Crank sprocket and crank sprocket mounting structure

Abstract

To provide a crank sprocket capable of suppressing the transmission of vibrations.SOLUTION: A crank sprocket is attached on one end side in an axial direction of a crank shaft of an internal combustion engine, and a timing chain is wound around the crank sprocket. The crank sprocket is equipped with a sprocket base body, and a damping resin layer formed on an inner peripheral surface of the sprocket base body or a teeth surface. The damping resin layer includes heat resistant resin, and a damping filler converting vibration energy into thermal energy.SELECTED DRAWING: Figure 3B

Description

[Technical field]

[0001] The present invention relates to a crank sprocket that is attached to one axial end of a crankshaft of an internal combustion engine and around which a timing chain is wound, and to a mounting structure for the crank sprocket. [Background technology]

[0002] In a conventional internal combustion engine such as a vehicle engine, a crankshaft passes through an internal combustion engine body including a cylinder block and one axial end of the crankshaft protrudes outside the cylinder block. A cylinder head is attached to the top of the cylinder block. An intake camshaft and an exhaust camshaft are disposed in the cylinder head. The crankshaft rotates the camshafts via a camshaft drive mechanism.

[0003] The camshaft drive mechanism includes a crank sprocket attached to one axial end of the crankshaft, an intake cam sprocket attached to one axial end of the intake camshaft, and an exhaust cam sprocket attached to one axial end of the exhaust camshaft. The camshaft drive mechanism further includes a timing chain that is wound around the crank sprocket and each cam sprocket and drives and rotates each cam sprocket in response to the rotation of the crank sprocket.

[0004] As a camshaft drive mechanism, for example, Patent Document 1 describes a drive mechanism that employs a chain guide consisting of a number of rollers that contact a timing chain and opposing side plate members arranged along the running direction of the timing chain and supporting both ends of the support shaft of the multiple rollers, in which vibration-damping material is housed between the support shaft of the rollers and support recesses of the side plate members that support both ends of the support shaft. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2012-189201 Summary of the Invention [Problem to be solved by the invention]

[0006] In the camshaft drive mechanism described in Patent Document 1, the chain guide houses vibration-damping material between the support shaft of the roller that contacts the timing chain and the support recesses of the side plate members that support both ends of the support shaft. This allows the vibration of the roller that occurs when it comes into contact with the timing chain to be absorbed by the vibration-damping material. This prevents vibration from being transmitted to the side plate members of the chain guide, thereby reducing vibration and noise.

[0007] In such a conventional camshaft drive mechanism, vibrations generated by contact between the timing chain and the chain guide are transmitted to the engine body and are prevented from being emitted to the outside as noise. However, in the camshaft drive mechanism, there is a need to further reduce vibrations caused by contact between the timing chain and other components and the noise generated by them. Furthermore, with the electrification of vehicles such as automobiles, the required level of NV (noise and vibration) performance is higher than ever before.

[0008] The present invention has been made in consideration of the above-mentioned points, and has as its object to provide a crank sprocket and a mounting structure for a crank sprocket that can suppress the transmission of vibrations. [Means for solving the problem]

[0009] In order to solve the above problems, the crank sprocket of the present invention is a crank sprocket that is attached to one axial end side of the crankshaft of an internal combustion engine and has a timing chain wound around it, the crank sprocket comprising a sprocket base and a vibration-damping resin layer formed on the inner surface or tooth surface of the sprocket base, the vibration-damping resin layer containing a heat-resistant resin and a vibration-damping filler that converts vibrational energy into thermal energy.

[0010] According to the crank sprocket of the present invention, the transmission of vibrations can be suppressed.

[0011] In the crank sprocket, the vibration-damping resin layer may be formed on the inner peripheral surface of the sprocket base.

[0012] In the crank sprocket, the vibration-damping resin layer may have a thickness of 10 μm or more.

[0013] The mounting structure for a crank sprocket of the present invention is a mounting structure for a crank sprocket in which a crank sprocket around which a timing chain is wound is mounted to one axial end side of a crankshaft of an internal combustion engine, characterized in that a vibration-damping resin layer is disposed between the inner surface of a sprocket base of the crank sprocket and the outer surface of a shaft base of the crankshaft, or on the tooth surface of the sprocket base, and the vibration-damping resin layer contains a heat-resistant resin and a vibration-damping filler that converts vibrational energy into thermal energy.

[0014] According to the mounting structure of the present invention, the transmission of vibrations can be suppressed.

