can be lengthened.

However, in order to make the slip torque Ts close to zero, when the spring 4 is accommodated between the outer rotating body 2 and the inner rotating body 3, the amount of diameter reduction of the rear end side region 4c of the spring 4 is compared. need to be as small as possible. In this case, the pressure contact force of the spring 4 with respect to the pressure contact surface 2a (clutch engaging portion) also becomes small (for example, the pressure contact force index becomes about 35). Here, the pressing force index is obtained by indexing the pressing force of the spring with 100 as the pressing force when the slip torque Ts is set to 3 N·m.

Therefore, unlike the first embodiment, if the pressure contact surface 2a were not formed with the groove 2d, the outer rotating member 2 would rotate relative to the inner rotating member 3 in the positive direction, and the spring 4 would rotate as described above. , the torsional deformation in the radially expanding direction causes insufficient gripping force between the spring 4 and the outer rotating body 2 when transmitting torque between the outer rotating body 2 and the inner rotating body 3, and the spring 4 and the outer rotor 2 may slip (idle). As a result, the torque transmission between the outer rotor 2 and the inner rotor 3 becomes unstable, and there is a risk that the engine torque will not be smoothly transmitted to the accessories.

Therefore, in the first embodiment, a groove portion 2d having a bottom portion 11 and corner portions 12 is formed in the pressure contact surface 2a. In this case, when the rear end region 4c of the spring 4 expands in diameter, the portion of the spring wire facing the groove 2d of the rear end region 4c moves over the top portion 13 as shown in FIG. 4(b). It falls down as a fulcrum and fits into the groove 2d. The portion of the rear end region 4c fitted in the groove 2d contacts the corner 12 at the corner 4g of the spring wire in addition to contacting the bottom 11 on the outer peripheral surface. As a result, when torque is transmitted between the outer rotor 2 and the inner rotor 3, a gripping force can be secured between the spring 4 and the outer rotor 2. It is possible to suppress the occurrence of slippage (idling) between As a result, torque transmission between the outer rotor 2 and the inner rotor 3 is stabilized.

Further, in the first embodiment, the contour shape of the corner portion 12 is the same shape as the contour shape of the corner portion 4 g of the spring wire of the spring 4 . Therefore, when the corner portion 4g of the spring wire and the corner portion 12 come into contact with each other, the contact between the corner portion 4g and the corner portion 12 is increased, and the grip force between the spring 4 and the outer rotor 2 is increased. can be sufficiently secured.

Further, in the case of the first embodiment, the bottom portion 11 is inclined with respect to the front-rear direction so as to move away from the pressure contact surface 2a in the radial direction of the outer rotating body 2 toward the front. Therefore, as shown in FIG. 4(b), the spring wire of the portion of the spring 4 facing the groove 2d inclines so as to approach the spring wire of the portion of the spring 4 located forward of this portion. As a result, the inclination angle of the helical direction of the spring wire in the rear end region 4c with respect to the plane perpendicular to the front-rear direction becomes smaller (the direction becomes closer to the direction parallel to the plane).

On the other hand, in the first embodiment, the groove portion 2d extends parallel to the plane orthogonal to the front-rear direction over the entire circumferential direction of the pressure contact surface 2a. As a result, the rear end region 4c, in which the helical direction of the spring wire is close to the plane, easily fits into the groove 2d. That is, the rear end region 4c is likely to come into contact with the bottom portion 11 at the outer peripheral surface and the corner portion 12 at the corner portion 4g of the spring wire. As a result, the gripping force between the spring 4 and the outer rotor 2 can be more reliably secured, and slippage (idling) between the spring 4 and the outer rotor 2 can be more reliably prevented. can be suppressed.

[Second embodiment]
Next, a preferred second embodiment of the invention will be described. As shown in FIGS. 5, 6A, and 6B, the pulley structure 20 according to the second embodiment differs from the groove 2d of the first embodiment in the shape of the groove 2e formed in the pressure contact surface 2a. Since it differs from the pulley structure 1 only in points, the groove 2e will be mainly described below.

