Frictional transmission belt

Abstract

To provide a frictional transmission belt capable of reducing noise generating when being wetted.SOLUTION: A frictional transmission belt includes a belt main body transmitting power to a pulley by frictional force generated by contact with the pulley. In a relation between a slip speed as a difference between a speed of the belt main body and a speed of the pulley, and a friction coefficient, a reduction rate Dm of the friction coefficient indicated by a following formula (1), in which a maximum friction coefficient is μx and a reference friction coefficient is μr, is 20% or less, when the slip speed indicating the maximum friction coefficient is a first slip speed, the friction coefficient in increasing the slip speed from the first slip speed to a second slip speed is a reference friction coefficient, and a difference between the second slip speed and the first slip speed is 500 mm / s. Dm=(μx-μr) / μx×100 ... (1)SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a friction drive belt.

Background Art

[0002] Conventionally, as a means for transmitting rotational power of an engine, a motor, etc., a pulley is fixedly provided on each of the driving side and driven side rotating shafts, and a friction drive belt such as a V-ribbed belt is passed around each pulley, which is widely used.

[0003] A friction drive belt (hereinafter referred to as a drive belt) may cause a phenomenon called stick-slip, for example, when it gets wet during operation, and this phenomenon may be accompanied by abnormal noise, in other words, the generation of a slip sound. Since the slip sound of the drive belt causes noise in the device, various countermeasures have been studied.

[0004] For example, in Patent Document 1, in a friction drive belt in which the surface on the pulley contact side of the belt body is covered with a knitted fabric, a thread that extends while reversing the traveling direction so as to reciprocate in the width direction of the friction drive belt, and has a reversing portion that reverses the traveling direction and a straight portion that extends connecting between the reversing portions is used to form the knitted fabric, and it is proposed to cover the surface on the pulley contact side with this knitted fabric so as to have a straight portion located on the surface side rather than the reversing portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Various means have been proposed to reduce the abnormal noise generated when exposed to water. However, the current effect of reducing abnormal noise is not at a satisfactory level, and further improvement is required.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a friction transmission belt capable of reducing abnormal noise generated when exposed to water.

Means for Solving the Problem

[0008] When the inventors of the present invention examined in detail the behavior of abnormal noise generation when exposed to water, they found that in the relationship between the slip speed and the friction coefficient, the decrease rate of the friction coefficient in the zone from when the friction coefficient shows the maximum friction coefficient until the slip speed increases by 500 mm / s is deeply involved in the generation of abnormal noise, and thus the present invention has been completed.

[0009] (1) The friction transmission belt of the present invention is a friction transmission belt including a belt body that transmits power to the pulley by the frictional force generated by contact with the pulley, in the relationship between the slip speed, which is the difference between the speed of the belt body and the speed of the pulley, and the friction coefficient, the slip speed at which the maximum friction coefficient is exhibited is defined as the first slip speed, and the friction coefficient when the slip speed is increased from the first slip speed to the second slip speed is defined as the reference friction coefficient. When the difference between the second slip speed and the first slip speed is 500 mm / s, taking the maximum friction coefficient as μx and the reference friction coefficient as μr, the decrease rate Dm of the friction coefficient represented by the following formula (1) is 20% or less. Dm = (μx - μr) / μx × 100 ·····(1)

[0010] In the above friction transmission belt, the decrease in the friction coefficient is suppressed in the zone from when the friction coefficient shows the maximum friction coefficient until the slip speed increases by 500 mm / s. In the above friction transmission belt, stick-slip due to exposure to water is less likely to occur. Therefore, the abnormal noise generated when exposed to water is reduced.

[0011] (2) In the above friction transmission belt, a zone from the first slip speed to the second slip speed is equally divided into n (n is a natural number of 2 or more) intervals. The slip speed at the start of each interval is defined as the start speed, the friction coefficient at the start speed is defined as the start friction coefficient, the slip speed at the end of the interval is defined as the end speed, and the friction coefficient at the end speed is defined as the end friction coefficient. When the start friction coefficient in the m-th (m is a natural number from 1 to n) interval is μsm and the end friction coefficient is μem, the reduction rate Dsm of the friction coefficient represented by the following formula (2) is preferably 20 / n% or less in all the above intervals. Dsm = (μsm - μem) / μsm × 100 ·····(2) In this case, in all intervals constituting the above zone, a significant decrease in the friction coefficient is prevented. In the above zone, the friction coefficient gradually decreases. In the above friction transmission belt, the occurrence of stick-slip due to water is effectively suppressed. Therefore, abnormal noise is less likely to occur when wet.

[0012] (3) In the above friction transmission belt, the belt body preferably includes a compression rubber layer that contacts the pulley, and the compression rubber layer is preferably composed of a rubber layer body made of a rubber composition and a fiber member layer laminated on the rubber layer body. In this case, the fiber member layer absorbs water. Therefore, it is difficult to form a water film between the belt body and the pulley. In the above friction transmission belt, a significant decrease in the friction coefficient is prevented.

[0013] (4) In the above friction transmission belt, the porosity in the surface layer portion of the compression rubber layer is preferably 10% or more. In this case, the voids formed in the surface layer portion contribute to the absorption of water. In the above friction transmission belt, it is difficult to form a water film between the belt body and the pulley.

[0014] (5) In the above friction transmission belt, the porosity is more preferably 20% or more. In this case, water is effectively absorbed by the voids formed in the surface layer portion. In the above friction transmission belt, it is difficult to form a water film between the belt body and the pulley.

[0015] (6) In the above friction transmission belt, the fiber member layer is preferably composed of a woven fabric, and the woven fabric preferably contains a cellulose-based fiber as a main fiber. The cellulose-based fiber has excellent water absorption performance. In the above friction transmission belt, it is difficult to form a water film between the belt body and the pulley.

[0016] (7) In the above friction transmission belt, it is preferable that a plurality of V ribs hanging downward on the inner peripheral side are formed in the compression rubber layer. This friction transmission belt is a V-ribbed belt. In the above friction transmission belt, stick-slip due to water is less likely to occur. Therefore, the abnormal noise generated when wetted is reduced.

Advantages of the Invention

[0017] In the friction transmission belt of the present invention, a decrease in the friction coefficient is suppressed in the zone from when the friction coefficient shows the maximum friction coefficient until the slip speed increases by 500 mm / s. In the above friction transmission belt, stick-slip due to water is less likely to occur. Therefore, the abnormal noise generated when wetted is reduced.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 4C

Figure 5A

Figure 5B

Figure 6A

Figure 6B

Figure 6C

Figure 7

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Friction Transmission Belt) FIG. 1 schematically shows a part of a friction transmission belt B according to an embodiment of the present invention. This friction transmission belt B is, for example, a V-ribbed belt used in an accessory drive belt transmission device provided in an engine room of an automobile. In this V-ribbed belt B, for example, the belt perimeter is 700 mm or more and 3000 mm or less, the belt width is 10 mm or more and 36 mm or less, and the belt thickness is 3.5 mm or more and 5.0 mm or less.

