WO2019194057A1 - Helical tooth belt and belt transmission - Google Patents

Abstract

Provided is a helical tooth belt (30) having a back portion (31), core wires (33) arranged and embedded in the belt width direction, and a plurality of teeth (32) provided at a predetermined interval along the belt longitudinal direction on one surface of the back portion (31), each tooth being inclined in the belt width direction, wherein the surface of the teeth (32) and a part of one surface of the back portion (31) are configured of a tooth cloth, the tooth pitch P of the tooth (32) is 1.5 mm or more and less than 2.0 mm, the thickness of the back portion (31) is 0.4 mm or more and 1.2 mm or less, the core wire (33) is a twisted cord including high-strength glass fiber or carbon fiber, and the ratio of the total value of the distance d between the core wire (33) and the core wire (33) adjacent in the belt width direction to the belt width W is in the range of 20% to 60%.

Description

Helical tooth belt and belt drive

The present invention relates to a helical tooth belt, and more particularly to a helical tooth belt and a belt transmission device that are applied to a belt transmission device that is driven at a high load or high speed.

For example, in a belt transmission device driven by a high load or high speed rotation, such as a reduction gear of an electric power steering device, when a straight tooth belt having teeth extending in parallel to the belt width direction is used, the teeth and pulleys Large noise and vibration are generated at the start and end of meshing with the teeth. As a countermeasure against this problem, a helical tooth belt is used in which tooth portions are arranged obliquely with respect to the belt width direction. In the helical belt, the meshing between the tooth portion and the tooth portion of the pulley proceeds sequentially from one end to the other end in the width direction of the tooth portion. Therefore, noise and vibration can be reduced as compared with a belt transmission device using a straight tooth belt.

However, even if a helical tooth belt is used, noise and vibration may not always be sufficiently reduced. On the other hand, for example, Patent Document 1 and Patent Document 2 propose a technique for further reducing noise and vibration in a belt transmission device that uses a helical belt and is driven at a high load or high speed. Yes.

In Patent Document 1, the tooth pitch is set to Pt, the belt width is set to W, and the tooth trace angle θ is set to a value satisfying −0.2 ≦ 1-W · tan θ / Pt ≦ 0.75. In addition, the backlash (gap) between the tooth portion of the helical belt and the tooth portion of the pulley is set to 1.6% to 3% of the tooth pitch Pt.

In Patent Document 2, the tooth trace angle θ is 7 degrees or more and 10 degrees or less. In addition, assuming that the thickness of the back part is tb and the tooth height of the tooth part is hb, the ratio of the thickness tb to the tooth height hb (100 × tb / hb) is set to 120% or more and 240% or less.

In recent years, since the quietness of automobiles has progressed, for example, belt transmission devices such as a reduction gear of an electric power steering device are required to further reduce noise. However, the techniques of Patent Literature 1 and Patent Literature 2 cannot reduce noise and vibration to a satisfactory level.

Japanese Unexamined Patent Publication No. 2004-308702 International Publication No. 2014/024377

In this respect, in order to reduce noise and vibration, it is conceivable to increase the rigidity (elastic modulus) of the helical belt. As a method of increasing the rigidity, a method of increasing the thickness of the helical belt (particularly the thickness of the back portion) can be mentioned. However, even if vibration and noise can be suppressed by this method, the bendability of the helical belt is deteriorated, so that bending fatigue on the pulley increases, and cracks are likely to occur particularly in a low temperature environment. Therefore, it is necessary to increase the rigidity without increasing the thickness of the helical belt and sufficiently ensure the bending fatigue resistance.

On the other hand, in order to suppress vibration and noise, it is necessary to ensure the transmission performance of the helical tooth belt (such as no jumping in engagement with the pulley around which the helical belt is wound).

Therefore, the present invention increases the rigidity without increasing the thickness of the helical tooth belt, and when used in a belt transmission device driven at a high load or high speed rotation, noise and vibration are maintained while maintaining transmission performance. An object of the present invention is to provide a helical tooth belt that can be further reduced.

The helical tooth belt of the present invention for solving the above problems is
Back,
In the back portion, the core wire arranged and buried in the belt width direction,
A helical tooth belt having a plurality of tooth portions provided on one surface of the back portion at predetermined intervals along the belt longitudinal direction, each inclined with respect to the belt width direction,
A part of the surface of the tooth part and the one surface of the back part is composed of a tooth cloth,
The tooth pitch of the plurality of tooth portions is 1.5 mm or more and less than 2.0 mm,
The thickness of the back part is 0.4 mm or more and 1.2 mm or less,
The core wire is a twisted cord containing high-strength glass fiber or carbon fiber,
The ratio of the total value of the distance between the cores adjacent to each other in the belt width direction to the belt width is in the range of 20% to 60%.

According to the said structure, since the surface by the side of the tooth | gear part of a back part is comprised by tooth cloth, it is reinforced and rigidity is improved. Moreover, the core wire embedded in the back portion is a twisted cord including high-strength glass fiber or carbon fiber, which is a high-strength (high elastic modulus) fiber material, and the core wire and the core wire adjacent to each other in the belt width direction. Since the ratio of the total value of the intervals to the belt width is in the range of 20% to 60%, the density of the core array can be made relatively dense. Thereby, the rigidity of a back part can be improved more with a core wire, ensuring the flexibility of a back part.
By increasing the rigidity of the back portion in this way, even if the helical tooth belt is used in a belt transmission device driven at high load or high speed rotation, it occurs when the tooth portion meshes with the tooth portion of the pulley. Vibration (string vibration) around the core of the tooth belt can be suppressed. Thereby, the noise which arises by a vibration can be reduced.
The helical belt has a tooth pitch of 1.5 mm or more and less than 2.0 mm, and a back portion thickness of 0.4 mm or more and 1.2 mm or less. Regarding these values, for example, compared with a conventional helical tooth belt used in a reduction gear of an electric power steering apparatus for automobiles, the thickness of the back portion is the same, but the tooth pitch is relatively small. Since the tooth pitch is a relatively small value as described above, the tooth scale (the length of the tooth in the belt longitudinal direction and the tooth height of the tooth) is correspondingly reduced. Therefore, compared with the conventional case, the rigidity of the back portion can be increased without increasing the thickness of the back portion, and sufficient bending fatigue resistance can be secured, and the tooth scale (the tooth portion in the longitudinal direction of the belt) can be secured. Since the length and the tooth height of the tooth portion are relatively small, vibration and noise can be further suppressed.

Further, according to one aspect of the present invention, in the above-described helical belt, the diameter of the core wire is in a range of 0.2 mm to 0.6 mm.

According to the above configuration, the diameter of the core wire is not less than 0.2 mm and not more than 0.6 mm. Therefore, the rigidity of the back portion can be further increased by the core wire while ensuring the flexibility of the back portion.

In addition, according to one aspect of the present invention, in the above-described helical belt, each core wire pitch between the core wires is arranged in a range of 0.45 mm to 1.0 mm. .

In the above configuration, the core wires embedded in the back portion are arranged so that the core wire pitch between the core wires is in the range of 0.45 mm to 1.0 mm. Thereby, the rigidity of the helical belt can be further increased without further increasing the thickness of the back portion or further increasing the diameter of the core wire (without sacrificing the flexibility).

In addition, according to one aspect of the present invention, in the above-described helical belt, the core wire embedded in the back portion is formed from one end to the other end of the helical belt in the belt width direction. The pitch is arranged so as to be a constant value in a range of 0.45 mm to 1.0 mm.

According to the above configuration, the rigidity of the helical belt can be further increased without further increasing the thickness of the back portion or further increasing the diameter of the core wire (without sacrificing the flexibility). Vibration and noise can be further suppressed.

