Auto tensioner

Abstract

To provide an auto tensioner capable of securing optimum belt tension and high followability, and excellent in durability.SOLUTION: The auto tensioner includes first and second pulley arms 9, 10, an oscillation fulcrum shaft 11 for oscillatably supporting each of the pulley arms 9, 10, an elastic member 22 for energizing both pulley arms 9, 10, and oscillation resistance members 33, 34 for giving oscillation resistance to the respective pulley arms 9, 10, the oscillation resistance members 33, 34 being formed of elastic materials having C-shaped circular parts 35a, 35b, respectively, the circular parts 35a, 35b each having a radial width formed larger at its center than at each end.SELECTED DRAWING: Figure 4

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 belt slack and properly adjust the belt tension, for example, the autotensioner shown in Patent Document 1 places an autotensioner pulley on each side of the belt span of the BSG pulley, and connects these pulleys with an intermediate member so that they can move relative to each other, thereby interlocking the pulleys to adjust the belt tension during normal operation and when the engine is restarted after an idling stop. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5634685 Summary of the Invention [Problem to be solved by the invention]

[0007] In the autotensioner shown in Patent Document 1, which adjusts the tension of the belt span on both sides of the BSG pulley by interlocking two pulleys, the belt tension is adjusted by the oscillation and biasing force of the entire autotensioner in response to fluctuations in the belt tension caused by fluctuations in engine rotation. However, when fluctuations in the belt tension become large, the oscillation of the entire autotensioner becomes large, which can cause abnormal noise due to vibration or contact with the locking mechanism, or the belt can become separated from the pulley, making it impossible to apply tension to the belt.

[0008] 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 suppress excessive oscillation of the pulley arm to ensure high tracking performance, and has excellent durability against repeated oscillation. [Means for solving the problem]

[0009] 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 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 The autotensioner is configured such that the rocking resistance member is made of an elastic material having a C-shaped arc portion, and the radial width of the arc portion is larger at the center than at both ends.

[0010] In this way, the unidirectional oscillation resistance provided by the oscillation resistance member can provide optimal belt tension both during normal operation and when the engine is restarted after an idling stop, and can ensure high compliance with the accessory belt by suppressing excessive oscillation of the pulley arm. Moreover, because the radial width of the arcuate portion of the oscillation resistance member is greater at the center than at both ends, it is possible to reduce stress concentration in the oscillation resistance member due to repeated oscillation, and it is possible to provide an autotensioner with excellent durability.

[0011] In the above configuration, It is preferable that one end side of the arc portion of the rocking resistance member is engaged with the rocking fulcrum shaft, while the other end side is provided on a receiving portion formed on the first pulley arm or the second pulley arm, so that when the first pulley arm and the second pulley arm rock in the one direction, the other end side engages with the receiving portion and the rocking resistance member elastically deforms, thereby generating rocking resistance in the first pulley arm and the second pulley arm.

[0012] In this way, when each pulley arm swings in the one direction, the swing resistance from the swing resistance member can be reliably applied to each pulley arm.

[0013] In the above configuration, The ratio w of the maximum radial width at the center to the minimum radial width at both ends max / w min It is preferable that the ratio is within the range of 1.2 to 3.0.

[0014] In this way, it is possible to achieve both the necessary amount of expansion required for the rocking resistance member and the rocking resistance force. max / w min If the ratio w is smaller than 1.2, stress is likely to concentrate in the center of the arc when rocking resistance is applied to the rocking resistance member, and the maximum stress may exceed the fatigue limit. max / w min If the relationship exceeds 3.0, a large external force must be applied to obtain a predetermined amount of radial expansion, and the maximum stress at the center of the arc portion having the maximum radial width becomes large, which may exceed the fatigue limit.

[0015] The ratio w max / w min In the configuration that defines the appropriate range of The minimum radial width w of the arcuate portion with respect to the axial thickness t min The ratio of min It is preferable that / t is within the range of 0.6 to 2.0.

[0016] In this way, the rocking resistance member can be smoothly formed by punching and pressing the base material. min When / t is less than 0.6, pressing becomes difficult, and when it is more than 2.0, a large load is required during pressing, which may shorten the life of the die. In either case, this may cause problems in smooth punching press processing of the vibration resistance member.

