Auto tensioner

Abstract

To provide an auto tensioner capable of ensuring optimal belt tension and high belt followability, and capable of preventing a coil spring for applying biasing force between pulley arms from being tilted.SOLUTION: An auto tensioner has: a first pulley arm 9; a second pulley arm 10; a swing fulcrum shaft 11 that swingably supports both pulley arms 9, 10; an elastic member 20 composed of a torsion coil spring that urges the second pulley arm 10 against the first pulley arm 9 so that the idler pulleys 7, 8 provided on each pulley arm 9, 10 approach each other; and swing resistance members 34, 35 that generate swing resistance for each pulley arm 9, 10 in only one of the swing directions. Each pulley arm 9, 10 has a cylindrical base part 12a, 12b that houses the elastic member 20, and is configured so that when there is no load on both pulley arms 9, 10, their outer peripheries are respectively supported by an inner surface of base parts 12a, 12b.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an autotensioner used in a belt system for driving accessories of an automobile engine, a timing belt, etc. [Background technology]

[0002] In recent years, an increasing number of mild hybrid vehicles are equipped with belt starter generators (hereinafter abbreviated as BSG) that restart the engine after idling stop and assist the engine power while driving, in addition to the functions of a conventional alternator, in belt systems for driving accessories of an automobile engine. This belt system for driving accessories has a belt transmission device that transmits power by an accessory belt (hereinafter abbreviated as belt) that is stretched between a crank pulley provided on the crankshaft of the engine and a pulley (hereinafter abbreviated as BSG pulley) provided on the drive shaft of the BSG.

[0003] This belt transmission device has the feature that the tension side and slack side of the belt are switched between normal operation when the crank pulley is in drive and when the BSG pulley is in drive, when the engine is restarted after an idling stop or when assisting drive while driving.

[0004] That is, during normal operation when the BSG operates as a generator, the crank pulley drives the BSG pulley via a belt, so the portion of the belt running from the BSG pulley to the crank pulley is the tight side, and the portion of the belt running from the crank pulley to the BSG pulley is the slack side. On the other hand, when the BSG restarts the engine after an idling stop or when providing drive assistance while traveling, the BSG pulley drives the crank pulley via a belt, so the portion of the belt running from the crank pulley to the BSG pulley is the tight side, and the portion of the belt running from the BSG pulley to the crank pulley is the slack side.

[0005] In order to prevent such slack in the belt and to properly adjust the belt tension, for example, in an autotensioner (belt tensioning device 21) shown in Patent Document 1, tension rollers 25, 26 supported by tension arms 23, 24 are applied to the belt spans on both sides of the pulley 12. In the configuration shown in FIG. 2 of Patent Document 1, a tension spring 27 is disposed between the two tension arms 23, 24, and the two tension rollers 25, 26 are biased in a direction in which they approach each other. In this way, the tension rollers 25, 26 are linked via the tension spring 27 to adjust the belt tension during normal operation and when the engine is restarted after idling stop. Also, for example, in an autotensioner (tension device 1) shown in Patent Document 2 below, as shown in FIG. 1 of Patent Document 2, a spring element 14 made of a coil spring is provided so as to be interposed between a pair of tension arms 7, 8, and the spring element 14 biases the two tension arms 7, 8 in a direction in which they move away from each other. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5634685 [Patent Document 2] Special Publication No. 2003-521639 Summary of the Invention [Problem to be solved by the invention]

[0007] In the configuration shown in Patent Document 1 in which the tension of the belt span on both sides of the pulley 12 is adjusted by interlocking two tension rollers 25, 26 (tension arms 23, 24), the belt tension is adjusted by the oscillation and biasing force of the entire autotensioner (belt tensioning device 21) in response to tension fluctuations in the belt 15 that accompany engine rotation fluctuations. However, when the tension fluctuations in the belt 15 become large, the oscillation of the entire autotensioner becomes large, which may cause abnormal noise due to vibration or contact with the locking mechanism, or the belt 15 and pulley 12 may separate, making it impossible to apply tension to the belt 15.

