JP2011084679A - Slide member for power transmission guide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slide member for power transmission guides that is made up of a composite resin composition in which a granular fluororesin having an excellent lubricity is mixed with an easily extrusion-moldable thermoplastic resin as the base material and is used for chain guides and chain tensioners for timing chains in automobile engines. <P>SOLUTION: The slide member for power transmission guides is obtained by molding a composite resin composition in which fluororesin particles are mixed with a base resin. The base resin is a thermoplastic resin. The fluororesin particles are denatured with electron beam irradiation, and has an average particle size of not larger than 10 μm. The content of the fluororesin particles is 5-50 wt.% of the aggregate of the composite resin composition. The fluororesin particles are PTFE particles having a primary particle size of not larger than 5 μm. The fluororesin has carboxyl groups and/or halogenated carboxylic acid groups at the terminals as functional groups created by the electron beam irradiation with a radiation of not less than 50 kGy. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power transmission guide sliding member, and more particularly to a power transmission guide sliding member used as, for example, a chain guide or chain tensioner used in a timing chain of an automobile engine.

  Conventionally, chain guides or chain tensioners have been used to prevent the timing chain of an internal combustion engine from swinging or to apply tension to the chain. These members are used for a long time in a harsh environment where oil is attached, for example, at an ambient temperature of −40 ° C. to 170 ° C. Further, since the chain slides with tension applied, the mechanical strength is of course In addition, it is required to have excellent heat resistance, slidability, and oil resistance.

  Conventional chain guides for internal combustion engines generally have a structure in which a shoe made of synthetic resin is joined to the outer surface of a metal support member made of aluminum die cast or the like, but a metal material is used for the support member. Therefore, the weight is increased as a whole, and the cost is high because both the resin and metal are used. Furthermore, since the joint portion between the resin material and the metal has a different coefficient of thermal expansion, there is a problem that peeling occurs during use.

  Therefore, a structural support member using a polyamide resin composition containing 10 to 60% by weight of glass fiber or carbon fiber in polyamide resin for 50 to 98% of the product volume, a slide lining member of the chain guide surface, and a chain guide surface There has been proposed a resin-made chain guide for an engine in which a part is made of a non-reinforced polyamide resin by a simultaneous molding or a stepwise molding method. However, when the temperature rises, the flexural modulus of polyamide resin (typically PA66) decreases sharply, and even with PA66 containing carbon fiber, when it exceeds 100 ° C., it becomes less than half that at room temperature, and the mechanical strength Is insufficient and deformation becomes large. Furthermore, the polyamide resin is known to be a material that absorbs water and undergoes drastic changes in physical properties due to water absorption, and has a problem that the flexural modulus is greatly reduced by water absorption.

  As an improvement measure, Patent Document 1 discloses a sliding member that is used in a chain system and is made of a resin composition. The resin composition contains a base material resin and a fluororesin. The content is 5 to 40% based on the total amount of the resin composition, the matrix resin is a thermoplastic resin having a number average molecular weight of 20000 or more, and the fluororesin has a surface energy of the fluororesin. A sliding member for a chain system is disclosed, which has a visible light transmittance of 10% or more at a wavelength of 600 nm and 200 to 400 μN / cm. Specifically, the fluororesin has an average particle size of 1 to 50 μm and a content of 10 to 20% based on the total amount of the resin composition. Further, the base material resin is a polyamide resin, and the fluororesin is a tetrafluoroethylene resin.

  On the other hand, in Patent Document 2, a compound comprising a polyamide material and a perfluoroalkyl material and a mixture of this compound and another polymer material are reacted with the modified perfluoroalkyl material and the polyamide compound in the form of a melt. Disclosed is a compound comprising a polyamide material and a perfluoroalkyl material and a mixture of this compound and other polymer materials, characterized by homogenization. Here, a fine powder of PTFE that has been radiochemically decomposed and modified with a radiation dose of 50 kGy or more and preferably with a radiation dose of 100 kGy or more is used as the perfluoroalkyl substance.

JP 2007-177037 A JP 2002-516374

  However, since the sliding member produced by the method described in Patent Document 1 has PTFE particles larger than 10 μm appearing on the surface as it is, the surface roughness becomes rough, which limits the reduction of the friction coefficient. . Although the friction coefficient is lower than that of the conventional sliding member mainly composed of PA66 and the wear is improved, it is not sufficient. For automobile engines, there is a particularly strong demand for smaller and lighter weight to improve fuel efficiency. Therefore, the advent of a resin composition for an injection-moldable sliding member that has improved sliding characteristics while maintaining impact resistance and mechanical strength, and a resin-made sliding member using the same is desired. Patent Document 2 mentions only superiority in dry sliding, and it is not clear whether it can be used under oil lubrication.

