Use of a timing belt

Abstract

Use of a toothed belt (16) for an electric power steering system, wherein the toothed belt (16) comprises: a backing (24) made of an elastic core; several oblique teeth (20) arranged at a predetermined pitch in a longitudinal direction of the belt on an inner circumferential surface of the backing (24); and a cord (22) spirally embedded in the backing (24) in the longitudinal direction of the belt and consisting of fibers, wherein the oblique teeth (20) comprise a toothed cloth (26) arranged on an inner circumferential side thereof, the direction of the flank lines of the oblique teeth (20) and the lateral direction of the belt form an angle of 8 degrees or more and 16 degrees or less, the fibers constituting the cord (22) form a single thread, and the direction of rotation of the thread is inclined in a direction opposite to the direction of the flank lines of the oblique teeth (20) relative to the lateral direction of the belt.a winding direction of the cord (22) is inclined in the same direction as the direction of the flank lines of the oblique teeth (20) relative to the width direction of the belt, the toothed cloth (26) is a twill cloth and a twill direction of the toothed cloth (26) is inclined in the opposite direction to the direction of the flank lines of the oblique teeth (20) relative to the width direction of the belt.

Description

technical field

[0001] The technology disclosed in this patent relates to a toothed belt with so-called helical teeth. Technical background

[0002] Timing belts are used in the fields of general industrial applications and electric power steering for power transmission. A problem with toothed belts is the noise generated during operation as they mesh with pulleys.

[0003] To solve this problem, a timing belt described in Patent Document 1 is provided with so-called helical teeth for the purpose of noise reduction; H. with teeth having tooth traces extending in a direction inclined relative to a width direction of the belt. List of citationspatent specifications

[0004] [Patent Document 1] Unexamined Japanese Patent Publication No. H10-184808 [Patent Document 2] Japanese Unexamined Patent Publication No. 2004-308702 [Patent Document 3] Japanese Unexamined Patent Publication No. 2009-014023 [Patent Document 4] Japanese Unexamined Patent Publication No. 2005-29145 Summary of the invention Technical problem

[0005] The inventor of the present invention assumed that the effect of reducing the noise improves as an angle formed by the extending direction of the tooth traces of the helical teeth and the width direction of the belt (may be referred to as a helix angle) increases. However, the increase in the helix angle increases a force biasing the driven belt to one side in the belt width direction and brings a side surface of the belt into contact with a flange of the pulley, thereby causing rapid wear of the side surface of the belt. Thus, when the helix angle reaches or exceeds a certain value, the noise reduction effect decreases and the belt may fail easily due to wear of its side surface.

[0006] In view of the problem, the present invention has been accomplished to provide a toothed belt that reduces noise without causing disadvantages. the solution of the problem

[0007] A toothed belt according to an embodiment of the present disclosure includes a back made of an elastic body, a plurality of helical teeth arranged at a predetermined pitch in a longitudinal direction of the belt on an inner peripheral surface of the back, and a cord spirally wound in the longitudinal direction of the belt in the back is embedded and consists of fibers. The helical teeth include a tooth cloth arranged on an inner peripheral side thereof, an extending direction of tooth traces of the helical teeth and a width direction of the belt form angles of 8 degrees or more and 16 degrees or less, the fibers constituting the cord form a single filament, and a twisting direction of the thread is inclined in a direction opposite to the extending direction of the tooth traces of the helical teeth relative to the width direction of the belt, and a winding direction of the cord is inclined in the same direction as the extending direction of the tooth traces of the helical teeth relative to the width direction of the belt. The expression “the same direction as the extending direction of the tooth traces of the helical teeth” does not mean that the winding direction of the cord and the extending direction of the tooth traces of the helical teeth are completely the same, but means that the winding direction of the cord and the extending direction of the tooth traces of the helical teeth are the same way (extending diagonally up-right or down-left).

[0008] With this configuration, even if the angle formed by the extending direction of the tooth traces of the helical teeth and the belt width direction increases, the force biasing the belt in the belt width direction is canceled. Thus, the noise is reduced and the belt is not quickly damaged. Advantages of the Invention

[0009] The toothed belt according to the embodiment of the present disclosure prevents the belt from being damaged and reduces the noise. Brief description of the drawings

[0010] figure 1 is a perspective view showing part of a toothed belt of an embodiment of the present disclosure.