In addition, according to one aspect of the present invention, in the above-described helical belt, the tooth height of the tooth portion is in a range of 0.6 mm to 1.0 mm and 40 to 50% with respect to the tooth pitch. The height of the range.

If the tooth pitch, that is, the tooth scale (the length of the tooth belt in the longitudinal direction of the tooth and the tooth height of the tooth) is reduced, vibration and noise can be further suppressed, while the tooth portion is too much. If the scale is made smaller, there is a concern that tooth jumping (jumping) is likely to occur in meshing with the pulley around which the helical belt is wound. Therefore, it is necessary to balance the suppression of vibration and noise with the difficulty of jumping (jumping).
In the case of the helical belt having the above configuration, the tooth height of the tooth portion is limited to a range of 0.6 mm to 1.0 mm and a height of 40 to 50% with respect to the tooth pitch. Even if it is used in a belt transmission device driven at a high load or high speed, it is possible to achieve traveling that strikes a balance between suppression of vibration and noise and difficulty in occurrence of tooth skipping (jumping).

Further, according to one aspect of the present invention, in the above-described helical belt, the back portion includes a rubber component, and the rubber component includes at least ethylene-propylene-diene terpolymer or hydrogenated nitrile rubber.

According to the above configuration, vibration and noise can be further suppressed.

In addition, according to one aspect of the present invention, in the above-described helical belt, the tooth cloth is formed of a woven cloth including warp and weft, and the warp or weft is arranged to extend in the belt longitudinal direction, The warp or weft arranged so as to extend in the longitudinal direction of the belt includes an elastic yarn having elasticity.

According to the above configuration, vibration and noise can be further suppressed.

One aspect of the present invention is the above-described helical belt, wherein the fibers constituting the tooth cloth include at least one fiber selected from the group consisting of nylon, aramid, polyester, polybenzoxazole, and cotton. It is out.

According to the above configuration, vibration and noise can be further suppressed.

Further, according to one aspect of the present invention, in the above-described helical belt, the other surface of the back portion is formed of a back cloth, and the fibers constituting the back cloth are made of nylon, aramid, and polyester. Contains at least one fiber selected from.

According to the above configuration, since the other surface of the back portion is constituted by a back cloth, and the fibers constituting the back cloth include at least one kind of fiber selected from the group consisting of nylon, aramid, and polyester, the back portion is Further, it is reinforced to increase the rigidity.

One aspect of the present invention is defined by the belt tension (N) per 1 mm of the belt width with respect to the belt elongation rate (%) when the helical belt is wound between pulleys with a predetermined mounting tension. The belt elastic modulus is 22 N /% or more.

According to the above configuration, it is possible to define a helical tooth belt having increased rigidity while ensuring flexibility in terms of belt elastic modulus. Thereby, the designer can objectively judge the design specification of the back part of the helical belt.

Further, the belt transmission device of the present invention includes a drive pulley that is rotationally driven by a drive source,
A driven pulley,
A belt transmission device comprising: the helical belt wound around the driving pulley and the driven pulley.

According to the above configuration, noise and vibration can be reduced in the belt transmission that transmits the driving force of the driving pulley to the driven pulley.

Further, according to one aspect of the present invention, in the belt transmission device, a rotational speed of the drive pulley is 1000 rpm or more and 4000 rpm or less.

According to the above configuration, noise and vibration can be sufficiently reduced in the belt transmission device driven at high speed.

Further, according to one aspect of the present invention, in the belt transmission device, a load of the driven pulley is 0.5 kW or more and 3 kW or less.

According to the above configuration, noise and vibration can be sufficiently reduced in a belt transmission device driven at a high load.

One aspect of the present invention is the belt transmission apparatus, wherein the driven pulley has an outer diameter larger than an outer diameter of the driving pulley,
The belt transmission is a reduction device for an electric power steering device for automobiles.

According to the above configuration, noise and vibration can be sufficiently reduced in the reduction device of the electric power steering device for automobiles.

A helical tooth that increases rigidity without increasing the thickness of the helical belt and can reduce noise and vibration while maintaining its transmission performance when used in a belt drive system driven at high load or high speed. A belt can be provided.

FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering device to which the helical belt of the present embodiment is applied. FIG. 2 is a side view of the speed reducer of the electric power steering apparatus. FIG. 3 is a partial perspective view of a helical belt. FIG. 4 is a view of the helical belt as viewed from the inner peripheral side. FIG. 5 is a sectional view of the helical belt in the belt width direction. FIG. 6 is an explanatory diagram of a biaxial torque measurement tester used in the jumping test.

Hereinafter, embodiments of the present invention will be described. The helical belt 30 of this embodiment is used for the speed reducer 20 (belt transmission device) of the electric power steering apparatus 1 for an automobile shown in FIG. 1, for example.

[Configuration of electric power steering system]
The electric power steering (EPS) device 1 includes a steering shaft 3 coupled to the steering wheel 2, an intermediate shaft 4 coupled to the steering shaft 3, and an intermediate shaft 4 coupled to the rotation of the steering wheel 2. And a steering mechanism 5 for steering the wheels 9.

The steering mechanism 5 includes a pinion shaft 6 connected to the intermediate shaft 4 and a rack shaft 7 that meshes with the pinion shaft 6. The rack shaft 7 extends along the left-right direction of the vehicle. A rack 7 a that meshes with a pinion 6 a provided on the pinion shaft 6 is formed in the middle of the rack shaft 7 in the axial direction. Wheels 9 are connected to both ends of the rack shaft 7 via tie rods 8 and knuckle arms (not shown). The rotation of the steering wheel 2 is transmitted to the pinion shaft 6 via the steering shaft 3 and the intermediate shaft 4. The rotation of the pinion shaft 6 is converted into the movement of the rack shaft 7 in the axial direction. Thereby, the wheel 9 is steered.

The electric power steering apparatus 1 can obtain a steering assist force according to the steering torque applied to the steering wheel 2. For this purpose, the electric power steering apparatus 1 includes a torque sensor 13 for detecting a steering torque, a control apparatus 14, an electric motor 15 (drive source) for assisting steering, and the driving force of the electric motor 15 as a steering mechanism 5. And a reduction gear device 20 as a transmission device.

In order to detect the steering torque by the torque sensor 13, the steering shaft 3 has an input shaft 10, a torsion bar 11, and an output shaft 12. When the steering wheel 2 is operated and steering torque is input to the input shaft 10, the torsion bar 11 is torsionally deformed, and the input shaft 10 and the output shaft 12 rotate relative to each other. The torque sensor 13 detects the steering torque input to the steering wheel 2 based on the relative rotational displacement amount between the input shaft 10 and the output shaft 12. The detection result of the torque sensor 13 is input to the control device 14. The control device 14 controls the electric motor 15 based on the steering torque detected by the torque sensor 13.

The speed reducer 20 has a drive pulley 21, a driven pulley 22, and a helical belt 30 wound around the drive pulley 21 and the driven pulley 22. The driven pulley 22 has a larger outer diameter than the drive pulley 21. The drive pulley 21 is fixed to the rotating shaft of the electric motor 15. The driven pulley 22 is fixed to the pinion shaft 6. As shown in FIG. 2, a plurality of helical teeth 21 a are formed on the outer peripheral surface of the drive pulley 21. A plurality of helical teeth 22 a are formed on the outer peripheral surface of the driven pulley 22. The rotational speed of the drive pulley 21 is 1000 rpm or more and 4000 rpm or less, for example. The load of the driven pulley 22 is, for example, not less than 0.5 kW and not more than 3 kW.