  Therefore, in view of the above-mentioned situation, the present invention intends to solve the problem by using a composite resin composition in which a fluororesin excellent in lubricity is compounded in a particle state with a base material of a thermoplastic resin that is easily injection-molded. Thus, the problem of sliding characteristics under oil lubrication is solved, and a power transmission guide sliding member that can be used as a chain guide or chain tensioner used in a timing chain of an automobile engine is provided.

  The present invention provides a sliding member for a power transmission guide, which is molded using a composite resin composition in which fluororesin particles are blended with a base material resin in order to solve the above-mentioned problems, and the base material resin is a thermoplastic resin. The fluororesin particles are modified by electron beam irradiation and have an average particle diameter of 10 μm or less, and the content of the fluororesin particles is 5 to 50% by weight based on the total amount of the composite resin composition. A sliding member for a power transmission guide characterized by the above is constituted (claim 1).

  Here, the primary particle diameter of the fluororesin particles is more preferably 5 μm or less (Claim 2).

  Here, the fluororesin particles are polytetrafluoroethylene resin particles, and have at least a carboxyl group and / or a halogenated carboxylic acid group as a functional group at the terminal by irradiation with an electron beam with a radiation dose of 50 kGy or more. Item 3).

  Further, the base material resin is a polyamide resin, preferably a PA66 resin (Claim 4).

  Then, the mixture of the base resin and the fluororesin particles is melt-kneaded and subjected to reactive extrusion to obtain a composite resin composition pellet in which the maximum particle size of the fluororesin particles is refined to 5 μm or less. (Claim 5).

  The sliding member for a power transmission guide molded using such a composite resin composition can have a surface roughness of an arithmetic average roughness of 0.1 μm or less (claim 6).

  The sliding member for power transmission guide according to the present invention has excellent sliding characteristics while maintaining impact resistance and mechanical strength, so it is preferably used as a chain guide or chain tensioner used in a timing chain of an automobile engine. Can do. In the present invention, when a thermoplastic resin matrix resin and fluororesin particles modified by electron beam irradiation and having an average particle diameter of 10 μm or less are melt-kneaded at a temperature equal to or higher than the melting point of the matrix resin, the matrix resin and the fluororesin are obtained. A composite resin composition in which particles are directly bonded and integrated is obtained, and molding with this composite resin composition provides a surface with excellent smoothness without damaging the mechanical properties of the base resin, And the sliding member provided with the desired sliding characteristic can be obtained by preparing content of a fluororesin particle in the range of 5 to 50 weight% on the basis of the whole quantity of a composite resin composition.

  Here, the average particle diameter of the fluororesin particles indicates the particle diameter of secondary particles in which smaller primary particles are aggregated. In the present invention, the mixture of the base resin and the fluororesin particles modified by electron beam irradiation is melt kneaded and subjected to reactive extrusion, so that the fluororesin particles are further refined than the primary particles. It was found that it was uniformly dispersed in the resin. Thereby, the fine fluororesin particles are uniformly exposed at the sliding interface of the sliding member, and the sliding characteristics and impact resistance are remarkably improved.

  In the present invention, the primary particle diameter of the fluororesin particles is 5 μm or less. However, the smaller the particle diameter, the more the surface roughness can be improved. However, when the primary particle size of the fluororesin particles becomes smaller than necessary, the secondary particle size also decreases accordingly, and handling becomes difficult due to problems such as floating, and it becomes difficult to knead with the matrix resin.

  Here, the fluororesin particles are polytetrafluoroethylene resin particles, and have at least a carboxyl group and / or a halogenated carboxylic acid group as a functional group at the terminal by irradiation with an electron beam with a radiation dose of 50 kGy or more, more preferably 500 kGy or more. In particular, it has excellent sliding properties, and is excellent in dispersibility and bondability with the base resin. When the base material resin is a polyamide resin, and preferably a PA66 resin, it is excellent in heat resistance, oil resistance, mechanical properties and sliding properties.

  Then, a mixture of fluororesin particles having a mean particle size of 10 μm or less, preferably 5 μm or less, or a primary particle size of 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less, and a base material resin is melt-kneaded. By performing reactive extrusion, the maximum particle size of the fluororesin particles can be reduced to 5 μm or less, and if the sliding member is molded using pellets of this composite resin composition, the moldability is excellent, and the surface Roughness can be improved. The sliding member for a power transmission guide molded using such a composite resin composition can have a surface roughness of an arithmetic average roughness of 0.1 μm or less, a low coefficient of friction, and a reduced amount of wear. , Sliding properties are excellent.