[0015] In the above mounting structure, the vibration-damping resin layer may be disposed between an inner peripheral surface of the sprocket base and an outer peripheral surface of the shaft base.

[0016] In the above mounting structure, the vibration-damping resin layer may be formed on the inner peripheral surface of the sprocket base and provided on the crank sprocket.

[0017] In the mounting structure, the vibration-damping resin layer may have a thickness of 10 μm or more. Effect of the Invention

[0018] According to the present invention, the transmission of vibrations can be suppressed. [Brief description of the drawings]

[0019] [Figure 1] 1 is an exploded perspective view showing a schematic diagram of an engine to which a mounting structure for a crank sprocket according to a first embodiment is applied; [Diagram 2] 1 is a schematic cross-sectional view of an engine showing a crank sprocket mounting structure and its surroundings according to a first embodiment. FIG. [Figure 3A] FIG. 3 is an enlarged view of a portion X shown in FIG. [Figure 3B] FIG. 3B is a cross-sectional view taken along line AA in FIG. 3A. [Figure 4] FIG. 1 is a cross-sectional view showing a typical example of a ball drop test machine. [Diagram 5] 1 is a graph showing the sound pressure level of sound generated when a steel ball impacted against the thickness of the vibration-damping resin layer in the test pieces of Examples 1 to 11 and Comparative Example 1. [Figure 6] 13 is a graph showing overall values ​​of sound pressure levels of vibrations transmitted to timing chain covers in mounted crank sprockets obtained in Example 8 and Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a crank sprocket and a mounting structure for a crank sprocket of the present invention will be described.

[0021] First, the crank sprocket and the mounting structure thereof according to the embodiment will be described with reference to the crank sprocket and the mounting structure thereof according to the first embodiment. FIG. 1 is an exploded perspective view showing an engine to which the mounting structure of the crank sprocket according to the first embodiment is applied. FIG. 2 is a schematic cross-sectional view of the engine showing the mounting structure of the crank sprocket according to the first embodiment and its surroundings. FIG. 3A is an enlarged view of the X portion shown in FIG. 2, and FIG. 3B is a cross-sectional view taken along the line AA in FIG. 3A.

[0022] In engine E (internal combustion engine) shown in FIG. 1, a cylinder head 11 (engine body) is attached to the upper part of a cylinder block 1 (engine body), and an oil pan 13 is attached to the lower part of the cylinder block 1 via a crankcase 12 (engine body).

[0023] The cylinder block 1 and the cylinder head 11 are made of metals such as iron (cast iron), aluminum, magnesium, etc., or alloys containing these metals. The cylinder block 1 and the cylinder head 11 are fastened together by a number of bolts via a gasket (not shown) (metal gasket or liquid gasket (FIPG: Formed In Place Gasket)).

[0024] An intake camshaft 14 and an exhaust camshaft 15 are disposed in the cylinder head 11. In addition, as shown in Fig. 2, a crankshaft 16 is disposed in the crankcase 12. The camshafts 14, 15 are rotationally driven by the crankshaft 16. A camshaft drive mechanism for rotationally driving the camshafts 14, 15 will be described below.

[0025] 1 and 2, the camshaft drive mechanism includes a crank sprocket 21 attached to one axial end of the crankshaft 16 so as to rotate integrally therewith, an intake cam sprocket 22 attached to one axial end of the intake camshaft 14 of the cylinder head 11 so as to rotate integrally therewith, and an exhaust cam sprocket 23 attached to one axial end of the exhaust camshaft 15 of the cylinder head 11 so as to rotate integrally therewith. The camshaft drive mechanism further includes a timing chain 24 that is wound around the crank sprocket 21 and each of the cam sprockets 22, 23 and drives and rotates each of the cam sprockets 22, 23 in response to the driving rotation of the crank sprocket 21.

[0026] As shown in FIGS. 3A and 3B, the crank sprocket 21 is made up of a sprocket base 21a and an inner peripheral surface 21ac of an annular portion 21ar of the sprocket base 21a (the inner peripheral surface 21ac of the annular portion 21ar of the sprocket base 21a). The sprocket base 21a has a vibration-damping resin layer 21b formed on its inner peripheral surface (the inner peripheral surface). This places the vibration-damping resin layer 21b between the inner peripheral surface 21ac of the annular portion 21ar of the sprocket base 21a and the outer peripheral surface 16ac of the shaft base 16a. The vibration-damping resin layer 21b contains a heat-resistant resin and a vibration-damping filler that converts vibration energy into thermal energy.