When the steering wheel 2 is operated, the steering torque is detected by the torque sensor 13, and the control device 14 drives the electric motor 15. When the electric motor 15 rotates the drive pulley 21, the helical belt 30 travels, and the driven pulley 22 and the pinion shaft 6 rotate. The rotational force of the electric motor 15 is decelerated by the reduction gear 20 and transmitted to the pinion shaft 6. As described above, the rotation of the steering wheel 2 is transmitted to the pinion shaft 6 via the steering shaft 3 and the intermediate shaft 4. Then, the rotation of the pinion shaft 6 is converted into the axial movement of the rack shaft 7, and the wheels 9 are thereby steered. Thus, the steering of the driver is assisted by the rotation of the pinion shaft 6 being assisted by the electric motor 15.

The configuration of the electric power steering apparatus 1 to which the helical belt 30 of the present invention can be applied is not limited to the configuration shown in FIG. For example, the driven pulley 22 of the speed reducer 20 may be fixed to the intermediate shaft 4 or the steering shaft 3. For example, the driven pulley 22 of the speed reducer 20 may be coupled to the rack shaft 7 via a conversion mechanism. The conversion mechanism is, for example, a ball screw mechanism or a bearing screw mechanism, and converts the rotational force of the driven pulley 22 into an axial force of the rack shaft 7 and transmits it to the rack shaft 7.

[Configuration of helical tooth belt]
As shown in FIG. 3, the helical tooth belt 30 includes a back portion 31 in which a core wire 33 is spirally embedded along the belt longitudinal direction, and an inner peripheral surface of the back portion 31 (corresponding to one surface of the back portion 31). And a plurality of tooth portions 32 provided at predetermined intervals along the longitudinal direction of the belt. In the present embodiment, the plurality of tooth portions 32 are integrally formed on the inner peripheral surface of the back portion 31. Moreover, as shown in FIG. 4, the tooth part 32 is inclined and extended with respect to the belt width direction. Further, the inner peripheral surface of the helical belt 30, that is, the surface of the tooth portion 32 and a part of the inner peripheral surface of the back portion 31 are covered with a tooth cloth 35. In this embodiment, the outer peripheral surface of the back portion 31 (corresponding to the other surface of the back portion 31) is not covered with a cloth or the like, but may be covered with a back cloth.

The circumferential length of the helical belt 30 is, for example, 150 to 400 mm. In this specification, the numerical range represented by “X to Y” means X or more and Y or less. The width W (see FIG. 4) of the helical belt 30 is, for example, 4 to 30 mm. The tooth pitch P (see FIG. 3) of the tooth portion 32 is 1.5 mm or more and less than 2.0 mm, preferably 1.6 to 1.8 mm. When the tooth pitch P is 1.5 mm or more and less than 2.0 mm, the thickness tb (see FIG. 3) of the back portion 31 is 0.4 to 1.2 mm. Further, the tooth height hb (see FIG. 3) of the tooth portion 32 is in the range of 0.6 mm or more and 1.0 mm or less and in the range of 40 to 50% with respect to the tooth pitch P. For example, if the tooth pitch P is 1.5 mm, the tooth height hb is a height in the range of 0.6 mm to 0.75 mm. If the tooth pitch P is 1.99 mm, the tooth height hb is 0. The height is in the range of 796 mm to 0.995 mm. The total thickness (maximum thickness) t (see FIG. 3) of the helical belt 30 is the sum of the thickness tb of the back portion 31 and the tooth height hb. The inclination angle θ (see FIG. 4) of the tooth portion 32 with respect to the belt width direction is, for example, 2 to 7 °, preferably 2 to 6 °.

As described above, in the present embodiment, the tooth pitch P (1.5 mm or more and less than 2.0 mm) of the helical belt 30 is relatively small as compared with the related art. Since the tooth pitch P is a relatively small value, the scale of the tooth portion 32 (the length hW of the tooth portion 32 in the belt longitudinal direction and the tooth height hb of the tooth portion 32: 3) is also small. As a result, the rigidity of the back portion 31 can be increased without increasing the thickness of the back portion 31 and the bending fatigue resistance can be sufficiently secured as compared with the conventional case, and the scale (tooth portion 32) of the tooth portion 32 can be secured. Since the length hW in the belt longitudinal direction and the tooth height hb) of the tooth portion 32 are relatively small, vibration and noise can be further suppressed.

However, if the tooth pitch P, that is, the scale of the tooth portion 32 (the length hW of the tooth portion 32 in the longitudinal direction of the belt and the tooth height hb of the tooth portion 32) is reduced, vibration and noise are further suppressed. On the other hand, if the scale of the tooth portion 32 is made too small, there is a concern that tooth jump (jumping) is likely to occur in meshing with the driving pulley 21 and the driven pulley 22 around which the helical belt 30 is wound. Therefore, by limiting the tooth height hb of the tooth portion 32 to a height in the range of 0.6 mm to 1.0 mm and in the range of 40 to 50% with respect to the tooth pitch P as described above. Even if the helical belt 30 is used in the speed reducer 20 driven with high load or high speed rotation, it is possible to run while balancing vibration and noise suppression and difficulty in jumping (jumping). Become.

[Back and teeth]
The back portion 31 and the tooth portion 32 are composed of a rubber composition. As rubber components of the rubber composition, chloroprene rubber (CR), nitrile rubber, hydrogenated nitrile rubber (HNBR), ethylene-propylene copolymer (EPM) ), Ethylene-propylene-diene terpolymer (EPDM), styrene-butadiene rubber, butyl rubber, chlorosulfonated polyethylene rubber, and the like. These rubber components can be used alone or in combination. A preferred rubber component is ethylene-propylene-diene terpolymer (EPDM), and chloroprene rubber and hydrogenated nitrile rubber (HNBR) are also preferably used. Particularly preferred is a configuration containing at least ethylene-propylene-diene terpolymer (EPDM) or hydrogenated nitrile rubber (HNBR). In the present embodiment, the back portion 31 and the tooth portion 32 are formed of the same rubber composition, but may be formed of different rubber compositions.

The rubber composition constituting the back portion 31 and the tooth portion 32 may contain various conventional additives (or compounding agents) as necessary. Additives include vulcanizing agents or crosslinking agents (for example, oximes (such as quinonedioxime), guanidines (such as diphenylguanidine), metal oxides (such as magnesium oxide and zinc oxide)), vulcanization aids, Sulfur accelerators, vulcanization retarders, reinforcing agents (carbon black, silicon oxide such as hydrous silica), metal oxides (eg, zinc oxide, magnesium oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide) , Aluminum oxide, etc.), filler (clay, calcium carbonate, talc, mica, etc.), plasticizer, softener (oils such as paraffin oil and naphthenic oil), processing agent or processing aid (stearic acid, stearin) Acid metal salts, wax, paraffin, etc.), anti-aging agents (aromatic amines, benzimidazole anti-aging agents, etc.) , Stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, etc.), lubricants, flame retardants, etc. can be exemplified antistatic agent. These additives can be used alone or in combination, and can be selected according to the type, application, performance, etc. of the rubber component.

