Toothed belt

Abstract

A toothed belt in which the tensile modulus of the rubber composition constituting the belt teeth satisfies the following relationships (1) and (2). (1) Tensile modulus X in the belt width direction < tensile modulus Y in the belt length direction (2) Tensile modulus X in the belt width direction

Description

Technical Field

[0001] The present invention relates to a toothed belt. This application claims priority based on Japanese Application No. 2023-116201 filed on July 14, 2023, and incorporates by reference all the descriptions set forth in the above-mentioned Japanese application.

Background Art

[0002] Toothed belts are suitable for applications that require synchronous rotation and are used in various fields. For example, toothed belts are used as power transmission means for motorcycles (see, for example, Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Toothed belts used for rear-wheel drive applications of electric motorcycles are toothed belts used for high-load transmission applications. Toothed belts used for high-load transmission applications are prone to damage such as tooth chipping. To avoid the occurrence of tooth chipping and extend the durability life, it can be considered to increase the tooth shear strength of the toothed belt. To increase the tooth shear strength, it can be considered to increase the modulus of elasticity of the belt teeth. And if the amount of the reinforcing material contained in the rubber composition constituting the belt teeth is increased, the modulus of elasticity of the rubber composition can be increased. On the other hand, when the content of the reinforcing material increases, the viscosity of the unvulcanized rubber composition increases, and it may not be possible to mold the tooth portion of the toothed belt.

Means for Solving the Problems

[0005] The present disclosure aims to provide a toothed belt in which tooth chipping is less likely to occur on the belt teeth and which has good durability.

[0006] The toothed belt according to one aspect of the present invention is a toothed belt in which the tensile elastic modulus of the rubber composition constituting the belt teeth satisfies the following relationships (A) and (B). (A) Tensile elastic modulus X in the belt width direction < Tensile elastic modulus Y in the belt length direction (B) Tensile elastic modulus X in the belt width direction < Tensile elastic modulus Z in the belt thickness direction

Advantages of the Invention

[0007] The toothed belt according to one aspect of the present invention is a toothed belt in which tooth chipping is less likely to occur on the belt teeth and which has good durability.

Brief Description of the Drawings

[0008]

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DETAILED DESCRIPTION OF THE INVENTION

[0009] The outline of the embodiments of the present invention will be listed and described. (1) A toothed belt in which the tensile elastic modulus of the rubber composition constituting the belt teeth satisfies the following relationships (A) and (B). (A) Tensile elastic modulus X in the belt width direction < Tensile elastic modulus Y in the belt length direction (B) Tensile elastic modulus X in the belt width direction < Tensile elastic modulus Z in the belt thickness direction

[0010] As described above, if the elastic modulus of the belt teeth is increased, the tooth shear strength of the toothed belt can be enhanced. In this regard, as a result of detailed verification by the present inventors, it has been found that the tensile elastic modulus in the belt width direction does not significantly affect the tooth shear strength, whereas the tooth shear strength increases as the tensile elastic modulus in the belt length direction and the tensile elastic modulus in the belt thickness direction increase. The toothed belt described in the above (1) is a toothed belt completed based on such findings. Since the tensile elastic modulus of the rubber composition constituting the belt teeth satisfies the above relationships (A) and (B), the tooth shear strength is strong and tooth chipping is less likely to occur.

[0011] (2) In the toothed belt of the above (1), it is preferable that the rubber composition contains short fibers. In this case, it is easy to mold the belt teeth that satisfy the above relationships (A) and (B) without impairing the moldability of the belt teeth.

[0012] (3) In the toothed belt of the above (1) or (2), the ratios of the tensile elastic modulus Y and the tensile elastic modulus Z to the tensile elastic modulus X are preferably both 1.1 or more. In this case, it is suitable for making the belt teeth have a strong tooth shear strength and be easy to mold.

[0013] (4) In the toothed belt of any one of the above (1) to (3), the tensile elastic modulus X is preferably 3.5 MPa or more. In this case, tooth chipping of the belt teeth is less likely to occur.

[0014] (5) In the toothed belt of any one of the above (1) to (4), the pitch of the belt teeth is preferably 8 mm or more and 14 mm or less.

[0015] (6) It is preferable that the toothed belt of any one of the above (1) to (5) further satisfies the following relationship (C). (C) Tensile elastic modulus Y in the belt length direction < Tensile elastic modulus Z in the belt thickness direction When the above relationship (C) is satisfied, the tooth shear strength is stronger and tooth chipping is less likely to occur.

[0016] (7) In the toothed belt of any one of the above (2) to (6), the rubber composition constituting the belt teeth is a crosslinked unvulcanized rubber composition containing a rubber component and short fibers, and the content of the short fibers is preferably 1 part by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0017] (8) In the toothed belt of the above (7), the rubber component is preferably any one of hydrogenated nitrile rubber, chloroprene rubber, and ethylene - propylene - diene rubber.