[0017] In all of the above configurations: The arc portion may have an inner edge arc constituting its inner edge and an outer edge arc constituting its outer edge, the center of the outer edge arc being on a line connecting the center of the inner edge arc and the central portion, and eccentric from the center of the inner edge arc toward the central portion. Alternatively, at least one of the inner edge or the outer edge of the arc portion may be formed by a curve other than an arc, and the shortest distance between the inner edge and the outer edge may be longest at the central portion.

[0018] In this way, by combining the positions and shapes of the inner edge arc and the outer edge arc, the rocking resistance member can be configured so that one end of each of the two ends of the arc portion has the minimum radial width and the central portion has the maximum radial width. Effect of the Invention

[0019] The autotensioner of the present invention is provided with a swing resistance member 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 radial width of the arc portion of this swing resistance member is formed to be greater at the center than at both ends.As a result, it is possible to provide optimal belt tension during normal operation and when the engine is restarted after an idling stop, and it is possible to suppress excessive swing of the pulley arm to ensure high tracking ability and to provide an autotensioner that has excellent durability against repeated swing. [Brief description of the drawings]

[0020] [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 taken along line III-III in Figure 2 [Figure 4] Cross-sectional view taken along line IV-IV in Figure 3. [Diagram 5]Cross-sectional view taken along line VV in Figure 3 [Figure 6] An exploded perspective view of the autotensioner shown in Figure 1. [Figure 7] FIG. 2 is a front view of a rocking resistance member used in the autotensioner shown in FIG. [Figure 8] 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 portion of the second pulley arm, and FIG. 2C is a cross-sectional view of a main portion of the first pulley arm. [Figure 9] FIG. 2A is a front view showing the function of the auto tensioner when the BSG is operating, FIG. 2B is a cross-sectional view of a main part of the first pulley arm, and FIG. 2C is a cross-sectional view of a main part of the second pulley arm. [Figure 10] FIG. 1 is a diagram showing a schematic diagram of maximum stress acting on a rocking resistance member; [Figure 11] FIG. 8 is a front view showing a modification of the rocking resistance member shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] 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.

[0022] 3 to 6, the 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 swingably supporting the first pulley arm 9 and the second pulley arm 10. Note that the belt 6 is omitted in FIG. 3.

[0023] The first idler pulley 7 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 second idler pulley 8 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 axis of a 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.

[0024] 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.

[0025] 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 small diameter cylinder parts 14a and 14b and the large diameter cylinder parts 15a and 15b are connected at one axial end by flanges 16a and 16b extending in the radial direction. Fan-shaped recessed receiving parts 17a and 17b are formed in a part of the cylinder of the small diameter cylinder parts 14a and 14b in the circumferential direction (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 about 50 degrees, but it can be changed appropriately within a range of, for example, 20 degrees to 80 degrees. Slits 18a and 18b are formed in a part of the cylinder of the large diameter cylinder parts 15a and 15b in the circumferential direction. The receiving parts 17a and 17b and the slits 18a and 18b are formed at positions shifted from each other in the circumferential direction. Slide bearings 19a, 19b are press-fitted into the inner diameter sides of the small diameter cylindrical portions 14a, 14b.

[0026] At the tips of the extension pieces 13a, 13b, through holes 21a, 21b are formed for passing the rotation shafts 20a, 20b 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.

[0027] A common elastic member 22 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. The elastic member 22 is a steel coil spring. Both ends of the elastic member 22 are bent pieces 23a, 23b bent radially outward. The bent piece 23a on one end side is engaged with a slit 18a formed in the large diameter cylindrical portion 15a of the first pulley arm 9, and the bent piece 23b on the other end side is engaged with a slit 18b formed in the large diameter cylindrical portion 15b of the second pulley arm 10. The elastic member 22 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.

[0028] 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.

[0029] 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.

[0030] The first fulcrum shaft 24 is positioned on the inner diameter side of a plain bearing 19a 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 19b pressed into the small diameter cylindrical portion 14b of the second pulley arm 10.

[0031] The swing fulcrum shaft 11 is provided with swing resistance members 33, 34 that 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 33, 34 are made of a plate-like elastic material having C-shaped arc sections 35a, 35b. As shown in FIG. 7, the arc sections 35a, 35b have an inner edge arc 36 that forms its inner edge and an outer edge arc 37 that forms its outer edge. The center c2 of the outer edge arc 37 is on a line connecting the center c1 of the inner edge arc 36 and the center of the arc sections 35a, 35b, and is eccentric from the center c1 of the inner edge arc 36 toward the center.