[0027] 1 and 2, an oil pump drive mechanism that rotates and drives an oil pump 32 by the crankshaft 16 is provided below the camshaft drive mechanism. The oil pump drive mechanism includes an oil pump sprocket 31 that is rotatably attached to the crankshaft 16 closer to the crankcase 12 than the crank sprocket 21, and an oil pump sprocket 32a that is rotatably attached to one end side of the oil pump 32. The oil pump drive mechanism further includes an oil pump drive chain 33 that is wound around the oil pump sprocket 31 and the oil pump sprocket 32a and drives and rotates the oil pump sprocket 32a by the driving rotation of the oil pump sprocket 31.

[0028] The camshaft drive mechanism and the oil pump drive mechanism are covered from the outside by an aluminum alloy timing chain cover 4 that is attached to the surfaces of the cylinder head 11, the cylinder block 1, and one end of the crankcase 12, and are housed in the internal space of the timing chain cover 4. In addition, in Fig. 1, reference numeral 25 denotes a chain tensioner device that adjusts the tension of the timing chain 24, and reference numeral 26 denotes a chain vibration damper that guides the tensioned portion of the timing chain 24 located between the exhaust cam sprocket 23 and the crank sprocket 21.

[0029] Engine oil is circulated in the space formed inside the timing chain cover 4 to lubricate the timing chain 24. For this purpose, a liquid gasket (not shown) is provided as a seal member on the end face of the timing chain cover 4, which is the joint face between the cylinder head 11 and the cylinder block 1. The liquid gasket prevents oil leakage from the outer edge of the timing chain cover 4. As shown in FIG. 2 and FIG. 3A, one axial end of the crankshaft 16 is inserted into the opening 42b of the timing chain cover 4 and protrudes outward from the timing chain cover 4. A crank pulley 41 for driving various auxiliary devices (such as an alternator and an air conditioner compressor) by belt transmission is attached to one axial end of the crankshaft 16 so as to rotate integrally with the crankshaft 16. An oil seal 60 for preventing oil leakage is provided in the gap of the opening 42b of the timing chain cover 4 through which the crankshaft 16 is inserted.

[0030] In the engine E, an engine mount bracket 5 for suspending the engine itself on the chassis is provided on the timing chain cover 4. The engine mount bracket 5 is made of highly rigid iron (cast iron). The engine mount bracket 5 is fastened to the timing chain cover 4 by a plurality of fastening bolts 51, 51, ... and is also fastened to the cylinder head 11. Furthermore, a water pump 45 is provided. The water pump 45 is driven by the rotational force of the crankshaft 16 to circulate the coolant.

[0031] In the engine E configured as above, in the mounting structure of the crank sprocket 21 according to the first embodiment, a vibration-damping resin layer 21b is disposed between the inner peripheral surface 21ac of the annular portion 21ar of the sprocket base 21a of the crank sprocket 21 and the outer peripheral surface 16ac of the shaft base 16a of the crankshaft 16, and the vibration-damping resin layer 21b contains a heat-resistant resin and a vibration-damping filler that converts vibration energy into thermal energy. Therefore, the vibration transmission between the sprocket base 21a and the shaft base 16a can be suppressed by the vibration-damping resin layer 31a. Specifically, for example, the transmission of vibrations such as vibrations generated by the meshing of the teeth 21at of the sprocket base 21a and the timing chain 24 can be suppressed. Therefore, the vibrations transmitted to the crankshaft 16 and then transmitted to the timing chain cover 4 via the oil seal 60 can be suppressed from being emitted to the outside as noise.

[0032] Furthermore, in the crank sprocket 21 according to the first embodiment, unlike the structure of the chain guide described in Patent Document 1, vibrations and noise can be suppressed simply by forming a new vibration-damping resin layer 21b without making significant changes to the existing structure of the part.

[0033] Therefore, the crank sprocket and the mounting structure for the crank sprocket according to the embodiment can suppress the transmission of vibrations and the noise generated by the vibrations. Furthermore, the vibrations and noise can be suppressed without significantly changing the existing structure of the parts.

[0034] Next, the crank sprocket and the mounting structure for the crank sprocket according to the embodiment will be described in detail.

[0035] 1. Crank sprocket The crank sprocket is attached to one axial end of the crankshaft of an internal combustion engine and has a timing chain wound around it. It comprises a sprocket base and a vibration-damping resin layer formed on the inner surface or tooth surface of the sprocket base.