[Core]
The core wire 33 is spirally embedded in the back portion 31 along the belt longitudinal direction with a predetermined distance d (0.5 mm or more and 0.6 mm or less) in the belt width direction. That is, as shown in FIG. 5, the core wire 33 is arranged on the back portion 31 with a predetermined interval d in the belt width direction. More specifically, the ratio (%) of the total value of the distance d between the core wires 33 adjacent to each other in the belt width direction to the belt width W is in the range of 20% to 60% (preferably 20%). The core wire 33 is embedded in the back portion 31 so as to be in the range of 40% or less. Note that the total value of the distance d between the core wires 33 adjacent to each other in the belt width direction includes the distance between the end of the belt and the core wire 33 (both end portions). That is, according to the present invention, the total value of the distance d between the cores 33 adjacent to each other in the belt width direction is calculated from the value of “belt width” to “total core wire diameter (core wire diameter × number of core wires”. It can be said that the value of “)” is subtracted. Therefore, the ratio (%) of the total value of the distance d between the core wires 33 adjacent to each other in the belt width direction to the belt width W is replaced with “relationship between the core wire diameter D and the core wire pitch SP”. It is possible (see Equation 1). Here, the smaller the ratio (%) of the distance d between the cores 33 adjacent to each other in the belt width direction to the belt width W, the smaller the distance d between the cores 33 and 33. Therefore, it can be said that the density of the core wire array becomes dense.

Further, as shown in FIGS. 3 and 5, the core wire 33 is the center of the core wire 33 and the core wire 33 embedded in a spiral shape from one end of the back portion 31 in the belt width direction to the other end. Each cord pitch SP, which is the distance between them, is arranged so as to have a constant value in a range of 0.45 mm to 1.0 mm. In the present specification, as shown in FIG. 5, the apparent number of the core wires arranged in a belt width direction at a predetermined core wire pitch SP in a cross-sectional view is treated as “the number of core wires”. . That is, when one core wire 33 is embedded in a spiral shape, the number of spirals is defined as “number of core wires”.

Here, it is desirable to count only the number (effective number) that affects the strength (elastic modulus) of the belt as the “number of cores”. Accordingly, the core wires 33 which are disposed at one end and the other end in the width direction of the back portion 31 of the helical belt 30 and are not circular in cross-sectional view are not included in the effective number and are cut in cross-sectional view. It is desirable to count the number of core wires 33 that are not present as the effective number.
However, since the core wire 33 is actually embedded in a spiral shape, the arrangement of the core wire 33 differs depending on the portion of the endless helical tooth belt 30 from which the cross-section is taken. Since the influence of the core wire 33 whose sectional view is not circular on the strength (elastic modulus) of the belt cannot be ignored, practically, each core wire pitch SP is constant within a range of 0.45 mm to 1.0 mm. Value obtained by dividing the belt width by the core pitch SP (a constant value in the range of 0.45 mm to 1.0 mm), and rounding down the value after the decimal point, It is considered as “number of cores” (effective number). For example, if the belt width is 25 mm and the core pitch SP is 0.56 mm, the calculated value is 44.64, and the “number of cores” (effective number) is assumed to be 44. If the belt width is 25 mm and the core pitch SP is 0.52 mm, the calculated value is 48.07, and the “number of cores” (effective number) is considered to be 48. If the belt width is 25 mm and the core pitch SP is 0.60 mm, the calculated value is 41.67, and the “number of cores” (effective number) is assumed to be 41.

Further, the core wire 33 is composed of a twisted cord formed by twisting a plurality of strands. One strand may be formed by bundling and aligning filaments (long fibers). The diameter of the core wire 33 is 0.2 to 0.6 mm. There are no particular restrictions on the twist configuration such as the thickness of the filament forming the twisted cord, the number of converging filaments, the number of strands, and the twisting method. The material of the filament is high-strength glass fiber or carbon fiber. Both the high-strength glass fiber and the carbon fiber have high strength and low elongation and are suitable as the material of the core wire 33, but from the viewpoint of low cost, the high-strength glass fiber is more preferable.

As the high-strength glass fiber, for example, a glass fiber having a tensile strength of 300 kg / cm ² or more, in particular, a glass fiber having a composition shown in Table 1 below having a larger Si component than an alkali-free glass fiber (E glass fiber) is preferably used. it can. In Table 1, the composition of E glass fiber is also shown for comparison. As such high-strength glass fiber, K glass fiber, U glass fiber (both manufactured by Nippon Glass Fiber Co., Ltd.), T glass fiber (manufactured by Nitto Boseki Co., Ltd.), R glass fiber (manufactured by Vetrotex), S glass fiber, S -2 glass fiber, ZENTRON glass fiber (all manufactured by Owens Corning Fiberglass) and the like.

Examples of the carbon fiber include pitch-based carbon fiber, polyacrylonitrile (PAN) -based carbon fiber, phenol resin-based carbon fiber, cellulose-based carbon fiber, and polyvinyl alcohol-based carbon fiber. Examples of commercially available carbon fibers include “Torayca (registered trademark)” manufactured by Toray Industries, Inc., “Tenax (registered trademark)” manufactured by Toho Tenax Co., Ltd., and “Dialead (registered trademark)” manufactured by Mitsubishi Chemical Corporation. Can be used. These carbon fibers can be used alone or in combination of two or more. Of these carbon fibers, pitch-based carbon fibers and PAN-based carbon fibers are preferable, and PAN-based carbon fibers are particularly preferable.

The twisted cord used as the core wire 33 is preferably subjected to an adhesion treatment in order to enhance the adhesion with the back portion 31. As the adhesion treatment, for example, a method is adopted in which a twisted cord is immersed in a resorcin-formalin-latex treatment solution (RFL treatment solution) and then dried by heating to form a uniform adhesion layer on the surface. The RFL treatment liquid is a mixture of an initial condensate of resorcin and formalin mixed with latex. Examples of latex used here include chloroprene, styrene-butadiene-vinylpyridine terpolymer (VP latex), hydrogenation. A nitrile, NBR, etc. are mentioned. In addition, as an adhesion | attachment process, after pre-processing with an epoxy or an isocyanate compound, there also exists the method of processing with an RFL process liquid.

[Tooth cloth]
The tooth cloth 35 is preferably composed of a woven cloth in which warp yarns and weft yarns are vertically and horizontally woven according to a certain rule. The weave of the woven fabric may be either a twill weave or a satin weave. The form of warp and weft is either a multifilament yarn in which filaments (long fibers) are aligned or twisted, a monofilament yarn that is a single long fiber, or a spun yarn in which short fibers are twisted (spun yarn). May be. When the warp or weft is a multifilament yarn or a spun yarn, it may be a blended yarn or a blended yarn using a plurality of types of fibers. The weft preferably includes an elastic yarn having stretchability. As the elastic yarn, for example, a material having elasticity such as spandex made of polyurethane or a processed yarn obtained by expanding / contracting a fiber (for example, Woolley processing, crimping processing, etc.) is used. Usually, elastic yarn is not used for warp. Therefore, weaving is easy. The tooth cloth 35 is preferably arranged so that the warp of the woven cloth extends in the belt width direction and the weft extends in the belt longitudinal direction. Thereby, the stretchability of the tooth cloth 35 in the belt longitudinal direction can be ensured. The tooth cloth 35 may be arranged so that the weft of the woven cloth extends in the belt width direction and the warp extends in the belt longitudinal direction. In this case, an elastic yarn having stretchability may be used as the warp. As the material of the fibers constituting the tooth cloth 35, any one of nylon, aramid, polyester, polybenzoxazole, cotton, or a combination thereof can be used.

The woven fabric used as the tooth cloth 35 may be subjected to an adhesion treatment in order to enhance the adhesion between the back part 31 and the tooth part 32. As an adhesion treatment, a method is generally used in which a woven fabric is immersed in resorcin-formalin-latex (RFL solution) and then dried by heating to form a uniform adhesion layer on the surface. However, the present invention is not limited to this. In addition to the method of pretreatment with an epoxy or isocyanate compound and then treatment with an RFL solution, the rubber composition is dissolved in an organic solvent such as methyl ethyl ketone, toluene, xylene, etc. to form rubber paste. A method of immersing a woven fabric in this rubber paste and impregnating and adhering the rubber composition can also be employed. These methods can be performed alone or in combination, and the processing order and the number of processing are not particularly limited.

