JP5783398B2 - Swing and rotary cam lifter and overhead valve engine - Google Patents

Description

  The present invention relates to a swing-rotating cam lifter that is slidably contacted with a timing cam in an overhead valve (OHV) engine. The present invention also relates to an OHV engine using this cam lifter.

  General-purpose engines such as generators, pumps, and brush cutters have a simple structure and are easy to maintain, and are lightweight and compact OHV engines. In particular, in a small OHV engine such as a brush cutter, an OHV engine provided with a rocking and rotating cam lifter that can be further reduced in weight and size is used.

  The above OHV engine includes an intake / exhaust valve positioned above the combustion chamber, a timing cam positioned near the crankshaft, and rotated by transmission of rotational power from the crankshaft, and a swinging slidable contact with the timing cam. A dynamic rotary cam lifter and a push rod for connecting the cam lifter and intake / exhaust valves are provided. In this configuration, by the rotation of the timing cam, the oscillating rotation type cam lifter slidingly contacting the oscillating rotation is oscillated, and the opening / closing power accompanying the oscillating rotation of the cam lifter is transmitted to the intake / exhaust valves via the push rod. Open and close the valve.

  Conventionally, as an OHV engine equipped with the above-described oscillating rotation type cam lifter, the valve of the engine in which the intake / exhaust valve can be operated by the cam lifter and the single cam and the backlash of the connecting portion of the constituent members is eliminated. Device (see Patent Document 1), or a valve drive device for a portable work machine that uses a cam lifter and a single cam to make the valve opening speeds of intake and exhaust valves different in purpose (see Patent Document 2) ) Etc. are disclosed. In addition, a direct lever type overhead valve device having a similar configuration is disclosed (see Patent Document 3). In these conventional OHV engine valve drive devices, the swing-rotating cam lifter (including the corresponding one) is made of metal and is in sliding contact with the metal timing cam.

  As a lubrication method for the sliding contact part etc. in the OHV engine, the oil stored in the oil pan is scraped up by a scraper provided on the rotating shaft of the crankshaft, and the inside of the crank and the valve rocker chamber are filled with mist oil. There are a system and a forced lubrication system that supplies oil to the sliding contact portion by an oil pump. Further, by having an intake passage from the carburetor to the intake valve of the cylinder head and a passage having a check valve branched from the bottom surface of the intake passage, a mixed gas of mixed fuel (oil and gasoline) and air Flows to the valve mechanism, and the oil contained in the mixed gas adheres to a cylinder, piston, timing cam, cam lifter or the like and is lubricated (see Patent Document 4).

JP 51-123416 A Japanese Patent Laid-Open No. 4-209905 Japanese translation of PCT publication No. 2003-522891 JP-A-11-223117

  However, in an OHV engine using a conventional oscillating rotary cam lifter, the sliding portion may be worn in a state where the lubrication action is not sufficient when oil is not sufficiently supplied, such as when the engine is first started. In particular, the wear of the sliding contact portion between the metal cam lifter and the timing cam is remarkable.

  The present invention has been made to cope with such a problem. An oscillating rotary cam lifter capable of suppressing wear even in a state of insufficient lubrication, and an OHV engine including the oscillating rotary cam lifter. The issue is to provide.

  The swing-rotating cam lifter of the present invention is a swing-rotating cam lifter that is slidably contacted with a timing cam of an OHV engine, and the cam lifter has a low friction material formed on the sliding contact surface with the timing cam. It is characterized by becoming.

  The low friction material is a coating film of a synthetic resin. Further, the matrix resin of the synthetic resin coating film is a polyamideimide (hereinafter referred to as PAI) resin.

  The synthetic resin coating film includes polytetrafluoroethylene (hereinafter referred to as PTFE) resin powder. The PTFE resin powder is a PTFE resin fired powder (hereinafter also referred to as PTFE fired powder).

  The PTFE fired powder is a powder having a particle size of 150 μm or less. The PTFE fired powder is a powder having a 50% particle size of 50 μm or less.

  The PTFE fired powder is a pulverized powder obtained by pulverizing a sintered body of PTFE resin. The PTFE fired powder is a powder having an aspect ratio of 3 or less.