[0018] (9) In any of the toothed belts (1) to (8) above, it is preferable that the Duro-A hardness of the rubber composition constituting the belt teeth is 85 or more and 98 or less.

[0019] (10) It is preferable that any of the toothed belts (1) to (9) above is provided with a reinforcing fabric that constitutes the inner peripheral surface of the belt.

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0021] (Toothed Belt) FIG. 1 is a perspective view showing a part of a toothed belt 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 3 is an end view taken along line B-B of FIG. 1. FIG. 1 shows a part of the toothed belt 1. The toothed belt 1 is an endless meshing transmission belt. The toothed belt 1 is a one-sided toothed belt.

[0022] In FIGS. 1 to 3, the direction indicated by the double-headed arrow X is the width direction of the toothed belt 1. The direction indicated by the double-headed arrow Y is the length direction of the toothed belt 1. The length direction is also the belt circumferential direction of the toothed belt 1. The direction indicated by the double-headed arrow Z is the thickness direction of the toothed belt 1. The upper side of each paper surface is the outer peripheral side of the toothed belt 1, and the lower side is the inner peripheral side.

[0023] The belt length (belt pitch line in belt length) of the toothed belt 1 is, for example, 225 mm or more and 6000 mm or less. The belt width Wb of the toothed belt 1 is, for example, 10 mm or more and 120 mm or less. The belt thickness Tb of the toothed belt 1 is, for example, 3.5 mm or more and 9.0 mm or less. The belt thickness Tb of the toothed belt 1 is the thickness of the thickest part of the toothed belt 1. The dimensions of the toothed belt according to the embodiment of the present invention are not necessarily limited to this range.

[0024] The toothed belt 1 has a back portion 11 and a plurality of belt teeth 12. The back portion 11 extends in the belt circumferential direction. The back portion 11 is endless and belt-shaped. In a cross-section perpendicular to the belt circumferential direction of the toothed belt 1, the cross-sectional shape of the back portion 11 is rectangular. The plurality of belt teeth 12 are provided on the inner peripheral side of the back portion 11. The plurality of belt teeth 12 are arranged at equal intervals in the belt circumferential direction. Each belt tooth 12 extends in the belt width direction. The pitch Pb of the belt teeth 12 is, for example, 8 mm or more and 14 mm or less. The tooth profile of the belt teeth 12 is, for example, an arc tooth profile.

[0025] (Configuration of toothed belt) The toothed belt 1 includes a belt body 2, a core wire 3, and a reinforcing cloth 4. The belt body 2, the core wire 3, and the reinforcing cloth 4 will be described below.

[0026] (Belt body) The belt body 2 has a belt shape. The belt body 2 includes a base portion 21 and a plurality of tooth portions 22. The base portion 21 extends in the belt circumferential direction. The core wire 3 is embedded in the base portion 21. The plurality of tooth portions 22 are provided on the inner peripheral side of the base portion 21. The plurality of tooth portions 22 are integral with the base portion 21. The plurality of tooth portions 22 are arranged at equal intervals in the belt circumferential direction. The surface of the tooth portion 22 is covered with the reinforcing cloth 4.

[0027] The belt body 2 is constituted by, for example, a rubber composition in which an unvulcanized rubber composition containing a rubber component and a rubber compounding agent is vulcanized by heating and pressurization (hereinafter, also referred to as a vulcanized rubber composition). Each of the base portion 21 and the tooth portion 22 of the belt body 2 is made of a vulcanized rubber composition. In the toothed belt 1 shown in FIG. 1, the base portion 21 and the tooth portion 22 are constituted by different vulcanized rubber compositions. The vulcanized rubber composition constituting the base portion 21 and the vulcanized rubber composition constituting the tooth portion 22 may have the same composition.

[0028] In the toothed belt 1 according to the present embodiment, the rubber composition constituting the tooth portion 22 of the belt body 2 satisfies the following relationships (A) and (B) with respect to the tensile modulus of the rubber composition. (A) Tensile modulus X in the belt width direction < Tensile modulus Y in the belt length direction (B) Tensile modulus X in the belt width direction < Tensile modulus Z in the belt thickness direction In the toothed belt 1, since the tensile modulus Y in the belt length direction and the tensile modulus Z in the belt thickness direction are larger than the tensile modulus X in the belt width direction, tooth chipping of the belt teeth is less likely to occur. In a toothed belt, the tensile modulus X does not significantly affect tooth chipping of the belt teeth, whereas the tensile moduli Y and Z significantly affect tooth chipping of the belt teeth. Therefore, in the toothed belt 1, the tensile moduli Y and Z that significantly affect tooth chipping of the belt teeth are increased to suppress the occurrence of tooth chipping of the belt teeth. Further, since the toothed belt 1 does not have a large tensile modulus in all directions (width direction, length direction, and thickness direction), it is not necessary to contain a large amount of a reinforcing material, and the moldability of the belt teeth is less likely to be impaired.

