KR20190041246A - Selection method of boots for constant velocity joint and constant velocity joint - Google Patents

Abstract

The present invention provides an evaluation method to evaluate a noise generating degree of a viscoeIasticity material without performing a repeated experiment in an actual using environment of the viscoeIasticity material through a selection method. Moreover, according to the present invention, boots for a constant velocity joint can restrict noise emitted to the outside by providing an excellent noise shielding force.

Description

[0001] SELECTION METHOD FOR BOOTS FOR CONSTANT VELOCITY JOINT AND CONSTANT VELOCITY JOINT [0002]

The present application relates to a selection method of boots for constant velocity joints and boots for constant velocity joints.

The power of the engine or the like is transmitted to the other components through various transmission devices. Such a power transmission apparatus is generally equipped with an external housing for noise shielding and / or prevention of intrusion of external pollutants. With such an outer housing material, a viscoelastic material may be used for realizing excellent sealing force and vibration damping function.

A constant velocity joint connected to the propulsion shaft of an automobile is an example of a power transmission device. It has boots for maintaining the airtightness of the grease applied to the constant velocity joint, shielding the noise and preventing entry of external contaminants. The boots are manufactured using rubber or polyester-based resin, and are required to have excellent heat resistance, fatigue resistance, oil resistance, and chemical resistance. There is also a demand for noise reduction caused by high rotation of the power train while being able to withstand heat, large deformation, and external shocks.

One object of the present invention is to provide a selection method that can evaluate whether or not noise of a boom for a constant velocity joint can be generated without performing repeated experiments in an actual use environment.

It is another object of the present invention to provide a boom for constant velocity joint which exhibits excellent noise suppression power.

In this specification, 'and / or' are used to mean at least one of the elements listed before and after.

In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprises " and / or " comprising " used in the specification do not exclude the presence or addition of components other than the components mentioned.

In the present specification, unless otherwise specified, each physical property is based on a value measured at room temperature / normal pressure. The term ambient temperature is a natural temperature that is neither warmed nor warmed, it may be any temperature in the range of 10 ° C to 30 ° C, specifically 23 ° C, 24 ° C or 25 ° C. Also, the term atmospheric pressure may mean atmospheric pressure, and may specifically mean about 1 atmosphere.

The present application relates to a method of selecting boots for constant velocity joints. The selection method of the present application comprises the steps of: determining a loss elastic modulus (LM) and a hysteresis loss (H) of a viscoelastic material; And determining a selection index (NP) according to the following general formula (1) from the loss elastic modulus (LM) and the hysteresis loss (H).

[Formula 1]

NP = LM x H

In the general formula (1), NP represents a selectivity index (MPa ² ), LM represents a loss elastic modulus (MPa), and H represents a hysteresis loss (MPa).

As used herein, the term viscoelastic material may refer to a material having both viscous and elastic properties, which may refer to a material which undergoes significant deformation upon load and which is restored to its original state upon complete removal of the load. It is possible to show the nonlinear elastic behavior under load and the velocity dependent viscoelastic behavior in which hysteresis occurs under cyclic loading.

In this specification, the term loss modulus can mean energy lost due to the viscosity of a viscoelastic material, and the strain or energy applied to the viscoelastic material is released as thermal energy or causes structural deformation It can mean energy that is not stored and lost. The loss elastic modulus can be measured by a resonance method or a non-resonance method. The loss elastic modulus can be measured using an analysis instrument such as DMA (dynamic mechanical analyzer) Q800 of TA Instruments. In this specification, the term hysteresis loss refers to a strain which can not return to its original size when an external force is applied to a viscoelastic material and then the external force is removed, and the strain caused by the strain is referred to as " Unlike this strain, it can mean energy loss that occurs because of some delay. The hysteresis loss may be a value measured according to the E method (2012 edition) described in JIS K 6400-2, and may be measured using an analysis instrument such as DMA (dynamic mechanical analyzer) Q800 of TA Instruments. The inventors of the present application discovered that the loss elastic modulus and hysteresis loss of a viscoelastic material are constantly related to the generation of noise of a viscoelastic material and derive a method capable of predicting the noise suppression power of a viscoelastic material from the loss elastic modulus and hysteresis loss of a viscoelastic material Respectively. As a result of the study by the present inventors, the selectivity index (NP) of the present application can be expressed as a product of a loss modulus (LM) and a hysteresis loss (H), and the selectivity index (NP) It was confirmed that there was a linear relationship with the incidence. The selection method of the present application can evaluate the noise of the booster for constant velocity joint to which the viscoelastic material is applied without repeated experiment in the actual use environment by evaluating the noise of the viscoelastic material through the loss elastic modulus and the hysteresis loss.