[0032] The radial width of the arcuate portions 35a, 35b is made larger at the center than at both ends by eccentrically displacing the center c2 of the outer edge arc 37 as described above. In this embodiment, the minimum radial width w min Maximum radial width at the center w max The ratio of max / w min is about 1.5. This ratio w max / w min can be appropriately changed within the range of 1.2 or more and 3.0 or less.

[0033] In this embodiment, the minimum radial width w of the arcuate portions 35a and 35b relative to the axial thickness t is min The ratio of min / t is about 1.6. This ratio w min / t can be appropriately changed within a range of 0.6 to 2.0. The central portion here refers to the vicinity of the portion corresponding to the opposite side of the opening of the arc portions 35a and 35b with respect to the center c1 of the inner edge arc 36 (near the 180-degree position of the opening), and includes a somewhat wide range in which, for example, when the central angle of the opening is 40 degrees, the central angle of the opposite side of the opening is about 60 degrees (the size of the central angle of the opening ±10 degrees).

[0034] One end side of the arcuate portions 35a, 35b is a terminal portion 38a, 38b that terminates along the circumferential direction, while the other end side is a bent portion 39a, 39b that is bent radially outward.

[0035] The oscillation resistance members 33, 34 are provided on both axial sides of a flange 29 formed on the outer periphery of the main shaft 26. A plurality of these oscillation resistance members 33, 34 (four in this embodiment) can be stacked together to exert the required oscillation resistance force (see FIG. 6, etc.). In the following, the oscillation resistance member 33 provided on the first fulcrum shaft 24 side will be referred to as the first oscillation resistance member 33, and the oscillation resistance member 34 provided on the second fulcrum shaft 25 side will be referred to as the second oscillation resistance member 34.

[0036] The first and second vibration resistance members 33, 34 are attached in opposite directions to the main shaft 26. That is, the terminal end 38a of the first vibration resistance member 33 abuts against the abutment portion 30 formed on the main shaft 26 from one circumferential direction, while the terminal end 38b of the second vibration resistance member 34 abuts against the abutment portion 30 formed on the main shaft 26 from the opposite circumferential direction. The bent portion 39a of the first vibration resistance member 33 is provided on the receiving portion 17a formed on the small diameter cylindrical portion 14a of the first pulley arm 9, and the bent portion 39b of the second vibration resistance member 34 is provided on the receiving portion 17b formed on the small diameter cylindrical portion 14b of the second pulley arm 10.

[0037] The bent portions 39a, 39b formed on the first and second oscillation resistance members 33, 34 are allowed to move within the 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. When attached to the accessory drive system, each of the bent portions 39a, 39b is in contact with the abutment portion 30 of the main shaft 26 with a slight preload. As shown in Figs. 4 and 5, the circumferential positions of the inner edges where the bent portions 39a, 39b contact are opposite in the first pulley arm 9 and the second pulley arm 10. However, in both pulley arms 9, 10, the direction from one circumferential end where the bent portions 39a, 39b 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 a result of the tension of the belt 6 pushing the first idler pulley 7 or the second idler pulley 8.

[0038] When the first pulley arm 9 shown in Fig. 4 is swung in one direction (the direction indicated by the arrow in Fig. 4) 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 39a of the first swing resistance member 33, causing the first swing resistance member 33 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 39a of the first swing resistance member 33 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 33.

[0039] 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 17b formed on the second pulley arm 10 comes into contact with the bent portion 39b of the second swing resistance member 34, causing the second swing resistance member 34 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 39b of the second swing resistance member 34 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 34.

[0040] An example of the operation of this autotensioner 1 will be described with reference to Figures 1, 8 and 9. 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.

[0041] During normal operation (power generation in the BSG) shown in FIG. 8(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 second pulley arm 10 receives tension from the belt 6 and swings in one direction (see arrow r2 in FIG. 8(a)). At this time, as shown in FIG. 8(b), a swing resistance acts on the second pulley arm 10 due to elastic deformation of the second swing resistance member 34, 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. 8(a)) so as to correspond to the slack of the belt 6. At this time, as shown in FIG. 8(c), since no rocking resistance is generated from the first rocking resistance member 33 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 22.