As shown in FIG. 5, the groove portion 2e extends parallel to a plane perpendicular to the front-rear direction over the entire circumferential direction of the pressure contact surface 2a. Moreover, as shown in FIGS. 6A and 6B, the groove 2e has a bottom 21 and corners 22. As shown in FIGS. The bottom portion 21 is inclined with respect to the front-rear direction so that the diameter increases toward the rear, and the front end thereof is connected to the pressure contact surface 2a. The inclination angle of the bottom portion 11 with respect to the front-rear direction is, for example, about 0.5°. In addition, in the radial direction of the outer rotor 2, the portion of the bottom portion 21 farthest from the pressure contact surface 2a (the right end in FIG. 6A) is about 40 μm away from the pressure contact surface 2a. That is, the maximum depth of the groove portion 2d is about 40 μm.

In a state where no external force is applied to the pulley structure 20, as shown in FIG. (hereinafter referred to as a top portion 23 ), and is separated from the portion of the bottom portion 21 located behind the top portion 23 . Also, at this time, the farther the portion of the bottom portion 21 from the top portion 23 (the portion on the right side in FIG. 6A), the greater the separation distance from the outer peripheral surface of the rear end side region 4c of the spring 4. As shown in FIG.

The corner portion 22 is a portion that connects the rear end of the bottom portion 21, which is the portion with the largest diameter, and the pressure contact surface 2a. The contour shape of the corner portion 22 is the same shape as the contour shape of the corner portion 4g of the spring wire of the spring 4 (for example, a curved surface with a radius of curvature of about 0.3 mm).

Then, as shown in FIG. 6(b), when the outer rotor 2 rotates relative to the inner rotor 3 in the positive direction, and the spring 4 is torsionally deformed in the diameter-expanding direction (the outer rotor 2 and the inner When torque is transmitted to and from the rotating body), the portion of the rear end region 4c facing the groove 2e tilts with the top 23 as a fulcrum and fits into the groove 2e. As a result, the portion of the rear end region 4c fitted in the groove 2e contacts the corner 22 at the corner 4g of the spring wire in addition to the bottom 21 on the outer peripheral surface. As a result, when torque is transmitted between the outer rotor 2 and the inner rotor 3, a gripping force can be secured between the spring 4 and the outer rotor 2. It is possible to suppress the occurrence of slippage (idling) between As a result, torque transmission between the outer rotor 2 and the inner rotor 3 is stabilized.

Further, in the second embodiment, the contour shape of the corner portion 22 is the same shape as the contour shape of the corner portion 4 g of the spring wire of the spring 4 . Therefore, when the corners 4g and the corners 22 of the spring wire come into contact with each other, the contact between the corners 4g and the corners 22 becomes high, and the grip force between the spring 4 and the outer rotor 2 is sufficiently increased. can be secured to

[Third embodiment]
Next, a preferred third embodiment of the invention will be described. As shown in FIGS. 7, 8A, and 8B, in the pulley structure 30 according to the third embodiment, the shape of the groove 2f formed in the pressure contact surface 2a is the same as that of the grooves of the first and second embodiments. 2d and 2e differ from the pulley structures 1 and 20 of the first and second embodiments only, so the groove 2f will be mainly described below.

As shown in FIG. 7, the groove 2f extends in a left-handed helical shape along the circumferential direction of the pressure contact surface 2a. The pitch of the grooves 2f in the longitudinal direction is approximately equal to the pitch of the spring wire of the spring 4 in the longitudinal direction. Further, as shown in FIGS. 8A and 8B, the groove portion 2f has a bottom portion 31 and corner portions 32. As shown in FIGS. The bottom portion 31 is inclined with respect to the front-rear direction so that the diameter increases toward the front, and the rear end thereof is connected to the pressure contact surface 2a. The inclination angle of the bottom portion 31 with respect to the front-rear direction is, for example, about 0.5°. In addition, in the radial direction of the outer rotor 2, the portion of the bottom portion 31 farthest from the pressure contact surface 2a (the left end in FIG. 8A) is about 40 μm away from the pressure contact surface 2a. That is, the maximum depth of the groove 2f is approximately 40 μm.

When no external force is applied to the pulley structure 30, as shown in FIG. (hereinafter referred to as a top portion 33 ), and is separated from the portion of the bottom portion 31 located forward of the top portion 33 . Also, at this time, the farther the portion of the bottom portion 31 from the top portion 33 (the left portion in FIG. 8(a)), the greater the separation distance from the outer peripheral surface of the rear end side region 4c of the spring 4. As shown in FIG.