[0029] In the toothed belt 1, the ratio of the tensile modulus Y to the tensile modulus X is preferably 1.1 or more. Also, the ratio of the tensile modulus Z to the tensile modulus X is preferably 1.1 or more. In these cases, the tooth shear strength of the toothed belt 1 is likely to be improved. The ratio of the tensile modulus Y to the tensile modulus X is at most about 8, and usually preferably 3 or less, even if it is large. Also, the ratio of the tensile modulus Z to the tensile modulus X is at most about 8, and usually preferably 3 or less, even if it is large.

[0030] The tensile modulus X is preferably 3.5 MPa or more. In this case, tooth chipping of the belt teeth is even less likely to occur, and the durability of the toothed belt 1 becomes even better. The preferable upper limit of both the tensile modulus Y and the tensile modulus Z is 30 MPa.

[0031] The toothed belt 1 preferably further satisfies the following relationship (C). (C) Tensile elastic modulus Y in the belt length direction < Tensile elastic modulus Z in the belt thickness direction By satisfying the above relationship (C), the tooth shear strength of the toothed belt 1 is likely to be stronger. Therefore, the toothed belt 1 is likely to have improved durability.

[0032] The tensile elastic moduli X, Y, and Z are measured by the following methods respectively. (Method for measuring tensile elastic modulus X) Figure 4 is a diagram for explaining the method for measuring the tensile elastic modulus X. (1) First, cut out one belt tooth 112 from the toothed belt 101. (2) Next, insert the blade of the cutting machine along the belt width direction and cut out a slice piece 161 with a width of about 1 mm including the tooth tip portion. (3) Next, cut out a strip from near the center of the portion corresponding to the tooth part of the slice piece 161 so that the length in the Z direction is about 2 mm, and use this as the test piece 162. The dimensions of the test piece 162 are about 1 mm in the Y direction and about 2 mm in the Z direction. The dimension in the X direction depends on the width dimension of the toothed belt. Grip both ends of the test piece 162 in the longitudinal direction (X direction) and conduct a tensile test to measure the tensile elastic modulus X.

[0033] <Tensile test> The tensile test is conducted at room temperature using a universal testing machine (Instron). Set the test piece 162 on the universal testing machine by gripping one end of the test piece 162 with the upper chuck of the Instron and holding the other end of the test piece 162 with the lower chuck so that the longitudinal direction of the test piece 162 is along the vertical direction. At this time, the distance between the chucks is 1 mm. Conduct a tensile test at a tensile speed of 10 mm / min to obtain an S-S curve (stress-strain curve), and calculate the tensile elastic modulus X based on the slope at 0 to 20% elongation.

[0034] (Method for measuring tensile elastic modulus Y) Figure 5 is a diagram for explaining the method for measuring the tensile elastic modulus Y. (1) First, cut out one belt tooth 112 from the toothed belt 101. (2) Next, insert the blade of the cutting machine along the belt length direction, and cut out a slice piece 171 with a width of about 2 mm from near the center in the width direction. (3) Next, cut out a strip with a length of about 1 mm in the Z direction from a portion near the base of the portion corresponding to the tooth part of the slice piece 171, and use this as the test piece 172. The dimensions of the test piece 172 are about 2 mm in the X direction and about 1 mm in the Z direction. The dimension in the Y direction depends on the tooth width dimension of the belt tooth. Grip both ends in the longitudinal direction (Y direction) of this test piece 172, conduct a tensile test, and calculate the tensile elastic modulus Y. The method of the tensile test is the same as that when measuring the tensile elastic modulus X. In addition, in the measurement of the tensile elastic modulus Y, set the test piece 172 on the Instron so that the crosslinked rubber composition constituting the tooth part 122 is located between the upper chuck and the lower chuck. In FIG. 5, 104 is a reinforcing cloth.

[0035] (Method for Measuring Tensile Elastic Modulus Z) FIG. 6 is a diagram for explaining the method of measuring the tensile elastic modulus Y. (1) In the same manner as (1) and (2) of the method for measuring the tensile elastic modulus Y, cut out a slice piece 171 of one belt tooth 112. (2) Next, cut out a strip with a length of about 1 mm in the Y direction from near the center of the portion corresponding to the tooth part of the slice piece 171, and use this as the test piece 173. The dimensions of the test piece 173 are about 2 mm in the X direction and about 1 mm in the Y direction. The dimension in the Z direction depends on the thickness dimension of the toothed belt. Grip both ends in the longitudinal direction (Z direction) of this test piece 173, conduct a tensile test, and calculate the tensile elastic modulus Z. The method of the tensile test is the same as that when measuring the tensile elastic modulus X. In addition, in the measurement of the tensile elastic modulus Z, set the test piece 173 on the universal testing machine so that the crosslinked rubber composition constituting the tooth part 122 is located between the upper chuck and the lower chuck. In FIG. 6, 103 is a core wire and 104 is a reinforcing cloth.

[0036] The Duro-A hardness of the crosslinked rubber composition constituting the belt teeth is preferably 85 or more and 98 or less. In this case, tooth chipping of the belt teeth is less likely to occur, and the durability of the toothed belt is better.