[Back cloth]
In the present embodiment, the outer peripheral surface of the back portion 31 (corresponding to the other surface of the back portion 31) is not covered with a cloth or the like, but may be covered with a back cloth 36. When the outer peripheral surface of the back portion 31 is covered with the back cloth 36, the back cloth 36 is a knitted cloth knitted with knitting yarn or a woven cloth woven by crossing warp and weft vertically and horizontally according to a certain rule. Preferably, it is configured.

A knitted fabric is a fabric having a structure in which one or two or more knitting yarns form a mesh (loop), and the next yarn is hooked on the loop to continuously create a new loop. That is, the knitted fabric is formed by making a loop without crossing yarns linearly. When a knitted fabric is used for the back cloth 36, the knitted fabric (or knitted fabric) may be either a weft knitted (or knitted fabric knitted by weft knitting) or a warp knitted (or knitted fabric knitted by warp knitting). It may be. The shape of the knitted fabric is not limited to a planar shape or a cylindrical shape (circular knitting), and the knitted fabric may be either the front surface or the back surface of the belt body. Examples of the weft knitting (or knitting organization of the weft knitting) include a flat knitting (tengu knitting), a rubber knitting, a Kanoko knitting, a smooth knitting, and a jacquard knitting. Examples of warp knitting (or warp knitting structure) include single denby, single cord, tricot, and half tricot.

When using a woven fabric for the back fabric 36, the woven fabric may be any of plain weave, twill weave, satin weave, and the like. From the viewpoint of ensuring the flexibility of the helical belt 30, it is preferable that the woven structure or the knitted structure is easily stretchable in the belt longitudinal direction in order to bend easily in the belt longitudinal direction. For this reason, it is preferable to use a woven fabric containing elastic elastic yarns as wefts and to arrange the warp yarns of the woven fabric in the belt width direction and the weft yarns in the belt longitudinal direction. The form of knitting yarn of knitted fabric or warp and weft of woven fabric is a multifilament yarn in which filaments (long fibers) are aligned or twisted, one monofilament yarn, which is a single long fiber, and short fibers are twisted Any spun yarn (spun yarn) may be used. When the warp or weft is a multifilament yarn or a spun yarn, it may be a blended yarn or a blended yarn using a plurality of types of fibers. As the material of the fibers constituting the back cloth 36, any one of nylon, aramid, polyester, or a combination thereof can be used. In this case, the back portion 31 is further reinforced, and the rigidity of the helical belt 30 is increased.

The woven or knitted fabric used as the back cloth 36 may be subjected to an adhesion treatment in order to enhance the adhesion with the back portion 31. As in the case of the tooth cloth 35, it is preferable to immerse the cloth in resorcin-formalin-latex (RFL solution) and then dry by heating to form a uniform adhesive layer on the surface. However, the present invention is not limited to this, and after pretreatment with an epoxy or isocyanate compound, the rubber composition is dissolved in an organic solvent such as methyl ethyl ketone, toluene, xylene, etc. A method of immersing a cloth in the rubber paste and impregnating and adhering the rubber composition can also be employed. These methods can be performed alone or in combination, and the processing order and the number of processing are not particularly limited. When the back cloth 36 is a knitted cloth, an unvulcanized rubber sheet wound on the knitted cloth in the heating / pressurizing process is impregnated in the knitted cloth in the method of manufacturing the helical belt 30 described later. Therefore, it is not necessary to perform the adhesion treatment.

Although details will be described later in the embodiment, it is defined by a belt tension (N) per 1 mm of belt width with respect to a belt extension rate (%) when the tooth belt 30 is wound between pulleys with a predetermined mounting tension. The belt elastic modulus is preferably 22 N /% or more (more preferably in the range of 30 N /% to 125 N /%, particularly preferably in the range of 30 N /% to 50 N /%).

[Method of manufacturing a helical tooth belt]
The helical belt 30 is manufactured, for example, by the following procedure.
First, a woven fabric that has been subjected to an adhesive treatment for forming the tooth cloth 35 is wound around a cylindrical mold (not shown) having a plurality of grooves corresponding to the plurality of tooth portions 32 of the helical tooth belt 30. Subsequently, a twisted cord constituting the core wire 33 is spirally spun around the outer peripheral surface of the wound woven fabric. Further, an unvulcanized rubber sheet for forming the back portion 31 and the tooth portion 32 is wound around the outer peripheral side to form an unvulcanized belt molded body.

In addition, when covering the back cloth 36, after winding the unvulcanized rubber sheet for forming the back part 31 and the tooth | gear part 32, the knitted fabric or woven cloth which forms the back cloth 36 is wound. When a woven fabric is used as the back fabric 36, it is preferable to perform an adhesion treatment on the woven fabric before winding. On the other hand, when a knitted fabric is used for the back cloth 36, the bonding process may not be performed.

Next, in a state where the unvulcanized belt molded body is arranged on the outer periphery of the cylindrical mold, a rubber jacket which is a steam blocking material is put on the outer side. Subsequently, the belt molded body and the cylindrical mold covered with the jacket are accommodated inside the vulcanizing can. Then, the belt molded body is heated and pressurized inside the vulcanizing can to vulcanize the rubber sheet. Thereby, the rubber composition of the rubber sheet is press-fitted into the groove portion of the mold, and the tooth portion 32 is formed. Then, the plurality of helical belts 30 are obtained by cutting the removed sleeve-shaped molded body into a predetermined width.

According to the helical belt 30 having the above-described configuration, since the surface of the back portion 31 on the tooth portion 32 side is constituted by the tooth cloth 35, it is reinforced and the rigidity is increased. The core wire 33 embedded in the back portion 31 is a twisted cord including high-strength glass fiber or carbon fiber, which is a high-strength (high-modulus) fiber material, and is adjacent to the core wire 33 adjacent in the belt width direction. Since the ratio of the total distance d to the line 33 to the belt width W is in the range of 20% or more and 60% or less, the density of the core array can be made relatively dense. Thereby, the rigidity of the back part 31 can be further increased by the core wire 33 while ensuring the flexibility of the back part 31.

By increasing the rigidity of the back portion 31 in this way, even if the helical belt 30 is used in the speed reducer 20 that is driven with a high load or high speed rotation, the tooth portion 32 can be connected to the drive pulley 21 or the driven pulley 22. It is possible to suppress vibration (string vibration) centered on the core wire 33 of the helical belt 30 that occurs when meshing with the tooth portion. Thereby, the noise which arises by a vibration can be reduced.

Moreover, the diameter D of the core wire 33 is 0.2 mm or more and 0.6 mm or less. Therefore, the rigidity of the back part 31 can be further increased by the core wire 33 while ensuring the flexibility of the back part 31.

Further, the core wires 33 embedded in the back portion 31 are arranged so that each core wire pitch SP between the core wires is in a range of 0.45 mm to 1.0 mm. Thereby, the rigidity of the helical belt 30 can be further increased without further increasing the thickness of the back portion 31 or further increasing the diameter of the core wire 33 (without sacrificing the flexibility). .