  The synthetic resin coating film is characterized by containing graphite in addition to the PTFE resin powder.

  The synthetic resin coating film includes 60 to 110 parts by weight of the PTFE resin powder and 5 to 30 parts by weight of graphite with respect to 100 parts by weight of the matrix resin.

  The cam lifter is made of a sintered metal.

  The OHV engine of the present invention includes a swing-rotating cam lifter that is slidably contacted with a timing cam and swings on an axis parallel to the camshaft, and the swing-rotating cam lifter is the cam lifter of the present invention. It is characterized by.

  The timing cam is a synthetic resin molded body. In addition, the synthetic resin forming the timing cam includes carbon fiber or aramid fiber. The timing cam is formed integrally with the timing gear.

  Since the low-friction material is formed on the sliding contact surface with the timing cam in the swing rotation type cam lifter of the present invention, the friction torque between the cam lifter and the timing cam does not increase even in a state of insufficient lubrication. Wear due to friction can be suppressed.

  Since the low-friction material is a synthetic resin coating film, it has excellent low-friction characteristics, low cost, and ease of manufacture. In particular, when the matrix resin is a PAI resin, it is excellent in heat resistance, wear resistance, and binding property with a base (cam lifter), and is suitable for use in an engine having a high temperature atmosphere.

  Since the synthetic resin coating film contains PTFE resin powder, the synthetic resin coating film is excellent in self-lubricity. In particular, by using a PTFE resin fired powder, the synthetic resin coating film is excellent in self-lubricity, heat resistance, and wear resistance. Since PTFE resin powder has poor binding properties, its properties are sufficiently exhibited when used in combination with a matrix resin such as PAI resin.

  Since the PTFE fired powder has a particle size of 150 μm or less, the wear resistance and self-lubricity are excellent in a high dimension. Moreover, since the PTFE fired powder has a 50% particle size of 50 μm or less, the wear resistance and self-lubricating property are further excellent in a high dimension.

  Since the PTFE fired powder is a pulverized powder obtained by pulverizing a sintered body of PTFE, the dispersibility in the matrix resin is excellent. Further, since the PTFE fired powder is a powder having an aspect ratio of 3 or less, the dispersibility in the matrix resin is particularly excellent. As a result, the synthetic resin coating film formed as a low friction material on the sliding contact surface with the timing cam in the swing-rotating cam lifter is excellent in wear resistance and self-lubrication.

  The synthetic resin coating film is further improved in wear resistance by containing graphite in addition to the PTFE resin powder. Further, the synthetic resin coating film contains 60 to 110 parts by weight of the PTFE resin powder and 5 to 30 parts by weight of the graphite with respect to 100 parts by weight of the matrix resin. It has a high binding property to the surface, has a low risk of peeling, and has excellent lubrication properties and wear resistance.

  Since the cam lifter is made of sintered metal, it is easy to manufacture and has excellent binding properties with a low friction material coating such as a synthetic resin coating.

  The OHV engine of the present invention includes a swinging rotary cam lifter that is slidably contacted with a timing cam and swings on an axis parallel to the camshaft, and the swinging rotary cam lifter is the cam lifter of the present invention. The timing cam and the cam lifter can be prevented from seizing even in a poor lubrication condition such as at the time of initial operation, and the life can be extended.

  Since the timing cam is a synthetic resin molded body, the sliding contact with the oscillating and rotating cam lifter is reduced in friction and further reduced in weight. In particular, the weight can be further reduced by integrally molding the timing cam with the timing gear.

It is a perspective view of the rocking | swiveling rotation type cam lifter of this invention. It is sectional drawing (one side) of the valve drive apparatus part of the OHV engine of this invention. It is sectional drawing (other side) of the valve drive part of the OHV engine of this invention.

  The rocking and rotating cam lifter of the present invention will be described with reference to FIG. FIG. 1 is a perspective view of a swing-rotating cam lifter. As shown in FIG. 1, the swing-rotating cam lifter 1 of the present invention has a low friction material 7 formed on a sliding contact surface 1b with a timing cam 2 (see FIG. 2). The low friction material 7 may be formed on at least the sliding contact surface 1 b of the cam lifter 1, or may be formed on the entire surface of the cam lifter 1. The cam lifter body is made of metal, but is preferably made of sintered metal because it is easy to manufacture and is advantageous for binding with a low friction material coating such as a synthetic resin coating. Examples of the sintered metal that can be used include iron-based sintered metal, copper-based sintered metal, and iron-copper-based sintered alloy.