[0037] As described above, the belt body 2 is composed of a crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition containing, for example, a rubber component and a rubber compounding agent. Examples of the rubber component include ethylene-α-olefin elastomers such as hydrogenated nitrile rubber (HNBR), chloroprene rubber (CR), ethylene-propylene-diene rubber (EPDM), chlorosulfonated polyethylene rubber, styrene-butadiene rubber, epichlorohydrin rubber, and the like. Among these, HNBR, CR, and EPDM are preferable.

[0038] The uncrosslinked rubber composition preferably contains short fibers as a rubber compounding agent. And the short fibers contained in the crosslinked rubber composition are preferably oriented in the Y direction and the Z direction and not in the X direction. In other words, the length direction of the short fibers is preferably oriented in the Y direction and the Z direction and not in the X direction. In these cases, it is easy to satisfy the above relationships (A) and (B) with respect to the tensile elastic modulus of the crosslinked rubber composition constituting the tooth portion 22. Further, it is easy to increase the tensile elastic modulus of the crosslinked rubber composition constituting the tooth portion without degrading the moldability of the belt teeth.

[0039] Furthermore, by orienting the short fibers more in the Z direction than in the Y direction, it becomes easier to satisfy the above relationship (C). For example, when manufacturing the toothed belt by the two-step manufacturing method described later, if the amount of the short fibers added to the rubber composition constituting the tooth portion is increased, the short fibers are more likely to be oriented in the Z direction than in the Y direction.

[0040] Examples of the short fibers include aramid short fibers, nylon short fibers, polyester short fibers, and the like. As the above aramid short fibers, para-aramid short fibers are preferred. These short fibers may be used alone or in combination of two or more. The length of the above short fibers is, for example, 0.5 mm or more and 3.5 mm or less. The fiber diameter of the above short fibers is, for example, 5 μm or more and 50 μm or less. The preferred content of the above short fibers is 1 part by mass or more and 7 parts by mass or less based on 100 parts by mass of the rubber component. When the content of the above short fibers exceeds 7 parts by mass, cracks are likely to occur in the tooth part. A more preferred content of the above short fibers is 1 part by mass or more and 3 parts by mass or less based on 100 parts by mass of the rubber component.

[0041] Examples of rubber compounding agents other than the above short fibers include, for example, vulcanization accelerator aids, anti-aging agents, reinforcing materials, plasticizers, co-crosslinking agents, crosslinking agents, processing aids, etc. Examples of the above vulcanization accelerator aids include, for example, metal oxides, metal carbonates, fatty acids and their derivatives, etc. Examples of the above metal oxides include, for example, zinc oxide (zinc white), magnesium oxide, etc. These vulcanization accelerator aids may be used alone or in combination of two or more. The content of the above vulcanization accelerator aids is, for example, 3 parts by mass or more and 20 parts by mass or less based on 100 parts by mass of the rubber component.

[0042] Examples of the above reinforcing materials include carbon black, silica, etc. The above reinforcing materials may be used in combination of carbon black and silica. Examples of the above carbon black include, for example, channel black, furnace black, thermal black, acetylene black, etc. Examples of the above furnace black include, for example, SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, N-234, etc. Examples of the above thermal black include, for example, FT, MT, etc. Carbon black may be used alone or in combination of two or more.

[0043] When using carbon black, its content is, for example, 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the rubber component. When using silica, its content is, for example, 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0044] Examples of the above plasticizer include dialkyl sebacate, dialkyl phthalate, dialkyl adipate and the like. Examples of the above dialkyl sebacate include polyether ester, dioctyl sebacate (DOS) and the like. Examples of the above dialkyl phthalate include dibutyl phthalate (DBP), dioctyl phthalate (DOP) and the like. Examples of the above dialkyl adipate include dioctyl adipate (DOA) and the like. These plasticizers may be used alone or in combination of two or more. The content of the above plasticizer is, for example, 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0045] Examples of the above co-crosslinking agent include trimethylolpropane trimethacrylate, m-phenylene dimaleimide, zinc dimethacrylate, triallyl isocyanurate and the like. These co-crosslinking agents may be used alone or in combination of two or more. The content of the above co-crosslinking agent is, for example, 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0046] Examples of the above crosslinking agent include sulfur, organic peroxides and the like. Sulfur and organic peroxides may be used in combination. Of course, either one of them may be used alone. When using sulfur and organic peroxides in combination as the above crosslinking agent, the total blending amount of the above crosslinking agent is preferably, for example, sulfur is 0.1 part by mass or more and 3 parts by mass or less, and organic peroxide is 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0047] Examples of the processing aids include stearic acid, polyethylene wax, metal salts of fatty acids, etc. Only one type of these processing aids may be used, or two or more types may be used in combination. The content of the processing aids is, for example, 0.5 parts by mass or more and 2 parts by mass part or less with respect to 100 parts by mass of the rubber component.