Further, the tooth belt 30 has a tooth pitch P of 1.5 mm or more and less than 2.0 mm, and the back portion 31 has a thickness of 0.4 mm or more and 1.2 mm or less. Regarding these values, for example, the thickness of the back portion 31 is comparable to that of a conventional helical belt used in the reduction gear 20 of an electric power steering device for automobiles, but the tooth pitch P is relatively low. small. Since the tooth pitch P is a relatively small value as described above, the scale of the tooth portion 32 (the length hW of the tooth portion 32 in the belt longitudinal direction and the tooth height hb of the tooth portion 32) correspondingly. Is also getting smaller. Therefore, the rigidity of the back part 31 can be increased without increasing the thickness of the back part 31 and the bending fatigue resistance can be sufficiently secured as compared with the conventional case, and the scale of the tooth part 32 (of the tooth part 32) can be secured. Since the length hW in the belt longitudinal direction and the tooth height hb) of the tooth portion 32 are relatively small, vibration and noise can be further suppressed.

In the helical belt having the above-described configuration, the tooth height hb of the tooth portion 32 is in the range of 0.6 mm to 1.0 mm and in the range of 40 to 50% with respect to the tooth pitch P. By limiting to the above, even when used in the speed reducer 20 driven at high load or high speed rotation, it is possible to travel while balancing vibration and noise suppression and difficulty of jumping (jumping). be able to.

Further, the use of the helical belt 30 in the speed reducer 20 of the electric power steering apparatus 1 for an automobile, in which the outer diameter of the driven pulley 22 is larger than the outer diameter of the driving pulley 21, the noise and vibration are sufficiently reduced. Can be reduced.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

The present invention is characterized in that the vibration and noise of the helical belt can be reduced by reducing the tooth pitch P compared to the conventional helical tooth belt, but when the tooth pitch P is reduced, the tooth height hb is also reduced. Therefore, there is a concern that tooth jumping (jumping) is likely to occur in meshing with a pulley around which a helical belt is wound. For this reason, in the present invention, it is necessary to achieve both reduction of the vibration and noise of the helical belt and difficulty in occurrence of tooth jumping (jumping).
Therefore, in this example, helical belts according to Examples 1 to 18 and Comparative Examples 1 to 5 were manufactured, and a sound pressure measurement test and a jumping test were performed, and comparative verification was performed.

As strands used for the helical belts of Examples 1 to 18 and Comparative Examples 1 to 5, twisted cords of A1 to A4 having configurations shown in Table 2 below were prepared.

The twisted cord of A1 was created according to the following procedure. Filaments of glass fiber of the designation KCG150 described in JIS R 3413 (2012) were bundled and aligned to form three strands. These three strands were immersed in an RFL solution (18 to 23 ° C.) having the composition shown in Table 3 below for 3 seconds, and then heated and dried at 200 to 280 ° C. for 3 minutes to uniformly adhere to the surface. A layer was formed. After this adhesion treatment, three strands were twisted at a twist rate of 12 times / 10 cm to give a twisted cord with a single twist and a diameter of 0.35 mm. The twisted cords A2 and A3 were prepared in the same manner as A1 except that the glass fibers were changed to UCG150 and ECG150. The A4 twisted cord is made in the same way as the core wires of A1 to A3, except that the strand used is a single strand of carbon fiber filaments (3K) bundled and aligned. Was a twisted cord of 0.53 mm.

(Configuration of core wire)

(Modulus of core wire)
Here, a method for measuring the elastic modulus (tensile elastic modulus) of the core wire (longitudinal direction) shown in Table 2 will be described. Attach a chuck to the lower fixing part and upper load cell connecting part of Autograph ("AGS-J10kN" manufactured by Shimadzu Corporation) to fix the core wire. Next, the upper chuck was raised, and stress (about 10 N) was applied to such an extent that the core wire was not loosened. The upper chuck position in this state was set as the initial position, and the upper chuck was raised at a speed of 250 mm / min. After the core wire stress reached 200 N, the upper chuck was immediately lowered and returned to the initial position. The slope (average slope) of the straight line in the region (100 to 200 N) having a relatively linear relationship in the stress-strain curve measured at this time was calculated as the tensile modulus of the core wire.

(RFL solution)

The tooth cloth used for the helical belts of Examples 1 to 18 and Comparative Examples 1 to 5 was one type. A twill weave was used as the tooth cloth, and the warp yarn of the woven fabric was arranged in the belt width direction and the weft yarn was extended in the belt longitudinal direction. As the weft of the woven fabric, multifilament yarn of 66 nylon having a fineness of 155 dtex and multifilament yarn of spandex (polyurethane elastic fiber) having a fineness of 122 dtex were used. As the warp for the woven fabric, 66 nylon multifilament yarn having a fineness of 155 dtex was used. Note that dtex (decitex) is the mass of a 10000 meter yarn expressed in grams.

The woven fabric used for the tooth cloth was immersed in the RFL solution shown in Table 3 and then heat-dried to give an adhesive treatment that uniformly forms an adhesive layer on the surface.

As unvulcanized rubber sheets for forming the back and teeth of the helical belts of Examples 1 to 18 and Comparative Examples 1 to 5, unvulcanized rubber sheets having compositions C1 to C3 shown in Table 4 below were prepared. did.

(Composition of unvulcanized rubber sheet)

* 1 “EPT” manufactured by Mitsui Chemicals, Inc.
* 2 “PM-40” manufactured by Denka
* 3 “Zetpole 2021” manufactured by Nippon Zeon
* 4 “NOCRACK MB” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
* 5 “N-cyclohexyl-2benzothiazole sulfenamide” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
* 6 "Seast 3" manufactured by Tokai Carbon Co., Ltd.
* 7 “Zinc oxide 3 types” manufactured by Shodo Chemical Industry Co., Ltd.

Examples 1 to 18 and Comparative Examples 1 to 5 were performed using the twisted cords (core wires) A1 to A4, the tooth cloth, and the unvulcanized rubber sheet having the composition C1 to C3 according to the procedure described in the above embodiment. A helical tooth belt was created. Vulcanization was performed at 161 ° C. for 25 minutes. The configurations of the helical belts of Examples 1 to 18 and Comparative Examples 1 to 5 are shown in Tables 5 to 10 below. The belt widths of the helical belts of Examples 1 to 18 and Comparative Examples 1 to 5 were all 25 mm, and the inclination angles of the tooth portions with respect to the belt width direction were all 5 °. In Examples 1 to 18 and Comparative Examples 1 to 5, the tooth height hb of the belt is varied, but the tooth gap depth of the pulley used in each test is as shown in Table 11. A pulley having a tooth gap depth corresponding to each tooth height hb was used.

In Table 5, the configurations of the helical belts of Examples 1 to 4 and Comparative Examples 1 and 2 are described for comparison with the tooth pitch P varied. Table 6 shows the configurations of the helical belts of Examples 2 and 5 to 8 for comparison with the tooth height hb varied based on the helical belt of Example 2. In Table 7, the configurations of the helical belts of Examples 2, 9 to 11 and Comparative Example 3 are described in order to make a comparison by varying the belt back thickness tb based on the helical belt of Example 2. is doing. Table 8 shows the configurations of the helical belts of Examples 2 and 12 to 13 for comparison with the rubber component changed based on the helical belt of Example 2. Further, in Table 9, the configurations of the helical belts of Examples 2, 14 to 16 and Comparative Example 4 are compared in order to compare the density of the core wire arrangement based on the helical belt of Example 2. It is described. Table 10 shows the configurations of the helical belts of Examples 17 to 18 and Comparative Example 5 in order to make a comparison in which the cord material was changed based on the helical belt of Example 2. ing.