  As the low friction material, any coating that can reduce the friction torque under non-lubricating conditions such as synthetic resin coating, Ni plating, Ni-P plating, diamond-like carbon (DLC), molybdenum coating, etc. can be adopted. Among these, a coating film made of a synthetic resin having self-lubricating properties is preferable because of its low friction characteristics, low cost, and excellent manufacturability.

  Cam lifters are used under high temperature conditions inside the engine. For this reason, as the matrix resin in the synthetic resin coating film, any heat-resistant resin can be used as long as it has heat resistance that does not deteriorate during use and can firmly adhere the synthetic resin coating film to the ground. be able to. In addition, since the cam lifter is used in an environment where it comes into contact with the lubricating oil containing the additive, it is preferably a resin having oil resistance to these lubricating oils.

  Examples of matrix resins include polyphenylene sulfide (hereinafter referred to as PPS) resin, polyether ether ketone (hereinafter referred to as PEEK) resin, polyimide resin, polyamide resin, wholly aromatic polyester resin, PAI resin, epoxy resin, and phenol. Resin etc. can be illustrated. Among these, it is preferable to use a PAI resin because it is excellent in heat resistance, wear resistance, and binding property with a cam lifter as a base. In addition, PAI resin is excellent in oil resistance and hardly swells and dissolves with lubricating oil during use.

  The PAI resin is a resin having an amide bond and an imide bond in the polymer main chain, and can be obtained by reacting a polycarboxylic acid or a derivative thereof with a diamine or a derivative thereof. Examples of the polycarboxylic acid include dicarboxylic acid, tricarboxylic acid, and tetracarboxylic acid. PAI resin includes (1) a combination of dicarboxylic acid and tricarboxylic acid and diamine, and (2) a combination of dicarboxylic acid and tetracarboxylic acid and diamine. A combination, (3) a combination of tricarboxylic acid and diamine, and (4) a combination of tricarboxylic acid and tetracarboxylic acid and diamine. Each of the polycarboxylic acid and the diamine may be a derivative. Examples of the polycarboxylic acid derivative include acid anhydrides and acid chlorides, and examples of the diamine derivative include diisocyanate. Diisocyanate may be used that has been stabilized with a blocking agent necessary to prevent the isocyanate group from changing over time. Examples of the blocking agent include alcohol, phenol and oxime. Moreover, an aromatic and an aliphatic compound can be used for polycarboxylic acid and diamine, respectively. In addition, diisocyanate-modified, BPDA-modified, sulfone-modified and rubber-modified resins of PAI resin can be used.

  Among the PAI resins, an aromatic PAI resin in which an imide bond and an amide bond are bonded via an aromatic group is preferable. When it is an aromatic PAI resin, it is excellent in binding property with the cam lifter as a base, and the heat resistance of the obtained coating film is particularly excellent.

The synthetic resin coating film preferably contains PTFE resin powder in order to improve its self-lubricating property. The PTFE _{resin, - (CF 2 -CF 2)} n- in can be used ordinary PTFE resin represented, also generally of PTFE resin perfluoroalkyl ether group _{(-C p} F 2p -O- ) (P is an integer of 1-4) or a modified PTFE resin into which a polyfluoroalkyl group (H (CF ₂ ) _q- ) (q is an integer of 1-20) or the like is introduced. These PTFE resins and modified PTFE resins may be obtained by employing either a suspension polymerization method for obtaining a general molding powder or an emulsion polymerization method for obtaining a fine powder.

  As said PTFE resin powder, it is preferable to use the PTFE baking powder which heat-fired PTFE resin above the melting | fusing point. The PTFE calcined powder is excellent in uniform dispersibility and abrasion resistance as compared with PTFE resin (molding powder, fine powder) that has not been calcined by heating.