[0008] Furthermore, in the case of a configuration in which a pair of tension arms 7, 8 are biased by a spring element 14 as shown in Patent Document 2, when the autotensioner (tension device 1) is in use, the spring element 14 contracts or expands in diameter as the torsion angle changes, and depending on the size of the clearance around the spring element 14, the spring element 14 may fall over (tilt from the axial direction). This causes the outer periphery of the spring element 14 to slide against the surrounding members, generating frictional resistance that may impair the tracking ability of the tension arms 7, 8 or generate wear powder that may cause seizure.

[0009] The problem that the present invention aims to solve is to provide an autotensioner that can apply optimal belt tension during normal operation and when the engine is restarted after an idling stop, can ensure high tracking performance by suppressing excessive oscillation of the pulley arm, and can prevent collapse of the torsion coil spring that is used as an elastic member that applies a biasing force between the pulley arms. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a first pulley arm supporting a first idler pulley in contact with the accessory belt; a second pulley arm supporting a second idler pulley in contact with the accessory belt; a swing fulcrum shaft that swingably supports the first pulley arm and the second pulley arm; an elastic member formed of a torsion coil spring that biases the second pulley arm relative to the first pulley arm so that the first idler pulley and the second idler pulley approach each other; a swing resistance member that generates swing resistance in only one swing direction of the first pulley arm and the second pulley arm; having Each pulley arm has a cylindrical base that houses the elastic member, and an autotensioner is configured such that, when there is no load on both pulley arms, the outer periphery of the elastic member is supported by the inner surface of the base.

[0011] In this way, the unidirectional swing resistance provided by the swing resistance member makes it possible to apply optimal belt tension both during normal operation and when the engine is restarted after an idling stop, and also to ensure high compliance with the accessory belt by suppressing excessive swing of the pulley arms. Furthermore, by supporting the outer periphery of the elastic member with the inner surface of the cylindrical base when both pulley arms are in a no-load state (a state in which the autotensioner is not assembled via the accessory belt), even if the diameter of this elastic member contracts when the autotensioner is assembled or in operation, the inner surface of the base and the outer periphery of the elastic member do not separate significantly, and this makes it possible to prevent the elastic member from collapsing.

[0012] In the above configuration, It is preferable that the bottom of the base further includes an elastic member support portion that is interposed between the elastic member and the bottom and supports the elastic member in the axial direction.

[0013] In this way, the axial gap between the bottom of the base and the elastic member consisting of the torsion coil spring is blocked, making it possible to more reliably prevent the torsion coil spring from collapsing when the diameter of the torsion coil spring is reduced as the autotensioner operates.

[0014] In the configuration having the elastic member support portion, It is preferable that the elastic member support portion is a protrusion that protrudes in the axial direction from the bottom portion, or a sloped portion whose axial height gradually changes along the circumferential direction of the base portion.

[0015] In this way, the elastic member support portion can be easily formed at the bottom of the base portion either simultaneously with the formation of the pulley arm or by attaching it later.

[0016] In all of the above configurations: It is preferable that the elastic member further includes elastic member locking portions that clamp and fix both ends of the elastic member from a radial direction inside the base portion.

[0017] In this way, there is no need to form a through hole in the base to fix both ends of the elastic member to the base, so water or dust can be prevented from entering the inside of the base through the through hole.

[0018] In the configuration having the elastic member locking portion, It is preferable that the elastic member has bent pieces formed at both ends thereof, the bent pieces being bent radially inward, and the bent pieces are sandwiched by the elastic member engaging portions from the radial direction.

[0019] In this way, the outer periphery of the elastic member in a free state can be supported by the inner surface of the cylindrical base, while the bent piece bent radially inward can be securely clamped by the elastic member engaging portion. Effect of the Invention