The corner portion 32 is a portion that connects the front end of the bottom portion 31, which is the portion with the largest diameter, and the pressure contact surface 2a. The contour shape of the corner portion 32 is the same shape as the contour shape of the corner portion 4g of the spring wire of the spring 4 (for example, a curved surface with a radius of curvature of about 0.3 mm).

In the third embodiment, as shown in FIG. 8(b), when the outer rotor 2 rotates in the positive direction relative to the inner rotor 3 and the spring 4 is torsionally deformed in the radially expanding direction (outer When torque is transmitted between the rotating body 2 and the inner rotating body), the portion of the rear end region 4c facing the groove 2f tilts with the top 33 as a fulcrum and fits into the groove 2f. As a result, the portion of the rear end region 4c fitted into the groove 2f contacts the corner 32 at the corner 4g of the spring wire in addition to contacting the bottom 31 on the outer peripheral surface. As a result, when torque is transmitted between the outer rotor 2 and the inner rotor 3, a gripping force can be secured between the spring 4 and the outer rotor 2. It is possible to suppress the occurrence of slippage (idling) between As a result, torque transmission between the outer rotor 2 and the inner rotor 3 is stabilized.

Further, in the third embodiment, the contour shape of the corner portion 32 is the same shape as the contour shape of the corner portion 4 g of the spring wire of the spring 4 . Therefore, when the corners 4g and the corners 32 of the spring wire come into contact with each other, the contact between the corners 4g and the corners 32 increases, and the gripping force between the spring 4 and the outer rotor 2 increases. can be sufficiently secured.

Further, in the case of the third embodiment, the groove portion 2f extends spirally, and the pitch of the groove portion 2f in the front-rear direction is substantially equal to the pitch of the spring wire of the spring 4 in the front-rear direction. As a result, when the outer rotor 2 rotates in the positive direction relative to the inner rotor 3 and the spring 4 is torsionally deformed in the radially expanding direction, the spring 4 rotates relative to the inner rotor 3 at least once. As described above, the portion of the rear end region 4c facing the groove 2f is fitted into the groove 2f until it rotates. As a result, the gripping force between the spring 4 and the outer rotor 2 can be more reliably secured, and slippage (idling) between the spring 4 and the outer rotor 2 can be more reliably prevented. can be suppressed.

[Fourth embodiment]
Next, a preferred fourth embodiment of the invention will be described. As shown in FIGS. 9, 10(a) and (b), in the pulley structure 40 according to the fourth embodiment, the shape of the groove 2g formed in the pressure contact surface 2a is similar to that of the grooves of the first to third embodiments. 2d, 2e, and 2f are different from the pulley structures 1, 20, and 30 of the first to third embodiments, so the groove 2g will be mainly described below.

As shown in FIG. 9, the groove 2g extends in a left-handed helical shape along the circumferential direction of the pressure contact surface 2a. The pitch of the grooves 2g in the longitudinal direction is approximately equal to the pitch of the spring wire of the spring 4 in the longitudinal direction. Further, as shown in FIGS. 10A and 10B, the groove portion 2g has a bottom portion 41 and a corner portion . The bottom portion 41 is inclined with respect to the front-rear direction so that the diameter increases toward the rear, and the front end thereof is connected to the pressure contact surface 2a. The inclination angle of the bottom portion 41 with respect to the front-rear direction is, for example, about 0.5°. In addition, in the radial direction of the outer rotor 2, the portion of the bottom portion 31 farthest from the pressure contact surface 2a (the right end in FIG. 10A) is about 40 μm away from the pressure contact surface 2a. That is, the maximum depth of the groove portion 2g is approximately 40 μm.

In a state where no external force is applied to the pulley structure 40, as shown in FIG. (hereinafter referred to as a top portion 43 ), and is separated from the portion of the bottom portion 41 located behind the top portion 43 . Also, at this time, the farther the portion of the bottom portion 41 from the top portion 43 (the portion on the right side in FIG. 10A), the greater the separation distance from the outer peripheral surface of the rear end side region 4c of the spring 4. As shown in FIG.

The corner portion 42 is a portion that connects the rear end of the bottom portion 41, which is the portion with the largest diameter, and the pressure contact surface 2a. The contour shape of the corner portion 42 is the same shape as the contour shape of the corner portion 4g of the spring wire (for example, a curved surface with a radius of curvature of about 0.3 mm).