In one example, the selection method of the present application may further comprise the step of selecting a viscoelastic material having a selectivity index (NP) equal to or greater than 2.5 MPa < ² >. If the choice index of viscoelastic material is more than 2.5 MPa ² , it can be evaluated that the noise suppression power is excellent. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a selection index (NP) of the present application and a result of a noise generation evaluation test described later. The NP and the noise generation cycle are derived from the correlation correlation coefficient of 0.98 according to the multiple correlation analysis method. Accordingly, the selection index (NP) of the present application and the noise generation cycle have a strong quantitative linear relationship can confirm. The correlation between the selection index (NP) and the noise generation cycle can be expressed by the following general formula (2).

[Formula 2]

C = 3.83 x NP - 8.22

In the general formula 2, C represents the noise generation cycle, and NP represents the above-mentioned selection index.

The noise generation cycle is a result of applying the noise generation test method described later and means a cycle in which noise is generated as a result of the noise generation test. If the noise generation cycle is less than 2 cycles, the noise suppression power can be evaluated as a low result. If the noise generation cycle is 2 cycles or more, the noise suppression power can be evaluated as an excellent result. From the above general formula 2, it can be seen that noise is generated in more than two cycles when the selectivity index (NP) is 2.5 MPa ² or more. Thus, when the selectivity index (NP) is 2.5 MPa ² or more, Can be evaluated.

(NP) of at least 2.5 MPa ^{2, at} least 2.7 MPa ^{2, at} least 2.9 MPa ^{2, at} least 3.3 MPa ^{2, at} least 3.5 MPa ^{2, at} least 3.7 MPa ^{2, at} least 3.9 MPa ^{2, at} least 4.1 MPa ² 4.3 MPa ² , 4.5 MPa ² or more, 4.7 MPa ² or more, 4.9 MPa ² or more, 5.1 MPa ² or more, 5.3 MPa ² or more, 5.5 MPa ² or more, 5.7 MPa ² or more, 6.1 MPa ² or more, 6.3 MPa ² or more, 6.5 MPa ² or more, 6.7 MPa ² or more, 6.9 MPa ² or more, or 7.00 MPa ² or more, and the upper limit is not particularly limited, but may be, for example, 100 MPa ² or less, 80 MPa ² Below, 60 MPa ² 50 MPa ² 40 MPa ² or less, or 20 MPa ² Or less. The higher the selected index (NP) can be evaluated to be more excellent in noise restraining force, such as not less than 4.7 MPa ² noise evaluation test results of the viscoelastic material, and a noise may occur in more than 10 cycles, the viscoelastic not less than 7.00 MPa ² As a result of the noise evaluation test of the material, noise may occur in more than 20 cycles. When the selectivity index (NP) satisfies the above range, it can be evaluated that the noise suppressing ability of the viscoelastic material is excellent without applying to the actual operating conditions.

In one example of the present application, the loss modulus can be a value measured within a strain range of 1% to 10%. As used herein, the term strain may mean the degree of morphological transformation as measured by the force exerted on the sample. In this specification, a strain of 0% means a state without strain of a sample, and a strain of 10% means that a sample is deformed by 10% with respect to a state without strain of the sample. The strain may be 1% or more, 2% or more, or 3% or more, and may be 10% or less, 9% or less, or 8% or less. When the strain is 10% or more, the sample may be broken during the modulus measurement, and the loss elastic modulus may not be accurately measured.

The loss elastic modulus may be a value measured within a frequency range of 0.1 Hz to 10 Hz. The frequency may be 0.1 Hz or more, 0.2 Hz or more, 0.3 Hz or more, 0.4 Hz or more, or 0.5 Hz or more and may be 10 Hz or less, 9 Hz or less, 8 Hz or less, 7 Hz or less, 6 Hz or 5 Hz or less , But is not limited thereto.