[0036] (1) Sprocket base The sprocket base has an inner peripheral surface or tooth surface, and typically includes an annular portion and teeth arranged on the outer peripheral surface of the annular portion, like the sprocket base of the first embodiment.

[0037] The annular portion has an insertion hole formed therein for insertion onto the crankshaft, and has an inner peripheral surface (the inner peripheral surface of the sprocket base). The material of the annular portion may be, for example, steel or the like. A plurality of teeth are usually arranged on the outer peripheral surface of the annular portion at an equal pitch, and have a tooth surface (the tooth surface of the sprocket base). The pitch of the teeth is not particularly limited as long as they can mesh with the timing chain. The material of the teeth may be, for example, steel or the like.

[0038] (2) Vibration-damping resin layer The vibration-damping resin layer is formed on the inner peripheral surface or tooth surfaces of the sprocket base body, and contains a heat-resistant resin and a vibration-damping filler that converts vibration energy into thermal energy.

[0039] The vibration-damping resin layer is preferably provided on the inner peripheral surface of the sprocket base, because there is no risk of peeling off since strong surface pressure is not applied when the teeth of the sprocket base mesh with the timing chain, as would be the case if the vibration-damping resin layer were provided on the tooth surfaces of the sprocket base.

[0040] The thickness of the vibration-damping resin layer is not particularly limited, but is preferably, for example, 10 μm or more, more preferably 20 μm or more, and particularly preferably 50 μm or more. This is because a sufficient vibration transmission blocking effect can be obtained. The thickness of the vibration-damping resin layer is preferably, for example, 400 μm or less, more preferably 200 μm or less, and particularly preferably 100 μm or less. This is because the improvement in the vibration blocking effect becomes saturated, and the layer can be easily formed by coating.

[0041] The heat-resistant resin is not particularly limited as long as it has a heat distortion temperature of 100°C or more, but is preferably one having a heat distortion temperature of 150°C or more. Examples of heat-resistant resins include, but are not limited to, polyamideimide resins, polyimide resins, phenolic resins, epoxy resins, polyethersulfone resins, polyphenylsulfide resins, etc. From the viewpoint of workability when forming a coating and heat resistance against heat generation due to friction, polyamideimide resins are more preferable. These heat-resistant resins may be used alone or in combination of two or more.

[0042] The vibration-damping filler converts vibration energy into thermal energy. The vibration-damping filler is not particularly limited, but can be roughly divided into a material that is easily deformed at a low elastic modulus and a material that is easily dissipated inside. More specifically, a material that is easily deformed at a low elastic modulus is a material that is solid but has both remarkably elastic properties and viscous properties. All materials have both elastic properties and viscous properties, but a material that is easily deformed at a low elastic modulus has both of these properties remarkably. For this reason, by including a material that is easily deformed at a low elastic modulus in the vibration-damping resin layer, the rubber elasticity of the vibration-damping resin layer itself in the normal temperature range can be increased. As a result, it is considered that the vibration input from the outside can be effectively absorbed by the vibration-damping resin layer and converted into thermal energy, thereby effectively blocking the transmission of vibration. On the other hand, a material that is easily dissipated inside has the effect of attenuating vibration by diffusely reflecting the vibration at the air layer present in the material and converting it into thermal energy. For this reason, it is believed that if a material that easily dissipates energy inside is contained in the vibration-damping resin layer, the vibration-damping resin layer can effectively block the transmission of vibration.

[0043] Examples of materials that are easily deformed with a low modulus of elasticity include thermoplastic elastomers, urethane-based compounds, polyethylene-based compounds, ester copolymers, and rubber-based materials. Thermoplastic elastomers generally have the properties of rubber at room temperature, and have the same performance as thermoplastic plastics at high temperatures. Examples of thermoplastic elastomers include styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, urethane-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers. Examples of these are listed in, for example, JP 2016-113614 A and JP 2017-197733 A. Examples of urethane-based compounds include urethane resins. Examples of these are listed in, for example, JP 8-183945 A. Examples of polyethylene-based compounds include ethylene homopolymers and copolymers of ethylene and α-olefin monomers. Examples of these are given in, for example, JP 2009-532570 A and the like. Examples of ester copolymers include acrylic acid ester copolymers and the like. Examples of these are given in, for example, JP 3209499 A and the like. Examples of rubber-based materials include butyl rubber, fluororubber and the like. Examples of these are given in, for example, JP 2009-236172 A and the like.