In the fourth embodiment, as shown in FIG. 10(b), when the outer rotor 2 rotates in the positive direction relative to the inner rotor 3, and the spring 4 is torsionally deformed in the diameter expanding direction (outer rotor 2). When torque is transmitted between the rotating body 2 and the inner rotating body), the portion of the rear end region 4c facing the groove 2g falls with the top 43 as a fulcrum and fits into the groove 2g. As a result, the portion of the rear end region 4c fitted into the groove 2g contacts the corner 42 at the corner 4g of the spring wire in addition to contacting the bottom 41 on the outer peripheral surface. As a result, when torque is transmitted between the outer rotating body 2 and the inner rotating body, a gripping force can be secured between the spring 4 and the outer rotating body 2. It is possible to suppress the occurrence of slippage (idling) during As a result, torque transmission between the outer rotor 2 and the inner rotor 3 is stabilized.

Further, in the fourth embodiment, the contour shape of the corner portion 42 is the same shape as the contour shape of the corner portion 4 g of the spring wire of the spring 4 . Therefore, when the corners 4g and 42 of the spring wire come into contact with each other, the contact between the corners 4g and the corners 42 increases, and the grip force between the spring 4 and the outer rotor 2 increases. can be sufficiently secured.

Further, in the case of the fourth embodiment, the groove portion 2g extends spirally, and the pitch of the groove portion 2g in the front-rear direction is substantially equal to the pitch of the spring wire of the spring 4 in the front-rear direction. As a result, when the outer rotor 2 rotates in the positive direction relative to the inner rotor 3 and the spring 4 is torsionally deformed in the radially expanding direction, the spring 4 rotates relative to the inner rotor 3 at least once. As described above, the portion of the rear end region 4c facing the groove 2g is fitted into the groove 2g until it rotates. As a result, the gripping force between the spring 4 and the outer rotor 2 can be more reliably secured, and slippage (idling) between the spring 4 and the outer rotor 2 can be more reliably prevented. can be suppressed.

Next, specific examples of the present invention will be described.

<Examples 1 to 4>
The pulley structures of Examples 1 to 4 have the same configurations as the pulley structures 1, 20, 30 and 40 of the first to fourth embodiments. In these pulley structures, the spring wire of the coil spring (4) is an oil-tempered spring wire (JIS G3560:1994). Also, the spring wire was a trapezoidal wire with an inner diameter side axial length of 3.8 mm, an outer diameter side axial length of 3.6 mm, and a radial length of 5.0 mm. The number of turns of the coil spring (4) was set to 7, and the winding direction was left-handed. Also, the axial compression rate of the spring (4) was set to about 20%.

Further, the outer rotating body (2) is made of carbon steel (S45C) and is subjected to surface hardening treatment by nitrocarburizing. Specifically, the surface hardness of the outer rotor (2) before the surface treatment was about HV200, while the surface hardness after the surface treatment was about HV600. Further, as described above, in Examples 1 to 4, the spring (4) is arranged between the outer rotor (2) and the inner rotor (3) so that the slip torque (Ts) is set to about 1 N·m. The amount by which the diameter of the rear end region (4c) of the spring (4) is reduced when it is housed in between is made relatively small.

<Comparative example>
The pulley structure of the comparative example differs from the pulley structures of Examples 1 to 4 in that a groove is not formed on the pressure contact surface (2a). Other than that, the pulley structure of the comparative example had the same configuration as the pulley structures of Examples 1-4.

<Reference example>
The pulley structure of the reference example differs from the pulley structures of Examples 1 to 4 in that a groove is not formed on the pressure contact surface (2a). Further, in the pulley structure of the reference example, the spring (4) is accommodated between the outer rotor (2) and the inner rotor (3) so that the slip torque (Ts) is set to about 3 N·m. It is different from the pulley structures of Examples 1 to 4 in that the amount of diameter reduction of the rear end region (4c) of the spring (4) is increased. Other than that, the pulley structure of the reference example had the same configuration as the pulley structures of Examples 1-4.

Then, for Examples 1 to 4, Comparative Example and Reference Example, the relationship between the torsion angle and torsion torque of the spring (4) was measured using the wear resistance tester 100 shown in FIG. A wear resistance test apparatus 100 includes a motor 101 , a torque meter 102 , an encoder 103 , a bearing 104 , a fixture 105 , a data logger 106 and a PC (Personal Computer) 107 . The target pulley structure is attached to the tip of the shaft 101 a of the motor 101 .