[0048] (Core wire) As described above, the core wire 3 is embedded in the base portion 21. Examples of the core wire 3 include glass core wire, aramid core wire, carbon core wire, steel core wire, etc. These core wires are preferably composed of twisted yarns. As the core wire 3, a carbon core wire and a steel core wire are preferable. Carbon and steel are materials with a high elastic modulus. Therefore, in a toothed belt provided with a carbon core wire or a steel core wire, the length hardly changes when a load is applied, and the change in tooth pitch is small. Therefore, a toothed belt provided with a carbon core wire or a steel core wire easily maintains a good meshing state with the toothed pulley.

[0049] The outer diameter of the core wire 3 preferably satisfies that the outer diameter φT in the belt thickness direction and the outer diameter φW in the belt width direction are each 0.90 mm or more and 1.70 mm or less. More preferable outer diameters φT and φW are 1.00 mm or more and 1.60 mm or less. The outer diameter φT in the belt thickness direction and the outer diameter φW in the belt width direction may be the same or different.

[0050] The core wire 3 has a pitch in the belt width direction and is provided so as to form a helix. For example, a core wire pair composed of an S-twisted core wire 3 and a Z-twisted core wire 3 may be provided so as to have a pitch in the belt width direction and form a helix.

[0051] The core wires 3 are arranged at intervals in the belt width direction and extend in parallel. Apparently, a plurality of core wires 3 are arranged side by side in the belt width direction. At this time, the number of core wires 3 per 10 mm of belt width is preferably 5 to 20 per 10 mm. The toothed belt 1 with the core wires 3 arranged in this way is suitable for ensuring excellent durability in high-load transmission and excellent tension maintenance in high-load transmission. From the same perspective, a more preferable number of core wires 3 is 6 to 10 per 10 mm. Also, the dimension of the gap between adjacent core wires 3 is, for example, 0.1 mm or more and 0.7 mm or less.

[0052] The core wire 3 may be subjected to an adhesion treatment to enhance the adhesive force with the belt body 2. Examples of the above adhesion treatment include an RFL treatment in which the core wire is immersed in an RFL aqueous solution and then heated, and a rubber paste treatment in which the core wire is immersed in a rubber paste and then dried. Only one of these adhesion treatments may be performed, or both may be performed. The core wire 3 may be subjected to a primer treatment before the above adhesion treatment. Examples of the above primer treatment include a treatment in which the core wire is immersed in an epoxy solution or an isocyanate solution and then heated. These adhesion treatments and primer treatments are performed before winding the core wire around the mold in the manufacturing method of the toothed belt described later.

[0053] (Reinforcing cloth) The reinforcing cloth 4 covers the surface of the tooth portion 22. The reinforcing cloth 4 constitutes the inner peripheral surface of the toothed belt 1. The inner peripheral surface of the toothed belt 1 includes the reinforcing cloth 4. The reinforcing cloth 4 is a woven fabric. Examples of the fibers constituting the reinforcing cloth 4 include polyamide fibers (nylon fibers), polyester fibers, aramid fibers, polyparaphenylene benzobisoxazole (PBO) fibers, cotton, and the like. As the reinforcing cloth 4, for example, a woven fabric of polyamide fibers is preferable. The thickness of the reinforcing cloth 4 is, for example, 0.5 mm or more and 2.0 mm or less. The reinforcing cloth 4 preferably has elasticity, such as a woven fabric in which the weft is subjected to a woolly process.

[0054] The reinforcing fabric 4 may be subjected to an adhesion treatment to enhance the adhesive force with the belt body 2. Examples of the adhesion treatment include an RFL treatment in which the fabric is immersed in an RFL aqueous solution and then heated, a soaking treatment in which the fabric is immersed in a low-viscosity rubber paste and then dried, and a coating treatment in which a high-viscosity rubber paste is applied to the surface on the belt body side and then dried. These may be carried out alone or in combination of two or more. Before the adhesion treatment, the reinforcing fabric 4 may be subjected to a primer treatment in which it is immersed in an epoxy solution or an isocyanate solution and then heated. These adhesion treatments and primer treatments are carried out before the reinforcing fabric 4 is wound around the mold in the method for manufacturing the toothed belt described below.

[0055] (Method for manufacturing a toothed belt) Next, a method for manufacturing the toothed belt 1 will be described. The toothed belt 1 can be manufactured, for example, by the method for manufacturing a toothed belt 1 or the method for manufacturing a toothed belt 2 described below.

[0056] (Method for manufacturing a toothed belt 1) Figs. 7 to 11 are diagrams for explaining the method for manufacturing the toothed belt 1. Figs. 7 to 11 show only a part of the mold 5 for belt forming and the belt (including the belt material). The method for manufacturing a toothed belt described with reference to Figs. 7 to 11 is also called a two-step manufacturing method because the tooth part and the base part are formed separately.