[0020] The autotensioner of the present invention is configured such that a swing resistance member is provided on a pulley arm that swings around a swing fulcrum axis, which generates swing resistance in only one direction of the swing of the pulley arm, and the outer periphery of the elastic member is supported by the inner surface of the base when there is no load on both pulley arms. Therefore, it is possible to apply optimal belt tension during normal operation and when the engine is restarted after an idling stop, and even if the elastic member contracts in diameter when the autotensioner is assembled or in operation, the inner surface of the base and the outer periphery of the elastic member do not separate significantly, preventing the elastic member from collapsing. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a front view showing an example of an accessory drive system using an autotensioner according to the present invention; [Diagram 2] A partially cutaway front view of the autotensioner shown in Figure 1. [Diagram 3] Cross-sectional view of the main part of Figure 2 (with accessory belts attached to both idler pulleys) [Figure 4] Cross-sectional view of the main part of Figure 2 (no load on both pulley arms) [Diagram 5] Cross-sectional view taken along line VV in Figure 4 [Figure 6] Cross-sectional view taken along line VI-VI in Figure 4 [Figure 7] Cross-sectional view taken along line VII-VII in Figure 4. [Figure 8] Cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] Exploded view of the main parts of the autotensioner shown in Figure 1 [Figure 10] An exploded perspective view of the autotensioner shown in Figure 1. [Figure 11] FIG. 2A is a front view showing the operation of the auto tensioner during normal operation, FIG. 2B is a cross-sectional view of a main part of a first pulley arm, and FIG. 2C is a cross-sectional view of a main part of a second pulley arm. [Figure 12]FIG. 2A is a front view showing the action of the auto tensioner when the BSG is operating, FIG. 2B is a cross-sectional view of a main part of a first pulley arm, and FIG. 2C is a cross-sectional view of a main part of a second pulley arm. [Figure 13] An exploded view of a modified example of the main part of the autotensioner shown in FIG. [Figure 14] A plan view of the main part of the autotensioner shown in Figure 13. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] An example of an accessory drive system using an autotensioner 1 according to the present invention is shown in Figures 1 and 2. This accessory drive system has a BSG pulley 3 attached to a BSG drive shaft 2 (accessory drive shaft) of a belt starter generator (hereinafter abbreviated as BSG), a crank pulley 5 attached to a crankshaft 4, an accessory belt 6 (hereinafter abbreviated as belt 6) stretched across the BSG pulley 3 and the crank pulley 5, and an autotensioner 1 that maintains the tension of the belt 6 within an appropriate range.

[0023] As shown in Figures 3 to 10, autotensioner 1 has a first idler pulley 7, a second idler pulley 8, a first pulley arm 9 supporting the first idler pulley 7, a second pulley arm 10 supporting the second idler pulley 8, and a swing fulcrum shaft 11 that swingably supports the first pulley arm 9 and the second pulley arm 10.

[0024] 1, the first idler pulley 7 is in contact with the outer peripheral surface of the portion of the belt 6 that runs from the BSG pulley 3 to the crank pulley 5. The second idler pulley 8 is in contact with the outer peripheral surface of the portion of the belt 6 that runs from the crank pulley 5 to the BSG pulley 3. The axis of the swing fulcrum shaft 11 that supports both pulley arms 9, 10 is disposed on a line connecting the axis of the crankshaft 4 and the axis of the BSG drive shaft 2.

[0025] The first pulley arm 9 and the second pulley arm 10 have bases 12a, 12b (hereinafter, the element on the first pulley arm 9 side is given the letter a, and the element on the second pulley arm 10 side is given the letter b) and extension pieces 13a, 13b extending radially outward from the bases 12a, 12b. The first pulley arm 9 and the second pulley arm 10 are arranged such that their respective bases 12a, 12b are aligned in the axial direction, and their respective extension pieces 13a, 13b are at different positions in the circumferential direction.

[0026] The bases 12a and 12b are composed of cylindrical small diameter cylinder parts 14a and 14b and large diameter cylinder parts 15a and 15b arranged concentrically. The axial ends of the small diameter cylinder parts 14a and 14b and the large diameter cylinder parts 15a and 15b are connected by radially extending flanges 16a and 16b, and these flanges 16a and 16b form the bottoms of the bases 12a and 12b. Fan-shaped recessed receiving parts 17a and 17b are formed in a part of the circumferential direction of the cylinder of the small diameter cylinder parts 14a and 14b (the inner diameter surface of the pulley arms 9 and 10). In this embodiment, the central angle of the receiving parts 17a and 17b is set to about 50 degrees, but it can be changed appropriately within a range of, for example, 20 degrees to 80 degrees.