[0020] This V-ribbed belt B includes an endless belt-shaped belt body 10. In this V-ribbed belt B, the belt body 10 transmits power to the pulley by the frictional force generated when the surface on the inner peripheral side of the belt body 10 comes into contact with the pulley. The belt body 10 includes a compression rubber layer 11 located on the inner peripheral side of the belt, an adhesive rubber layer 12 located in the middle, and a back reinforcement cloth 13 located on the outer peripheral side of the belt.

[0021] The compression rubber layer 11 extends in the belt length direction. The compression rubber layer 11 comes into contact with pulleys such as drive pulleys and driven pulleys. The compression rubber layer 11 is composed of a rubber layer main body 14 and a fiber member layer 15. The rubber layer body 14 is also referred to as a compression rubber layer body. The thickness of the rubber layer body 14 is, for example, 2.0 mm or more and 3.2 mm or less. The rubber layer body 14 is made of a rubber composition containing a crosslinked rubber component (hereinafter referred to as a crosslinked rubber composition). The rubber composition is a crosslinked product obtained by heating and pressurizing an uncrosslinked rubber composition (raw material composition) in which various rubber compounding agents including a crosslinking agent are compounded and kneaded in the rubber component, and the rubber component is crosslinked by the crosslinking agent.

[0022] Examples of the rubber component contained in the above raw material composition include ethylene-α-olefin elastomers such as ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene copolymer (EPM), ethylene-butene copolymer (EDM), and ethylene-octene copolymer (EOM); chloroprene rubber (CR); chlorosulfonated polyethylene rubber (CSM); hydrogenated acrylonitrile rubber (H-NBR), etc. It is preferable to use one or more of these rubber components, more preferably to use an ethylene-α-olefin elastomer, and even more preferably to use EPDM.

[0023] Examples of the crosslinking agent contained in the above raw material composition include sulfur and organic peroxides. Examples of rubber compounding agents other than the crosslinking agent include reinforcing materials such as carbon black, fillers, anti-aging agents, softeners, vulcanization accelerators, vulcanization acceleration aids, co-crosslinking agents, short fibers, etc.

[0024] The fiber member layer 15 is laminated on the inner peripheral surface of the rubber layer body 14. The fiber member layer 15 constitutes the inner peripheral surface of the belt body 10. The thickness of the fiber member layer 15 is, for example, 0.1 mm or more and 1.5 mm or less. In this V-ribbed belt B, the fiber member layer 15 covers the entire inner peripheral surface of the rubber layer body 14. The fiber member layer 15 may be laminated on the inner peripheral surface so as to cover a part of the inner peripheral surface.

[0025] The fiber member layer 15 may be composed of a woven fabric or a knitted fabric. Examples of the fabric texture of the woven fabric include plain weave, twill weave, satin weave, and their modified textures. Examples of the fabric texture of the knitted fabric include, for example, in weft knitting, plain knitting, rubber knitting, pearl knitting, and other modified textures, and in warp knitting, single denim knitting, single bandik knitting, and other modified textures. From the viewpoint of being rich in elasticity and being able to uniformly cover the rubber layer body 14, the fiber member layer 15 is preferably composed of a knitted fabric. In this V-ribbed belt B, the fiber member layer 15 may be a crosslinked rubber composition containing short fibers.

[0026] When the fiber member layer 15 is composed of a woven fabric or a knitted fabric, in this V-ribbed belt B, a fiber member layer 15 subjected to an adhesion treatment may be used, or a fiber member layer 15 not subjected to an adhesion treatment may be used. From the following viewpoints (1) and (2), in this V-ribbed belt B, when the fiber member layer 15 is composed of a woven fabric or a knitted fabric, it is preferable to use a fiber member layer 15 not subjected to an adhesion treatment. (1) In the V-ribbed belt B, since the rubber layer body 14 of the compression rubber layer 11 is made of a crosslinked rubber composition, even if the fiber member layer 15 is not subjected to an adhesion treatment, the rubber layer body 14 and the fiber member layer 15 adhere with sufficient adhesive force. (2) Also, in the V-ribbed belt B provided with a fiber member layer 15 not subjected to an adhesion treatment, the generation of abnormal noise during water immersion is suppressed as compared with the V-ribbed belt B provided with a fiber member layer 15 subjected to an adhesion treatment. This is presumably because the fiber member layer 15 not subjected to an adhesion treatment tends to have better water absorption characteristics than the fiber member layer 15 subjected to an adhesion treatment.

[0027] In the friction transmission belt B of the present invention, the fact that the fiber member layer 15 is not subjected to an adhesion treatment means that the fiber member layer 15 is not subjected to an adhesion treatment of immersing it in an adhesive, and no adhesive adheres to the surface of the fiber member layer 15. In the present invention, the "adhesion treatment by immersion in an adhesive" is a treatment of immersing in an epoxy resin solution or an isocyanate resin solution and heating, a treatment of immersing in an RFL aqueous solution and heating, and a treatment of immersing in a rubber paste and drying.

[0028] When the fiber member layer 15 is composed of a woven fabric, warp and weft yarns are used for forming the fiber member layer 15. When the fiber member layer 15 is composed of a knitted fabric, knitting yarns are used for forming the fiber member layer 15. Examples of the fibers constituting the yarns used for forming the fiber member layer 15 include natural fibers such as cellulose-based fibers, wool, and silk; synthetic fibers such as polyurethane fibers, aliphatic polyamide fibers (nylon 66 fibers), aromatic polyamide fibers (para-type, meta-type), polyester fibers, acrylic fibers, and polyvinyl alcohol fibers. The reinforcing fabric may be formed of one of these fibers or may be formed of two or more types of fibers. As the fibers constituting the fiber member layer 15, cellulose-based fibers are preferable from the viewpoint of having good water absorption performance.

[0029] In this V-ribbed belt B, since the fiber member layer 15 is suitable for ensuring good water absorption characteristics, it is preferable that the fiber member layer 15 contains cellulose-based fibers as the main fibers. As described above, from the viewpoint of being rich in stretchability and being able to uniformly cover the rubber layer main body 14, the fiber member layer 15 is preferably composed of a knitted fabric. Therefore, in this V-ribbed belt B, the fiber member layer 15 is a knitted fabric, and it is more preferable that this knitted fabric contains cellulose-based fibers as the main fibers.