[0057] In the manufacturing of the toothed belt 1, a mold 5 for belt forming is used. The mold 5 is cylindrical. On the outer periphery of this mold 5, a recess 51 extending in the axial direction and a protrusion 52 extending in the axial direction are provided. The recess 51 has a cross-sectional shape corresponding to the belt teeth 12 and is a groove extending in the axial direction (a direction perpendicular to the plane of Fig. 7). The recesses 51 are provided at regular pitches with intervals in the circumferential direction. The protrusion 52 is provided between adjacent recesses 51.

[0058] (1) Prepare the materials. The rubber component is kneaded, and then a rubber compounding agent is added and kneaded to obtain an uncrosslinked rubber composition. The obtained uncrosslinked rubber composition is molded to produce an uncrosslinked rubber sheet 23. At this time, as a molding method of the uncrosslinked rubber sheet 23, for example, calender molding or the like can be adopted.

[0059] The core wire 3 and the reinforcing cloth 4 are prepared, and if necessary, adhesion treatment or base treatment is applied to each of them. Furthermore, the reinforcing cloth 4 is formed into a cylindrical shape.

[0060] (2) As shown in FIG. 7, first, the reinforcing cloth 4 formed into a cylindrical shape is covered on the outer peripheral surface of the mold 5. Next, the uncrosslinked rubber sheet 23A is wound around the reinforcing cloth 4. At this time, only one uncrosslinked rubber sheet 23A may be wound, or a plurality of uncrosslinked rubber sheets 23A may be wound. Thereby, a first uncrosslinked molded body 13A in which the reinforcing cloth 4 and the uncrosslinked rubber sheet 23A are laminated is molded on the mold 5. The uncrosslinked rubber sheet 23A wound in this step is an uncrosslinked rubber sheet for forming the tooth portion.

[0061] At this time, the uncrosslinked rubber sheets 23A are preferably laminated so that the alignment direction corresponds to the belt length direction. In this case, it is easy to mold a crosslinked rubber composition in which the short fibers are oriented in the Y direction and the Z direction and not in the X direction. When a plurality of uncrosslinked rubber sheets 23A are wound, each uncrosslinked rubber sheet may have the same composition or different compositions.

[0062] Thereafter, as shown in FIG. 8, a rubber sleeve 6 is covered on the first uncrosslinked molded body 13A on the mold 5, and this is placed in a vulcanizing kettle and sealed. Next, the vulcanizing kettle is filled with high-temperature and high-pressure steam. Further, this state is maintained for a predetermined time. Thereby, the first uncrosslinked molded body 13A is pressed against the mold 5 side and heated. As a result, the uncrosslinked rubber sheet 23A flows into each of the plurality of recesses 51 of the mold 5 while pressing the reinforcing fabric 4 and is crosslinked. At this time, the uncrosslinked rubber sheet 23A is heated so as to be in a semi-crosslinked state. As a result, as shown in FIG. 9, a plurality of semi-crosslinked tooth portions 122 are formed.

[0063] (3) Next, as shown in FIG. 10, the core wire 3 is spirally wound around the outer periphery of the formed tooth portion 122. Furthermore, an uncrosslinked rubber sheet 23B is wound thereon. The uncrosslinked rubber sheet 23B is wound one or a plurality of sheets (one sheet in FIG. 10). As a result, a second uncrosslinked molded body 13B in which the core wire 3 and the uncrosslinked rubber sheet 23B are laminated is formed on the mold 5 (on the tooth portion 122). At this time, the uncrosslinked rubber sheet 23B is preferably laminated so that the alignment direction corresponds to the belt length direction. The uncrosslinked rubber sheet wound in this step is the uncrosslinked rubber sheet that forms the base.

[0064] The composition of the uncrosslinked rubber sheet 23B may be the same as or different from the composition of the uncrosslinked rubber sheet 23A. When a plurality of uncrosslinked rubber sheets 23B are wound, each uncrosslinked rubber sheet may have the same composition or different compositions.

[0065] (4) As shown in FIG. 11, the rubber sleeve 6 is put on the second uncrosslinked molded body 13B on the mold 5, and this is placed in a vulcanizing kettle and sealed. Next, the vulcanizing kettle is filled with high-temperature and high-pressure steam. Further, this state is maintained for a predetermined time. As a result, the second uncrosslinked molded body 13B is pressed against the mold 5 side and heated. At this time, the uncrosslinked rubber sheet 23B passes between the core wires 3 and is crosslinked while being pressed against the plurality of semi-crosslinked tooth portions 122 formed in the plurality of recesses 51. As a result, a cylindrical belt slab 14A having the integrated and completely crosslinked tooth portion 22 and base portion 21 is formed.

[0066] (5) Depressurize the inside of the vulcanizer to release the seal. Subsequently, demold the belt slab 14A molded between the mold 5 and the rubber sleeve 6 and then. After that, cut the demolded belt slab 14A into pieces. By going through such steps, the toothed belt 1 is obtained.