[0027] At the tips of the extension pieces 13a, 13b, through holes 19a, 19b are formed for passing the rotation shafts 18a, 18b of the first idler pulley 7 and the second idler pulley 8. The lengths of the first pulley arm 9 and the second pulley arm 10 are determined so that the swing radius of the first idler pulley 7 (the distance from the axis of the swing fulcrum shaft 11 to the contact point between the first idler pulley 7 and the belt 6) and the swing radius of the second idler pulley 8 (the distance from the axis of the swing fulcrum shaft 11 to the contact point between the second idler pulley 8 and the belt 6) are the same. Note that the term "same" here does not only mean "completely same" but also includes cases where there is some difference as long as it does not significantly affect the tension of the belt 6.

[0028] A common elastic member 20 is provided in the radial gap between the small diameter cylindrical portions 14a, 14b and the large diameter cylindrical portions 15a, 15b of the first pulley arm 9 and the second pulley arm 10 so as to straddle both pulley arms 9, 10. This elastic member 20 is a steel torsion coil spring. This elastic member 20 biases the second pulley arm 10 relative to the first pulley arm 9 so that the first idler pulley 7 and the second idler pulley 8 approach each other when the pulleys are attached to the accessory drive system.

[0029] At both ends of the elastic member 20, bent pieces 21a, 21b are formed which are bent inward in the radial direction. As shown in Fig. 3, when the autotensioner 1 is attached to the BSG pulley 3 and the crank pulley 5 via the belt 6, or when tension acts on the idler pulleys 7, 8 to change the oscillation angles of the pulley arms 9, 10, the elastic member 20 contracts in diameter and the outer periphery of the elastic member 20 is separated from the inner surfaces of the bases 12a, 12b. On the other hand, as shown in Fig. 4, when the belt 6 is released and the pulley arms 9, 10 are put into an unloaded state, the outer periphery of the elastic member 20 is supported by the inner surfaces of the large diameter cylindrical parts 15a, 15b of the bases 12a, 12b which house the elastic member 20.

[0030] The bottom of the base 12a, 12b of each pulley arm 9, 10 (on the inner surface side of the flanges 16a, 16b) is provided with an elastic member support portion 22 that is interposed between the elastic member 20 and the bottom and supports the elastic member 20 in the axial direction. The elastic member support portion 22 is a protrusion 22A that protrudes from the bottom in the axial direction. The height of the protrusion 22A is determined according to the size of the axial gap between the bottom and the seat surface of the elastic member 20, and gradually changes depending on the circumferential position of the elastic member 20. In this embodiment, the protrusions 22A are formed at three places on the bottom, but the number and positions are not limited, and for example, they may be provided at only one place on the circumferential opposite side to the installation positions of the elastic member locking portions 23a, 23b described later.

[0031] Elastic member locking portions 23a, 23b that clamp and fix the bent pieces 21a, 21b formed on both ends of the elastic member 20 from both radial sides are provided inside the base portions 12a, 12b of each pulley arm 9, 10. The elastic member locking portions 23a, 23b are arranged in pairs on the outer circumferential surfaces of the small diameter cylindrical portions 14a, 14b and on the inner circumferential surfaces of the large diameter cylindrical portions 15a, 15b.

[0032] It is also possible that, without forming bending pieces 21a, 21b at both ends of the elastic member 20, the elastic member 20 can be fixed by pressing both ends of the elastic member 20 radially outward only by the elastic member engaging portions 23a, 23b provided on the outer peripheral surfaces of the small diameter cylindrical portions 14a, 14b.

[0033] The above-mentioned elastic member support portion 22 and elastic member locking portions 23a, 23b can be attached after the formation of the pulley arms 9, 10 (for example, by screwing a screw into the bottom portion of the base portions 12a, 12b to form the protrusion portion 22A as the elastic member support portion 22), but can also be integrally molded when the pulley arms 9, 10 are formed.