[0011] figure 2(a) is a side view showing part of the toothed belt of the embodiment of the present disclosure, and figure 2(b) is a plan view showing the part of the toothed belt viewed from a helical gear surface.

[0012] figure 3 is a plan view of a part of the toothed belt viewed from the helical-toothed surface, showing an extending direction of tooth traces of the helical teeth, a spiral direction (a winding direction) of a cord, a twisting direction of a thread constituting the cord, and a twill direction of the toothcloth.

[0013] figure 4(a) is a cross-sectional view of the toothed belt of the embodiment of the present disclosure along the line in FIG figure 2(a) line IVa-IVa shown, and figure 4(b) is an enlarged view showing a cross section of the toothed belt along a longitudinal direction of the belt.

[0014] figure 5(a) shows the results of a noise measurement test, and figure 5(b) is a schematic diagram showing a method of noise measurement.

[0015] figure 6(a) shows the results of a durability test, and figure 6(b) is a schematic diagram showing an apparatus used for the durability test.

[0016] figure 7(a) shows the results of a belt pretension test, and figure 7(b) is a schematic diagram showing an apparatus used for the belt pretension test.

[0017] figure 8 shows the results of a belt preload test conducted with a fixed helix angle of the helical teeth.

[0018] figure 9 shows the results of a measurement made under conditions where the helix angle of the helical teeth is fixed, an SZ twist cord is used, and an angle of a twill direction of the toothcloth is changed. Description of embodiments - toothed belt configuration -

[0019] Hereinafter, a configuration of a toothed belt of an embodiment of the present disclosure will be described with reference to the drawings.

[0020] figure 1 is a perspective view showing part of the toothed belt of the present embodiment. A toothed belt 16 according to the present embodiment, as in figure 1, a back 24 from an elastic body, several helical teeth 20 formed at a predetermined pitch in a longitudinal direction of the belt on an inner peripheral surface of the back 24 are arranged, and a cord 22 , spiraling in the longitudinal direction of the belt in the back 24 is embedded and consists of fibers. Each of the helical teeth 20 includes a dental rubber 28 and a tooth towel 26 for example, twill fabric arranged on the inner peripheral side of the helical teeth.

[0021] figure 2(a) is a side view showing part of the toothed belt 16 of the embodiment of the present disclosure, and figure 2(b) is a plan view showing the part of the toothed belt 16 from the one with the helical teeth 20 provided surface (as seen from the inner peripheral surface of the belt). A direction of progression of tooth traces of the helical teeth 20 may be inclined in one direction relative to a width direction of the belt. In the example of figure 2(a) and figure 2(b) the tooth traces of the helical teeth extend 20 diagonally upwards to the right, taking the direction in which the belt runs as the upwards direction. figure 3 is a plan view of the part of the toothed belt 16 from the one with the helical teeth 20 provided surface seen showing the direction of flow 1 of flank lines of the helical teeth 20 , a spiral direction 3 (a winding direction) of the cord 22 , a direction of rotation 5 one the cord 22 forming thread and a twill direction7 of the toothcloth 26 indicates. figure 4(a) is a cross-sectional view of the toothed belt 16 of the embodiment of the present disclosure along the in figure 2(a) line IVa-IVa. figure 4(b) is an enlarged view showing a cross section of the toothed belt 16 along the longitudinal direction of the belt.

[0022] The gradient direction 1 the flank lines of the helical teeth 20 and the width direction of the belt preferably form an angle θ of 8 degrees or more and 16 degrees or less. The angle θ is more preferably 9 degrees or more and 15 degrees or less.

[0023] The Cord 22 constituting fibers form a single thread, and the direction of twist 5 of the thread is in a direction opposite to the direction of travel 1 the flank lines of the helical teeth 20 inclined relative to the width direction of the belt. If the flank lines of the helical teeth 20 extending diagonally to the upper right, the yarn is S-twisted (when a two-ply yarn is used, the cord is SS-twisted).

[0024] The winding direction 3 of the cord 22 is in the same direction as the gradient direction 1 of the tooth traces of the helical teeth relative to the belt width direction. in the in figure 3 shown example runs the winding direction 3 of the cord 22 diagonally to the upper right relative to the belt width direction. The Cord 22 forming thread can be changed from a double layer thread to a single thread, the corduroy 22 may be wound at a different pitch or the diameter of the cord 22 can according to the angle θ subtended by the course direction 1 of the flank lines of the oblique teeth 20 and the width direction of the belt is formed can be changed.

