Stopper for two-arm auto-tensioner, two-arm auto-tensioner comprising the same and method for forming stopper for two-arm auto-tensioner

Abstract

To reduce collision sound during operation mode switching and improve durability in a two-arm type auto-tensioner.SOLUTION: In a two-arm type auto-tensioner, a stopper for an arm type auto-tensioner is fitted into a stopper accommodating recess part of at least one of a pair of arms or a tensioner body, and collides with the other of the pair of arms or the tensioner body to stop the behavior of the arms. The stopper for an arm type auto-tensioner forms a see-island structure comprising a continuous phase made of a thermoplastic resin component or a thermosetting resin component, and a dispersed phase made of a rubber component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a stopper for a two-arm autotensioner, a two-arm autotensioner including the same, and a method for molding a stopper for a two-arm autotensioner. [Background technology]

[0002] Conventionally, two-arm autotensioners have been known that have a stopper made of thermoplastic polyester elastomer attached to the tensioner arm and that suppresses the movement of the tensioner arm by colliding with a bulge in the base (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 20596 [Patent Document 2] Special Publication No. 2019-525098 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the two-arm autotensioners in Patent Documents 1 and 2 have stoppers made of thermoplastic polyester elastomer, which is designed to be durable against collisions at high temperatures, and this is too hard, resulting in a loud collision noise when switching between operating modes.

[0005] On the other hand, it is known that reducing the compressive modulus of the stopper material is effective in reducing impact noise. However, a decrease in the compressive modulus of the stopper material causes problems such as deformation due to repeated high-load compression at high temperatures and an increase in the resulting permanent set.

[0006] The present invention was made in consideration of these points, and its purpose is to reduce the impact noise that occurs when switching operation modes in a two-arm autotensioner, and to improve durability. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention uses a stopper containing a resin component and a rubber component in a dispersed state.

[0008] Specifically, the first invention is directed to a stopper for a two-arm autotensioner that is fitted into a stopper accommodating recess of at least one of a pair of arms and a tensioner body in a two-arm autotensioner, and collides with the other of the pair of arms and the tensioner body to stop the movement of the arms, The two-arm auto tensioner stopper is The polymer has an island-in-a-sea structure comprising a continuous phase made of a thermoplastic resin component or a thermosetting resin component and a dispersed phase made of a rubber component.

[0009] According to the above configuration, the rubber particles are dispersed at a distance from each other within the base material of the thermoplastic or thermosetting resin component in the two-arm autotensioner stopper. When stress is applied to the stopper, the molecular membrane surrounding the rubber component fibrillates, absorbing the impact energy. The stress also creates shear bands in the resin surrounding the rubber component, further absorbing the impact energy. This results in a greater impact noise reduction effect relative to the compressive modulus of the material compared to stoppers made solely from resin. Furthermore, sufficient sound pressure reduction can be achieved with a higher compressive modulus than stoppers made solely from resin, thereby achieving both durability and durability. The term "continuous phase" refers to a phase in which two or more distinct phases are connected, while the term "dispersed phase" refers to a phase in which two or more distinct phases are dispersed in droplets. The "island-in-a-sea structure" allows for functional separation between the rubber component, which improves impact resistance, and the resin component, which maintains durability.

[0010] In the second invention, in the first invention, The compressive modulus of elasticity is 145 MPa or less at room temperature.

[0011] That is, if the compressive elastic modulus is greater than 145 MPa at room temperature, the material is too hard and does not exhibit a sound pressure reducing effect.However, with the above-mentioned configuration, a moderate sound pressure reducing effect can be exhibited.

[0012] In a third aspect of the present invention, in the first or second aspect of the present invention, The compressive modulus of elasticity is 20 MPa or more at 120°C.

[0013] In other words, if the compressive modulus is less than 20 MPa at 120°C, the material is too soft to withstand the load during use and deforms excessively, making it impossible to use repeatedly. However, with the above-mentioned configuration, deformation and the resulting permanent set can be suppressed, thereby improving durability.

[0014] In a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, The rubber component has a glass transition temperature of −49° C. or lower.

[0015] If the glass transition temperature of the rubber component is higher than -49°C, the impact energy absorption effect is less likely to be exhibited, but with the above-mentioned configuration, an appropriate sound pressure reduction effect is exhibited.