[0034] The swing fulcrum shaft 11 swingably supports the first pulley arm 9 and the second pulley arm 10. The swing fulcrum shaft 11 has a first fulcrum shaft 24, a second fulcrum shaft 25, and a main shaft 26 that is connected by press-fitting the first fulcrum shaft 24 and the second fulcrum shaft 25. The first fulcrum shaft 24 and the second fulcrum shaft 25 are both cylindrical members, and at the end facing the main shaft 26, reduced diameter portions 27a, 27b having smaller outer diameters than other portions are formed. In addition, stepped press-fit steps 28a, 28b are formed at the axial end opposite to the reduced diameter portions 27a, 27b formed on the first fulcrum shaft 24 and the second fulcrum shaft 25.

[0035] The main shaft 26 is a cylindrical member, and a flange 29 standing outward in the radial direction is formed around the entire circumference at the center in the axial direction. In addition, a contact portion 30 standing outward in the radial direction and extending along the axial direction is formed at one location in the circumferential direction of the main shaft 26. The first fulcrum shaft 24 and the second fulcrum shaft 25 are press-fitted into both ends of the main shaft 26 to be integrated. A washer 31 is press-fitted into press-fit step portions 28a, 28b formed at both ends of the first fulcrum shaft 24 and the second fulcrum shaft 25 integrated with the main shaft 26. A bolt 32 for fixing the autotensioner 1 to the engine E or the like is inserted through the axis of the oscillating fulcrum shaft 11.

[0036] The first fulcrum shaft 24 is positioned on the inner diameter side of a plain bearing 33a pressed into the small diameter cylindrical portion 14a of the first pulley arm 9, and the second fulcrum shaft 25 is positioned on the inner diameter side of a plain bearing 33b pressed into the small diameter cylindrical portion 14b of the second pulley arm 10.

[0037] The swing fulcrum shaft 11 is provided with swing resistance members 34, 35 which generate swing resistance in only one of the swing directions of the first pulley arm 9 and the second pulley arm 10. The swing resistance members 34, 35 are made of an elastic material and have a C-shaped arc shape. One end of the arc shape is a terminal portion 36a, 36b which terminates in the circumferential direction, while the other end is a bent portion 37a, 37b which is bent radially outward. The swing resistance members 34, 35 are provided on both axial sides of a flange 29 formed on the outer periphery of the main shaft 26. In the following, the swing resistance member 34 provided on the first fulcrum shaft 24 side is referred to as the first swing resistance member 34, and the swing resistance member 35 provided on the second fulcrum shaft 25 side is referred to as the second swing resistance member 35.

[0038] The first and second rocking resistance members 34 and 35 are attached in opposite directions to the main shaft 26. That is, the terminal end 36a of the first rocking resistance member 34 abuts against the abutment portion 30 formed on the main shaft 26 from one circumferential direction, while the terminal end 36b of the second rocking resistance member 35 abuts against the abutment portion 30 formed on the main shaft 26 from the opposite circumferential direction. The bent portion 37a of the first rocking resistance member 34 is provided in a receiving portion 17a formed on the small diameter cylindrical portion 14a of the first pulley arm 9, and the bent portion 37b of the second rocking resistance member 35 is provided in a receiving portion 17b formed on the small diameter cylindrical portion 14b of the second pulley arm 10. When mounted on the accessory drive system, the terminal end 36a and the bent portion 37a of the first oscillation resistance member 34, and the terminal end 36b and the bent portion 37b of the second oscillation resistance member 35, are in contact with the abutment portion 30 formed on the main shaft 26 with a slight preload.

[0039] The bent portions 37a, 37b formed on the first and second oscillation resistance members 34, 35 are allowed to move within an angular range of the central angle of the receiving portions 17a, 17b formed on the small diameter cylindrical portions 14a, 14b of the first pulley arm 9 or the second pulley arm 10. As shown in Figures 5 and 6, the circumferential positions of the inner edges where the bent portions 37a, 37b contact are opposite in the first pulley arm 9 and the second pulley arm 10, but in both pulley arms 9, 10, the direction from one circumferential end where the bent portions 37a, 37b contact the inner edges of the receiving portions 17a, 17b to the other circumferential end of the receiving portions 17a, 17b is referred to as "one direction" and the direction opposite to the one direction is referred to as "reverse direction". This one direction corresponds to the direction in which the first pulley arm 9 or the second pulley arm 10 swings as the first idler pulley 7 or the second idler pulley 8 is pushed by the tension of the belt 6 .