[0042] During the BSG operation shown in FIG. 9(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 first pulley arm 9 receives tension from the belt 6 and swings in one direction (see arrow r1 in FIG. 9(a)). At this time, as shown in FIG. 9(b), a swing resistance acts on the first pulley arm 9 due to elastic deformation of the first swing resistance member 33, 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. 9(a)) so as to correspond to the slack of the belt 6. At this time, as shown in FIG. 9(c), since no swing resistance acts on the second pulley arm 10 from the second swing resistance member 34, the second pulley arm 10 swings smoothly in the direction of biasing the belt 6 due to the biasing force of the elastic member 22.

[0043] During normal operation and BSG operation, the diameter of each of the rocking resistance members 33, 34 frequently expands and contracts. During this expansion and contraction, stress concentration occurs near the center of the arcuate sections 35a, 35b of the rocking resistance members 33, 34. If the maximum stress value of this stress concentration exceeds the fatigue limit stress, the life of the rocking resistance members 33, 34 may be rapidly reduced.

[0044] The value of this maximum stress is determined by the minimum radial width w min Maximum radial width at the center w max The ratio of max / w min For example, as shown by the dashed curve in Figure 10, when the radial width of the arcuate portions 35a, 35b of the oscillating resistance members 33, 34 is constant from both ends to the center (see the leftmost point on the dashed curve), a large stress concentration occurs when a specified oscillating resistance force (torque) (e.g., 10 N m) is generated in the oscillating resistance members 33, 34, and the maximum stress generated in the oscillating resistance members 33, 34 exceeds the fatigue limit stress. In contrast, when the ratio w max / w min When the stress concentration is increased, the degree of stress concentration decreases, and the maximum stress generated in the rocking resistance members 33, 34 falls below the fatigue limit stress.

[0045] On the other hand, as shown by the solid curve in FIG. 10, when the rocking resistance members 33, 34 are expanded in diameter by a predetermined angle (for example, 10 degrees), the maximum stress generated in the rocking resistance members 33, 34 is the minimum radial width w min Maximum radial width at the center w max The ratio of max / w min The larger the stress, the greater the fatigue stress, and eventually exceeds the fatigue limit stress.

[0046] That is, the ratio w for obtaining a predetermined amount of expansion while generating a predetermined resistance force required for the rocking resistance members 33 and 34 is max / w minIt has become clear that there is an optimum range for , and in the above configuration, it is appropriate to set it within the range of 1.2 or more and 3.0 or less (the appropriate range shown in FIG. 10).

[0047] 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 33, 34. 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 to follow the belt 6.

[0048] Furthermore, in the above-described autotensioner 1, since the oscillation resistance members 33, 34 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 33, 34 on only one of the pulley arms 9, 10.

[0049] In addition, in the above autotensioner 1, the oscillation resistance members 33, 34 are made of an elastic material having C-shaped arc portions 35a, 35b, so that a compact configuration can provide oscillation resistance from the oscillation fulcrum shaft 11 to the pulley arms 9, 10. Moreover, the oscillation resistance members 33, 34 are formed with bent portions 39a, 39b, which are provided on receiving portions 17a, 17b consisting of sector-shaped recesses formed in the pulley arms 9, 10, so that oscillation resistance is generated only in one direction, that is, the oscillation direction of the pulley arms 9, 10. This makes it possible to instantly follow any slack in the belt 6 while suppressing excessive oscillation of the entire autotensioner 1, and to maintain appropriate belt tension.

[0050] Moreover, because the radial width of the C-shaped arcuate portions 35a, 35b of the oscillation resistance members 33, 34 is made larger at the center than at both ends, the maximum stress generated in the oscillation resistance members can be suppressed to a value below the fatigue limit stress. This makes it possible to provide an autotensioner 1 with excellent durability against repeated oscillation. In particular, the minimum radial width w min Maximum radial width at the center w max The ratio of max / w min Since is set within the range of 1.2 to 3.0, it is possible to reliably prevent the maximum stress from exceeding the fatigue limit stress.

[0051] In the above-described autotensioner 1, the minimum radial width w of the arcuate portions 35a, 35b relative to the axial thickness t is min The ratio of min Since / t is within the range of 0.6 to 2.0, the oscillation resistance members 33, 34 can be easily formed by punching and pressing.

[0052] In the above autotensioner 1, the center C2 of the outer edge arc 37 of the arc portions 35a, 35b is located on a line connecting the center C1 of the inner edge arc 36 and the center of the arc portions 35a, 35b, and is eccentric from the center c1 of the inner edge arc 36 toward the center. Therefore, the combination of the positions and shapes of the inner edge arc 36 and the outer edge arc 37 determines the minimum radial width w min , and the central part has a maximum radial width w max The oscillation resistance members 33, 34 can be configured so as to satisfy the above condition.