Torque meter 102 is attached to shaft 101 a and is electrically connected to data logger 106 and PC 107 . Torque meter 102 transmits a torque signal indicating the torque value of shaft 101a (corresponding to torsional torque in FIGS. 12(a) to 12(c) described later) to data logger 106 and PC 107. FIG.

The encoder 103 is attached to the shaft 101a and electrically connected to the data logger 106 and the PC107. The encoder 103 transmits a rotation angle signal indicating the rotation angle of the shaft 101a (corresponding to the twist angle in FIGS. 12(a) to 12(c)) to the data logger 106 and the PC 107. FIG.

Fixture 105 includes a pair of blocks 105a and 105b. Each block 105a, 105b is made of metal, for example, and has a V-shaped concave surface. The pair of blocks 105a and 105b are arranged so that their concave surfaces face each other, and while holding a pulley structure attached to the tip of the shaft 101a therebetween, the concave surfaces are pressed toward each other in the facing direction. , to non-rotatably fix the outer rotating body (2) of the pulley structure.

Then, in the pulley structures of Examples 1 to 4, Comparative Example, and Reference Example, the outer rotating body (2) is non-rotatably fixed by the fixture 105 as described above. Then, the motor 101 is driven to rotate the inner rotor (3) together with the shaft 101a. At this time, the rotation speed of the shaft 101a (relative rotation speed between the outer rotor and the inner rotor) was set to 2 rpm. Moreover, the atmospheric temperature at this time was set to 25±5°C.

To explain the rotation of the inner rotor (3) in more detail, the inner rotor (3) is rotated in the opposite direction relative to the non-rotatably fixed outer rotor (2), and the spring (4) is rotated. A torque meter 102 is used to detect a change in the torque value of the inner rotor (3) until the twist angle in the direction of radial contraction reaches 30°. A change in the detected torque value is recorded in the data logger 106 by a signal transmitted from the torque meter 102 . 12(a) to 12(c), the torsion angles indicated by negative values such as "-30°" indicate the torsion angles in the diameter-reducing direction.

Subsequently, the inner rotor (3) is rotated in the positive direction relative to the non-rotatably fixed outer rotor (2) until the torsion angle of the spring (4) reaches θ2 (approximately 70°). A torque meter 102 is used to detect changes in the torque value of the inner rotor (3). A change in the detected torque value is recorded in the data logger 106 by a signal transmitted from the torque meter 102 . Here, the torsion angle θ2 (approximately 70°) in the radial expansion direction is the maximum torsion angle (the torsion angle when the lock mechanism described above operates) in Examples 1 to 4 and the reference example.

By processing the changes in the torque value recorded in the data logger 106 with the PC 107, graphs showing the relationship between the torsion angle and the torsion torque of the spring (4) in FIGS. Obtained. FIG. 12(a) is a graph of Examples 1 to 4, FIG. 12(b) is a graph of a comparative example, and FIG. 12(c) is a graph of a reference example.

As shown in FIGS. 12(a) and 12(b), it was confirmed that the slip torque (Ts) was set to about 1 N·m in Examples 1 to 4 and Comparative Example. Further, in Examples 1 to 4 and Comparative Example, the torsion angle θ3 in the diameter-reducing direction was about 4° when the slip torque (Ts) was about 1 N·m. In other words, in Examples 1 to 4 and the comparative example, the torsion torque in the diameter reduction direction is maintained at about 1 Nm when the torsion angle is from θ3 (about 4°) to about 30°, and the spring (4) is engaged. It was confirmed that it was in a released state (sliding state).

As shown in FIG. 12(c), in the reference example, it was confirmed that the slip torque (Ts) was set to approximately 3 N·m. Further, in the reference example, the torsion angle θ4 in the diameter-reducing direction was about 10° when the slip torque (Ts) was about 3 N·m. That is, in the reference example, the torsion torque is maintained at about 3 Nm when the torsion angle in the diameter contracting direction is from θ4 (about 10°) to about 30°, and the spring (4) is disengaged (slidable). state).

On the other hand, in the pulley structures of Examples 1 to 4 shown in FIG. However, when the clutch is engaged, there is no slippage (idling) between the spring (4) and the outer rotor (2), and torque is generated between the outer rotor (2) and the inner rotor (3). It was found that the instability of transmission could be suppressed.