[0040] When the first pulley arm 9 shown in Fig. 5 is swung in one direction (the direction indicated by the arrow in Fig. 5) relative to the swing fulcrum shaft 11, the inner edge of the receiving portion 17a formed on the first pulley arm 9 comes into contact with the bent portion 37a of the first swing resistance member 34, causing the first swing resistance member 34 to elastically deform. As a result, a swing resistance acts on the first pulley arm 9. On the other hand, when the first pulley arm 9 is swung in the opposite direction relative to the swing fulcrum shaft 11, the inner edge of the receiving portion 17a formed on the first pulley arm 9 and the bent portion 37a of the first swing resistance member 34 separate from each other, allowing the first pulley arm 9 to swing in the opposite direction without receiving swing resistance from the first swing resistance member 34.

[0041] 6 is swung in one direction (the direction indicated by the arrow in FIG. 6) relative to the swing fulcrum shaft 11, the inner edge of the receiving portion 17b formed on the second pulley arm 10 comes into contact with the bent portion 37b of the second swing resistance member 35, causing the second swing resistance member 35 to elastically deform. As a result, a swing resistance acts on the second pulley arm 10. On the other hand, when the second pulley arm 10 is swung in the opposite direction relative to the swing fulcrum shaft 11, the inner edge of the receiving portion 17b formed on the second pulley arm 10 and the bent portion 37b of the second swing resistance member 35 separate from each other, allowing the second pulley arm 10 to swing in the opposite direction without receiving swing resistance from the second swing resistance member 35.

[0042] An example of the operation of this autotensioner 1 will be described with reference to Figures 1, 11 and 12. When the engine is stopped, the BSG pulley 3 and the crank pulley 5 are both stopped, as shown in Figure 1. At this time, the belt tension of the belt 6 where both the idler pulleys 7, 8 are in contact is balanced due to the biasing forces acting on the belt 6 from the first idler pulley 7 and the second idler pulley 8.

[0043] During normal operation (power generation in the BSG) shown in FIG. 11(a), the crank pulley 5 drives the BSG pulley 3 via the belt 6, and the portion of the belt 6 running from the BSG pulley 3 to the crank pulley 5 is the tight side, and the portion of the belt 6 running from the crank pulley 5 to the BSG pulley 3 is the slack side. Then, the first pulley arm 9 receives tension from the belt 6 and swings in one direction (see arrow r1 in FIG. 11(a)). At this time, as shown in FIG. 11(b), a swing resistance acts on the first pulley arm 9 due to elastic deformation of the first swing resistance member 34, so that the swing of the first pulley arm 9 is suppressed. On the other hand, the second pulley arm 10 swings in the opposite direction (see arrow r2 in FIG. 11(a)) to correspond to the slack of the belt 6. At this time, as shown in FIG. 11(c), since no rocking resistance acts on the second pulley arm 10 from the second rocking resistance member 35, the second pulley arm 10 rocks smoothly in the direction of biasing the belt 6 due to the biasing force of the elastic member 20.

[0044] During the BSG operation shown in FIG. 12(a) (when the engine is restarted after idling stop, when the driving force of the engine is assisted, etc.), the BSG pulley 3 drives the crank pulley 5 via the belt 6, and the portion of the belt 6 running from the crank pulley 5 to the BSG pulley 3 is the tension side, and the portion of the belt 6 running from the BSG pulley 3 to the crank pulley 5 is the slack side. Then, the second pulley arm 10 receives tension from the belt 6 and swings in one direction (see arrow r2 in FIG. 12(a)). At this time, as shown in FIG. 12(b), a swing resistance acts on the second pulley arm 10 due to the elastic deformation of the second swing resistance member 35, so that the swing of the second pulley arm 10 is suppressed. On the other hand, the first pulley arm 9 swings in the opposite direction (see arrow r1 in FIG. 12(a)) so as to correspond to the slack of the belt 6. At this time, as shown in FIG. 12(c), since no rocking resistance is generated from the first rocking resistance member 34 to the first pulley arm 9, the first pulley arm 9 rocks smoothly in the direction in which it biases the belt 6 due to the biasing force of the elastic member 20.