[0030] When the fiber member layer 15 contains cellulose-based fibers as the main fibers, the proportion of cellulose-based fibers in the fibers constituting the fiber member layer 15 is preferably 50% by mass or more, more preferably 70% by mass or more. The proportion of this cellulose-based fiber may be 100% by mass. When the fiber member layer 15 contains cellulose-based fibers as the main fibers, from the viewpoint of ensuring excellent water absorption characteristics, it is preferable that cellulose-based fibers are exposed on the surface of the fiber member layer 15 (the inner peripheral surface of the belt main body 10).

[0031] When the fiber member layer 15 contains cellulose-based fibers as the main fibers, the fiber member layer 15 can contain other fibers in addition to the cellulose-based fibers. In this case, as the other fibers, polyurethane fibers and aliphatic polyamide fibers are preferable. From the viewpoint of ensuring stretchability, as the other fibers, polyurethane fibers are more preferable.

[0032] Examples of the cellulose-based fibers include natural plant-derived cellulose fibers such as softwood and hardwood pulp, bamboo fibers, sugarcane fibers, cotton fibers, kapok seed hair fibers, bast fibers of hemp, mulberry, and mitsumata, leaf fibers of manila hemp and New Zealand hemp; animal-derived cellulose fibers such as tunicate cellulose; bacterial cellulose fibers; algal cellulose fibers; cellulose ester fibers; regenerated cellulose fibers such as rayon, cupra, and lyocell. Among these, cotton fibers are preferable from the viewpoint of practicality as a fiber material.

[0033] The adhesive rubber layer 12 is a belt extending in the belt length direction and having a horizontally long rectangular cross section. The thickness of the adhesive rubber layer 12 is, for example, 1.0 mm or more and 2.5 mm or less. The adhesive rubber layer 12 is composed of an adhesive rubber layer main body 16 and a core wire 17 covered with the adhesive rubber layer main body 16.

[0034] The adhesive rubber layer main body 16 is made of a crosslinked rubber composition. As described above, the compression rubber layer main body 14 is also made of a crosslinked rubber composition. In this V-ribbed belt B, the compression rubber layer main body 14 and the adhesive rubber layer main body 16 may be composed of the same rubber composition or different rubber compositions.

[0035] The core wire 17 is located at the middle part in the belt thickness direction of the adhesive rubber layer 12. The core wire 17 is wound so as to form a helix having a pitch in the belt width direction and is embedded in the adhesive rubber layer main body 16.

[0036] The core wire 17 is composed of a twisted yarn such as polyamide fiber, polyester fiber, aramid fiber, or polyamide fiber. The diameter of the core wire 17 is, for example, 0.5 mm or more and 2.5 mm or less. The shortest distance between adjacent core wires 17 in the cross section of the adhesive rubber layer 12 is, for example, 0.05 mm or more and 0.20 mm or less. Preferably, the core wire 17 is subjected to one or more of the following adhesion treatments: an adhesion treatment of immersing in an epoxy resin solution or an isocyanate resin solution and heating, an adhesion treatment of immersing in an RFL aqueous solution and then heating, and an adhesion treatment of immersing in a rubber paste and then drying.

[0037] The back reinforcement cloth 13 is composed of, for example, a cloth material woven by using yarns such as cotton, polyamide fiber, polyester fiber, or aramid fiber in plain weave, twill weave, satin weave, etc., a knitted fabric, a non-woven fabric, etc. The thickness of the back reinforcement cloth 13 is, for example, 0.4 mm or more and 1.2 mm or less. The back reinforcement cloth 13 may be subjected to an adhesion treatment of immersing in an RFL aqueous solution and heating before molding and / or an adhesion treatment of coating a rubber paste on the outer peripheral surface of the adhesive rubber layer 12 and drying in order to impart adhesiveness to the adhesive rubber layer 12. The back reinforcement cloth 13 may be attached to the adhesive rubber layer 12 via a rubber layer (not shown).

[0038] In this V-ribbed belt B, instead of the back reinforcement cloth 13, a back rubber layer having a thickness of, for example, 0.4 mm or more and 0.8 mm or less may be used. In this case, it is preferable that the cloth pattern of the woven fabric is transferred to the surface of the back rubber layer from the viewpoint of suppressing the generation of noise during back driving. From the viewpoint of suppressing adhesion due to the contact between the back of the belt and the flat pulley, the back rubber layer is preferably composed of a rubber composition that is slightly harder than the adhesive rubber layer main body 16. Further, when providing the back rubber layer, the back rubber layer may be composed of the same rubber composition as one or both of the compression rubber layer main body 14 and the adhesive rubber layer main body 16, or may be composed of a rubber composition different from both the compression rubber layer main body 14 and the adhesive rubber layer main body 16. When the back rubber layer is made of a rubber composition different from that of the adhesive rubber layer main body 16, from the viewpoint of suppressing adhesion caused by contact between the back of the belt and the flat pulley, the back rubber layer is preferably made of a rubber composition slightly harder than that of the adhesive rubber layer main body 16.

[0039] As shown in FIG. 1, in this V-ribbed belt B, a plurality of V-ribs 18 hanging downward on the inner peripheral side are formed in the compression rubber layer 11 of the belt main body 10. The plurality of V-ribs 18 are ridges extending in the belt length direction and having a substantially inverted triangular cross section. The plurality of V-ribs 18 are arranged side by side in the belt width direction. Each V-rib 18 has, for example, a rib height of 2.0 mm or more and 3.0 mm or less, and a width between the proximal ends of 1.0 mm or more and 3.6 mm or less. The number of V-ribs 18 is, for example, 3 or more and 10 or less (6 in FIG. 1).

[0040] In this V-ribbed belt B, a plurality of V-rib main bodies 14a are formed on the rubber layer main body 14 of the compression rubber layer 11 so as to hang downward on the inner peripheral side. By covering each of the plurality of V-rib main bodies 14a with the fiber member layer 15, the V-ribs 18 are formed. In this V-ribbed belt B, the surface of the V-rib 18 covered with the fiber member layer 15 becomes the pulley contact surface.

[0041] The inventors of the present invention have investigated in detail the behavior of the generation of abnormal noise when the friction transmission belt B is wetted with water. As a result, in the relationship between the slip speed and the friction coefficient, it has been found that the decrease rate of the friction coefficient in the zone from when the friction coefficient shows the maximum friction coefficient until the slip speed increases by 500 mm / s is deeply involved in the generation of abnormal noise, and the present invention has been completed. Hereinafter, the relationship between the slip speed and the friction coefficient of the friction transmission belt B shown in FIG. 1 will be described. Before that, the belt running tester used to obtain this relationship and the evaluation method for obtaining this relationship will be described.