In one example, the loss elastic modulus was measured at a frequency of 1 Hz at a strain of 5% in a dynamic mechanical analyzer mounted on a plate-like specimen of viscoelastic material having thickness, width and length of 0.5 mm, 6 mm and 10 mm, respectively And may be a loss elastic modulus at 2.5 Hz confirmed by a frequency sweep test in which the frequency is increased in increments of 0.5 Hz up to 3 Hz. The thickness, width, and length of the specimen may be indicative of only the size to be measured in the state of being mounted on the dynamic mechanical analyzer. The dynamic mechanical analyzer can use commercially available equipment without limitation, and can be measured using, for example, an analysis instrument such as DMA (dynamic mechanical analyzer) Q800 of TA Instruments.

In another example, the selection method of the present application may further comprise the step of selecting a viscoelastic material having a loss modulus within the range of 1 MPa to 10 MPa. The loss modulus may be 1 MPa or more, 1.5 MPa or more, 2.0 MPa or more, 2.5 MPa or more, 3.0 MPa or more, 3.5 MPa or more, 4.0 MPa or more, 4.5 MPa or more, 5.0 MPa or more, 5.5 MPa or 6.0 MPa or more, The upper limit is not particularly limited, but may be, for example, 10 MPa or less. When the loss elastic modulus measured under the above-described measurement conditions satisfies the above range, the viscoelastic material can exhibit excellent noise shielding ability.

In one example of the present application, the hysteresis loss is 0.5% per minute from 0% to 3% dynamic strain in a dynamic mechanical analyzer with a plate specimen of viscoelastic material having thickness, width and length of 0.5 mm, 6 mm and 10 mm, respectively, , And then subtracting the difference from 3% to 0% by 0.5% per minute from the difference of the integrated value of the stress-strain curve. The thickness, width, and length of the specimen may be indicative of only the size to be measured in the state of being mounted on the dynamic mechanical analyzer. The stress-strain curve may refer to a curve for the relationship between stress and strain on a two-dimensional plane with strain (%) on the x-axis and strain (MPa) on the y-axis. The difference in the integrated value of the stress-strain curve may mean the difference between the integrated value for the curve when the dynamic strain increases and the integrated value for the curve for the dynamic strain decrease. The description of the strain is the same as that described in the loss elastic modulus and will be omitted.

In another example of the present application, the selection method of the present application may further comprise the step of selecting a viscoelastic material having a hysteresis loss in the range of 0.1 MPa to 5 MPa. The hysteresis loss may be 0.1 MPa or more, 0.2 MPa or more, 0.3 MPa or more, 0.4 MPa or more, 0.5 MPa or more, 0.6 MPa or more, 0.7 MPa or more, 0.8 MPa or more, 0.9 MPa or more, 1.0 MPa or 1.1 MPa or more, But is not limited to, 5.0 MPa or less, 4.5 MPa or less, 4.0 MPa or less, 3.5 MPa or less, 3.0 MPa or less, 2.5 MPa or 2.0 MPa or less. When the hysteresis loss satisfies the above range, a sufficient level of vibration damping capability can be ensured, and thus, the viscoelastic material can be evaluated as having excellent noise shielding ability.

In one example, the viscoelastic material can be a thermoplastic elastomer. The thermoplastic elastomer may be an elastomeric or thermoplastic interpolymer. The thermoplastic elastomer is not particularly limited as long as it satisfies the above-described loss modulus and / or hysteresis loss.

Examples of the thermoplastic elastomer include thermoplastic elastomers such as natural rubber, synthetic rubber, thermoplastic polyurethane (TPU), thermoplastic polyester-polyether elastomer (TPEE), thermoplastic polyamide (TPAE) Based thermoplastic elastomer (TPO), a thermoplastic polyvinylchloride (TPVC), and a thermoplastic styrenic block copolymer (SBC).

The natural rubber may be one known as natural rubber (NR), and is not limited to the country of origin, and may include modified natural rubber. The denatured natural rubber means denatured or refined the general natural rubber, and examples thereof include epoxidized natural rubber (ENR), deproteinized natural rubber (DPNR) and hydrogenated natural rubber.