[0045] During the normal operation and BSG operation, the pulley arms 9, 10 swing relative to one another, causing the elastic member 20 interposed between the pulley arms 9, 10 to expand and contract in the axial direction. At this time, the elastic member 20 may expand and contract in diameter, causing its outer periphery to move slightly away from the inner surfaces of the large-diameter cylindrical portions 15a, 15b of the bases 12a, 12b, but the elastic member support portions 22 (projections 22A) provided at both ends of the elastic member 20 support the seating surfaces of the elastic member 20 from the axial direction, thereby maintaining the elastic member 20 in an upright state in the axial direction.

[0046] In the above-described autotensioner 1, even when the pulley arms 9, 10 swing so as to move the idler pulleys 7, 8 away from the belt 6 due to the tension of the belt 6 during normal operation or BSG operation, the swing is suppressed by the swing resistance of the swing resistance members 34, 35. As a result, optimal belt tension can be applied in either case, during normal operation or BSG operation, and excessive swing of the pulley arms 9, 10 can be suppressed to improve the ability of the pulley arms 9, 10 to follow the belt 6.

[0047] Furthermore, in the above autotensioner 1, since the outer periphery of this elastic member 20 is configured to be supported by the inner surfaces of the large diameter cylindrical portions 15a, 15b of the bases 12a, 12b when there is no load on both pulley arms 9, 10, even if the elastic member 20 contracts in diameter when the autotensioner 1 is assembled or in operation, the inner surfaces of the bases 12a, 12b and the outer periphery of the elastic member 20 do not separate significantly, preventing the elastic member 20 from falling over. This reliably prevents frictional resistance caused by the sliding between the outer periphery of the elastic member 20 and its surrounding members, which could impair the tracking ability of the pulley arms 9, 10, or cause wear powder to be generated and result in seizure.

[0048] Furthermore, in the above-described autotensioner 1, protrusions 22A that protrude in the axial direction from the bottoms of bases 12a, 12b (the inner surface sides of flanges 16a, 16b) are used as elastic member support parts 22. This closes the axial gap between the bottoms of bases 12a, 12b and the seating surfaces of elastic members 20 consisting of torsion coil springs, making it possible to more reliably prevent collapse of the torsion coil springs when their diameter contracts as the autotensioner 1 operates.

[0049] Furthermore, in the above-described autotensioner 1, the elastic member locking portions 23a, 23b are provided to clamp and fix both ends of the elastic member 20 inside the bases 12a, 12b from the radial direction, so there is no need to form through holes in the bases 12a, 12b to fix both ends of the elastic member 20 to the bases 12a, 12b, and it is possible to prevent water or dust from entering the inside of the bases 12a, 12b through the through holes. Particularly in the above-described embodiment, the elastic member 20 has bent pieces 21a, 21b bent radially inwardly formed at both ends thereof, and the bent pieces 21a, 21b are clamped from both radial sides by the elastic member locking portions 23a, 23b, so that the bent pieces 21a, 21b bent radially inwardly can be reliably clamped by the elastic member locking portions 23a, 23b while maintaining a state in which the outer periphery of the elastic member 20 in a free state is supported by the inner surfaces of the cylindrical bases 12a, 12b.

[0050] Furthermore, in the above-described autotensioner 1, since the oscillation resistance members 34, 35 are provided on both the first pulley arm 9 and the second pulley arm 10, the belt tension can be appropriately maintained both during normal operation and when the engine is restarted after an idling stop. Note that it is also possible to provide the oscillation resistance members 34, 35 on only one of the pulley arms 9, 10.