[0025] The body direction 7 of the toothcloth 26 is in the direction opposite to the direction of travel 1 the flank lines of the helical teeth 20 inclined relative to the width direction of the belt. in the in figure 3 is the twill direction of the toothcloth 26 diagonally lower right (or diagonally upper left) relative to the belt width direction.

[0026] A pitch P, at which the helical teeth 20 arranged (see figure 2(a)) is not particularly limited, but is preferably 3 mm or less. A width W of the belt (see figure 2(b)) is also not particularly limited, but is preferably 15 mm or more. The timing belt 16 is an endless belt in the shape of a ring and has a circumference of about 300 mm to 400 mm, for example.

[0027] A thickness t of the toothed belt 16 is, for example, about 1.0 mm to 2.6 mm, and a thickness tb of the ridge 24 is, for example, about 0.2 mm to 1.85 mm. A height hb of the helical teeth 20 is, for example, about 0.5 mm to 1.2 mm. A width Wt of helical teeth 20 is, for example, about 1.0 mm or more and 2.0 mm or less in the longitudinal direction of the belt.

[0028] A material for the back 24 and the dental rubber 28 can be, for example, rubber which can withstand a temperature range from a low temperature of about -40°C to a high temperature of about 120°C, and preferably hydrogenated nitrile rubber (HNBR) is used. Materials other than this, for example, chloroprene rubber (CR), ethylene propylene diene rubber (EPDM), styrene butadiene rubber, epichlorohydrin rubber or polyurethane rubber, can also be used for the backing 24 and the dental rubber 28 be used. A known reinforcing fiber or an additive can be added to these rubbers.

[0029] For the cord 22 a material with high elasticity is preferably used. For example, glass fiber is preferably used. For the cord 22 other fibers, such as aramid fibers, can also be used.

[0030] A preferred material for the toothcloth 26is, for example, nylon fiber or nylon fiber to which aramid fiber is added. The Toothcloth 26 has a thickness of, for example, about 0.1 mm or more and 0.3 mm or less. A material for the toothcloth 26 can also be nylon fiber such as, for example, 6,6-nylon and 4,6-nylon, aramid fiber, or polyparaphenylene benzobisoxazole (PBO) fiber.

[0031] The timing belt 16 The present embodiment is wound around a drive pulley and a driven pulley both provided with helical teeth for transmitting power with the helical teeth 20 to grab. The timing belt 16 is used, for example, in electric power steering (EPS).

[0032] For example, in an exemplary electric power steering system (not shown), when a handle is operated, rotation is imparted to an input axle and a torsion bar is twisted by the rotation to impart rotation to a pinion gear. When the rotation of the pinion is transmitted to a rack shaft, the rack shaft moves in an axial direction. When a torque detector detects the torsion amount of the torsion bar, a controller receives an output signal from the torque detector and rotates an assist motor. The rotation of the assisting motor is driven by the drive pulley through the toothed belt 16 transferred to the driven pulley. During this process, the supporting motor supports the work of the handle. -Effects and advantages of the toothed belt of the embodiment of the present disclosure-

[0033] At the timing belt 16 of the present embodiment form the extending direction of the tooth traces of the helical teeth 20 and the belt width direction has an angle of 8 degrees or more. Thus, when the belt is driven, a pulley tooth and a belt tooth mesh evenly from side to side of these teeth. This reduces noise caused by the meshing of the pulley's helical teeth and the helical teeth 20 of the toothed belt 16 is produced. If, on the other hand, the through the direction of the flank lines of the helical teeth 20 and the belt width direction angle θ formed at 16 degrees or less becomes one by the helical teeth 20 generated thrust force (a biasing force) is controlled within an adjustable range.

[0034] If the through the direction of the flank lines of the helical teeth 20 and the angle θ formed in the width direction of the belt is set to 9 degrees or more and 15 degrees or less, the thrust force is easily canceled while the noise reducing effect is maintained at a high level. Thus, the angle θ within this range is preferable because it improves the durability of the toothed belt 16 improved.

[0035] The Cord 22 constituent fibers form at the toothed belt 16 a single thread in the present embodiment, and the twisting direction of the thread is in a direction opposite to the extending direction of the tooth traces of the helical teeth 20 inclined relative to the width direction of the belt. If the timing belt 16 thus rotates, there will be a thrust force in the direction opposite to that by the helical teeth 20 generated thrust force (preload force) generated. This raises the through the helical teeth 20 generated thrust and thus the side surface of the toothed belt 16 not easily brought into contact with the flange of the pulley. At the timing belt 16 the present embodiment is thus, even if the extending direction of the tooth traces of the helical teeth 20 is more inclined, the side surface of the belt is not easily worn, and the noise generated by the side surface of the belt and the flange rubbing against each other is effectively reduced.