The synthetic rubber may be a synthetic polymer compound having properties similar to those of natural rubber, such as rubber elasticity at room temperature. The synthetic rubber may be a urethane, ester, amide, olefin, vinyl chloride and / or styrenic thermoplastic elastomer May be referred to as a synthetic polymer compound. The synthetic rubber may be at least one selected from the group consisting of styrene butadiene rubber (SBR), modified styrene butadiene rubber, butadiene rubber (BR), modified butadiene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, fluorine rubber, silicone rubber, (NBR), modified nitrile butadiene rubber, chlorinated polyethylene rubber, styrene ethylene butylene styrene (SEBS) rubber, ethylene propylene rubber, ethylene propylene diene (EPDM) rubber, hyaluron rubber, chloroprene rubber, ethylene Vinyl acetate rubber, acrylic rubber, hydrin rubber, vinyl benzyl chloride styrene butadiene rubber, bromomethyl styrene butyl rubber, maleic styrene butadiene rubber, carboxylic styrene butadiene rubber, epoxy isoprene rubber, ethylene ethylene propylene rubber, Butadiene rubber, Rommie Ney suited polyisobutyl isoprene-co-p-methylstyrene may be a (brominated polyisobutyl isoprene-co-paramethyl styrene, BIMS), and one selected from the group consisting of.

As the urethane-based thermoplastic elastomer, known thermoplastic polyurethanes (TPU) may be used, and they may be used alone or in combination of two or more. The thermoplastic polyurethane may be a polymer of a composition comprising an isocyanate compound and a polyol. The isocyanate compound may be an aliphatic isocyanate compound such as 1,3-trimethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate or 1,6-hexamethylene diisocyanate; Alicyclic isocyanate compounds such as 1,3-cyclopentane diisocyanate or 1,4-cyclohexane diisocyanate; aromatic isocyanate compounds such as m-phenylene diisocyanate, p-phenylene diisocyanate or 2,4-tolylene diisocyanate; An aromatic aliphatic isocyanate compound having at least one aromatic ring structure in the molecule such as 1,3-xylene diisocyanate or 1,4-xylene diisocyanate; And / or polyisocyanate compounds such as 1,6-hexamethylene diisocyanate, but are not limited thereto. Examples of the polyol include, but are not limited to, polyether polyol, polyester polyol, polycarbonate polyol, polyolefin polyol, and polyacrylic polyol.

As the ester-based thermoplastic elastomer, known polyester-based thermoplastic elastomers may be used, and they may be used alone or in combination of two or more. As the polyester-based thermoplastic elastomer, for example, a polyester-based thermoplastic elastomer having a hard segment consisting of an aromatic polyester unit and a soft segment composed of an aliphatic polyether unit and / or an aliphatic polyester unit as a main constituent unit can be used have.

The aromatic polyester unit is mainly composed of an aromatic dicarboxylic acid or an ester forming derivative thereof (C1-4 alkyl ester, acid halide, etc.) and a diol or an ester forming derivative thereof (such as an acetylate or an alkali metal salt) May be formed. Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, anthracene dicarboxylic acid, , 4'-dicarboxylic acid, diphenoxyethane dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sulfoisophthalic acid, sodium 3-sulfoisophthalate , But is not limited thereto. Specific examples of the diol include diols having a molecular weight of 400 or less, for example, aliphatic diols such as 1,4-butanediol, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol and decamethylene glycol; Alicyclic diols such as 1,1-cyclohexane dimethanol, 1,4-dicyclohexanedimethanol and tricyclodecane dimethanol; Bis [4- (2-hydroxyethoxy) phenyl] propane, bis [p-hydroxyphenyl] Aromatic, such as 4,4'-di (2-hydroxyethoxy) phenyl] sulfone, 1,1-bis [4- (2-hydroxyethoxy) phenyl] cyclohexane, But are not limited to, diols. These aromatic dicarboxylic acids or ester-forming derivatives thereof, diols or ester-forming derivatives thereof may be used in combination of two or more kinds. The aromatic polyester unit includes a polybutylene terephthalate unit derived from terephthalic acid and / or dimethyl terephthalate and 1,4-butanediol, a polybutylene terephthalate unit derived from terephthalic acid and / or dimethyl terephthalate, Or polybutylene isophthalate units derived from dimethyl isophthalate and 1,4-butanediol, but the present invention is not limited thereto.