[0016] The two-arm auto tensioner of the fifth invention is the tensioner body; the pair of arms swingably connected to the tensioner body; The stopper is provided with any one of the first to fourth aspects of the present invention.

[0017] The above configuration provides a highly marketable two-arm autotensioner equipped with a stopper that can reduce impact noise when switching between operating modes without excessively reducing the durability of conventional products.

[0018] A sixth aspect of the present invention is a method for molding the stopper for a two-arm autotensioner according to any one of the first to fourth aspects of the present invention, comprising: a kneading step of kneading a flowable thermoplastic resin material or a thermosetting resin material and a particulate rubber component in a kneader; The material kneaded in the kneader is introduced into an injection molding machine, melted, and then injected into a mold to form a stopper.

[0019] According to the above configuration, a stopper that has a sufficient sound pressure reducing effect and maintains durability can be obtained by a simple manufacturing method. [Effects of the Invention]

[0020] As described above, according to the present invention, it is possible to reduce the impact noise that occurs when switching between operating modes in a two-arm autotensioner without excessively reducing the durability of conventional systems. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a front view showing a belt layout including a two-arm autotensioner according to an embodiment of the present invention. [Figure 2] FIG. 10 is a rear view showing the second tensioner arm attached to the tensioner body. [Figure 3A] FIG. 2 is a front view showing the tensioner body. [Figure 3B] FIG. 2 is a rear view showing the tensioner body. [Figure 4A] FIG. 4 is a front view showing the second tensioner arm. [Figure 4B] FIG. 4 is a rear view showing the second tensioner arm. [Figure 5] 1A is a perspective view of a stopper, FIG. 1B is a front view of the stopper, and FIG. 1C is a plan view of the stopper. [Figure 6] 1 is a table showing the evaluation results of impact absorption and durability. [Figure 7] (a) is a diagram explaining the principle of craze generation, and (b) is a diagram explaining the formation of shear bands. [Figure 8] 1 is a graph showing the relationship between the compressive modulus of elasticity of a material at room temperature and the sound pressure reduction value. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0023] FIG. 1 shows a belt system 2 that drives accessories of a vehicle engine E, for example, in a belt layout having two or more pulleys. A crankshaft pulley 4 is provided on a crankshaft 4a of the engine E so as to rotate integrally with the crankshaft, and drives two or more accessories (not shown in detail) via a belt 3. The accessories may include a motor / generator unit (MGU), an air conditioning compressor, a water pump, a power steering pump, etc. In this embodiment, the belt system 2 has two drive sources, with the engine E serving as a first drive source and the MGU serving as a second drive source. The belt system 2 switches between a first operating mode and a second operating mode depending on the driving conditions of the first and second drive sources.

[0024] Although not shown in detail, in this embodiment, the engine E has two accessories: a first accessory which is an MGU and a second accessory which is an air conditioning compressor, but the number of accessories may be three or more. For example, as shown in Fig. 1, the belt 3 engages with a crankshaft pulley 4, a first accessory pulley 5, and a second accessory pulley 6. As the number of accessories increases, the belt 3 engages with the corresponding pulleys.

[0025] Under normal operating conditions, the belt system 2 is operable in a first operating mode in which the belt system 2 is driven by the engine E, and the belt 3 drives the first accessory pulley 5. In this first operating mode, the tension in the first belt span 3a is less than the tension in the second belt span 3b. Because the first accessory is driven by the engine E, it is operable in the first operating mode as an alternator, for example, to charge the vehicle battery.

[0026] On the other hand, when the first accessory operates as an electric motor in the second operating mode, it drives the first accessory pulley 5, which in turn drives the belt 3. In this case, conversely, the tension in the second belt span 3b becomes smaller than the tension in the first belt span 3a.

[0027] As shown in Figure 1, the belt system 2 is provided with an autotensioner 10. The autotensioner 10 includes a tensioner body 15 that is generally C-shaped in plan view, as shown in Figures 2, 3A, and 3B, for example, and this tensioner body 15 is attached to a first accessory or some other fixed member by fastening or the like. The material of the tensioner body 15 is not particularly limited, but in this embodiment it is made of metal such as an aluminum alloy.

[0028] As shown in Figures 1 and 2, the tensioner body 15 is swingably connected to a first tensioner arm 12 having a first swing shaft insertion hole 12a in the middle of its longitudinal direction, and a second tensioner arm 14 having a second swing shaft insertion hole 14a in the middle of its longitudinal direction, with each arm swing shaft 17 inserted into the swing shaft insertion hole 15a of the tensioner body 15.