[0036] At the timing belt 16 of the present embodiment is also the winding direction of the cord 22 in the same direction as the running direction of the tooth traces of the helical teeth 20inclined relative to the belt width direction. This also generates the thrust force in the direction opposite to that by the helical teeth 20 generated thrust when turning the toothed belt 16 . This causes the through the helical teeth 20 generated thrust is canceled and the flange of the pulley and the side face of the timing belt 16 are not brought into contact so quickly.

[0037] At the timing belt 16 of the present embodiment is the twill direction of the toothcloth 26 relative to the belt width direction in the direction opposite to the extending direction of the tooth traces of the helical teeth 20 inclined. This configuration also generates the thrust force in the direction opposite to that by the helical teeth 20 generated thrust when turning the toothed belt 16 . This causes the through the helical teeth 20 generated thrust is canceled and the flange of the pulley and the side face of the timing belt 16 are not brought into contact so quickly.

[0038] The ones through the toothcloth 26 The shearing force generated increases particularly as the angle subtended by the twill direction of the toothcloth increases 26 and the width direction of the belt is formed. Appropriate adjustment of the angle of the body direction according to the direction of progression of the tooth traces of the helical teeth 20 thus allowing a cancellation of the force pretensioning the belt.

[0039] As described above allow for the toothed belt 16 of the present embodiment appropriate adjustments of the twisting direction of the cord 22 forming thread, the winding direction of the cord 22 and the twill direction of the toothcloth 26 according to the inclination of the helical teeth 20 a reduction in drive noise and prevention of rapid damage to the belt.

[0040] The toothed belt described above 16 Fig. 11 is an example of the embodiment, and the material, shape and size of the belt can be changed appropriately without departing from the scope of the present invention. If, for example, the helical teeth 20 are inclined in the opposite direction become the winding direction of the cord 22 , the twist direction of the thread and the twill direction of the toothcloth 26 compared to those of the toothed belt 16 vice versa. This reduces noise and effectively prevents damage to the belt.

[0041] According to the inclination of the helical teeth 20 can be any of the winding direction of the cord 22 , twist direction of the thread and twill direction of the toothcloth 26 compared to that of the toothed belt 16 of the present embodiment are reversed. – Process for manufacturing the toothed belt –

[0042] Now, an example method for making the timing belt 16 described. This method uses a cylindrical mold and a vulcanizer in which the cylindrical mold can be used. In an outer peripheral surface of the cylindrical shape, there are grooves for forming the helical teeth at regular intervals in a circumferential direction 2 arranged and inclined by a helix angle θ relative to the axial direction of the mold.

[0043] First, a fibrous material such as nylon is used for the toothcloth 26 and rubber cement is applied to one of the surfaces of the fibrous material using a knife coater or a roll coater. Then, the fibrous material is formed into a tube so that the surface to which the rubber cement made of HNBR, for example, is applied faces outward.

[0044] Additionally, an uncrosslinked rubber sheet is used to form the backing 24 of the toothed belt 16 and a fiberglass twisted filament to form the cord 22 manufactured. A thread with an S-twist is used as the twisted thread if the flank lines of the helical teeth formed in this way 20 extending diagonally to the upper right, and a Z-twist thread is used when the flank lines of the helical teeth 20 extending diagonally down to the right.

[0045] Then the cylindrical form is covered with the fiber material around which the twisted thread is spirally wound at regular intervals. At this time is the winding direction of the cord 22 in the same direction as the running direction of the tooth traces of the helical teeth 20 inclined relative to the belt width direction. Further, a sheet of unvulcanized rubber composition is wrapped around the mold. At this time, the fiber material, the twisted thread and the unvulcanized rubber sheet are layered in this order on the peripheral surface of the cylindrical mold.

[0046] Then, the cylindrical mold provided with the layered material is placed in the vulcanizer, and the temperature and pressure are adjusted to predetermined values, respectively. At this time, the unvulcanized rubber composition flows into the grooves formed in the cylindrical mold, so that the tooth cloth is pressed into the grooves, thereby forming the helical teeth 20 are formed.