Examples of the aliphatic polyether constituting the aliphatic polyether unit include poly (ethylene oxide) glycol, poly (propylene oxide) glycol, poly (tetramethylene oxide) glycol, poly (hexamethylene oxide) glycol, But are not limited to, a copolymer of a seed and propylene oxide, an ethylene oxide addition polymer of poly (propylene oxide) glycol, a copolymer glycol of ethylene oxide and tetrahydrofuran, and the like. The proportion of the soft segment composed of the aromatic polyester unit and the aliphatic polyether unit and / or the aliphatic polyester unit in the polyester thermoplastic elastomer is not particularly limited. For example, the former / the latter (weight ratio) = 1/99 to 99.5 / 0.5, preferably 50/50 to 99/1.

As the amide-based thermoplastic elastomer, known polyamide-based thermoplastic elastomers may be used. These amide-based thermoplastic elastomers may be used alone or in combination of two or more. As the polyamide thermoplastic elastomer, for example, a polyamide thermoplastic elastomer having a hard segment consisting of a polyamide unit and a soft segment composed of an aliphatic polyether unit and / or an aliphatic polyester unit as a main constituent unit may be used. Examples of the polyamide constituting the polyamide unit include nylon 6, nylon 66, nylon 11 and nylon 12, but are not limited thereto. Examples of the aliphatic polyether constituting the aliphatic polyether unit include the same aliphatic polyether exemplified in the section of the polyester-based thermoplastic elastomer.

As the olefinic thermoplastic elastomer, known polyolefinic thermoplastic elastomers may be used, and they may be used alone or in combination of two or more. The olefinic thermoplastic elastomer is obtained by copolymerizing a polyolefin compound such as polyethylene or polypropylene with an ethylene-propylene-diene copolymer (ethylene-propylene-diene rubber; EPDM), an ethylene-propylene copolymer (ethylene- But are not limited to, natural rubber, nitrile butadiene rubber (NBR), and / or styrene-butadiene rubber (SBR).

The vinyl chloride thermoplastic elastomer may be a known polyvinyl chloride thermoplastic elastomer, and may be used alone or in combination of two or more. Examples of the polyvinyl chloride thermoplastic elastomer include, but are not limited to, polyvinyl chloride compounds and mixtures or polymers of nitrile butadiene rubber (NBR), polyurethane resin or polyester resin.

The styrenic thermoplastic elastomer may be a known hydrogenated or non-hydrogenated styrenic thermoplastic elastomer, and may be used alone or in combination of two or more. The styrenic thermoplastic elastomer may be at least one selected from the group consisting of a styrene isoprene block copolymer, a hydride of a styrene isoprene block copolymer (SEP), a hydride of a styrene isoprene styrene block copolymer (SEPS; polystyrene polyethylene / propylene polystyrene block copolymer), a styrene butadiene copolymer , And a hydride of a styrene butadiene block copolymer (SEBS; polystyrene polyethylene / butylene polystyrene block copolymer). However, the present invention is not limited thereto.

The present application also relates to boots for constant velocity joints. The boots for constant-velocity joints of the present application may have a selectivity index (NP) of 2.5 MPa ^{2 or} more calculated by the following general formula (1).

[Formula 1]

NP = LM x H

In the general formula (1), NP represents a selectivity index (MPa ² ), LM represents a loss modulus (MPa), and H represents a hysteresis loss (MPa).

As described above, when the noise generation cycle is less than 2 cycles, the noise suppression power can be evaluated as a low result. If the noise generation cycle is 2 cycles or more, the noise suppression power can be evaluated as an excellent result. From the above-mentioned general formula 2, it can be seen that when the selectivity index (NP) is 2.5 MPa ² or more, noise is generated in ^two or more cycles, and when the selectivity index NP is 2.5 MPa ² or more, .