On the other hand, from the relationship between the torsion angle and torsion torque of the spring in the pulley structure of the comparative example shown in FIG. (Torsion torque at this time is about 12 Nm), and torque transmission between the outer rotor (2) and the inner rotor (3) becomes unstable. rice field.

Further, in the comparative example, as described above, slippage (idling) occurs between the spring (4) and the outer rotating body (2) in the clutch engaged state. Even when the torsion angle is θ2 (approximately 70°), the lock mechanism described above does not work. The torsion torque when the torsion angle of the spring (4) in the radial expansion direction was θ2 (approximately 70°) was about 20 Nm in Examples 1 to 4 and the reference example. In the comparative example, it was about 15 N·m.

In the relationship shown in FIG. 12(b), after the slip (slip) occurs only once, the spring deforms to expand its diameter up to the torsion angle θ2 (approximately 70°) without causing the slip (slip). did. However, the balance between the magnitude of the torsional torque input to the spring (4) and the magnitude of the gripping force between the rear end region (4c) of the spring (4) and the clutch engagement portion, and the two rotating bodies The torsion angle, degree of slipping (slipping), frequency of slipping (slipping), etc. may change depending on the level of the relative rotational speed of the clutch.

Therefore, for example, the magnitude of the torsional torque input to the spring (4) is excessively greater than the magnitude of the gripping force between the rear end region (4c) of the spring (4) and the clutch engaging portion. or when the level of the relative rotational speed of the two rotating bodies becomes relatively large, the above slip ( slipping) occurs frequently, and torque transmission between the outer rotating body (2) and the inner rotating body (3) may become even more unstable.

Comparing the results of Examples 1 to 4 shown in FIG. 12(a) with the results of the comparative example shown in FIG. Even if the torque (Ts) is set close to zero, in the clutch engaged state where torque is transmitted between the outer rotor (2) and the inner rotor (3), the rear end side of the spring (4) It was found that the engagement force (grip force) between the region (4c) and the outer rotor (2) can be ensured.

From the results of the reference example shown in FIG. 12(c), when the slip torque (Ts) is set to a relatively large value of about 3 N·m, grooves are formed in the pressure contact surface (clutch engaging portion). Even if not, in the clutch engaged state, there is no slippage (idling) between the spring (4) and the outer rotor (2), and between the outer rotor (2) and the inner rotor (3) It was found that the torque was stably transmitted. As a result, slippage (idling) occurs between the spring (4) and the outer rotor (2) when torque is transmitted between the outer rotor (2) and the inner rotor (3). The problem of unstable torque transmission between the outer rotor (2) and the inner rotor (3) is likely to occur when the slip torque (Ts) is set to be small. I found out.

As described above, the preferred first to fourth embodiments of the present invention have been described, but the present invention is not limited to the first to fourth embodiments, and various modifications can be made within the scope of the claims. is possible.

In the first to fourth embodiments, the contour shape of the corner is the same shape as the contour shape of the corner of the cross section of the spring wire in the rear end region 4c of the spring 4, but it is not limited to this. If the corner 4g of the spring wire of the spring 4 is in contact with the corner when the rear end region 4c of the spring 4 is fitted into the groove, the contour of the corner 4g is It may have a shape different from the shape.

In the first to fourth embodiments, the slip torque Ts is set to be approximately 1 N·m, but it is not limited to this. The slip torque Ts may be set to be smaller than 1 N·m. In this case, when torque is transmitted between the outer rotor 2 and the inner rotor 3, the gripping force between the spring and the pressure contact surface 2a is even greater than in the first to fourth embodiments. It is small, and slippage (idling) between the spring 4 and the outer rotor 2 is more likely to occur. Therefore, it is of great significance to provide the groove portion on the pressure contact surface 2a to ensure the gripping force.

Alternatively, the slip torque may be greater than 1 N·m. Even in this case, when torque is transmitted between the outer rotor 2 and the inner rotor 3, the grip force between the spring 4 and the outer rotor 2 can be increased. 3, an effect of suppressing torque transmission from becoming unstable can be obtained.