[0067] (Manufacturing method 2 of toothed belt) The manufacturing method of the toothed belt 1 is not limited to the two-step manufacturing method described above, and it can also be manufactured by the following method. Figs. 12 to 14 are diagrams for explaining 2 the manufacturing method of the toothed belt 1. Only a part of the mold 5 for belt molding and the belt (including the belt material) are shown in Figs. 12 to 14. The manufacturing method of the toothed belt described with reference to Figs. 12 to 14 is also referred to as a one-step manufacturing method because the teeth and the base are crosslinked simultaneously. In this manufacturing method 2, the same mold 5 for belt molding as in manufacturing method 1 is used.

[0068] (1) Prepare the materials in the same manner as in manufacturing method 1. That is, prepare the uncrosslinked rubber sheet 23, the core wire 3 subjected to adhesion treatment, and the reinforcing cloth 4 subjected to adhesion treatment and formed into a tubular shape.

[0069] (2) As shown in Fig. 12, first, cover the outer peripheral surface of the mold 5 with the reinforcing cloth 4 formed into a tubular shape. Wind the core wire 3 spirally from above the reinforcing cloth 4. After winding the core wire 3, further wind insect the uncrosslinked go insect - rt 23. The uncrosslinked go insect - rt 23 is wound in a plurality of layers (two layers in Fig. 12). Thereby, an uncrosslinked molded body 13C in which the reinforcing cloth 4, the core wire 3, and the uncrosslinked go insect - rt 23 are laminated is formed on the outer periphery of the mold 5. In the lamination of the materials, it is preferable that the uncrosslinked go When winding up a plurality of unvulcanized rubber sheets 23, each unvulcanized rubber sheet may have the same composition or different compositions.

[0070] (3) As shown in FIG. 13, cover the unvulcanized molded body 13C on the mold 5 with a rubber sleeve 6. The unvulcanized molded body 13 covered with the rubber sleeve 6 C is placed inside a vulcanizing can (not shown) together with the mold 5 and the vulcanizing can is sealed. Fill the vulcanizing can with high-temperature and high-pressure steam. Hold in this state for a predetermined time. As a result, the unvulcanized molded body 13C is pressed against the mold 5 side and heated. Unvulcanized rubber insect -sheet 23 flows in the cavity formed between the mold 5 and the rubber sleeve 6. Unvulcanized rubber insect -sheet 23 passes between the core wires 3. Unvulcanized rubber insect -sheet 23 flows into each of the plurality of recesses 51 provided in the mold 5 while pressing the reinforcing cloth 4. Unvulcanized rubber insect -sheet 23 is integrated with the core wires 3 and the reinforcing cloth 4 while flowing in the cavity in this way and is vulcanized. As a result, as shown in FIG. 14, a cylindrical belt slab 14B is formed.

[0071] (4) Reduce the pressure inside the vulcanizing can to release the seal. Demold the belt slab 14B formed between the mold 5 and the rubber sleeve 6. Cut the demolded belt slab 14B into pieces. By going through such steps, the toothed belt 1 is also obtained.

Example

[0072] Hereinafter, the embodiments of the present invention will be described more specifically by way of examples, but the embodiments of the present invention are not limited to the following examples. Here, a plurality of toothed belts were manufactured and their performance was evaluated.

[0073] (Belt raw material) (1) Unvulcanized rubber composition Unvulcanized rubber compositions A1 to A4 and B1 to B2 having the formulations shown in Table 1 were prepared. The unvulcanized rubber compositions were prepared by kneading the rubber component and then adding and kneading rubber compounding agents.

[0074]

Table 1

[0075] In Table 1, HNBR(1) is ZP2010 (manufactured by Zeon Corporation, Japan), HNBR(2) is ZSC2195CX (manufactured by Zeon Corporation, Japan), and CR(1) is Skyprene 505 (manufactured by Toray Industries, Inc.). Also, in Table 1, the aramid short fibers are para-aramid short fibers having a fiber length of 1 mm and a wire diameter of 12 μm, and the organic peroxide is Peroximon F40 (manufactured by NOF Corporation).

[0076] (2) Core wire A carbon core wire was used. The outer diameter φT in the belt thickness direction and the outer diameter φW in the belt direction of the carbon core wire are both 1.10 mm. width

[0077] (3) Reinforcing fabric The following adhesion treatment was performed on a fabric made of polyamide fibers for the warp and weft. As the adhesion treatment, a soaking treatment in which the fabric was immersed in a low-viscosity rubber paste and then dried, and a coating treatment in which a high-viscosity rubber paste was applied to the surface on the belt body side of the fabric and dried were performed.

[0078] (Dimensions of toothed belt) A toothed belt of the type called S8M was manufactured. The dimensions of this toothed belt are as follows for the dimensions of the symbols shown in Fig. 15. Pb = 8.00 mm, Tb = 5.00 mm, h1 = 2.05 mm, h2 = 2.95 mm, R = 5.20 mm, W = 5.20 mm, a = 0.00 mm, r1 = 0.80 mm, r2 = 0.80 mm, PLD = 0.686 mm. ​In addition, the toothed belt has a belt length of 840 mm and a belt width of 8 mm.