  The PTFE fired powder may be a powder obtained by heating and firing the PTFE resin powder, but a PTFE resin that has not been fired and fired is formed into a molded body, which is heated and fired at a melting point or higher to obtain a sintered body, which is then pulverized and powdered Any of these may be used. However, the latter is preferred because it is excellent in dispersibility in the matrix resin and the formed synthetic resin coating film is excellent in wear resistance and self-lubricating property.

  The PTFE fired powder is preferably a powder having an aspect ratio of 3 or less. When the aspect ratio exceeds 3, the dispersibility in the matrix resin is inferior, and the wear resistance and the like of the formed synthetic resin coating film may be reduced.

  The PTFE fired powder is preferably fine particles having a particle size of 150 μm or less. When the particle diameter exceeds 150 μm, the abrasion resistance of the synthetic resin coating film may be lowered. Moreover, it is preferable that the 50% particle diameter is a fine particle of 50 μm or less. If the 50% particle diameter exceeds 50 μm, the wear resistance of the synthetic resin coating film may be reduced as described above.

  50% particle diameter (median diameter) is a particle whose accumulated solid particle amount is 50% of the total solid particle amount when a particle size distribution curve of particle size and solid particle amount is obtained by a laser analysis particle size distribution measuring device. Is the diameter. In addition, as a laser analysis particle size distribution measuring apparatus, there is Microtrac HRA manufactured by Leeds & Northrup.

  The PTFE fired powder may be a powder obtained by further irradiating a heat-fired powder with γ rays or electron beams. Uniform dispersibility becomes better than this treatment.

  Examples of commercially available PTFE calcined powders that can be used in the present invention include Kitamura: KT300M, KT400M, KTL610, KTL450, KTL8N, KTL10N, Asahi Glass: Fullon L169J, L170J, L172J, L173J, Sumitomo 3M TF9207 and the like. Examples of the powder irradiated with γ-rays or electron beams after heating and baking include KTL 610, KTL450, KTL8N, KTL10N, and the like.

  The blending ratio of the PTFE resin powder is preferably 60 to 110 parts by weight with respect to 100 parts by weight of the matrix resin. If the blending ratio of the PTFE resin powder is less than 60 parts by weight, the synthetic resin coating film is inferior in self-lubricating property and may not be able to prevent wear in a state of poor lubrication conditions such as at the time of initial motion. When the blending ratio of the PTFE resin powder exceeds 110 parts by weight, the binding property to the base (cam lifter) is inferior, and the synthetic resin coating film may be peeled off.

  In order to improve the abrasion resistance, the synthetic resin coating film preferably contains graphite in addition to the PTFE resin powder. Graphite powder is roughly classified into natural graphite and artificial graphite, and there are flakes, granules, spheres, etc., and any of them can be used. Artificial graphite is generally not suitable for lubricants because it is difficult to make graphite with sufficiently advanced graphitization because it is difficult to make artificial graphite because it is carborundum produced during the manufacturing process. . Since natural graphite is produced that is completely graphitized, it has very high lubricating properties and is suitable as a solid lubricant. However, since the impurity contains a lot of impurities and this impurity lowers the lubricity, the impurities must be removed, but it is difficult to completely remove them.

  As the graphite powder, artificial graphite having 98.5% or more of fixed carbon is preferable because the wear resistance of the synthetic resin coating film can be improved while maintaining low friction characteristics.

  The blending ratio of the graphite is preferably 5 to 30 parts by weight with respect to 100 parts by weight of the matrix resin. When the blending ratio of graphite is less than 5 parts by weight, the effect of improving the wear resistance cannot be sufficiently obtained. When the blending ratio of graphite exceeds 30 parts by weight, the binding property to the base (cam lifter) may be inferior.

  Using a resin composition (varnish) in which the above PTFE resin powder is blended with the matrix resin, by spray coating method, dip coating method, electrostatic coating method, tumbler coating method, electrodeposition coating method, etc. A synthetic resin coating film is formed as a low friction material on at least the sliding surface of the cam lifter with the timing cam. After the coating film is formed, the solvent is removed, dried, melted, cross-linked, etc. by heat treatment to complete. In the process of forming the coating film, excess varnish adhered can be removed by physical and chemical methods such as wiping, centrifuging, and air blowing, and adjusted to a desired thickness. When the film thickness is increased, it may be overcoated. It is also possible to perform machining or tumbling after the coating is completed. In addition, it is preferable that the film thickness of a synthetic resin coating film is 10-50 micrometers.