[0029] The first tensioner pulley 11 is attached to the tip of the first tensioner arm 12 so as to be rotatable around a first pulley shaft 11a. The second tensioner pulley 13 is attached to the tip of the second tensioner arm 14 so as to be rotatable around a second pulley shaft 13a.

[0030] The first and second tensioner arms 12 and 14 have biasing member fixed ends 12b and 14b that protrude from their base ends, respectively, and a tensioner biasing member 16, typically a compression coil spring, is attached to both of them in a compressed state. As a result, the first and second tensioner pulleys 11 and 13 are biased in first and second biasing directions X1 and X2, respectively, as shown in Figure 1. More specifically, the tensioner biasing member 16 is capable of applying a tensioner biasing force F to the first and second tensioner arms 12 and 14 in the first biasing direction X1 and the second biasing direction X2, respectively.

[0031] The tensioner biasing member 16 may be configured not only by the linear compression coil spring shown in FIG. 1 but also by a torsion coil spring or the like.

[0032] In the embodiment shown in FIG. 1, the first tensioner pulley 11 and the second tensioner pulley 13 press the belt 3 in the first and second biasing directions X1 and X2 by the tensioner biasing member 16, and also receive a reaction force from the belt 3, thereby maintaining tension in the belt 3 to prevent it from loosening.

[0033] 2, the autotensioner 10 includes a first stopper 31 arranged to limit movement of the first tensioner arm 12 in a direction opposite the first biasing direction X1 (a first unloading direction). Similarly, the autotensioner 10 includes a second stopper 32 arranged to limit movement of the second tensioner arm 14 in a direction opposite the second biasing direction X2 (a second unloading direction).

[0034] The tensioner body 15 has protruding portions 21 that protrude in positions facing the first collision surface 33 of the first stopper 31 and the second collision surface 34 of the second stopper 32. These paired protruding portions 21 are capable of coming into contact with the first collision surface 33 of the first stopper 31 attached to the first tensioner arm 12 and the second collision surface 34 of the second stopper 32 attached to the second tensioner arm 14, respectively, when switching the operating mode, etc.

[0035] The forces acting on the autotensioner 10 are described in detail in Patent Document 2 and the like, but will not be described here.

[0036] In a first operating mode of the belt system 2, the crankshaft pulley 4 drives the belt 3, the second drive device (such as an MGU) does not drive the belt 3, and the tension in the first belt span 3a of the belt 3 is less than the tension in the second belt span 3b of the belt 3. The belt system 2 can also operate in a second operating mode in which the second drive device drives the belt 3. In some instances, during the second operating mode (e.g., during a BAS event), the crankshaft pulley 4 does not drive the belt 3. In some instances of the second operating mode (e.g., during a boost event), the crankshaft pulley 4 drives the belt 3 in conjunction with the second drive device.

[0037] The first and second collision surfaces 33, 34 are positioned such that the second collision surface 34 collides with the bulge portion 21 and the first collision surface 33 is spaced away from the bulge portion 21 during at least a portion of the time that the belt system 2 operates in the first operating mode. On the other hand, the second collision surface 34 is spaced away from the bulge portion 21 and the first collision surface 33 collides with the bulge portion 21 during at least a portion of the time that the belt system 2 operates in the second operating mode. In addition, in some embodiments, the first and second collision surfaces 33, 34 are positioned such that the second collision surface 34 abuts against the bulge portion 21 and the first collision surface 33 is spaced away from the bulge portion 21 during substantially the entire time that the belt system 2 operates in the first operating mode. Further, in some embodiments, the first and second collision surfaces 33, 34 are positioned such that the second collision surface 34 contacts the bulge portion 21 and the second collision surface 34 is spaced apart from the bulge portion 21 during a portion of the time that the belt system 2 operates in the second operating mode.

[0038] -Stopper configuration- 5(a) to 5(c) show the shape of the second stopper 32. In this embodiment, the first stopper 31 has the same shape as the second stopper 32, and therefore a description thereof will be omitted, but the two may have different sizes or shapes.