[0047] Finally, the cylindrical mold is taken out of the vulcanizer, and a cylindrical belt precursor formed on the peripheral surface of the cylindrical mold is removed therefrom. Then the pre-product is cut into pieces of a predetermined width to fit the timing belt 16 to obtain.

[0048] The manufacturing process of the toothed belt 16 is not limited to the above, and may optionally be replaced with other methods. [Examples] - Toothed belt configuration -

[0049] Results of tests conducted on the toothed belts are described below. The toothed belts of Examples and Comparative Examples were made with their backings, tooth rubbers, cords and tooth cloths of the same materials, respectively, with the pitch between the helical teeth set at 2 mm and the height of the teeth set at 1.31 mm and the following parameters were changed. However, the twisting direction of the thread constituting the cord was appropriately changed. Tables 1 and 2 show configurations of the toothed belts of Examples and Comparative Examples. A durability test described later was conducted on the toothed belts, which had a width of 6 mm and were manufactured by the same method. [Table 1] [Table 2] (Example 1)

[0050] As shown in Table 2, the helix angle of the helical teeth extending diagonally to the upper right was set at 8 degrees. The toothcloth had the twill line extending diagonally upward left and the angle of the twill line (i.e., the angle formed by the belt width direction and the twill direction) set at 41 degrees. The winding direction of the cord was diagonally to the top right. The cord consisted of two threads with an S twist.

[0051] The toothed belts of Examples 1-4 and Comparative Examples described below were manufactured by the method described above. The back and tooth rubber of each of the timing belts were made of HNBR and the cord was made of glass fiber. A cloth woven from warp and weft yarns of 66 nylon was used as the tooth cloth. The toothed belts of Examples 1-4 and Comparative Examples described below had a belt width of 24 mm and a belt circumference of 332 mm. (Example 2)

[0052] As shown in Table 2, the helix angle of the helical teeth extending diagonally to the upper right was set at 9 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord was diagonally to the top right. The cord consisted of two threads with an S twist. (Example 3)

[0053] As shown in Table 2, the helix angle of the helical teeth extending diagonally to the upper right was set at 12 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of two S-twisted filaments. (Example 4)

[0054] As shown in Table 2, the helix angle of the helical teeth extending diagonally to the upper right was set at 15 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of two S-twisted filaments. (Example 5)

[0055] As shown in Table 2, the helix angle of the helical teeth extending diagonally to the upper right was set at 16 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of two S-twisted filaments. (Comparative Example 1)

[0056] As shown in Table 1, the toothed belt of Comparative Example 1 had straight teeth. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of an S-twist yarn and a Z-twist yarn. (Comparative example 2)

[0057] As shown in Table 1, the helix angle of the helical teeth extending diagonally to the upper right was set at 5 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of an S-twist yarn and a Z-twist yarn. (Comparative example 3)

[0058] As shown in Table 1, the helix angle of the helical teeth extending diagonally to the upper right was set at 7 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 31 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of an S-twist yarn and a Z-twist yarn. (Comparative example 4)

[0059] As shown in Table 1, the helix angle of the helical teeth extending diagonally to the upper right was set at 7 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 36 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of an S-twist yarn and a Z-twist yarn. (Comparative Example 5)

[0060] As shown in Table 1, the helix angle of the helical teeth extending diagonally to the upper right was set at 7 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of an S-twist yarn and a Z-twist yarn. (Comparative Example 6)

[0061] As shown in Table 1, the helix angle of the helical teeth extending diagonally to the upper right was set at 7 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 46 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of an S-twist yarn and a Z-twist yarn. (Comparative Example 7)

[0062] As shown in Table 1, the helix angle of the helical teeth extending diagonally to the upper right was set at 7 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 51 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of an S-twist yarn and a Z-twist yarn. (Comparative Example 8)

[0063] As shown in Table 2, the helix angle of the helical teeth extending diagonally to the upper right was set at 7 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of two S-twisted filaments. (Comparative Example 9)

[0064] As shown in Table 2, the helix angle of the helical teeth extending diagonally to the upper right was set at 7 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of two Z-twisted yarns. (Comparative Example 10)

[0065] As shown in Table 2, the helix angle of the helical teeth extending diagonally to the upper right was set at 9 degrees. The toothcloth had the twill line extending diagonally to the upper left and the twill line angle set at 41 degrees. The winding direction of the cord extended diagonally to the upper right, and the cord consisted of an S-twist yarn and a Z-twist yarn. – Noise measurement method –

[0066] figure 5(b) is a schematic view showing a method of noise measurement.