  An example of the OHV engine provided with the swing rotation type cam lifter of the present invention will be described with reference to FIGS. As shown in FIG. 2 and FIG. 3, the valve drive device for the OHV engine includes a single timing cam 2 and a pair of swing-rotating cam lifters 1 in contact with the timing cam 2. The pair of oscillating and rotating cam lifters 1 are configured to rotate around the cam lifter shaft 1a. The timing cam 2 and the timing gear 3 are supported coaxially by a cam shaft so as to be rotatable. The cam shaft and the shaft of the cam lifter shaft portion 1a are parallel to each other. The timing gear 3 of the timing cam 2 is formed so as to mesh with the crank gear 4 b in the crank 4. One swing-rotating cam lifter 1 is connected to an exhaust valve push rod 5, and the other swing-rotating cam lifter 1 is connected to an intake valve push rod 5. Reference numeral 6 denotes an intake passage.

  The usage state of the valve drive device for the OHV engine will be described. By rotating the crankshaft 4a of the crank 4, the timing gear 3 meshing with the crank gear 4b is rotated. As a result, the timing cam 2 is rotated, and one of the pair of oscillating rotary cam lifters 1 that are in contact with the timing cam 2 is rotated about the lifter shaft portion 1a, and the exhaust valve is pushed via the push rod 5 for the exhaust valve. To open. Next, when the timing cam 2 is further rotated, the other oscillating and rotating cam lifter 1 that contacts the timing cam 2 rotates about the lifter shaft portion 1a, via the push rod 5 for the intake valve. Open the intake valve. The operation of the valve is completed by closing the exhaust valve at a predetermined time and further closing the intake valve. In this configuration, since the pair of oscillating rotary cam lifters 1 are rotated by one timing cam 2, the length of the timing cam 2 in the axial direction is reduced, and a single timing cam is sufficient. Lightweight.

  As a lubrication method in the OHV engine of the present invention, any conventional type can be adopted. In the present invention, since the low friction material 7 is formed in the sliding contact portion 1b with the timing cam 2 in the oscillating rotation type cam lifter 1, no matter what type of lubrication is employed, the wear at the sliding contact portion Can be prevented.

  In the OHV engine of the present invention, the timing cam 2 may be a synthetic resin molded body. When the timing cam 2 is made of synthetic resin, the weight can be further reduced, which is suitable for a portable OHV engine such as a brush cutter.

  Examples of the synthetic resin forming the timing cam 2 include a PPS resin, a PEEK resin, a polyimide resin, a polyamide resin, and a wholly aromatic polyester resin. When the timing cam 2 is made of the above synthetic resin, it is preferable that the timing cam and the timing gear are integrally formed. In this case, the weight can be further reduced.

  When the timing cam or the like is made of a synthetic resin, it is preferable to add a fibrous reinforcing material such as carbon fiber or aramid fiber to the synthetic resin in order to improve mechanical strength. However, it is not desirable to use glass fibers as the fibrous reinforcing material because there is a risk of attacking the synthetic resin coating film of the swing-rotating cam lifter.

  The fibrous reinforcing material blended in the synthetic resin forming the timing cam is preferably 5 to 40 parts by weight with respect to 100 parts by weight of the synthetic resin. When the fibrous reinforcing material is less than 5 parts by weight, the effect of improving the strength of the timing cam is small. On the other hand, when the fibrous reinforcing material exceeds 40 parts by weight, the surface smoothness is lowered, which may be a factor of reducing the wear resistance of the synthetic resin coating film against sliding contact with the cam lifter.

  The present invention will be specifically described with reference to examples and comparative examples, but is not limited to these examples.