[0039] The second stopper 32 has a rectangular shape when cut horizontally in Figure 5(b), and its width gradually increases from the base end 32a toward the collision surface 34, which has an arc-shaped curved surface when viewed from the front. As shown in Figure 4B, when fitted into the stopper accommodating recess 20 of the tensioner body, the base end 32a fits snugly into the stopper accommodating recess 20, while a slight gap is maintained between the base end 32a and the collision surface 34 and the inner surface of the stopper accommodating recess 20. This also serves to ensure that the second stopper 32 can be crushed in the event of a collision.

[0040] The side surface that forms the peripheral edge of the stopper accommodating recess 20 when fitted into the stopper accommodating recess 20 is chamfered 32b. This is to allow the corners of the side surface to be inserted into the corners of the second tensioner arm 14 and other parts at the back of the stopper accommodating recess without interference. This is to prevent the corners of the side surface from interfering with the movement of movable parts such as the second tensioner arm 14.

[0041] The shape of the stoppers 31 and 32 is not limited to that of this embodiment, and may be a shape that matches the shape and size of the stopper accommodating recess 20.

[0042] A feature of this embodiment is that the stoppers 31 and 32 form an island-in-a-sea structure having a continuous phase made of a thermoplastic resin component or a thermosetting resin component and a dispersed phase made of a rubber component.

[0043] The resin component is not limited to this, but for example, a thermoplastic polyester elastomer having flexibility and excellent heat resistance is used.

[0044] The thermoplastic resin component is an injection-moldable resin, such as general-purpose plastics, engineering plastics, and elastomers such as styrene-based, olefin-based, vinyl chloride-based, ester-based, and amide-based elastomers. Resins with particularly high heat resistance include polyester and polyamide. More preferred are flexible resins such as polyester-based elastomers and olefin-based dynamically crosslinked elastomers.

[0045] The thermosetting resin component is a resin that can be injection molded, such as a phenolic, epoxy, silicone, etc. Examples of resins that have high heat resistance and flexibility include epoxy and silicone resins.

[0046] Examples of rubber components include styrene-butadiene rubber, butadiene rubber, acrylic rubber, acrylic-styrene rubber, silicone rubber, and EPDM. Butadiene rubber and acrylic rubber are preferred because of their high flexibility and impact resistance. Rubber components should preferably be compatible with the base resin. For example, those made using a multilayer polymer particle design (core-shell technology) that are easily dispersed in the base resin are suitable.

[0047] The amount of rubber component is preferably less than 50 wt%, and more preferably 1 wt% to 40 wt%. If the amount of rubber component is 50 wt% or more, the particles are difficult to disperse during the kneading process, making it difficult to obtain impact resistance. In addition, the entire material becomes too soft, resulting in poor durability.

[0048] The particle size of the rubber component is preferably 100 nm or more and 500 nm or less, and more preferably 100 nm or more and 300 nm or less.

[0049] In this embodiment, as shown in Figure 7(a), the rubber particles of the rubber component are dispersed at a distance within the resin component, and when a load is applied to stoppers 31 and 32, the stress causes the molecular chains around the rubber particles to fibrillate, which is thought to absorb the impact energy.

[0050] Furthermore, as shown in Figure 7(b), when a load is applied to the stopper, the stress causes a shear band to form in the resin around the rubber particles. This shear band is thought to absorb the impact energy.

[0051] -Stopper molding method- Next, a method for manufacturing the stoppers 31 and 32 will be described.

[0052] First, in the kneading step, a thermoplastic resin material or a thermosetting resin material having fluidity and a particulate rubber component are kneaded in a kneader.

[0053] The rubber particles are used for kneading in the form of secondary particles formed by aggregation of primary particles having an average particle size of, for example, 100 nm to 500 nm. The secondary particles preferably have an average particle size of 30 μm to 500 μm, more preferably 30 μm to 150 μm.

[0054] Examples of injection molding machines used for injection molding include those equipped with a hopper for feeding injection molding material, a heating cylinder for melting and mixing the injection molding material, a screw placed inside the heating cylinder for extruding the molten resin while mixing it, and a nozzle for injecting the molten resin into a mold.

[0055] First, the thermoplastic resin component and rubber component were dry blended (premixed) at the compounding ratio shown in Figure 6 and placed in a hopper, then heated and kneaded at a specified temperature using a twin-screw extruder to obtain a pelletized resin composition. The manufacturing conditions for twin-screw mixing were: two screws rotating in the same direction, screw rotation speed of 150 rpm, cylinder temperature of 250-255°C (approximately +20-40°C from the melting point of the base resin), strand water cooling, and a discharge rate of 10 kg / hour.