[0042] (Belt running tester) Figure 2 shows an example of the pulley layout of the belt running test machine 20 for evaluating the dynamic friction coefficient during water immersion. This belt running test machine 20 (hereinafter referred to as the test machine) is configured to evaluate the dynamic friction coefficient during water immersion of a V-ribbed belt B composed of six V-ribs 18 (belt length = 1080 mm) as the friction transmission belt B. In this test machine 20, by changing the specifications of the pulleys, it is possible to evaluate other friction transmission belts B such as V-belts and flat belts. This test machine 20 includes four pulleys 21. The four pulleys 21 are (1) The first drive pulley 22 which is a rib pulley, (2) The second drive pulley 23 which is a rib pulley and is located to the right of the first drive pulley 22, (3) The driven pulley 24 which is a rib pulley and is located above the second drive pulley 23, and (4) The idler pulley 25 which is a flat pulley and is located in the lower left of the driven pulley 24 are. The pulley diameter of each pulley 21 is 50 mm. Each pulley 21 is made of SUS. The surface roughness (arithmetic mean roughness Ra) of the contact surface of each pulley 21 with the V-ribbed belt B is 3.2 μm. In this test machine 20, the rib side of the V-ribbed belt B contacts the first drive pulley 22, the second drive pulley 23, and the driven pulley 24. The back side of the V-ribbed belt B contacts the idler pulley 25. A motor and a torque meter are connected to each of the first drive pulley 22 and the second drive pulley 23. In this test machine 20, it is possible to control the rotational speeds of the first drive pulley 22 and the second drive pulley 23 and measure the torques generated in the first drive pulley 22 and the second drive pulley 23. A weight is connected to the driven pulley 24 so that a constant tension is applied to the V-ribbed belt B. In this test machine 20, the dead weight DW is set so that a tension of 10 kgf (98 N) is generated per V-rib 18. Table 1 below shows the exact arrangement of each pulley 21. In this Table 1, the center coordinates of each pulley 21 are shown when the center of the first drive pulley 22 is taken as the origin (0, 0) of the XY coordinates in Fig. 2. For example, the center coordinates (200, 308.91) of the driven pulley 24 indicate a position 200 mm to the right and 308.91 mm upward with respect to the center of the first drive pulley 22 which is the origin.

[0043] [Table 1]

[0044] In this testing machine 20, by arranging each pulley 21 as shown in Table 1, the contact angle with the second drive pulley 23 of the friction transmission belt B (V-ribbed belt B) is set to 90 degrees.

[0045] (Evaluation Method) The relationship between the slip speed and the friction coefficient in the V-ribbed belt B as the friction transmission belt B is obtained as follows. This evaluation method is carried out at an ambient temperature of 18°C to 28°C. (1) The V-ribbed belt B shown in Fig. 1 is wound around each pulley 21. (2) A weight is connected to the driven pulley 24. Since this V-ribbed belt B has six V-ribs 18, the tension of the V-ribbed belt B is set to 588 N (60 kgf). (3) The motor is driven to rotate the first drive pulley 22 and the second drive pulley 23. (4) At the entry part of the V-ribbed belt B to the first drive pulley 22, water is dropped onto the rib side of the V-ribbed belt B at a rate of 40 ml per minute. (5) The rotational speeds of each of the first drive pulley 22 and the second drive pulley 23 are set to 1000 rpm, and the V-ribbed belt B is run at a constant speed. (6) 30 seconds after starting the constant-speed running, the rotational speed of the second drive pulley 23 is decelerated to 500 rpm in 30 seconds at a constant acceleration, and the torque of the second drive pulley 23 in this deceleration process is measured. (7) From the measured torque, the tension side tension T1 (N) represented by the tension between the first drive pulley 22 and the second drive pulley 23 and the slack side tension T2 (N) represented by the tension between the second drive pulley 23 and the driven pulley 24 are obtained, and the dynamic friction coefficient (hereinafter referred to as the friction coefficient) is calculated using Euler's formula. Thereby, the relationship between the slip speed, which is the difference between the speed of the belt body 10 and the speed of the second drive pulley 23, and the friction coefficient is obtained.

[0046] (Relationship between slip speed and friction coefficient) FIG. 3A shows the measurement results of the friction coefficient of the friction drive belt B (V-ribbed belt B) shown in FIG. 1 obtained using the belt running tester 40 shown in FIG. 2. In this FIG. 3A, the relationship between the slip speed and the friction coefficient is shown. In this FIG. 3A, the horizontal axis V is the slip speed (mm / s). The slip speed V at the start of deceleration of the second drive pulley 23 is 0 mm / s. The vertical axis μ is the friction coefficient.

[0047] As shown in FIG. 3A, in the friction drive belt B, when the second drive pulley 23 starts to decelerate and the slip speed V increases, the friction coefficient μ increases rapidly. Thereafter, the increase rate of the friction coefficient μ gradually decreases. After the friction coefficient μ shows the maximum friction coefficient, it gradually decreases as the slip speed V increases. In FIG. 3A, the symbol μx is the maximum friction coefficient, the symbol V1 is the slip speed indicating the maximum friction coefficient μx, that is, the first slip speed. The symbol V2 is the second slip speed, and the symbol μr is the friction coefficient when the slip speed V is increased from the first slip speed V1 to the second slip speed V2, that is, the reference friction coefficient. As shown in FIG. 3A, the reference friction coefficient μr is lower than the maximum friction coefficient μx.

[0048] In this friction drive belt B, in the relationship between the slip speed V and the friction coefficient μ, with the maximum friction coefficient being μx and the reference friction coefficient being μr, the decrease rate Dm of the friction coefficient μ is represented by the following formula (1). Dm = (μx - μr) / μx × 100 ·····(1) In this friction transmission belt B, when the difference (V2 - V1) between the second slip speed V2 and the first slip speed V1 is 500 mm / s, the reduction rate Dm of the friction coefficient μ represented by the formula (1) is 20% or less.

[0049] In this friction transmission belt B, the reduction of the friction coefficient μ is suppressed in the zone from when the friction coefficient μ exhibits the maximum friction coefficient μx until the slip speed V increases by 500 mm / s. In this friction transmission belt B, stick-slip due to water is less likely to occur. Therefore, the abnormal noise generated when wetted is reduced.

[0050] Figure 3B is an enlarged view of the graph shown in Figure 3A. In this Figure 3B, the relationship between the slip speed V and the friction coefficient μ in the zone from the first slip speed V1 to the second slip speed V2 (hereinafter referred to as the evaluation target zone) is shown.