The compounding material of the resin composition used for each Example and each comparative example is shown below.
(1) PAI resin: Glass transition temperature 245 ° C product (2) PTFE calcined powder: manufactured by Kitamura Co., Ltd .; KTL610 (maximum particle diameter 63 μm, 50% particle diameter 12 ± 3 μm (Microtrack HRA))
(3) Graphite powder: artificial product with an average particle size of 10 μm

Example 1, Example 2, Comparative Example 1, and Comparative Example 2
About the cam lifter of each Example, the synthetic resin coating film was formed as a low friction material film by the method shown below. PTFE calcined powder and graphite powder were mixed with the solid content of the PAI resin varnish dispersed with N-methylpyrrolidone at a ratio shown in Table 1 until sufficiently uniformly dispersed by a ball mill. The mixed solution was coated on the surface of a test iron-based sintered alloy cam lifter by a spray method. This was dried and then baked at 240 ° C. to form a synthetic resin coating film.

  A cam having a diameter of 35 mm, an eccentricity of 3.5 mm, and a thickness of 6.5 mm was brought into contact with the obtained iron-based sintered alloy cam lifter with a load of 3 kgf at 3000 rpm under non-lubricating conditions. Rotated for 120 minutes. 120 minutes later, the sliding surface between the cam lifter and the cam was visually observed. The results are also shown in Table 1.

  In Examples 1 and 2 in which a synthetic resin coating film was formed as a low friction material coating on the sliding surface of the cam lifter with the cam, the sliding surface of the cam lifter and the cam was contacted even after being slid and rotated for 120 minutes under non-lubricating conditions. No wear was observed. On the other hand, in Comparative Examples 1 and 2 in which the low friction material was not formed on the sliding surface of the cam lifter with the cam, wear was observed on the sliding surface of the cam lifter.

  The swing-rotating cam lifter of the present invention can be used for generators, pumps, brush cutters, etc., because the friction torque between the cam lifter and the timing cam does not increase even when lubrication is insufficient, and the wear due to the cam lifter friction can be suppressed. It can be suitably used as a rocking and rotating cam lifter for a lightweight, compact OHV engine.

DESCRIPTION OF SYMBOLS 1 Oscillating rotation type cam lifter 2 Timing cam 3 Timing gear 4 Crank 5 Push rod 6 Intake passage 7 Low friction material

Claims (9)

An oscillating rotary cam lifter that is slidably contacted with a timing cam of an overhead valve engine,
The cam lifter is made of sintered metal, is a sliding contact surface with the timing cam, and a low friction material made of a synthetic resin coating film having a thickness of 10 to 50 μm is formed on the sintered metal surface.
The synthetic resin coating film comprises only three components: a polyamide-imide resin as a matrix resin , a calcined powder of a polytetrafluoroethylene resin having an aspect ratio of 3 or less, and an artificial graphite having a fixed carbon of 98.5% or more. Oscillating and rotating cam lifter. Wherein the poly calcined powder of tetrafluoroethylene resin, rocking rotary cam lifter according to claim 1, characterized in that the following powder particle size 150 [mu] m. The rocking rotary cam lifter according to claim 1 or 2, wherein the calcined powder of the polytetrafluoroethylene resin is a powder having a 50% particle diameter of 50 µm or less. Wherein the poly calcined powder of tetrafluoroethylene resin, claim 1, characterized in that the pulverized powder obtained by pulverizing a sintered body of polytetrafluoroethylene resin, rocking rotary claim 2 or claim 3, wherein cam lifter . The synthetic resin coating film includes 60 to 110 parts by weight of the calcined powder of the polytetrafluoroethylene resin and 5 to 30 parts by weight of the artificial graphite with respect to 100 parts by weight of the matrix resin. The rocking | swiveling rotation type cam lifter as described in any one of Claim 1 thru | or 4 . 6. An overhead valve engine comprising an oscillating rotary cam lifter slidably contacted with a timing cam and oscillating on an axis parallel to the camshaft, wherein the oscillating rotary cam lifter is any one of claims 1 to 5. An overhead valve engine characterized by being the cam lifter described in the item. The overhead valve engine according to claim 6 , wherein the timing cam is a synthetic resin molded body. The overhead valve engine according to claim 7, wherein the synthetic resin forming the timing cam comprises carbon fiber or aramid fiber. It said timing cam, claim 7 or claim 8 overhead-valve engine as claimed, characterized in that formed by integrally with the timing gear molding.

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