[0056] Next, in the injection molding process (injection process), the material kneaded in the kneader is fed into an injection molding machine, melted, and then injected into a mold to form a stopper in which particulate rubber components are dispersed at a distance from each other inside a substrate made of a thermoplastic resin component or a thermosetting resin component.

[0057] In Example 5, a dynamically crosslinked elastomer in which the rubber component and the resin component were already mixed was used for injection molding.

[0058] Specifically, a molten resin composition is injected into a mold (temperature: 50 to 80°C) to produce an injection-molded product in the shape of a test piece or product. In the case of a thermosetting resin, the cylinder temperature is about 50°C and the mold temperature is about 150 to 180°C.

[0059] As for the shape of the molded article, for example, a cylindrical test piece (diameter 29 mm, thickness 12.7 mm; for compression test) and a product shape (stopper shape) were actually molded.

[0060] As described above, in this embodiment, a stopper having a sufficient sound pressure reducing effect and high durability can be obtained by a simple manufacturing method.

[0061] As shown in FIG. 6, stoppers composed only of polyester-based thermoplastic elastomer (TPEE) were prepared as Comparative Examples 1 to 3. Furthermore, as Examples 1 and 2, stoppers containing TPEE as a continuous phase and 15 to 30 wt% of an acrylic rubber component having a glass transition temperature of −49°C as a dispersed phase were prepared. As Example 3, stoppers containing TPEE as a continuous phase and 30 wt% of an acrylic rubber component having a glass transition temperature of less than −90°C (measurement not possible below −90°C) as a dispersed phase were prepared. As Example 4, a stopper containing TPEE as a continuous phase and 30 wt% of a butadiene rubber component having a glass transition temperature of −82°C as a dispersed phase was prepared. As Example 5, a stopper containing polypropylene (PP) as a continuous phase and an ethylene propylene diene rubber component having a glass transition temperature of −50°C as a dispersed phase was prepared. As Example 6, a stopper containing epoxy resin as a continuous phase and 45 wt% of an acrylic rubber component having a glass transition temperature of −49°C as a dispersed phase was prepared.

[0062] Comparative Examples 1 to 3 have a homogeneous structure with no dispersed phase formed, while Examples 1 to 6 have a sea-island structure in which the resin component is formed as a continuous phase and the rubber component is formed as a dispersed phase.

[0063] -Compression modulus test- The compressive modulus was measured in accordance with JIS-K-6254 (Method A). The test specimen was set to a diameter of 29 mm and a thickness of 11.7 mm (±0.1 mm). The surface of the molded product was ground to remove sink marks and extrusion pin marks on the surface and to make it smooth.

[0064] The test temperature was room temperature, 23°C, or 120°C. When the test temperature was 120°C, the test was performed after preheating for 30 minutes in a thermostatic chamber heated to 120°C at room temperature of 23°C. The test speed was 10.0 mm / min back and forth, and the compressive modulus was calculated from the compressive force at a compressive strain of 10%.

[0065] -Glass transition temperature test- The glass transition temperature Tg was measured in accordance with JIS-K-7121. Differential scanning calorimetry (DSC) was performed. The test conditions were a nitrogen atmosphere with a flow rate of 20 mL / min, a temperature range of -100 to 255°C, a heating and cooling rate of 10°C / min, and a sample weight of 10±1 mg.

[0066] The specific test method was as follows: primary melting was held at -100°C → 255°C (10°C / min) for 10 minutes, cooling was held at 255°C → -100°C (10°C / min) for 10 minutes, and secondary melting was held at -100°C → 255°C (10°C / min) for 10 minutes.

[0067] -Sound pressure test- Noise tests were conducted by varying the types and compounding ratios of the thermoplastic resin component and the rubber component. Arnitel (registered trademark) PM581 from DSM was used as the material for Comparative Example 2 in Figure 6. Using the sound pressure of this material as a reference, the extent to which the sound pressure changed in each of Comparative Examples 1 and 3 and Examples 1 to 6 compared to Comparative Example 2 was confirmed.

[0068] The test conditions were as follows: the test piece shape was a stopper shape, and the test equipment used was a pendulum-type impact test equipment (dedicated equipment) and a precision sound level meter. The sound pressure measurement conditions were A-weighted.