[0044] Examples of materials in which energy dissipation is likely to occur include microcapsule-based materials and low-density materials. Examples of microcapsule-based materials include thermally expandable microcapsules that contain a vaporized substance that expands when a certain temperature range is reached inside a shell made of a thermoplastic polymer. These examples are listed in JP 2013-18855 A and the like. Examples of low-density materials include, for example, materials that contain an air layer inside the material in general, and specifically, for example, foamed materials, porous bodies, nonwoven fabrics, layered compounds, and the like. These examples are listed in, for example, JP 3-221173 A and JP 4203589 A and the like. The vibration-damping fillers listed above may be used alone or in combination of two or more types.

[0045] The vibration-damping resin layer may contain optional components such as solid lubricants and hard particles in addition to the heat-resistant resin and the vibration-damping filler. This is because the vibration-damping resin layer can be provided with properties such as wear resistance, seizure resistance, and low friction characteristics. The solid lubricants are not particularly limited, and examples thereof include polytetrafluoroethylene (PTFE), molybdenum disulfide (MoS2), graphite, and the like. These solid lubricants may be used alone or in combination of two or more. The hard particles are not particularly limited, and examples thereof include alumina (Al2O3), silica, and the like. These hard particles may be used alone or in combination of two or more.

[0046] The volume ratio of the vibration-damping filler to the total volume of the heat-resistant resin and the vibration-damping filler in the vibration-damping resin layer is not particularly limited, but is preferably, for example, 20% by volume or more and 80% by volume or less, and more preferably, 40% by volume or more and 60% by volume or less. By being above the lower limit of these ranges, vibration energy can be converted into heat energy more efficiently by the filler. Also, by being below the upper limit of these ranges, durability as a resin coating (e.g., abrasion resistance, adhesion, etc.) can be ensured. The volume ratio of any component other than the heat-resistant resin and the vibration-damping filler in the vibration-damping resin layer is not particularly limited, and can be selected according to the type.

[0047] The vibration-damping resin layer is not particularly limited as long as it can suppress the transmission of vibrations of a desired frequency, but it is preferable that it suppresses the transmission of vibrations of a frequency of, for example, 2 kHz. This is because noise can be particularly effectively suppressed. In order to adjust the vibration-damping resin layer to suppress the transmission of vibrations of a desired frequency, for example, the type and content of each component, such as the vibration-damping filler and heat-resistant resin, in the vibration-damping resin layer, and the thickness of the vibration-damping resin layer may be adjusted.

[0048] The method for forming the vibration-damping resin layer is not particularly limited, but examples thereof include the following methods. First, a solution is prepared by dissolving a predetermined amount of heat-resistant resin in an organic solvent. Next, a predetermined amount of vibration-damping filler is added to the solution, and any other components are added as necessary, and the mixture is kneaded to prepare a coating material. Next, the coating material is applied to the inner peripheral surface or tooth surface of the sprocket base. Next, the coating material applied to the sprocket base is heated, dried, and cured. This forms a vibration-damping resin layer.

[0049] The organic solvent used in the above method is not particularly limited and is selected according to the type of heat-resistant resin. For example, when a polyamide-imide resin is used as the heat-resistant resin, examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), 1,3-dimethyl-2-imidazolidinone (DMI), γ-butyrolactone (GBL), etc. When an epoxy resin is used, examples of the organic solvent include methyl ethyl ketone (MEK), toluene, etc.

[0050] The kneading method for preparing the coating material may be, for example, a method in which kneading is performed for 1 hour using a kneader. The method for applying the coating material to the sprocket base body is not particularly limited and may be any common coating method, such as spray coating, screen printing, dipping, etc. The heating conditions for drying and curing the coating material are not particularly limited and may be, for example, heating at a temperature of 100°C or higher and 370°C or lower for 30 minutes to 3 hours.

[0051] 2. Crank sprocket mounting structure The crank sprocket mounting structure is a structure in which a crank sprocket around which a timing chain is wound is mounted to one axial end of a crankshaft of an internal combustion engine. In the crank sprocket mounting structure, a vibration-damping resin layer is disposed between the inner peripheral surface of a sprocket base of the crank sprocket and the outer peripheral surface of a shaft base of the crankshaft, or on the tooth surface of the sprocket base. The vibration-damping resin layer includes a heat-resistant resin and a vibration-damping filler that converts vibration energy into thermal energy.

[0052] A preferred mounting structure for the crank sprocket is one in which the vibration-damping resin layer is disposed between the inner peripheral surface of the sprocket base and the outer peripheral surface of the shaft base, because there is no risk of peeling off since strong surface pressure is not applied when the teeth of the sprocket base and the timing chain mesh, as is the case when the vibration-damping resin layer is formed on the tooth surfaces of the sprocket base.