[0051] As shown in Figure 3B, in this friction transmission belt B, the change in the friction coefficient μ is suppressed to be small within the evaluation target zone. Therefore, in this friction transmission belt B, stick-slip due to water is less likely to occur, and abnormal noise is less likely to occur when wetted. However, even if the reduction rate Dm of the friction coefficient μ represented by the above formula (1) is 20% or less, it cannot be denied that there is a case where there is a section in the evaluation target zone where the friction coefficient μ decreases significantly. In such a case, stick-slip due to water may occur, and there is concern that abnormal noise may occur. Therefore, when the evaluation target zone is equally divided into n (n is a natural number of 2 or more) sections, the starting slip speed of each section is defined as the start speed, the friction coefficient μ at this start speed is defined as the start friction coefficient, the ending slip speed of this section is defined as the end speed, and the friction coefficient μ at this end speed is defined as the end friction coefficient, when the start friction coefficient in the m-th (m is a natural number from 1 to n) section Sm is μsm and the end friction coefficient is μem, it is preferable that the reduction rate Dsm of the friction coefficient μ represented by the following formula (2) is 20 / n% or less in all sections. Dsm = (μsm - μem) / μsm × 100 ·····(2)

[0052] FIG. 3B shows the case where the evaluation target zone is equally divided into five sections. Hereinafter, taking this case as an example, it will be explained that the reduction rate Dsm of the friction coefficient μ represented by the above formula (2) is 20 / n% or less in all sections.

[0053] In FIG. 3B, the regions indicated by reference numerals S1 to S5 represent the respective sections formed by equally dividing the evaluation target zone into five. The first section S1 is the section with the first sliding speed V1 as the start speed, and the fifth section S5 is the section with the second sliding speed V2 as the end speed. Since the width of the evaluation target zone is 500 mm / s, when the evaluation target zone is equally divided into five, the width of each section Sm is 100 mm / s.

[0054] Reference numeral Vs1 is the start speed of the first section S1. Reference numeral μs1 is the friction coefficient at the start speed Vs1, and this friction coefficient μs1 is the start friction coefficient of the first section S1. Since the first section S1 is the section with the first sliding speed V1 as the start speed Vs1, the start friction coefficient μs1 is also the maximum friction coefficient μx. Reference numeral Ve1 is the end speed of the first section S1. Reference numeral μe1 is the friction coefficient at the end speed Ve1, and this friction coefficient μe1 is the end friction coefficient of the first section S1. Therefore, the reduction rate Ds1 of the friction coefficient μ in the first section S1 is represented by the following formula (2a). Ds1=(μs1 - μe1) / μs1×100 ·····(2a)

[0055] Reference numeral Vs2 is the start speed of the second section S2. Reference numeral μs2 is the friction coefficient at the start speed Vs2, and this friction coefficient μs2 is the start friction coefficient of the second section S2. Since the start speed Vs2 is the above-mentioned end speed Ve1, the start friction coefficient μs2 is also the above-mentioned end friction coefficient μe1. Reference numeral Ve2 is the end speed of the second section S2. Reference numeral μe2 is the friction coefficient at the end speed Ve2, and this friction coefficient μe2 is the end friction coefficient of the second section S2. Therefore, the reduction rate Ds2 of the friction coefficient μ in the second section S2 is represented by the following formula (2b). Ds2 = (μs2 - μe2) / μs2 × 100 ·····(2b)

[0056] The symbol Vs3 is the start speed of the third section S3. The symbol μs3 is the friction coefficient at the start speed Vs3, and this friction coefficient μs3 is the start friction coefficient of the third section S3. Since the start speed Vs3 is the above-mentioned end speed Ve2, the start friction coefficient μs3 is also the above-mentioned end friction coefficient μe2. The symbol Ve3 is the end speed of the third section S3. The symbol μe3 is the friction coefficient at the end speed Ve3, and this friction coefficient μe3 is the end friction coefficient of the third section S3. Therefore, the reduction rate Ds3 of the friction coefficient μ in the third section S3 is represented by the following formula (2c). Ds3 = (μs3 - μe3) / μs3 × 100 ·····(2c)

[0057] The symbol Vs4 is the start speed of the fourth section S4. The symbol μs4 is the friction coefficient at the start speed Vs4, and this friction coefficient μs4 is the start friction coefficient of the fourth section S4. Since the start speed Vs4 is the above-mentioned end speed Ve3, the start friction coefficient μs4 is also the above-mentioned end friction coefficient μe3. The symbol Ve4 is the end speed of the fourth section S4. The symbol μe4 is the friction coefficient at the end speed Ve4, and this friction coefficient μe4 is the end friction coefficient of the fourth section S4. Therefore, the reduction rate Ds4 of the friction coefficient μ in the fourth section S4 is represented by the following formula (2d). Ds4 = (μs4 - μe4) / μs4 × 100 ·····(2d)

[0058] The symbol Vs5 is the start speed of the fifth section S5. The symbol μs5 is the friction coefficient at the start speed Vs5, and this friction coefficient μs5 is the start friction coefficient of the fifth section S5. Since the start speed Vs5 is the above-mentioned end speed Ve4, the start friction coefficient μs5 is also the above-mentioned end friction coefficient μe4. The symbol Ve5 is the end speed of the fifth section S5. The symbol μe5 is the friction coefficient at the end speed Ve5, and this friction coefficient μe5 is the end friction coefficient of the fifth section S5. Since the fifth section S5 is a section with the second sliding speed V2 as the end speed Vs5, the end friction coefficient μe5 is also the reference friction coefficient μr. Therefore, the reduction rate Ds5 of the friction coefficient μ in the fifth section S5 is expressed by the following formula (2e). Ds5=(μs5 - μe5) / μs5×100 ·····(2e)

[0059] In this friction transmission belt B, preferably, the reduction rate Ds1 of the friction coefficient μ in the first section S1, the reduction rate Ds2 of the friction coefficient μ in the second section S2, the reduction rate Ds3 of the friction coefficient μ in the third section S3, the reduction rate Ds4 of the friction coefficient μ in the fourth section S4, and the reduction rate Ds5 of the friction coefficient μ in the fifth section S5 are 4% or less. In other words, preferably, in all the sections constituting the evaluation target zone, the reduction rate Dsm of the friction coefficient μ represented by the above formula (2) is 20 / 5%, that is, 4% or less. Thereby, in all the sections constituting the evaluation target zone, a significant decrease in the friction coefficient μ is prevented. The friction coefficient μ gradually decreases in the entire evaluation target zone. In this friction transmission belt B, since the variation of the friction coefficient μ is suppressed to be small, the occurrence of stick-slip due to water is effectively suppressed. Therefore, abnormal noise is less likely to occur when water is applied.