(Measurement of belt elastic modulus)
The belt elastic modulus (tensile elastic modulus) was measured for the helical belts of Examples 1 to 18 and Comparative Examples 1 to 5 (belt longitudinal direction). A method for measuring the belt elastic modulus will be described. A pair of pulleys (30 teeth outer diameter 18.6 mm) were attached to the lower fixed part and upper load cell connecting part of Autograph (Shimadzu Corporation "AGS-J10kN"), and a helical belt was hung on the pulley. . Next, the upper pulley was raised, and tension (about 10 N) was applied to such an extent that the helical belt did not loosen. The position of the upper pulley in this state is set as the initial position, the upper pulley is raised at a speed of 50 mm / min, and immediately after the tension of the helical belt reaches 500 N, the upper pulley is lowered and returned to the initial position. It was. In the stress-strain curve (SS diagram) showing the relationship between the belt tension (N) and the belt elongation (%) measured at this time, a straight line in a relatively linear region (100 to 500 N) is shown. From the inclination (average inclination), the value (N /%) of the belt tension (N) relative to the belt elongation ratio (%) was calculated, and this was defined as the belt elastic modulus (tensile elastic modulus). When converted into a belt elastic modulus per 1 mm belt width and the value was 22 N /% or more, it was evaluated that the helical belt had high rigidity.

(Sound pressure measurement test)
A sound pressure measurement test was performed on the helical belts of Examples 1 to 18 and Comparative Examples 1 to 5 to evaluate noise during belt running. A two-axis running tester was used for the test. The two-axis running test machine has a configuration including a drive pulley 21 and a driven pulley 22 having a diameter larger than that of the drive pulley 21, similarly to the speed reducer 20 shown in FIG. 2. As the driving pulley 21 and the driven pulley 22, pulleys having the number of teeth shown in Table 12 were used. A helical belt is wound between the drive pulley 21 and the driven pulley 22, the distance between the pulley axes is adjusted so that the belt tension is 90N, a load of 5 Nm is applied to the driven pulley, and the drive pulley is The toothed belt was run at a rotational speed of 1200 rpm. The ambient temperature was 23 ° C. Then, the sound pressure (noise level) was measured with the sound collecting microphone M of the sound level meter. In order to explain the position of the sound collecting microphone M, the sound collecting microphone M is displayed on the speed reducer 20 shown in FIG. Specifically, the sound collecting microphone M is a straight line A that is perpendicular to a straight line T that passes through the center position S of the drive pulley 21 and passes through the center position S of the drive pulley 21 and the center position K of the driven pulley 22. Is moved by 25 mm in the direction of the driven pulley 22 and arranged at a position 30 mm away from the outer peripheral surface of the helical belt 30 in the vertical direction from the portion B in contact with the outer peripheral surface of the helical belt 30. . Tables 5 to 10 show the measurement results measured with the sound collecting microphone M. In the measurement results of Tables 5 to 10, the sound pressure value is described as an integer value rounded to one decimal place. Based on the results, ranks are used using ranks A, B, and C according to the numerical value of sound pressure. If sound pressure (an integer value rounded to the first decimal place) is 55 dBA or less, rank A, 56 to 57 dBA Is rank B, and rank C if 58 dBA or higher. From the viewpoint of appropriateness as a practical noise level of the helical belt, the rank A and B belts are preferable, and the rank A belt is particularly preferably used.

(Jumping test)
Jumping tests were conducted on the helical belts of Examples 1 to 18 and Comparative Examples 1 to 5. A biaxial torque measurement tester was used for the test. In the layout used in the above sound pressure measurement test, a helical belt was wound between the driving pulley and the driven pulley, and the distance between the axes of the pulleys was adjusted so that the belt tension was 50N. Then, as shown in FIG. 6, after fixing the driven pulley so as not to rotate, the hexagon wrench inserted into the shaft of the drive pulley is manually turned in the direction of the arrow in FIG. The load torque applied to the drive shaft when jumping (jumping) occurred was measured as the jumping torque. The measurement results are shown in Tables 5 to 10. As a judgment of jumping performance (hardness of tooth jumping), the jumping torque value is used as an index (the larger the torque value, the more difficult the tooth jumping), and the jumping torque value is 11.2 N · m or higher rank A, 11 Rank B was assigned when the value was greater than or equal to 0.0 N · m and less than 11.2 N · m, and rank C was designated when it was less than 11.0 N · m. From the viewpoint of appropriateness for actual use in this application, the belts of ranks A and B were set to pass levels.

(Cold resistance test)
Moreover, the test of cold resistance (low temperature durability) was implemented using the 2-axis running test machine of the same layout as the said sound pressure measurement test. The driving temperature of the drive pulley 21 was rotated at 2000 rpm with no load at an atmospheric temperature of −40 ° C. The operation of running for 6 seconds and then stopping for 10 minutes was performed as 1000 cycles for one cycle. Then, at 500th cycle and 1000th cycle, it was visually confirmed whether or not a crack was generated on the surface of the back portion of the helical belt.
The confirmation results are shown in Tables 5 to 10 using ranks A, B, and C. Rank A is the case where no cracks occurred even at the 1000th cycle. Rank B is a case where cracks did not occur in the 500th cycle and cracks occurred in the 1000th cycle. Rank C is when cracks occurred at the 500th cycle. As an index of cold resistance (low temperature durability), when using a belt in a cold area where the minimum temperature reaches -40 ° C, it is likely to reach a crack life in the order of ranks B and C compared to a rank A belt. The grade is inferior in durability. From the viewpoint of appropriateness for actual use in a cold region where the minimum temperature reaches −40 ° C., the rank A and B belts are preferred, and the rank A belt is particularly preferred.

(Test results)
For the helical tooth belts of Examples 1 to 18 and Comparative Examples 1 to 5, the measured values of the belt elastic modulus and the results of each ranking in the sound pressure test, jumping test, and cold resistance test were comprehensively determined according to the following criteria. Dominance judgment was performed.
-A judgment: When all test items are rank A-B judgment: There are no test items of rank C, but there is at least one test item of rank B-C judgment: One test item of rank C is If there is

(Test result: Comparison with variable tooth pitch P)
The helical belts of Examples 1 to 4 and Comparative Examples 1 and 2 shown in Table 5 are helical belts having the same configuration except that the tooth pitch P is varied. The helical belts of Examples 1 to 4 have a sound pressure (rank A or rank B) that is lower than that of a conventional helical belt (comparative example 2) having a tooth pitch (2.0 mm), jumping properties, Cold resistance was also at an acceptable level (rank A), and the overall judgment was A or B.
On the other hand, Comparative Example 1 is an example (1.40 mm) in which the tooth pitch P is further reduced as compared with Examples 1 to 4, but the sound pressure is reduced, but it is rejected (rank C) in terms of jumping properties. became.

(Comparison with variable tooth height hb)
The helical belts of Examples 5 to 8 shown in Table 6 are based on the helical belt of Example 2 (tooth pitch 1.75 mm), and the tooth height hb is changed with the tooth pitch 1.75 mm. This is an example. In Example 6 (41%), Example 2 (44%), and Example 7 (49%) in which the tooth height hb is 40 to 50% of the tooth pitch P, the sound pressure is Reduced (rank A), jumping properties and cold resistance were also acceptable levels (rank A), and A was determined as a comprehensive determination. In Example 5 in which the tooth height hb is 37% with respect to the tooth pitch P, the jumping property is slightly small (rank B), and the tooth height hb is 54% with respect to the tooth pitch P. In Example 8, the sound pressure was slightly high (rank B), and the overall determination was B determination.