[0069] The test was conducted in a soundproof room using a dedicated device. The impact speed was varied over six levels (0.5, 0.9, 1.2, 1.6, 2.0, and 2.3 m / s) by adjusting the arm length and angle of the dedicated device, and the sound pressure (dB) generated during impact at each impact speed was measured using a precision sound level meter. The sound pressure value at each impact speed minus the sound pressure value of the reference sample (Comparative Example 2) was calculated as the "sound pressure reduction value (dB)," and the average of the sound pressure reduction values ​​at the six impact speed levels was calculated as the "average sound pressure reduction value (dB)."

[0070] -Durability test- To determine durability, a stopper was used and a high-load, repeated compression test was conducted for 40 hours in a high-temperature environment. The stopper height was measured before and after the test, and the value obtained by subtracting the height after the test from the height before the test was used to evaluate the "permanent set (mm)."

[0071] As specific test conditions, the maximum load was the load when a 10% strain was applied in the height direction to the stopper of Comparative Example 2, and this was also applied to the other Comparative Examples and Examples. Furthermore, during the 40-hour repeated compression test, the test was stopped when the displacement reached the displacement limit value of -10 mm, and the result in this case was deemed NG, meaning that the permanent set amount could not be measured.

[0072] The measurement results of Comparative Examples 1 to 3 show that the lower the compressive modulus of the material, the greater the amount of permanent set after the durability test, and the more likely the material is to be unable to withstand 40 hours of repeated compression and fail. On the other hand, the lower the compressive modulus of the material, the more likely it is that the better the impact absorption properties are, and it can be seen that there is a trade-off between durability and impact absorption properties.

[0073] Example 1 was the most excellent in that it showed a sound pressure reduction effect of 3 dB or more compared to Comparative Example 2, which was used as the benchmark, and the amount of permanent set after the durability test was suppressed to about 1.5 times that of Comparative Example 2.

[0074] On the other hand, Example 2 was inferior to Example 1 in the amount of permanent set after the durability test, but was superior to Comparative Example 2 in that it exhibited a sound pressure reduction effect of 4 dB or more.

[0075] Furthermore, Examples 4 and 6 were inferior to Examples 1 and 2 in terms of impact absorption, but were as excellent as Example 1 in terms of durability.

[0076] Although Example 5 was inferior to Examples 1 and 2 in both impact absorption and durability, it was excellent in that it was able to achieve both impact absorption and durability.

[0077] These effects are thought to be due to the functional separation resulting from the sea-island structure of the resin component and the rubber component.

[0078] Furthermore, in Example 3, the glass transition temperature of the rubber component was less than -90°C (the exact temperature is unknown because temperatures below -90°C cannot be measured), and it is thought that the impact energy absorption effect was less pronounced compared to Examples 1 and 2.

[0079] As shown in Examples 1 to 6 in Fig. 6, the compressive modulus of the stopper having an island-sea structure of resin components and rubber components was suitable, being 68 to 145 MPa at room temperature and 20 to 101 MPa at 120°C. Therefore, excluding Comparative Examples 1 to 3 which were not suitable for achieving both sound pressure reduction effect and durability, it was found that the compressive modulus is preferably 145 MPa or less at room temperature and 20 MPa or more at 120°C.

[0080] In other words, as shown in Figure 6, if the compressive modulus is greater than 145 MPa at room temperature, the sound pressure reduction effect is not achieved, and if the compressive modulus is less than 20 MPa at 120°C, the material will not be able to withstand the load during use and will deform excessively, making it impossible to use repeatedly. However, if the compressive modulus is 145 MPa or less at room temperature and 20 MPa or more at 120°C, the material will be able to achieve a moderate sound pressure reduction effect while suppressing deformation and the resulting permanent set, thereby improving durability.

[0081] Furthermore, if the average particle size of the rubber component particles of stoppers 31, 32 is smaller than 100 nm or larger than 500 nm, it is difficult to achieve the impact energy absorption effect. However, in this embodiment, the average particle size of the rubber component particles of stoppers 31, 32 is 100 nm or more and 500 nm or less, so an appropriate sound pressure reduction effect is achieved. In this embodiment, in the kneading process, rubber component particles in the form of secondary particles with an average particle size of 30 to 500 μm, which are formed by agglomeration of primary particles with an average particle size of 100 nm or more and 500 nm or less, are kneaded. Since the rubber component particles are dispersed and arranged in an appropriate size within the resin component matrix, an appropriate sound pressure reduction effect is achieved.