[0053] The vibration-damping resin layer in the mounting structure is preferably provided on the crank sprocket. Specifically, the vibration-damping resin layer is preferably formed on the inner peripheral surface or tooth surface of the sprocket base and provided on the crank sprocket. This is because, compared with a case in which the vibration-damping resin layer is formed on the outer peripheral surface of the shaft base and provided on the crankshaft, it is easier to handle the components during the vibration-damping resin layer formation process, etc. The vibration-damping resin layer in the mounting structure is preferably formed on the inner peripheral surface of the sprocket base and provided on the crank sprocket.

[0054] The thickness of the vibration-damping resin layer in the mounting structure and the heat-resistant resin and vibration-damping filler contained in the vibration-damping resin layer are the same as those described in the section "1. Crank sprocket (2) Vibration-damping resin layer," so explanation of them will be omitted here. EXAMPLES

[0055] EXAMPLES Hereinafter, the crank sprocket and the mounting structure for the crank sprocket according to the embodiment will be described more specifically with reference to examples and comparative examples.

[0056] [Example 1] First, a coating material to be used for forming the vibration-damping resin layer of the crank sprocket was prepared. Specifically, polyamide-imide resin was prepared as a heat-resistant resin, and a solution was prepared by dissolving a predetermined amount in N-ethyl-2-pyrrolidone (NEP) (organic solvent). Next, a thermoplastic elastomer was prepared as a vibration-damping filler, and a predetermined amount was added to the solution, followed by kneading for 1 hour using a kneader. In this way, a coating material was prepared so that the volume ratio of the vibration-damping filler to the total volume of the heat-resistant resin and the vibration-damping filler in the vibration-damping resin layer was 50 volume %.

[0057] Next, a test piece was prepared in which a vibration-damping resin layer was formed on the surface of a block-shaped substrate. Specifically, a block-shaped substrate made of SUS440C was first prepared, and a predetermined amount of coating material was applied to the surface of the substrate by spray coating. Next, the coating material applied to the substrate was heated at 180°C for 90 minutes to volatilize the organic solvent and dry and harden the coating material. As a result, a vibration-damping resin layer with a thickness of 1 μm was formed on the surface of the substrate, and a test piece was prepared.

[0058] [Example 2] A test piece was prepared in the same manner as in Example 1, except that the vibration-damping resin layer was formed to a thickness of 5 μm.

[0059] [Example 3] A test piece was prepared in the same manner as in Example 1, except that the vibration-damping resin layer was formed to a thickness of 10 μm.

[0060] [Example 4] A test piece was prepared in the same manner as in Example 1, except that the vibration-damping resin layer was formed to a thickness of 20 μm.

[0061] [Example 5] A test piece was prepared in the same manner as in Example 1, except that the vibration-damping resin layer was formed to a thickness of 50 μm.

[0062] [Example 6] A test piece was prepared in the same manner as in Example 1, except that the vibration-damping resin layer was formed to a thickness of 100 μm.

[0063] [Example 7] A test piece was prepared in the same manner as in Example 1, except that the vibration-damping resin layer was formed to a thickness of 200 μm.

[0064] [Example 8] First, a coating material was prepared in the same manner as in Example 1, except that a urethane resin was prepared as a vibration-damping filler and added in a predetermined amount to the solution.

[0065] Next, a test piece was prepared in the same manner as in Example 1, except that a vibration-damping resin layer was formed to a thickness of 100 μm using the coating material prepared in this example.

[0066] Next, a crank sprocket having a vibration-damping resin layer formed on the inner peripheral surface of the sprocket base was produced, and then mounted on an engine to produce a mounted crank sprocket.

[0067] Specifically, a sprocket base made of SUS440C was first prepared. Next, a predetermined amount of the coating material prepared in this example was applied to the inner peripheral surface of the sprocket base by spray coating. Next, the coating material applied to the sprocket base was heated at 180°C for 90 minutes to volatilize the organic solvent and dry and harden the coating material. In this way, a vibration-damping resin layer with a thickness of 100 μm was formed on the inner peripheral surface of the sprocket base, thereby producing a crank sprocket.