[0067] A belt was used as an evaluation target around biaxial pulleys of a drive pulley 33 and a driven pulley 31 wound to measure a noise level while rotating the drive pulley 33 of 1000 rpm. to 5000 rpm. was changed. The drive pulley 33 had 45 teeth, the driven pulley 31 had 138 teeth and the pitch between the teeth of the pulleys was 2 mm. The drive pulley had a diameter of 28.14 mm and the driven pulley had a diameter of 87.35 mm. The helix angle of the teeth of the pulleys was the same as that of the belt as the evaluation target. A belt tension was set at 100N, and the noise level was measured using a precision sound level meter (LA-5560 manufactured by Ono Sokki Co., Ltd.). Directional microphones were arranged in a lateral direction (the width direction of the belt) at a distance of 30 mm from an end face of the belt and at a distance of 20 mm from the center of the driving pulley in a direction toward the center of the driven pulley. The measurement was performed on each of the belts at 1000 rpm to 5000 rpm and 300-400 points, and an average of the measurements at the 300-400 points was obtained. – durability test –

[0068] figure 6(b) is a schematic view showing an apparatus used for a durability test.

[0069] A belt was used as an evaluation target around biaxial pulleys of a drive pulley 35 and a driven pulley 37 wound, and the speed of the drive pulley 35 was set to 1800 rpm. fixed. At this time, the time until cracking of 1 / 2 or more of the tooth width occurred was measured. Both the drive pulley 35 as well as the driven pulley 37 had 45 teeth and the pitch between the teeth was set at 2 mm. Both the drive pulley 35 as well as the driven pulley 37 had a diameter of 28.14 mm. The teeth of the pulleys had the same helix angle as the belt as the evaluation target. An initial tension of the belt was set at 80N. The measurement was performed in an environment at 125°C. – belt tension test –

[0070] figure 7(b) is a view schematically showing an apparatus used for a belt pretension test.

[0071] A belt was used as an evaluation target around biaxial pulleys of a drive pulley 41 and a driven pulley 39 wound, and the speed of the drive pulley 41 was set to 1000 rpm. fixed. A force generated in the width direction of the belt (a belt pretensioning force) was measured by a sensor in this test 43 measured.

[0072] The drive pulley 41 had 45 teeth, the driven pulley 39 had 138 teeth and the pitch between the teeth of the pulleys was fixed at 2 mm. The drive pulley had a diameter of 28.14 mm and the driven pulley had a diameter of 87.35 mm. The teeth of the pulleys had the same helix angle as the belt as the evaluation target. – test results –

[0073] figure 5(a) shows the results of the noise measurement test. The results shown in this figure reveal that the noise level decreased as the helix angle of the helical teeth increased within the range of 0 degrees or more and 7 degrees or less (Comparative Examples 1, 2 and 5). However, when the cord was SZ-twisted, the noise level was similar to that measured at the 7 degree helix angle, even when the helix angle was fixed at 9 degrees, i. H. the noise level did not decrease (Comparative Examples 5 and 10). A suspected cause of this is that when the helix angle increased too much, the belt was pre-tensioned and rubbing with the flange, causing the noise.

[0074] Contrary to these results, it was shown that when the cord was SS twisted (Example 2), the noise level decreased significantly even when the helix angle of the helical teeth was the same. It was also shown that the noise level decreased when the helix angle of the helical teeth was set at 8 degrees (Example 1). Further, it was shown that when the cord was SS twisted, the noise level was kept low when the helix angle of the helical teeth was in the range of 16 degrees or less (Examples 2, 3 and 5).

[0075] figure 6(a) shows the results of the durability test. The results shown in this figure reveal that the durability of the belt gradually decreased as the helix angle of the helical teeth increased.

[0076] It is considered that the force pressing the side face of the belt to the flange increased with the increase in the helix angle of the slap test and the temperature of the belt rose, thereby causing the belt to be chipped. The results of Comparative Examples 2, 5 and 10 show that when the cord was SZ turned and the helix angle of the helical teeth was 9 degrees or more, the side surface of the belt was rubbed against the flange, thereby significantly reducing the durability of the belt.