[0053] A modified example of the rocking resistance members 33, 34 is shown in Fig. 11. Similar to the configuration shown in Fig. 7, these rocking resistance members 33, 34 are made of a plate-like elastic material having C-shaped arc sections 35a, 35b, and are common in that the arc sections 35a, 35b have an inner edge arc 36 that forms their inner edge and an outer edge arc 37 that forms their outer edge. However, they differ in that at least one of the inner edge or outer edge of the arc sections 35a, 35b is made up of a curve other than an arc, and the shortest distance between the inner edge and the outer edge is greatest at the center.

[0054] Specifically, the inner edge of the arc portions 35a, 35b is formed by an inner edge arc 36, and the outer edge is formed by an outer edge elliptical arc 40. The centers c1, c3 of the inner edge arc 36 and the outer edge elliptical arc 40 coincide. The direction of the major axis of the outer edge elliptical arc 40 coincides with a straight line connecting the openings and central portions of the arc portions 35a, 35b. In this case, as when the inner and outer edges of the arc portions 35a, 35b are formed by arcs, the combination of the shapes of the inner edge arc 36 and the outer edge elliptical arc 40 determines whether or not both ends of the arc portions 35a, 35b have a minimum radial width w min , and the central part has a maximum radial width w max In this modification, the outer edge is configured as an elliptical arc, but it is possible to select from a variety of patterns, such as making the outer edge a parabola, making the inner edge an elliptical arc and the outer edge a circular arc, or making both the inner and outer edges elliptical arcs.

[0055] 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]

[0056] 2 BSG drive shaft (auxiliary drive shaft) 3 BSG pulley (auxiliary pulley) 4 Crankshaft 5 Crank pulley 6 Auxiliary belt (belt) 7 First idler pulley 8 Second idler pulley 9 First Pulley Arm 10 Second pulley arm 11 Swing fulcrum axis 17a, 17b Receiving part 22 Elastic member 33 First rocking resistance member 34 Second rocking resistance member 35a, 35b Arc section 36 Inner Arc 37 Outer arc 39a, 39b bent part c1 Center of the inner arc c2 Center of the outer arc w min Minimum radial width w max Maximum radial width t Thickness

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 (22) for biasing 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 (33, 34) that generates swing resistance in only one swing direction of the first pulley arm (9) and the second pulley arm (10); having The oscillating resistance member (33, 34) is made of an elastic material having a C-shaped arc portion (35a, 35b), and the radial width of the arc portion (35a, 35b) is larger at the center than at both ends.

2. 2. The autotensioner according to claim 1, wherein one end side of the arcuate portion (35 a, 35 b) of the oscillation resistance member (33, 34) is engaged with the oscillation fulcrum shaft (11), while the other end side is provided on a receiving portion (17 a, 17 b) formed on the first pulley arm (9) or the second pulley arm (10), so that when the first pulley arm (9) and the second pulley arm (10) oscillate in the one direction, the other end side engages with the receiving portion (17 a, 17 b) and the oscillation resistance member (33, 34) elastically deforms, thereby generating oscillation resistance in the first pulley arm (9) and the second pulley arm (10).

3. The minimum radial width (w ｍｉｎ ) to the maximum radial width (w ｍａｘ ) ratio (w ｍａｘ / w ｍｉｎ 2. The autotensioner according to claim 1, wherein the ratio of the friction coefficient to the friction coefficient is within a range of 1.2 to 3.

0.

4. The minimum radial width (w ｍｉｎ ) ratio (w ｍｉｎ 4. The autotensioner according to claim 3, wherein the ratio (ratio) of the tensioner force to the tensioner force is within a range of 0.6 to 2.

0.

5. 5. The autotensioner according to claim 1, wherein the arc portion (35a, 35b) has an inner edge arc (36) constituting its inner edge and an outer edge arc (37) constituting its outer edge, a center (c2) of the outer edge arc (37) is on a line connecting a center (c1) of the inner edge arc (36) and the central portion, and is eccentric from the center of the inner edge arc (36) toward the central portion.

6. 5. The autotensioner according to claim 1, wherein at least one of an inner edge or an outer edge of the arc portion (35a, 35b) is formed by a curve other than a circular arc, and the shortest distance between the inner edge and the outer edge is greatest at the central portion.

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