(NP) of at least 2.5 MPa ^{2, at} least 2.7 MPa ^{2, at} least 2.9 MPa ^{2, at} least 3.3 MPa ^{2, at} least 3.5 MPa ^{2, at} least 3.7 MPa ^{2, at} least 3.9 MPa ^{2, at} least 4.1 MPa ² 4.3 MPa ² , 4.5 MPa ² or more, 4.7 MPa ² or more, 4.9 MPa ² or more, 5.1 MPa ² or more, 5.3 MPa ² or more, 5.5 MPa ² or more, 5.7 MPa ² or more, 6.1 MPa ² or more, 6.3 MPa ² or more, 6.5 MPa ² or more, 6.7 MPa ² or more, 6.9 MPa ² or more, or 7.00 MPa ² or more, and the upper limit is not particularly limited, but may be, for example, 100 MPa ² or less, 80 MPa ² 60 MPa < ^{2 >} 50 MPa ² 40 MPa ² or less, or 20 MPa ² Or less. The higher the selected index (NP) can be evaluated to be more excellent in noise restraining force, such as not less than 4.7 MPa ² noise evaluation test results of the viscoelastic material, and a noise may occur in more than 10 cycles, the viscoelastic not less than 7.00 MPa ² As a result of the noise evaluation test of the material, noise may occur in more than 20 cycles. When the selection index (NP) satisfies the above range, it is possible to provide a constant-velocity joint boots excellent in noise suppression ability.

In one example, the loss elastic modulus of the boots for constant velocity joints of the present application may be in the range of 1 MPa to 10 MPa. The loss modulus may be 1 MPa or more, 1.5 MPa or more, 2.0 MPa or more, 2.5 MPa or more, 3.0 MPa or more, 3.5 MPa or more, 4.0 MPa or more, 4.5 MPa or more, 5.0 MPa or more, 5.5 MPa or 6.0 MPa or more, The upper limit is not particularly limited, but may be, for example, 10 MPa or less. When the loss elastic modulus measured under the above-described measurement conditions satisfies the above range, the constant velocity joint boots can exhibit excellent noise shielding ability.

In another example, the hysteresis loss of the constant velocity joint boot of the present application may be in the range of 0.1 MPa to 5 MPa. The hysteresis loss may be 0.1 MPa or more, 0.2 MPa or more, 0.3 MPa or more, 0.4 MPa or more, 0.5 MPa or more, 0.6 MPa or more, 0.7 MPa or more, 0.8 MPa or more, 0.9 MPa or more, 1.0 MPa or 1.1 MPa or more, But is not limited to, 5.0 MPa or less, 4.5 MPa or less, 4.0 MPa or less, 3.5 MPa or less, 3.0 MPa or less, 2.5 MPa or 2.0 MPa or less. When the hysteresis loss satisfies the above range, a vibration damping capability of a sufficient level can be ensured, thereby providing a boom for a constant velocity joint having an excellent noise shielding force.

Since the loss elastic modulus and hysteresis measurement method are the same as those described above, they will be omitted.

The constant velocity joint boot may include, but is not limited to, the above-described thermoplastic elastomer. The description of the thermoplastic elastomer is the same as that described above, and therefore, it will be omitted.

The present application also relates to a constant velocity joint comprising a constant velocity joint boot having a selectivity index (NP) of 2.5 MPa < ² > A constant velocity joint may mean a device that mechanically connects the shaft to transmit the torque between the drive shaft and the driven shaft. More specifically, this may mean that the power transmission between the two shafts is performed at a constant speed even if the power transmission angle between the two shafts changes, that is, even at a predetermined joint angle, without varying the rotational speed. More specifically, the present invention relates to a joint between materials that allow power transmission to be made uniform between the driven shaft and the driven shaft, which is not in line with the drive shaft, by attaching joints having large angles of flexure to both ends of the shaft, It is said. Examples include, but are not limited to, demodulating type, burfield type, weathertight type, tractor type, and the like. The constant velocity joint including the boots for constant velocity joint can exhibit excellent noise suppression.

The present application also relates to a power transmission system comprising a constant velocity joint boot having a selectivity index (NP) of 2.5 MPa < ² > The power transmission system may include a power generating device and a power transmitting device, and the power transmitting device may be surrounded by the boots for the constant velocity joint. The power generation apparatus can be used without limitation as long as it can generate kinetic energy. Examples of the power generation apparatus include an engine and a motor, but the present invention is not limited thereto. The power transmission device is exemplified by a friction transmission device, a gear transmission device, and a belt transmission device, and specifically, a constant velocity joint can be exemplified, but the present invention is not limited thereto. When the above-described boot is applied to the boot surrounding the power transmission device, it is possible to effectively prevent the intrusion of foreign substances such as dust and water, and to suppress the noise emitted to the outside by having excellent noise shielding force.