[0051] Furthermore, in the above autotensioner 1, the oscillation resistance members 34, 35 are made of a C-shaped arc-shaped elastic material, so that a compact configuration can provide oscillation resistance from the oscillation fulcrum shaft 11 to the pulley arms 9, 10. Moreover, by forming bent portions 37a, 37b in the oscillation resistance members 34, 35 and providing these bent portions 37a, 37b on receiving portions 17a, 17b that are sector-shaped recesses formed in the pulley arms 9, 10, oscillation resistance is generated only in one direction, the oscillation direction of the pulley arms 9, 10, so that excessive oscillation of the entire autotensioner 1 is suppressed while the autotensioner 1 can instantaneously follow any slack in the belt 6 and maintain an appropriate belt tension.

[0052] A modified example of the autotensioner 1 is shown in Figures 13 and 14. In the autotensioner 1, the protrusion 22A that protrudes in the axial direction from the bottom of the bases 12a, 12b (the inner surface side of the flanges 16a, 16b) is used as the elastic member support part 22, but in this modified example, an inclined part 22B whose axial height gradually changes along the circumferential direction of the bases 12a, 12b is used as the elastic member support part 22. The inclination angle of this inclined part 22B is approximately the same as the inclination angle of the seating surface of the elastic member 20 facing the bottom. The inclined part 22B is interposed between the elastic member 20 and the bottom of the bases 12a, 12b, thereby supporting the seating surface of the elastic member 20 in the axial direction.

[0053] In this modification, the magnitude of the central angle of inclined portion 22B is approximately 225 degrees, but the magnitude (circumferential length) can be changed appropriately (for example, within ranges of 45 degrees or more and 300 degrees or less, or 90 degrees or more and 250 degrees or less). In the case where inclined portion 22B is provided in this manner, as in the case where protrusion 22A is provided, it is possible to more reliably prevent the torsion coil spring from collapsing when the autotensioner 1 operates.

[0054] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0055] 6 Auxiliary belt (belt) 7 First idler pulley 8 Second idler pulley 9 First Pulley Arm 10 Second pulley arm 11 Swing fulcrum axis 12a, 12b base 20 Elastic member 21a, 21b bent piece 22 Elastic member support part 22A protrusion 22B Slope 23a, 23b Elastic member locking portion 34 First rocking resistance member 35 Second rocking resistance member 36a, 36b Termination section 37a, 37b bent part

Claims

1. a first pulley arm (9) supporting a first idler pulley (7) in contact with the accessory belt (6); a second pulley arm (10) supporting a second idler pulley (8) in contact with the accessory belt (6); a swing fulcrum shaft (11) that swingably supports the first pulley arm (9) and the second pulley arm (10); an elastic member (20) made of a torsion coil spring that biases the second pulley arm (10) relative to the first pulley arm (9) so that the first idler pulley (7) and the second idler pulley (8) approach each other; a swing resistance member (34, 35) that generates swing resistance in only one swing direction of the first pulley arm (9) and the second pulley arm (10); having Each of the pulley arms (9, 10) has a cylindrical base (12a, 12b) that houses the elastic member (20), and the autotensioner is configured so that, when there is no load on both of the pulley arms (9, 10), the outer periphery of the elastic member (20) is supported by the inner surface of the base (12a, 12b).

2. 2. The autotensioner according to claim 1, further comprising an elastic member support portion (22) at a bottom portion of the base portion (12a, 12b) interposed between the elastic member (20) and the bottom portion to support the elastic member (20) in the axial direction.

3. 3. The autotensioner according to claim 2, wherein the elastic member support portion (22) is a protrusion (22A) that protrudes in the axial direction from the bottom portion, or a sloped portion (22B) whose axial height gradually changes along the circumferential direction of the base portion (12a, 12b).

4. 4. The autotensioner according to claim 1, further comprising elastic member locking portions (23a, 23b) that radially clamp and fix both ends of the elastic member (20) inside the base portions (12a, 12b).

5. 5. The autotensioner according to claim 4, wherein bent pieces (21 a, 21 b) bent radially inward are formed on both ends of the elastic member (20), and the bent pieces (21 a, 21 b) are clamped from the radial direction by the elastic member engaging portions (23 a, 23 b).

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