[0068] Next, a cylinder block, a cylinder head, a crankshaft, a camshaft, a cam sprocket, a timing chain, a timing chain cover, etc. were prepared. Next, a crank sprocket was attached to one end of the crankshaft in the axial direction so as to rotate integrally with the crankshaft. At this time, a vibration-damping resin layer was disposed between the inner peripheral surface of the sprocket base of the crank sprocket and the outer peripheral surface of the shaft base of the crankshaft. Next, the cylinder block, the cylinder head, the crankshaft, the camshaft, and the cam sprocket were assembled, and the crankshaft to which the crank sprocket was attached was attached to them. Next, a timing chain was wound around the crank sprocket and the cam sprocket, and a timing chain cover, etc. were attached to the cylinder block, etc. In this way, an engine was produced and an installed crank sprocket was produced.

[0069] [Example 9] First, a test piece was prepared in the same manner as in Example 8, except that a vibration-damping resin layer was formed to a thickness of 200 μm.

[0070] [Example 10] First, a coating material was prepared in the same manner as in Example 1, except that microcapsules were prepared as a vibration-damping filler and added in a predetermined amount to the solution.

[0071] Next, a test piece was prepared in the same manner as in Example 1, except that a vibration-damping resin layer was formed to a thickness of 100 μm using the coating material prepared in this example.

[0072] [Example 11] First, a test piece was prepared in the same manner as in Example 10, except that a vibration-damping resin layer was formed to a thickness of 200 μm.

[0073] [Comparative Example 1] First, a block-shaped substrate similar to that in Example 1 was prepared, and used as a test piece as is without forming a vibration-damping resin layer.

[0074] Next, a sprocket base similar to that of Example 8 was prepared, and an engine was manufactured and an installed crank sprocket was manufactured in the same manner as in Example 1, except that the vibration-damping resin layer was not formed and the crank sprocket was used as it was.

[0075] [Evaluation of the effect of the thickness of the vibration-damping resin layer on NV performance in a ball drop test] A ball drop test was carried out on the test pieces obtained in Examples 1 to 11 and Comparative Example 1 to evaluate the influence of the thickness of the vibration-damping resin layer on the NV performance. Fig. 4 is a cross-sectional view that shows a schematic diagram of a ball drop tester.

[0076] In the ball drop test, as shown in FIG. 4, the test piece was placed on a steel plate on an acceleration pickup installed on the top of the base of the ball drop tester. When the test pieces of Examples 1 to 11 were placed, the vibration-damping resin layer was made to abut against the steel plate. This is because the purpose of the ball drop test is to measure the degree to which noise is suppressed when an impact is applied to the vibration-damping resin layer arranged in the gap between parts. In the ball drop tester, a φ6.3 mm SUJ2 steel ball is held by an electromagnet directly above the test piece. In the ball drop test, the height of the steel ball before it is dropped (the distance from the top surface of the test piece) is set to 500 mm, and the magnetic force of the ball drop tester is turned off to drop the steel ball and cause it to collide with the test piece. Then, the sound generated at the time of the collision was collected by a microphone installed directly above the test piece, and the overall sound pressure level was measured in the frequency band of 20 Hz to 10 kHz. The measurement results are shown in Table 1 below. FIG. 5 is a graph showing the sound pressure level of the sound generated when a steel ball impacted against the thickness of the vibration-damping resin layer in the test pieces of Examples 1 to 11 and Comparative Example 1.

[0077] As shown in Table 1 and FIG. 5 below, the sound pressure level decreases with an increase in the thickness of the vibration-damping resin layer, so it is considered that the NV performance improves with an increase in the thickness of the vibration-damping resin layer. When comparing the test piece made of only the substrate of Comparative Example 1 with the test pieces of Examples 1 to 7 having the same composition of the vibration-damping resin layer, the test piece with the vibration-damping resin layer thinner than 10 μm has a sound pressure level reduction effect compared to the test piece made of only the substrate, but the reduction effect is not significant. On the other hand, the test piece with the vibration-damping resin layer thicker than 10 μm has a sound pressure level reduction effect of 5 dB or more compared to the test piece made of only the substrate. Therefore, it is considered that the thickness of the vibration-damping resin layer is preferably 10 μm or more, more preferably 20 μm or more, and particularly preferably 50 μm or more. Furthermore, as shown in Table 1 and FIG. 5 below, even if the type of vibration-damping filler in the vibration-damping resin layer is changed, the same tendency is observed.