[0079] [Examples 1 to 4, Comparative Example 1] The toothed belts were manufactured by the above-described two-step manufacturing method, using the combinations of belt raw materials shown in Table 2.

[0080] [Comparative Example 2] The toothed belts were manufactured by the above-described one-step manufacturing method, using the combinations of belt raw materials shown in Table 2.

[0081] [Table 2]

[0082] (Evaluation) The following evaluations were performed on the toothed belts manufactured in the examples and comparative examples. The results are shown in Table 3. (1) Hardness of belt teeth As the hardness of the crosslinked rubber composition constituting the belt teeth, the Duro-A hardness was measured by the following method. It was measured using a commercially available Type A durometer. Here, the rubber hardness meter was pressed perpendicularly to the side surface of the tooth portion of the belt body (the end surface in the belt width direction of the tooth portion) for measurement.

[0083] (2) Tensile modulus of belt teeth For the crosslinked rubber composition constituting the belt teeth, the tensile modulus in the X direction, the tensile modulus in the Y direction, and the tensile modulus in the Z direction were each measured. The measuring method for the tensile modulus in each direction is as already described.

[0084] (3) Tooth shear strength The measurement was carried out in accordance with the tooth shear strength test described in 6.5 of "Toothed Belt Transmission - Physical Property Test Methods" of JIS B 1865 (2021). This evaluation was performed using a shear tooth tip for S tooth profile. The results are shown as relative values with the measured value of Example 4 taken as 100.

[0085] (4) Running Test (Durability Evaluation) A toothed belt was wound around a two-shaft pulley having a driving pulley (tooth number: 22, pitch diameter: 56.02 mm) 91 and a driven pulley (tooth number: 33, pitch diameter: 84.03 mm) 92 to constitute a transmission system 90. FIG. 16 shows the pulley layout of the transmission system 90. Using this transmission system, a running test was conducted at a driving-side rotational speed of 4212 rpm, a driven-side rotational speed of 2808 rpm, a driven-side load of 34.3 N·m, a span tension of 304 N, a set weight of 608 N, and an ambient temperature of 60°C, and the time until tooth chipping occurred in the belt teeth was measured. The results are shown as relative values with the measured value of Example 4 taken as 100.

[0086]

Table 3

[0087] As shown in Table 4, it was revealed that the belt teeth according to the embodiment of the present invention are less likely to have tooth chipping and are excellent in durability.

[0088] It should be considered that all the embodiments disclosed this time are illustrative and not restrictive in any way. The scope of the rights of the present invention is indicated by the scope of the claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of the claims be included.

Explanation of Reference Numerals

[0089] 1, 101 Toothed belt 11 Back 12, 112 Belt teeth 13A, 13B, 13C Uncrosslinked formed body 14A, 14B Belt slab 2 Belt body 21 Base 22, 122 Tooth part 23, 23A, 23B Uncrosslinked rubber sheet 3, 103 Core wire 4. 104 Reinforcing Cloth 5. Mold 51. Concave Portion 52. Convex Portion 6. Rubber Sleeve 90 transmission System 91. Driving Pulley 92. Driven Pulley 161, 171. Slice Pieces 162, 172, 173. Test Specimens

Claims

1. A toothed belt, wherein the tensile modulus of elasticity of a rubber composition constituting the belt teeth satisfies the following relationships (A) and (B): (A) Tensile elastic modulus X in the belt width direction < tensile elastic modulus Y in the belt length direction (B) Tensile elastic modulus X in the belt width direction < tensile elastic modulus Z in the belt thickness direction

2. The toothed belt according to claim 1 , wherein the rubber composition contains short fibers.

3. 3. The toothed belt according to claim 1, wherein each of the ratios of the tensile modulus Y and the tensile modulus Z to the tensile modulus X is 1.1 or more.

4. 3. The toothed belt according to claim 1, wherein the tensile elastic modulus X is equal to or greater than 3.5 MPa.

5. 3. The toothed belt according to claim 1, wherein the belt tooth pitch is between 8 mm and 14 mm.

6. 3. The toothed belt according to claim 1, further satisfying the following relationship (C): (C) Tensile elastic modulus Y in the belt length direction < tensile elastic modulus Z in the belt thickness direction

7. 3. The toothed belt according to claim 2, wherein a rubber composition constituting the belt teeth is obtained by crosslinking an uncrosslinked rubber composition containing a rubber component and short fibers, and a content of the short fibers is 1 part by mass or more and 7 parts by mass or less per 100 parts by mass of the rubber component.

8. 8. The toothed belt according to claim 7, wherein the rubber component is any one of hydrogenated nitrile rubber, chloroprene rubber, and ethylene-propylene-diene rubber.

9. 3. The toothed belt according to claim 1, wherein a rubber composition constituting said belt teeth has a Duro-A hardness of 85 or more and 98 or less.

10. 3. The toothed belt according to claim 1, further comprising a reinforcing fabric constituting an inner peripheral surface of the belt.

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