In one example, the power generating device may be an automotive engine or motor, and the power transmitting device may be an automotive constant velocity joint, but is not limited thereto.

The selection method of the present application can provide a selection method of selecting a viscoelastic material having excellent noise shielding ability without repeatedly performing experiments in a practical use environment of a viscoelastic material applied to boots for constant velocity joints.

In addition, the boots for constant-velocity joints according to the present application exhibit excellent noise shielding ability and can suppress the noise emitted to the outside.

Fig. 1 is a diagram showing a selection index (NP) of the present application and a result of a noise generation evaluation test.
Figure 2 is a diagram illustrating hysteresis loss for an embodiment of the present application.

Hereinafter, the present application will be described in detail by way of examples and comparative examples according to the present application, but the scope of the present application is not limited by the following examples.

1. Measuring Loss Modulus

The loss elastic modulus was measured by the following method. The constant velocity joint boots were made into specimens with thickness of 0.5mm, width of 6mm and length of 10mm, and experiments were conducted to change the frequency by DMA (dynamic mechanical analyzer) Q800 of TA Instruments. The size of the specimen was based on the actual size to be measured by the dynamic mechanical analyzer. At this time, the experimental conditions were room temperature (25 ° C), dynamic strain was 5%, and a frequency sweep test was used in which the frequency increased from 0.5 Hz to 1 Hz. The loss elastic modulus measured at 2.5 ㎐ was used as a representative value.

2. How to measure hysteresis loss

The hysteresis loss was measured by the following method. The constant velocity joint boots were made into specimens with a thickness of 0.5mm, width of 6mm and length of 10mm, and experiments were conducted to change the dynamic strain by DMA (Dynamic Mechanical Analyzer) Q800 of TA Instruments. The size of the specimen was based on the actual size to be measured by the dynamic mechanical analyzer. The experimental conditions were room temperature (25 ℃) and the dynamic strain was increased from 0% to 3% by 0.5% per minute and then from 3% to 0% by 0.5% per minute. In the stress-strain curve obtained after the experiment, the difference in area between the curve in which the dynamic strain increases and the curve in which the dynamic strain increases is calculated as the hysteresis loss.

3. Noise Generation Test Method

Keep the drive shaft and the driven shaft at a constant angle of 40 ° at a constant speed joint (25 ° C) and a rotation speed of 150 RPM, and spray water and soil alternately to simulate various foreign matter flying from the road surface. This was repeated one cycle, and the point at which noise occurred was evaluated as a noise generation cycle. The noise generation test was performed twice for each sample, and the average value was evaluated as a noise generation cycle. The noise criterion was 75 ㏈ or higher and ambient noise was measured at 65 ㏈ or lower.

The loss elastic modulus and hysteresis loss were measured for an ester type thermoplastic elastomer (HB9242D, manufactured by LG Chemical) for constant velocity joint boots. As a result, the loss elastic modulus was 3.38 MPa, the hysteresis loss was 0.916 MPa, and the selectivity index (NP) was 3.095 MPa ² .

An experiment was conducted under the same conditions as in Example 1, except that an ester-based thermoplastic elastomer for constant velocity joint boots was used in the same manner as in Example 1, except that HB5242D Type 2 (a product obtained by adding 3 wt% of polyethylene and styrene acrylonitrile additive to HB9242D product) .

The experiment was carried out under the same conditions as in Example 1, except that the ester-based thermoplastic elastomer for constant velocity joint boots was used in an amount of HB5242D Type 1 of LG Chemical (HB9242D product containing 3% by weight of a siloxane additive added thereto).