[0078] [Evaluation of NV performance of implemented crank sprocket] The assembled crank sprockets obtained in Example 8 and Comparative Example 1 were evaluated for NV performance. Specifically, a microphone for measuring sound pressure was placed 30 cm in front of the timing chain cover of the engine on which the mounted crank sprocket was mounted. The engine was then driven by manually rotating the engine actuator at a rotation speed of 1000 to 5000 rpm. The microphone was then used to measure the overall value of the sound pressure level in the frequency band of 20 Hz to 20 kHz emitted from the timing chain cover. The measurement results are shown in Table 1 below. FIG. 6 is a graph showing the overall value of the sound pressure level of vibration transmitted to the timing chain cover with the mounted crank sprocket obtained in Example 8 and Comparative Example 1. In Table 1 and FIG. 6 below, the overall value of the sound pressure level in the comparative example is set as a reference value, and the overall value of the sound pressure level in the examples is shown as a relative value to the reference value.

[0079] As shown in Table 1 below and Figure 6, the mounted crank sprocket obtained in Example 8 exhibits a significant reduction in sound pressure level compared to the mounted crank sprocket obtained in Comparative Example 1. When a vibration-damping resin layer is formed on the inner peripheral surface of the sprocket base, it is believed that vibrations, such as those generated when the teeth of the sprocket base and the timing chain mesh, can be prevented from being transmitted from the sprocket base to the shaft base.

[0080] [Table 1]

[0081] The above describes in detail the embodiments of the crank sprocket and mounting structure for the crank sprocket of the present invention. However, the present invention is not limited to the above embodiments, and various design modifications can be made without departing from the spirit of the present invention as set forth in the claims. [Explanation of symbols]

[0082] E Engine (internal combustion engine) 1 Cylinder block (engine body) 4 Timing chain cover 11 Cylinder head (engine body) 12 Crankcase (engine body) 13 Oil pan 14 Intake camshaft 15 Exhaust camshaft 16 Crankshaft 16a Shaft base 16ac outer surface 21 Crank sprocket 21a Sprocket base 21ac inner surface 21b Vibration-damping resin layer 22 Intake cam sprocket 23 Exhaust cam sprocket 24 Timing chain 25 Chain tensioner device 26 Chain vibration damper 31 Oil pump sprocket 32 Oil pump 32a oil pump sprocket 33 Oil pump drive chain 41 Crank pulley 42b opening 60 Oil seal

Claims

1. A crank sprocket attached to one end of a crankshaft of an internal combustion engine in an axial direction and around which a timing chain is wound, The crank sprocket comprises a sprocket base and a vibration-damping resin layer, the sprocket base includes an annular portion having an inner peripheral surface and an outer peripheral surface, and teeth disposed on the outer peripheral surface of the annular portion, an insertion hole into which the crankshaft is inserted is formed on the inner circumferential surface of the annular portion; the vibration-damping resin layer is formed on a portion of the inner circumferential surface of the annular portion excluding the insertion hole, the vibration-damping resin layer is not formed inside the insertion hole on the inner circumferential surface of the annular portion, The vibration-damping resin layer comprises a heat-resistant resin and a vibration-damping filler that converts vibration energy into thermal energy.

2. 2. The crank sprocket according to claim 1, wherein the vibration-damping resin layer has a thickness of 10 μm or more.

3. 2. The crank sprocket according to claim 1, wherein a volume ratio of the vibration-damping filler to a total volume of the heat-resistant resin and the vibration-damping filler in the vibration-damping resin layer is within a range of 40 volume % or more and 60 volume % or less.

4. 2. The crank sprocket according to claim 1, wherein said vibration-damping filler is a thermoplastic elastomer.

5. 2. The crank sprocket according to claim 1, wherein the vibration-damping filler is a urethane compound.

6. 2. The crank sprocket according to claim 1, wherein said vibration-damping filler is a polyethylene compound.

7. 2. The crank sprocket according to claim 1, wherein said vibration-damping filler is an ester copolymer.

8. 2. The crank sprocket according to claim 1, wherein the vibration-damping filler is a rubber-based material.

9. 2. The crank sprocket according to claim 1, wherein the vibration-damping filler is a microcapsule-based material.

10. 2. The crank sprocket according to claim 1, wherein the vibration-damping filler is a low-density material containing an air layer therein.

11. The vibration-damping resin layer is made of polytetrafluoroethylene (PTFE), molybdenum disulfide (MoS ２ 2. The crank sprocket according to claim 1, further comprising a solid lubricant containing at least one selected from the group consisting of tungsten carbide, ... graphite, and the like.

12. The vibration-damping resin layer is made of alumina (Al ２ O ３ 2. The crank sprocket according to claim 1, further comprising hard particles containing at least one selected from the group consisting of tungsten carbide, ...

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