In addition, in the first to fourth embodiments, the rear end region 4c of the spring 4 is in contact with the top portion, which is the connecting portion between the pressure contact surface 2a and the bottom portion, when no external force is applied to the pulley structure. However, it is not limited to this. The rear end region 4c of the spring 4 may be spaced apart from the top portion when no external force is applied to the pulley structure. In this case, when the outer rotor 2 rotates relative to the inner rotor 3 in the forward direction and the spring 4 is torsionally deformed in the direction of radial expansion (torque is generated between the outer rotor 2 and the inner rotor 3). during transmission), after the rear end region 4c of the spring 4 comes into contact with the top, the portion of the rear end region 4c facing the groove collapses with the top as a fulcrum in the same manner as described above. get stuck in.

Further, in the first to fourth embodiments, the outer rotating body 2 has the pressure contact surface 2a as the clutch engaging portion, but the present invention is not limited to this. The inner rotating body may have a spring and a clutch engaging portion that slides.

In the first to fourth embodiments, the engaged state is established when the spring 4 is torsionally deformed in the radially expanding direction, and the disengaged state is established when the spring 4 is torsionally deformed in the radially contracting direction. However, it is not limited to this. When the spring 4 is torsionally deformed in the diameter-reducing direction, it is in the engaged state, and when the spring 4 is torsionally deformed in the diameter-expanding direction, it is in the disengaged state by sliding on the outer rotating body 2 or the inner rotating body 3. It may be configured as

Reference Signs List 1 pulley structure 2 outer rotor 2d groove 3 inner rotor 4 spring 11 bottom 12 corner 20 pulley structure 2e groove 21 bottom 22 corner 30 pulley structure 2f groove 31 bottom 32 corner 40 pulley structure 2g groove 41 bottom 42 corner

Claims (5)

a cylindrical outer rotating body around which the belt is wound;
an inner rotating body provided radially inside the outer rotating body and rotatable relative to the outer rotating body about the same rotation axis as that of the outer rotating body;
a torsion coil spring provided between the outer rotating body and the inner rotating body and compressed in the axial direction along the rotation axis, the pulley structure comprising:
One of the outer rotating body and the inner rotating body is a portion located on one end side in the axial direction, and is the portion of the torsion coil spring in which an external force is not applied to the pulley structure. A region on one end side has a clutch engagement portion that is in contact with the torsion coil spring due to self-elastic restoring force against diameter expansion or diameter contraction,
The torsion coil spring is
By being torsionally deformed in a radially expanding or contracting direction, it becomes an engaged state in which it engages with the outer rotating body and the inner rotating body, and transmits torque between the outer rotating body and the inner rotating body. ,
Torsional deformation in a direction opposite to that during torque transmission results in a disengaged state in which the one rotating body slides against the clutch engagement portion, and between the outer rotating body and the inner rotating body. configured to block the transmission of torque,
A groove is formed in a peripheral surface forming the clutch engaging portion of the one rotating body,
The groove is
A portion that extends obliquely with respect to the axial direction and faces the region on the one end side in the radial direction while being spaced apart from the outer rotating body when no external force is applied to the pulley structure. a bottom portion that contacts the peripheral surface of the one end side region of the torsion coil spring that is torsionally deformed in a diameter-expanding or diameter-reducing direction when torque is transmitted between the inner rotating body;
A portion of the bottom portion that is most distant in the radial direction from the region on the one end side when no external force is applied to the pulley structure, and a portion that connects the clutch engaging portion, the outer rotating body. and the inner rotating body, the corner portion of the torsion coil spring, which is torsionally deformed in the radially expanding or radially contracting direction, in contact with the corner portion of the cross section of the spring wire in the one end region and a pulley structure. The bottom portion is arranged in the axial direction so as to be spaced apart in the radial direction from the region on the one end side in a state in which no external force is applied to the pulley structure, toward the other end side in the axial direction. It extends at an angle,
2. The pulley structure according to claim 1, wherein said groove extends parallel to a plane perpendicular to said rotation axis. 2. The pulley structure according to claim 1, wherein the groove portion is formed in a helical shape with a pitch in the axial direction equal to the pitch in the axial direction of the spring wire. The pulley structure according to any one of claims 1 to 3, wherein the contour shape of the corner portion is the same shape as the contour shape of the corner portion. The pulley structure according to any one of claims 1 to 4, wherein the torsion torque of the torsion coil spring in the disengaged state is set to 1 N·m or less.

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