[0077] Contrary to these results, it was shown that when the cord was SS twisted, the belt durability was greatly improved even when the helix angle of the helical teeth was set to 9 degrees. This is presumably because the thrust force (the biasing force) generated by the cord cancels the thrust force generated by the helical teeth. The results of Examples 1-3 reveal that the belt maintained sufficient durability when the helix angle of the helical teeth was within the range of 9 degrees or more and 16 degrees or less. However, when the helix angle of the helical teeth exceeded 16 degrees (Example 5), the life decreased significantly. It is considered that when the helix angle of the helical teeth exceeded 16 degrees, the thrust force generated by the helical teeth was not canceled even when using the SS twist cord. It was shown that life increased significantly when the helix angle of the helical teeth was 15 degrees or less.

[0078] figure7(a) shows the results of the belt pretension test. The figure shows the results obtained on the toothed belts using the SZ twist cord and the helix angle of the helical teeth were 0 degrees, 5 degrees, 7 degrees and 9 degrees, respectively (Comparative Examples 1, 2, 5 and 10 ), and the results obtained on the toothed belt using the SS twist cord and the helix angle of the helical teeth was 9 degrees (Example 1).

[0079] The results shown in this figure reveal that the pretensioning force of the belt increased with the increase in the helix angle of the helical teeth, and that the pretensioning force of the belt was increased by inclining the rotating direction of the filaments constituting the cord in the direction opposite to the extending direction of the helical teeth and inclining the winding direction of the cord has been canceled in the same direction as the extending direction of the helical teeth.

[0080] figure 8 shows the results of the belt preload test performed with the helix angle of the helical teeth fixed. This figure shows the results of measurements performed on Comparative Example 9 comprising the ZZ twist cord, Comparative Example 5 comprising the SZ twist cord, and Comparative Example 8 comprising the SS twist cord. The results reveal that the thrust force was generated in the same direction as the thrust force generated by the helical teeth when the two filaments constituting the cord were both Z-twisted, and that the thrust force was generated in the direction opposite to the thrust force , which was generated by the helical teeth when the two threads constituting the cord were both S-twisted.

[0081] figure 9 shows the results of the measurements made under the conditions that the helix angle of the helical teeth was fixed, the cord was SZ-twisted, and the angle of the twill line of the toothcloth was changed. This figure shows the results of measurements made on Comparative Examples 3, 4, 6 and 7. The results show that the preload force increased as the angle of the twill line increased. Thus, with the twill direction of the toothcloth inclined in the direction opposite to the extending direction of the flank lines of the helical teeth, appropriate adjustment of the angle of the twill direction makes it possible to cancel the thrust force generated by the helical teeth. Commercial Applicability

[0082] As described above, the toothed belt of the present disclosure is used for power transmission in various types of devices such as power steering of automobiles. Reference List 16 toothed belt 20 helical teeth 22 cords 24 backs 26 Tooth Towel 28 tooth rubber 31, 37, 39 driven pulley 33, 35, 41 drive pulley 43 sensors

Claims

[1] Timing belt, comprising: a back made of an elastic body; several oblique teeth arranged at a predetermined division in a longitudinal direction of the belt on an inner circumferential surface of the back; and a cord which is spirally embedded in the back in the longitudinal direction of the strap and consists of fibers, wherein the oblique teeth comprise a tooth cloth that is arranged on an inner circumferential side of the same, The direction of the flank lines of the helical teeth and the width direction of the belt form an angle of 8 degrees or more and 16 degrees or less, the fibers making up the cord form a single thread and the direction of rotation of the thread is inclined in a direction opposite to the direction of the flank lines of the oblique teeth relative to the width direction of the belt and The winding direction of the cord is inclined in the same direction as the direction of the flank lines of the oblique teeth relative to the width direction of the belt. [2] Timing belt according to claim 1, wherein the toothbrush is a body cloth and The body direction of the toothed cloth is inclined in the direction opposite to the direction of the flank lines of the oblique teeth relative to the width direction of the belt. [3] Toothed belt according to claim 1 or 2, wherein the direction of the flank lines of the helical teeth and the width direction of the belt form an angle of 9 degrees or more and 15 degrees or less. [4] Toothed belt according to one of claims 1–3, wherein the multiple helical teeth are arranged at a pitch of 3 mm or less. [5] Timing belt according to any one of claims 1–4, wherein the belt has a width of 15 mm or more. [6] Timing belt according to one of claims 1–5, wherein the timing belt is used for electric power steering.