[0060] In this friction drive belt B, from the viewpoint of effectively suppressing the generation of abnormal noise when wetted, the number n of sections constituting the evaluation target zone is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. Although a larger number n is more preferable, if the number n is too large, the noise caused by the measurement accuracy of the slip speed V and the friction coefficient μ increases. From the viewpoint of being able to accurately determine the suppression effect of abnormal noise generation when wetted, this number n is preferably 15 or less, more preferably 12 or less, and even more preferably 10 or less.

[0061] In this friction drive belt B, from the viewpoint of effectively suppressing the generation of abnormal noise when wetted and improving the power transmission efficiency, the upper limit of the decrease rate Dm of the friction coefficient μ represented by the above formula (1) may be set to 15%. In this case, it is more preferable that the decrease rate Dsm of the friction coefficient μ represented by the above formula (2) is 15 / n% or less in all sections. From the viewpoint of more effectively suppressing the generation of abnormal noise when wetted and further improving the power transmission efficiency, the upper limit of the decrease rate Dm of the friction coefficient μ represented by the above formula (1) may be set to 10%. In this case, it is more preferable that the decrease rate Dsm of the friction coefficient μ represented by the above formula (2) is 10 / n% or less in all sections.

[0062] As described above, in this friction drive belt B, the compression rubber layer 11 is composed of a rubber layer main body 14 and a fiber member layer 15. This fiber member layer 15 constitutes the inner peripheral surface of the belt main body 10 that contacts the pulley 21. In this friction drive belt B, the fiber member layer 15 absorbs water. Therefore, it is difficult to form a water film between the belt main body 10 and the pulley 21. In this friction drive belt B, a significant decrease in the friction coefficient μ is prevented. In this friction drive belt B, since the variation in the friction coefficient μ is suppressed to be small, the occurrence of stick-slip due to wetting is effectively suppressed. Therefore, abnormal noise is less likely to occur when wetted. From this viewpoint, it is preferable that the belt main body 10 includes the compression rubber layer 11 that contacts the pulley 21, and this compression rubber layer 11 is composed of the rubber layer main body 14 and the fiber member layer 15 laminated on this rubber layer main body 14.

[0063] In this friction transmission belt B, the surface of the compression rubber layer 11 comes into contact with the pulley 21. When the surface of the compression rubber layer 11 is composed of the fiber member layer 15 as in the V-ribbed belt B shown in FIG. 1, voids are formed in the surface layer portion of the compression rubber layer 11 due to the presence of this fiber member layer 15. This void contributes to the absorption of water.

[0064] In this friction transmission belt B, when the portion from the surface of the compression rubber layer 11 to a depth of 200 μm in the depth direction is defined as the surface layer portion, the porosity in this surface layer portion is preferably 10% or more. Thereby, the voids formed in the surface layer portion contribute to the absorption of water. In this friction transmission belt B, it is difficult to form a water film between the belt body 10 and the pulley 21. In this friction transmission belt B, a significant decrease in the friction coefficient μ is prevented. Since the variation of the friction coefficient μ is suppressed to be small, the occurrence of stick-slip due to water is effectively suppressed. Therefore, abnormal noise is less likely to occur when exposed to water. From this viewpoint, the porosity is more preferably 20% or more. From the viewpoint of ensuring the rigidity of the surface layer portion, this porosity is preferably 70% or less.

[0065] The porosity in the surface layer portion of the compression rubber layer 11 can be calculated, for example, using a cross-sectional image of the friction transmission belt B taken by a computed tomography apparatus (the "TOSCANER-30902μhd" manufactured by Toshiba Corporation). In the calculation of the porosity, for example, a three-dimensional image of the surface layer portion can be obtained by trimming the taken cross-sectional image of the friction transmission belt B.

[0066] FIG. 4A schematically shows an image of a three-dimensional image of the surface layer portion K obtained by trimming. In FIG. 4A, the length indicated by the symbol T is the thickness of the surface layer portion K used for calculating the porosity. This thickness T corresponds to the depth from the surface of the compression rubber layer 11 and is set to 200 μm. The length indicated by the symbol W is the width of the surface layer portion K. This width W is set to 800 μm. The length indicated by the symbol L is the length of the surface layer portion K. This length L is set to 2000 μm. The volume of the surface layer portion K obtained by this trimming is represented by the product of the thickness T, the width W, and the length L.

[0067] When a three-dimensional image of the surface layer portion K is obtained, using the binarization method of the Stack Histogram, this three-dimensional image is separated into an image of an object portion made of rubber or fiber and an image of other void portions. Based on the image of the void portions thus grasped, the volume of the void portions in the surface layer portion K is calculated, and the porosity in the surface layer portion K of the compression rubber layer 11, which is represented by the ratio of the volume of the void portions to the volume of the surface layer portion K, is calculated. Note that FIG. 4B shows an image of the object portion obtained by the binarization process of the three-dimensional image. FIG. 4C shows an image of the void portions obtained by removing the image of the object portion from the three-dimensional image.

[0068] Next, the manufacturing method of the V-ribbed belt B described above will be described with reference to the drawings. FIGS. 5A and 5B are diagrams showing a crosslinking device 30 used in the manufacture of the V-ribbed belt B according to the present embodiment. FIGS. 6A, 6B, and 6C are diagrams for explaining the manufacturing method of the V-ribbed belt B according to the present embodiment.

[0069] This crosslinking device 30 includes a base 31, a columnar expansion drum 32 erected thereon, and a cylindrical mold 33 provided outside thereof.

[0070] The expansion drum 32 has a drum body 32a formed in a hollow cylindrical shape and a cylindrical rubber expansion sleeve 32b externally fitted on its outer periphery. A large number of ventilation holes 32c communicating with the inside are formed in the outer peripheral portion of the drum body 32a. Both ends of the expansion sleeve 32b are sealed by fixing rings 34 and 35 with the drum body 32a, respectively. The crosslinking device 30 is provided with a pressurizing means (not shown) for introducing and pressurizing high-pressure air into the inside of the drum body 32a. When high-pressure air is introduced into the inside of the drum body 32a by the above pressurizing means, the crosslinking device 30 is configured such that the high-pressure air enters between the drum body 32a and the expansion sleeve 32b through the ventilation holes 32c and expands the expansion sleeve 32b radially outward.