[0082] As shown in FIG. 6, the glass transition temperature of the rubber component of the stoppers 31 and 32 is −49° C. or lower.

[0083] If the glass transition temperature of the rubber component is higher than -49°C, the effect of absorbing collision energy is not easily achieved, but in this embodiment, an appropriate effect of reducing sound pressure is achieved.

[0084] The rubber particles in this embodiment are dispersed and arranged in the resin component while maintaining a distance from one another, based on the principle explained in Fig. 7. Therefore, as shown in Fig. 8, a sufficient sound pressure reduction effect can be obtained with a higher compressive elastic modulus than when the stopper is made of a conventional thermoplastic resin alone or a thermoplastic resin containing an inorganic filler, and therefore durability can also be achieved.

[0085] As described above, in this embodiment, the stoppers 31, 32 have a sea-island structure with a continuous phase made of a thermoplastic resin component or a thermosetting resin component and a dispersed phase made of a rubber component, so that when stress is applied to the stoppers, the molecular film around the rubber component fibrillates, absorbing the impact energy, and the stress also causes shear bands in the resin around the rubber component, thereby absorbing the impact energy. This results in a greater impact noise reduction effect relative to the compressive elastic modulus of the material than when the stoppers are made of resin alone.

[0086] Therefore, according to this embodiment, it is possible to reduce the impact noise that occurs when switching between operation modes in a two-arm autotensioner without excessively reducing the durability of conventional systems.

[0087] (Other embodiments) The present invention may be configured as follows in relation to the above embodiment.

[0088] That is, in the above embodiment, stoppers 31, 32 are fitted into the pair of arms 12, 14, respectively, and collide with bulges 21 of tensioner body 15 to stop the movement of arms 12, 14, but conversely, stoppers may be fitted into the tensioner body and these stoppers may collide with the pair of arms to stop the movement of the arms. However, since the installation space for the tensioner body is often limited, fitting stoppers into the pair of arms is advantageous in terms of installation space.

[0089] It should be noted that the above-described embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses. [Explanation of symbols]

[0090] 2 Belt System 3 Belt 3a First Belt Span 3b Second Belt Span 4 crankshaft pulley 4a Crankshaft 5. First accessory pulley 6. Second auxiliary pulley 10 Auto tensioner 11 No. 1 tensioner pulley 11a First pulley shaft 12 First tensioner arm 12a First swing shaft insertion hole 12b, 14b Fixed end of biasing member 13 No. 2 tensioner pulley 13a Second pulley shaft 14 Second tensioner arm 14a Second swing shaft insertion hole 15 Tensioner body 15a Oscillating shaft insertion hole 16 Tensioner biasing member 17 Arm swing axis 20 Stopper receiving recess 21 Bulge 31 First stopper 32 Second stopper 32a Proximal end 33 First collision surface 34 Second collision surface X1,X2 2nd biasing direction

Claims

1. A stopper for a two-arm autotensioner is fitted into a stopper accommodating recess of at least one of a pair of arms and a tensioner body in a two-arm autotensioner, and collides with the other of the pair of arms and the tensioner body to stop movement of the arms, A sea-island structure is formed, which has a continuous phase made of a thermoplastic resin component or a thermosetting resin component and a dispersed phase made of a rubber component. A two-arm autotensioner stopper characterized by the above features.

2. Compressive modulus of elasticity is 145 MPa or less at room temperature 2. The two-arm autotensioner stopper according to claim 1, wherein:

3. Compressive modulus of elasticity is 20 MPa or more at 120°C 3. The two-arm autotensioner stopper according to claim 1 or 2.

4. The glass transition temperature of the rubber component is −49° C. or lower.

3. The two-arm autotensioner stopper according to claim 1 or 2.

5. the tensioner body; the pair of arms swingably connected to the tensioner body; The stopper according to claim 1 or 2 is provided. A two-arm auto tensioner characterized by the above features.

6. a kneading step of kneading a flowable thermoplastic resin material or a thermosetting resin material and a particulate rubber component in a kneader; and an injection molding step of feeding the material kneaded in the kneader into an injection molding machine, melting the material, and then injecting the material into a mold to form a stopper.

3. The method for molding a stopper for a two-arm autotensioner according to claim 1 or 2.

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