It is a perspective view which shows the shape of the test body for investigating a sliding characteristic with a thrust tester. The result of having observed the torn surface of a molded object by SEM is shown, (a) is the SEM image of the cut surface of this invention goods, (b) is the SEM image of the cut surface of the material of patent document 1. FIG. The result of having observed the surface of the molding of this invention by TEM is shown, (a) is a 5000 times TEM image, (b) is a 10000 times TEM image.

  The sliding member for a power transmission guide according to the present invention is a sliding member for a power transmission guide formed by using a composite resin composition in which a fluororesin particle is blended with a matrix resin, and the matrix resin is a thermoplastic resin. The fluororesin particles are modified by electron beam irradiation and have an average particle diameter of 10 μm or less, and the content of the fluororesin particles is 5 to 50% by weight based on the total amount of the composite resin composition. Here, if the average particle diameter of the fluororesin particles is larger than 10 μm, the flatness of the sliding interface cannot be improved. Further, if the content of the fluororesin particles is less than 5% by weight, sufficient sliding characteristics cannot be obtained, and if it is more than 50% by weight, the mechanical properties of the base resin cannot be maintained.

  In general, when the particle size of the fine particles is reduced, the primary particles are aggregated into a secondary particle state, and the secondary particles are handled as a raw material. In the present invention, fluororesin particles having an average particle diameter of 10 μm or less are used, but the primary particle diameter is 5 μm or less.

  It is more preferable to use polytetrafluoroethylene resin particles (hereinafter referred to as “PTFE particles”) as the fluororesin particles. The PTFE particles of the present invention are characterized by having at least a carboxyl group and / or a halogenated carboxylic acid group as a functional group at the terminal by irradiation with an electron beam with a radiation dose of 50 kGy or more. Further, the PTFE particles can be easily pulverized by electron beam irradiation.

  On the other hand, it is preferable to use a polyamide resin as the base material resin. In particular, it is more preferable to use PA66 resin as a base material resin because it is excellent in heat resistance, oil resistance, mechanical characteristics and sliding characteristics.

  Other thermoplastic resins include polyethylene resin, polypropylene resin, polyamide resin, polyphenylene sulfide resin, polyacetal resin, polyester resin, polyether sulfone resin, polyether ether ketone resin, polyether imide resin, polyamide imide resin, polyimide resin. Etc. can be used, and these can be used alone or in combination.

  Then, the mixture of the base resin and the fluororesin particles is melt-kneaded at a temperature equal to or higher than the melting temperature of the base resin using a twin-screw kneading extruder and subjected to reactive extrusion, whereby the maximum particle size of the fluororesin particles is obtained. Can be obtained in a finely divided composite resin composition of 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. A power transmission guide sliding member is molded using the composite resin composition pellets. Specifically, a chain guide and a chain tensioner (both not shown) used for a timing chain of an automobile engine are formed.

  The power transmission guide sliding member molded using such a composite resin composition can have a surface roughness of an arithmetic average roughness of 0.1 μm or less. The fluororesin particles are uniformly dispersed in the base material resin and have a structure in which they are firmly bonded to each other. As will be described later, the PTFE particles are finely dispersed so that the PTFE particles cannot be confirmed even when the fracture surface of the molded product is observed with a scanning electron microscope (SEM) at a magnification of 2000 times. .

The composite resin composition used for the sliding member of the present invention is produced as follows.
(Material preparation method)
PA66 (UBE2026B manufactured by Ube Industries) is used as the base material resin.
PTFE particles are used as the fluororesin particles. PTFE particles having a primary particle diameter of 0.2 μm, an average particle diameter of 3 μm (secondary particles), a specific surface area of 9 m ² / g, and an electron beam irradiation amount of 1000 kGy are used.
The blending ratio of PA66 and PTFE particles is 90 parts by weight for PA66 and 10 parts by weight for PTFE particles.

(Kneading)
The above-mentioned mixture of PA66 and PTFE particles is melt-kneaded with a twin-screw kneading extruder and subjected to reactive extrusion. The extruder used here is BT-30 (L / D: 30) manufactured by Plastic Engineering Laboratory Co., Ltd. The kneading conditions are cylinder temperature: 280 ° C. and screw rotation speed: 300 rpm. The mixture was extruded with this biaxial kneading extruder to produce pellets of the composite resin composition.