[0071] The cylindrical mold 33 is configured to be detachable from the base 31. The cylindrical mold 33 attached to the base 31 is provided concentrically with a space between it and the expansion drum 32. On the inner circumferential surface of the cylindrical mold 33, a plurality of V-rib forming grooves 33a extending in the circumferential direction are continuously provided in the axial direction (groove width direction). Each V-rib forming groove 33a is formed to be narrower toward the groove bottom side. Specifically, the cross-sectional shape is formed to be the same as that of the V-rib 18 of the V-ribbed belt B to be manufactured. The crosslinking device 30 is provided with heating means and cooling means (both not shown) for the cylindrical mold 33, and is configured such that the temperature of the cylindrical mold 33 can be controlled by these heating means and cooling means.

[0072] In the method for manufacturing the V-ribbed belt B according to the embodiment, first, each rubber compounding agent including a crosslinking agent is compounded into a rubber component, and kneaded with a kneader such as a kneader or a Banbury mixer. The obtained uncrosslinked rubber composition is formed into a sheet shape by calendering or the like to produce an uncrosslinked rubber sheet 14' for the rubber layer main body 14 of the compression rubber layer 11. Similarly, an uncrosslinked rubber sheet 16' for the rubber layer main body 16 of the adhesive rubber layer 12 is also produced. Further, a fiber member layer 15 made of a woven fabric or a knitted fabric and a back reinforcing fabric 13 made of a woven fabric or a knitted fabric are prepared, and an adhesion treatment is performed as necessary. In this manufacturing method, the fiber member layer 15 is formed in a cylindrical shape in advance. The back reinforcing fabric 13 may also be formed in a cylindrical shape in advance. Furthermore, a core wire 17 is prepared, and an adhesion treatment is performed on the core wire 17 as necessary.

[0073] Next, as shown in FIG. 6A, a rubber sleeve 37 is placed on a cylindrical drum 36 with a smooth surface, and the back reinforcing fabric 13 and the uncrosslinked rubber sheet 16' for the adhesive rubber layer main body 16 are wound and laminated thereon in sequence. The core wire 17 is wound spirally thereon from above, and then the uncrosslinked rubber sheet 16' for the adhesive rubber layer main body 16 and the uncrosslinked rubber sheet 14' for the compression rubber layer main body 14 are wound thereon in sequence. Finally, the uncrosslinked slab S' is formed by covering the uncrosslinked rubber sheet 14' with the cylindrical fiber member layer 15.

[0074] Next, remove the rubber sleeve 37 provided with the uncrosslinked slab S' from the cylindrical drum 46, and as shown in FIG. 6B, after fitting it inside the inner peripheral surface side of the cylindrical mold 33, the cylindrical mold 33 provided with the uncrosslinked slab S' is provided so as to cover the expansion drum 32 and attached to the base 31.

[0075] Subsequently, while heating the cylindrical mold 33, as shown in FIG. 6C, high-pressure air is injected through the vent hole 32c between the drum body 32a and the expansion sleeve 32b of the expansion drum 32 to expand the expansion sleeve 32b. At this time, the uncrosslinked slab S' is pressed against the cylindrical mold 33, and the uncrosslinked rubber sheets 14', 16' press and stretch the fiber member layer 15 and flow into the V-rib forming groove 33a. At the same time, the crosslinking of their rubber components proceeds and integrates, and is combined with the fiber member layer 15, the core wire 17, and the back reinforcing cloth 13. Finally, the cylindrical belt slab S is molded. The molding temperature of this belt slab S is, for example, 100°C or higher and 180°C or lower, the molding pressure is, for example, 0.5 MPa or higher and 2.0 MPa or lower, and the molding time is, for example, 10 minutes or longer and 60 minutes or shorter.

[0076] Then, after discharging the high-pressure air from between the drum body 32a and the expansion sleeve 32b of the expansion drum 32, the belt slab S molded on the inner peripheral surface of the cylindrical mold 33 is taken out, and the belt slab S is cut into a predetermined number of V-ribs 18 and turned inside out to obtain a V-ribbed belt B.

[0077] Note that by adjusting the elongation rate of the fiber member layer 15 and the molding pressure, the porosity in the surface layer portion K of the compression rubber layer 11 described above is controlled. The elongation rate of the fiber member layer 15 is adjusted by stretching the fiber member layer 15 in the height direction or the circumferential direction of the cylindrical mold 33. This elongation rate is represented by the ratio of the width of the fiber member layer 15 after stretching to the width or the circumference of the fiber member layer 15 before stretching.

[0078] So far, the embodiment of the V-ribbed belt as the friction transmission belt according to the embodiment of the present invention has been described. However, the friction transmission belt according to the embodiment of the present invention is not limited to this, and may be a V-belt, a flat belt, or the like.

Example

[0079] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples. Here, the V-ribbed belts of Examples 1 to 6 and Comparative Example 1 were produced and evaluated.

[0080] <Material for the fiber member layer> For the formation of the fiber member layer, without performing an adhesion treatment, the following three types of knitted fabrics were prepared. (Knitted fabric A) A circular knitted fabric knitted with a knitting yarn composed of cotton fiber and polyurethane fiber (Knitted fabric B) A circular knitted fabric knitted with a knitting yarn composed of cotton fiber, nylon fiber and polyurethane fiber (Knitted fabric C) A circular knitted fabric knitted with a knitting yarn composed of nylon fiber and polyurethane fiber The proportion of cellulose-based fiber (cotton fiber) in the fibers constituting the fiber member layer was 84% for knitted fabric A, 47% for knitted fabric B, and 0% for knitted fabric C.

[0081] <Material for the compression rubber layer main body and the adhesive rubber layer main body> After kneading an unvulcanized rubber composition compounded with an EPDM and a rubber compounding agent containing sulfur, it was rolled with a calender roll to produce an unvulcanized rubber sheet for the compression rubber layer main body and an unvulcanized rubber sheet for the adhesive rubber layer main body.

[0082] <Material for the core wire> As the material for the core wire, a twisted yarn of polyester fiber was prepared, immersed in an RFL aqueous solution, and then, the one subjected to an adhesion treatment of heating and drying was prepared.

[0083] <Material for the back reinforcement cloth> As the back reinforcement cloth, a woven fabric using a cotton-polyester blended yarn was immersed in an RFL aqueous solution, and then, the one subjected to an adhesion treatment of heating and drying was prepared.

[0084] [Example 1] A V-ribbed belt having the same configuration as the above-described embodiment, using a knitted fabric A as the fiber member layer, and using the above-described materials for the compression rubber layer body material, the adhesive rubber layer body material, the core wire, and the back reinforcing fabric, was produced by the manufacturing method described with reference to FIGS. 5A to 6C, and was used as the V-ribbed belt of Example 1. In this Example 1, the elongation rate of the fiber member layer was set to 180%, and the molding pressure was set to 0.7 MPa. The porosity in the surface layer portion of the compression rubber layer was 38%.