(Comparison by varying the thickness tb of the belt back)
The helical belts of Examples 9 to 11 and Comparative Example 3 shown in Table 7 are examples in which the thickness tb of the back part is varied based on the helical belt of Example 2 (back part thickness 0.85 mm). . In Example 9 (0.4 mm), Example 10 (0.6 mm), and Example 11 (1.2 mm) in which the thickness tb of the belt back portion is in the range of 0.4 to 1.2 mm, the sound pressure is Reduced (rank A or B), jumping property and cold resistance were also acceptable levels (rank A or B), and were judged as A or B in the overall judgment. On the other hand, in Comparative Example 3 in which the thickness of the back portion is as large as 1.35 mm, the cold resistance (low temperature durability) was rejected (rank C) due to the lowering of the flexibility of the belt, and therefore the C determination was made as a comprehensive determination. It was.

Here, the decrease in cold resistance means that defects such as cracks are likely to occur when used (bent running) in a low temperature environment. When using a helical tooth belt for automobile applications, cold resistance assuming use in a cold region (for example, −40 ° C.) is also important. According to Examples 2 and 9 to 11 and Comparative Example 3 described above, a helical tooth belt having a small back thickness tb has increased vibration (sound pressure) due to a decrease in belt rigidity (improved flexibility). While quietness is reduced, cold resistance is improved. On the other hand, a helical belt with a large back portion thickness tb reduces vibration (sound pressure) and improves quietness, but decreases cold resistance due to an increase in belt rigidity (decrease in flexibility). Therefore, the upper and lower limits of the back thickness tb are important. According to Examples 2, 9 to 11 and Comparative Example 3, when the tooth pitch P is 1.75 mm, the thickness tb of the back is 0.4 to 1.2 mm is appropriate, and 0.6 mm to 0.9 mm is particularly preferable.

(Comparison with changed rubber components)
The helical belts of Examples 12 to 13 shown in Table 8 are examples in which the rubber component is changed based on the helical belt of Example 2 (EPDM). In Example 12 in which the rubber component is CR and Example 13 in which H-NBR is used, the effect of reducing the sound pressure (rank A) is observed as in Example 2 (EPDM), and the jumping property is also equivalent. . However, from the characteristics of CR and H-NBR, in Examples 12 and 13, the cold resistance was slightly inferior (rank B), so that the overall judgment was B.

(Comparison by varying the density of the core array)
The helical belts of Examples 14 to 16 and Comparative Example 4 shown in Table 9 are based on the helical belt of Example 2 (ratio of the total value of the distance d to the belt width W: 37.5%). This is an example in which the ratio is varied by changing the core pitch SP. Example 14 (22.2%), Example 15 (46.2%), and Example 16 (56.3%) in which the ratio of the total distance d to the belt width W is in the range of 20% to 60%. ), The sound pressure was reduced (rank A or B), the jumping property and cold resistance were also acceptable levels (rank A or B), and the overall judgment was A or B. On the other hand, in Comparative Example 4 in which the ratio of the total value of the distance d to the belt width W is as large as 61.1%, the density of the core wire array is small, so that the belt elastic modulus that can suppress vibration cannot be obtained (belt The width was less than 22 N /% per mm, and the sound pressure did not decrease (rank C).

From the above results, the ratio of the total value of the distance d to the belt width W is preferably in the range of 20 to 60%, particularly preferably in the range of 20 to 40%. The belt elastic modulus per 1 mm belt width is preferably 22 N /% or more, and particularly preferably 30 N /% or more.

(Comparison by changing the core material)
The helical belts of Examples 17 to 18 and Comparative Example 5 shown in Table 10 are based on the helical belt of Example 2 (K glass fiber: A1), and the fiber material constituting the core wire was changed. It is an example. In Example 17 using a core wire of high-strength glass fiber (U glass fiber: A2) different from Example 2, and Example 18 using a core wire of carbon fiber (A4), it is equivalent to Example 2. It was performance. On the other hand, although the comparative example 5 is an example using the core wire of the glass fiber (E glass fiber: A3) which is not high-strength glass fiber, vibration was not suppressed and sound pressure was not reduced (rank C). Furthermore, the jumping performance was also rejected (rank C).

This application is based on Japanese Patent Application No. 2018-073961 filed on Apr. 6, 2018 and Japanese Patent Application No. 2019-056782 filed on Mar. 26, 2019, the contents of which are incorporated herein by reference.

1 Electric power steering device 15 Electric motor (drive source)
20 Reduction gear (belt transmission)
21 Driving pulley 22 Driven pulley 30 Helical belt 31 Back 32 Teeth 33 Core wire 35 Tooth cloth P Tooth pitch SP Core wire pitch hW Length of tooth in longitudinal direction of belt t Total thickness of helical belt tb Thickness hb Teeth height

Claims (14)

Back,
In the back portion, the core wire arranged and buried in the belt width direction,
A plurality of teeth provided on the one surface of the back portion at predetermined intervals along the longitudinal direction of the belt, each inclined with respect to the belt width direction;
A helical tooth belt having
A part of the surface of the tooth part and the one surface of the back part is composed of a tooth cloth,
The tooth pitch of the plurality of tooth portions is 1.5 mm or more and less than 2.0 mm,
The thickness of the back part is 0.4 mm or more and 1.2 mm or less,
The core wire is a twisted cord containing high-strength glass fiber or carbon fiber,
A helical belt in which the ratio of the total value of the distance between the core wires adjacent to each other in the belt width direction to the belt width is in the range of 20% to 60%. The helical belt according to claim 1, wherein the core wire has a diameter in a range of 0.2 mm to 0.6 mm. The helical belt according to claim 1 or 2, wherein each core wire pitch between the core wires is arranged in a range of 0.45 mm to 1.0 mm. The core wire embedded in the back portion has a constant pitch in the range of 0.45 mm or more and 1.0 mm or less from one end to the other end in the belt width direction of the helical tooth belt. The helical belt according to claim 3, which is arranged to be a value. The tooth height of the tooth portion is in a range of 0.6 mm to 1.0 mm, and a height in a range of 40 to 50% with respect to the tooth pitch. The helical tooth belt described in the item. The helical tooth belt according to any one of claims 1 to 5, wherein the back portion includes a rubber component, and the rubber component includes at least ethylene-propylene-diene terpolymer or hydrogenated nitrile rubber. The tooth fabric is composed of a woven fabric including warp and weft, the warp or weft is arranged to extend in the belt longitudinal direction, and the warp or weft arranged to extend in the belt longitudinal direction is stretchable. The helical belt according to any one of claims 1 to 6, comprising an elastic yarn having the following. The lotus according to any one of claims 1 to 7, wherein the fibers constituting the tooth cloth include at least one fiber selected from the group consisting of nylon, aramid, polyester, polybenzoxazole, and cotton. Tooth belt. The other surface of the back part is composed of a back cloth,
The helical belt according to any one of claims 1 to 8, wherein the fibers constituting the back fabric include at least one fiber selected from the group consisting of nylon, aramid, and polyester. The belt elastic modulus defined by the belt tension (N) per 1 mm of belt width with respect to the belt elongation rate (%) when wound between pulleys with a predetermined mounting tension is 22 N /% or more. The helical tooth belt according to any one of 1 to 9. A drive pulley that is rotationally driven by a drive source;
A driven pulley,
The helical belt according to any one of claims 1 to 10, which is wound around the driving pulley and the driven pulley;
A belt transmission device comprising: The belt transmission device according to claim 11, wherein the rotational speed of the drive pulley is 1000 rpm or more and 4000 rpm or less. The belt transmission device according to claim 11 or 12, wherein a load of the driven pulley is 0.5 kW or more and 3 kW or less. An outer diameter of the driven pulley is larger than an outer diameter of the driving pulley;
The belt transmission device according to any one of claims 11 to 13, wherein the belt transmission device is a reduction device of an electric power steering device for an automobile.

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