(Molding)
Next, the aforementioned pellets are molded into a predetermined shape by a 60-ton injection molding machine. The molding machine used here is PS60E5H manufactured by Nissei Plastic Industry Co., Ltd. The molding conditions were cylinder temperature: 280 ° C., mold temperature: 80 ° C., and a φ20 bush-shaped test piece molding die was used as the die. A test specimen 1 molded with this mold is shown in FIG. This test body 1 is a cylindrical member, and is formed by forming four grooves 3 communicating with the inside and outside in the radial direction on the sliding surface 2 at equiangular positions.

  As comparative examples, a test body using a PA66 non-reinforcing material and a test body using the material of Patent Document 1 were prepared.

  First, the injection-molded product was immersed in liquid nitrogen, cooled and then fractured, and the fractured surface was observed with an SEM. SEM is manufactured by Hitachi High-Technologies Corporation (model number: S-3400N), and the acceleration voltage is 10 kV. FIG. 2A shows a fracture surface of the product of the present invention, with the upper part being 500 times and the lower part being 2000 times. No clear PTFE particles are observed on the fracture surface of the product of the present invention, and the cut surface has fine irregularities such as the entire torn surface. This is evidence that the maximum particle diameter of PTFE particles is uniformly dispersed at 1 μm or less in the base material PA66 resin and that PA66 and PTFE particles are firmly bonded. On the other hand, FIG. 2B shows a fracture surface of the material of Patent Document 1, but the cut surface is relatively smooth, and PTFE particles having a particle size of 10 μm or more appear clearly separated in some places. is doing. In other words, it can be assumed that the bond is very weak because the PTFE particles exist in the raw material PA66 resin as they are, and are separated at the interface between the PA66 resin and the PTFE particles. is there.

  Next, the result of observing the surface of the injection-molded product of the present invention with a transmission electron microscope (TEM) is shown in FIG. 3A is a TEM image at a magnification of 5000 times and FIG. 3B is a TEM image at a magnification of 10,000 times, and it can be seen that the maximum particle diameter of PTFE particles is 500 nm at most. Actually, the particle diameter of the PTFE particles appearing on the surface of the molded article of the present invention is about several tens of nm to 500 nm, which is a very dense sliding surface with excellent flatness.

  Next, the sliding characteristics of the test pieces having the shapes shown in FIG. 1 were tested. The thrust tester is manufactured by Takachiho Seiki Co., Ltd. (model: TRI-S-500N). The test conditions are shown in Table 1.

  Tables 2 and 3 show the test results of the sliding characteristics of the test specimens. Table 2 shows the friction coefficient results, and Table 3 shows the wear length results. The wear length is the sum of the wear thicknesses of the specimen and the mating material (S45C).

  From the above results, the material of Patent Document 1 has an improved friction coefficient and wear length compared to the PA66 non-reinforced material, but the product of the present invention has a further higher friction coefficient and wear length than the material of Patent Document 1. It was confirmed that it was improved. Furthermore, it was confirmed that the product of the present invention is stable with a small dependence on both friction coefficient and wear.

1 Specimen 2 Sliding surface 3 Groove

Claims (6)

  A sliding member for a power transmission guide molded using a composite resin composition in which fluororesin particles are blended with a base resin, wherein the base resin is a thermoplastic resin, and the fluororesin particles are irradiated by electron beam irradiation. A sliding member for a power transmission guide, which is modified and has an average particle diameter of 10 μm or less, and the content of the fluororesin particles is 5 to 50% by weight based on the total amount of the composite resin composition.   The power transmission guide sliding member according to claim 1, wherein a primary particle diameter of the fluororesin particles is 5 μm or less.   3. The power according to claim 1, wherein the fluororesin particles are polytetrafluoroethylene resin particles and have at least a carboxyl group and / or a halogenated carboxylic acid group as a functional group at a terminal by irradiation with an electron beam having a radiation dose of 50 kGy or more. Slide member for transmission guide.   The power transmission guide sliding member according to any one of claims 1 to 3, wherein the base material resin is a polyamide resin, preferably a PA66 resin.   A mixture composed of a base resin and fluororesin particles is melt-kneaded and subjected to reactive extrusion to form a composite resin composition pellet in which the maximum particle size of the fluororesin particles is reduced to 5 μm or less. The sliding member for power transmission guides according to any one of claims 1 to 4, which is formed by molding. The sliding member for a power transmission guide according to claim 1, wherein the surface roughness is an arithmetic average roughness of 0.1 μm or less.