[0085] [Examples 2 to 4 and Comparative Example 1] V-ribbed belts of Examples 2 to 4 and Comparative Example 1 were produced in the same manner as in Example 1, except that the elongation rate and the molding pressure were as shown in Table 2 below. The porosity of the surface layer portion in each of Examples 2 to 4 and Comparative Example 1 was as shown in Table 2.

[0086] [Example 5] A V-ribbed belt of Example 5 was produced in the same manner as in Example 1, except that a knitted fabric B was used for the fiber member layer, and the elongation rate and the molding pressure were as shown in Table 2 below. In this Example 4, the porosity of the surface layer portion was 22%.

[0087] [Example 6] A V-ribbed belt of Example 6 was produced in the same manner as in Example 1, except that a knitted fabric C was used for the fiber member layer, and the elongation rate and the molding pressure were as shown in Table 2 below. In this Example 6, the porosity of the surface layer portion was 20%.

[0088] [Evaluation of Dynamic Friction Coefficient When Wetted with Water] Using the belt running test machine 20 shown in Fig. 2, in accordance with the above-described evaluation method, for Examples 1 to 6 and Comparative Example 1, the relationship between the slip speed and the friction coefficient was obtained, and the reduction rate Dm of the friction coefficient represented by the above formula (1) was determined. Further, the zone from the first slip speed V1 to the second slip speed V2 was equally divided into five intervals, and for each interval, the reduction rate Dsm of the friction coefficient represented by the above formula (2), that is, the reduction rates Ds1, Ds2, Ds3, Ds4, and Ds5 were determined. The results are shown in Table 2 below.

[0089] <Noise evaluation when wetted> Fig. 7 shows the pulley layout of the belt running test machine 40 for noise evaluation when wetted. In Fig. 7, reference symbol B is a V-ribbed belt.

[0090] The belt running test machine 40 for noise evaluation when wetted includes a driving pulley 41 which is a ribbed pulley with a pulley diameter of 140 mm. A first driven pulley 42 which is a ribbed pulley with a pulley diameter of 75 mm is provided to the right of the driving pulley 41. Also, a second driven pulley 43 which is a ribbed pulley with a pulley diameter of 50 mm is provided diagonally above and to the right of the driving pulley 41 and above the first driven pulley 42. Further, an idler pulley 44 which is a flat pulley with a pulley diameter of 75 mm is provided between the driving pulley 41 and the second driven pulley 43. And this belt running test machine 40 for noise evaluation when wetted is configured such that the V-rib side of the V-ribbed belt contacts the driving pulley 41, the first and second driven pulleys 42, 43 which are ribbed pulleys, and the back side contacts the idler pulley 44 which is a flat pulley and is wound around.

[0091] For each of the V-ribbed belts of Examples 1 to 6 and Comparative Example 1, it was set on the above-described belt running test machine 40 for evaluating abnormal noise during water immersion, the pulley was positioned so that a belt tension of 49 N per rib was applied, a resistance was applied to the alternator attached to the second driven pulley 43 so that a current of 60 A flowed through it, and at room temperature, the driving pulley 41 was rotated at a rotational speed of 800 rpm, and water was dropped onto the V-rib side of the V-ribbed belt at a rate of 1000 ml per minute at the entry portion of the V-ribbed belt into the driving pulley 41. Then, the occurrence situation of abnormal noise during belt running was evaluated in five grades of "S: No abnormal noise is observed at all. A: Slight abnormal noise is observed. B: Slight abnormal noise is observed. C: Obvious abnormal noise is observed. D: Intense abnormal noise is observed."

[0092]

Table 2

[0093] As shown in Table 2, according to the V-ribbed belt according to the embodiment of the present invention, a decrease in the friction coefficient is suppressed, and a reduction in abnormal noise generated during water immersion is achieved. It has also been confirmed that the larger the porosity in the surface layer portion of the compression rubber layer, the smaller the reduction rate of the friction coefficient can be suppressed.

Industrial Applicability

[0094] The V-ribbed belt of the present disclosure is useful, for example, in an accessory drive belt transmission device of an automobile.

Explanation of Signs

[0095] 10 Belt body 11 Compression rubber layer 12 Adhesive rubber layer 13 Back reinforcement cloth 14 Rubber layer body (compression rubber layer body) 14a V-rib body 15 Fiber member layer 16 Adhesive rubber layer body 17 Core wire 18 V-rib 20 and 40 Travel Test Machine 30 Bridge Erection Device Unerected Rubber Sheets of 14’ and 16’ B Friction Transmission Belt (V-ribbed Belt) K Surface Layer

Claims

1. A friction transmission belt comprising a belt body that transmits power to a pulley by frictional force generated by contact with the pulley, in the relationship between the slip speed, which is the difference between the speed of the belt body and the speed of the pulley, and the coefficient of friction, the slip speed indicating the maximum coefficient of friction is defined as the first slip speed, and the coefficient of friction when the slip speed is increased from the first slip speed to the second slip speed is defined as the reference coefficient of friction. When the difference between the second slip speed and the first slip speed is 500 mm / s, using μx as the maximum coefficient of friction and μr as the reference coefficient of friction, the reduction rate Dm of the coefficient of friction represented by the following formula (1) is 20% or less, A friction transmission belt. Dm = (μx - μr) / μx × 100 ・・・・・(1)

2. The zone from the first slip speed to the second slip speed is equally divided into n (n is a natural number of 2 or more) intervals. Taking the starting slip speed of each interval as the start speed, the coefficient of friction at the start speed as the start coefficient of friction, the ending slip speed of the interval as the end speed, and the coefficient of friction at the end speed as the end coefficient of friction, when using μsm as the start coefficient of friction and μem as the end coefficient of friction in the m-th (m is a natural number from 1 to n) interval, the reduction rate Dsm of the coefficient of friction represented by the following formula (2) is 20 / n% or less in all the intervals, The friction transmission belt according to Claim 1. Dsm = (μsm - μem) / μsm × 100 ・・・・・(2)

3. The belt body includes a compression rubber layer that contacts the pulley, the compression rubber layer is composed of a rubber layer body made of a rubber composition and a fiber member layer laminated on the rubber layer body, The friction transmission belt according to Claim 1 or 2.

4. The porosity of the surface layer portion of the compression rubber layer is 10% or more, The friction transmission belt according to Claim 3.

5. The porosity is 20% or more, The friction transmission belt according to Claim 4.

6. The fiber member layer is composed of a woven fabric, the woven fabric contains cellulose-based fibers as main fibers, The friction transmission belt according to any one of Claims 3 to 5.

7. A plurality of V ribs that hang down on the inner peripheral side are formed on the compression rubber layer, The friction transmission belt according to any one of Claims 3 to 6.

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