Example 1 Example 2 Example 3 Loss modulus (MPa) 3.38 4.26 4.32 Hysteresis loss (MPa) 0.916 0.936 1.027 Selective Index (MPa ² ) 3.096 3.987 4.436 Noise Cycle 3.5 7.5 8.5 Loss modulus: 25 캜, frequency 2.5 Hz, strain 5% (unit: MPa)
Hysteresis loss: 25 ℃, Strain 0% ~ 3% (Unit: MPa)
Selection index: product of loss modulus and hysteresis loss (unit: MPa ² )
Noise generation cycle: Average value of two measurements for each sample

Table 1 shows the measurement results of Examples 1 to 3, and FIG. 1 shows the selection index (NP) of the present application and the results of the noise generation evaluation test. The NP and the noise generation cycle are derived from the correlation correlation coefficient of 0.98 according to the multiple correlation analysis method. Accordingly, the selection index (NP) of the present application and the noise generation cycle have a strong quantitative linear relationship can confirm. Therefore, the selection method of the present application can estimate the noise generation cycle of the viscoelastic material through calculation of the selection index (NP), and the degree of noise generation can be evaluated without repeating experiments in a practical use environment of the viscoelastic material .

Claims (14)

Confirming the loss elastic modulus (LM) and the hysteresis loss (H) of the viscoelastic material; And determining a selection index (NP) according to the following general formula (1) from the loss elastic modulus (LM) and the hysteresis loss (H):
[Formula 1]
NP = LM x H
In the general formula 1, NP represents a selectivity index (unit: MPa ² ), LM represents loss modulus (unit: MPa), and H represents hysteresis loss (unit: MPa).
The selection method according to claim 1, further comprising the step of selecting a viscoelastic material having a selectivity index (NP) of 2.5 MPa ² or more.
The method according to claim 1, wherein the loss elastic modulus of the plate-shaped specimen of viscoelastic material having a thickness, a width and a length of 0.5 mm, 6 mm and 10 mm, respectively, is set in a dynamic mechanical analyzer under the condition of 5% And the loss elastic modulus at 2.5 Hz confirmed by a frequency sweep method in which the frequency is increased in increments of 0.5 Hz from 3 Hz to 3 Hz.
The selection method according to claim 1, further comprising the step of selecting a viscoelastic material having a loss modulus within a range of 1 MPa to 10 MPa.
The hysteresis loss according to claim 1, wherein the hysteresis loss is 0.5% or less per minute from 0% to 3% of dynamic strain in a dynamic mechanical analyzer mounted on a plate-shaped specimen of viscoelastic material having a thickness, a width and a length of 0.5 mm, 6 mm and 10 mm, From the difference of the integrated value of the stress-strain curve obtained by increasing by% and then decreasing from 3% to 0% by 0.5% per minute.
The method of claim 1, further comprising selecting a viscoelastic material having a hysteresis loss in the range of 0.1 MPa to 5 MPa.
The selection method according to claim 1, wherein the viscoelastic material is a thermoplastic elastomer.
The thermoplastic elastomer composition according to claim 7, wherein the thermoplastic elastomer comprises at least one of natural rubber, synthetic rubber, urethane thermoplastic elastomer, ester thermoplastic elastomer, amide thermoplastic elastomer, olefin thermoplastic elastomer, vinyl chloride thermoplastic elastomer and styrene thermoplastic elastomer Selecting method to include.
Boots for constant velocity joints having an optional index (NP) of 2.5 MPa ² or more calculated by the following general formula:
[Formula 1]
NP = LM x H
In the general formula 1, NP represents a selectivity index (unit: MPa ² ), LM represents loss modulus (unit: MPa), and H represents hysteresis loss (unit: MPa).
The constant velocity joint boom according to claim 9, wherein the loss elastic modulus is in the range of 1 MPa to 10 MPa.
The constant velocity joint boom according to claim 9, wherein the hysteresis loss is in the range of 0.1 MPa to 5 MPa.
The thermoplastic elastomer composition according to claim 9, wherein at least one selected from the group consisting of natural rubber, synthetic rubber, urethane thermoplastic elastomer, ester thermoplastic elastomer, amide thermoplastic elastomer, olefin thermoplastic elastomer, vinyl chloride thermoplastic elastomer and styrene thermoplastic elastomer Boots for constant velocity joints, including thermoplastic elastomers.
A constant velocity joint comprising the boot for a constant velocity joint of paragraph 9.
A power transmission system comprising the boot for a constant velocity joint of claim 9.

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